Hydraulic roller lifter issue?

Dear Rene,

            I suffered a clicking sound for months and it was getting worse.  The short story is that after pulling the valve cover the cause was a push rod that had worn about 6 mm shorter than it was supposed to be. 

           My engine builder/machinist told me that, in addition to the quality problems with other engine parts, push rod heat treatment (?) has become unreliable.  He claimed that using his own hardness durometer (?) to test *new* pushrods,  he was finding roughly a 10 to 15% fail rate. 

          He told me to pull the other push rods for testing.  Out of the sixteen push rods there was a total of two abnormally worn rods and two that only failed the hardness testing.   I now have replacements for the four bad ones and a finally quiet engine.

          It is easy to pull the push rods and check their ends for abnormal wear.  I do not know how easily you can find someone to test the hardness.

          For what it is worth, if it was built in the last ten years, it *might* be a push rod, if nothing else is found.

                  Warmest regards, Chuck Engles

@cengles posted:

Dear Rene,

            I suffered a clicking sound for months and it was getting worse.  The short story is that after pulling the valve cover the cause was a push rod that had worn about 6 mm shorter than it was supposed to be.

           My engine builder/machinist told me that, in addition to the quality problems with other engine parts, push rod heat treatment (?) has become unreliable.  He claimed that using his own hardness durometer (?) to test *new* pushrods,  he was finding roughly a 10 to 15% fail rate.

          He told me to pull the other push rods for testing.  Out of the sixteen push rods there was a total of two abnormally worn rods and two that only failed the hardness testing.   I now have replacements for the four bad ones and a finally quiet engine.

          It is easy to pull the push rods and check their ends for abnormal wear.  I do not know how easily you can find someone to test the hardness.

          For what it is worth, if it was built in the last ten years, it *might* be a push rod, if nothing else is found.

                  Warmest regards, Chuck Engles

Just asking… The 6 mm push rod part - was it missing or just smooshed … because if it was missing where did it go?

The last engine I built was the 408W for my Bronco.  I used Hydraulic Roller lifters with a dog bone as the block is a 1994 351W block and designed for roller cam.  I had problems with three of the 16 lifters.  One would not pump up at all and two would collapse shortly after shutting off the engine.  We constructed a test apparatus to pump oil into the lifter to test if it pumps up and if oil does indeed travel to the hole at the push rod.  I found more bad lifters.  I ended up buying more lifters and sending back the bad ones until I got a set that passed the test.  The engine has been in the truck for three years now with no problems.

BTW the reason we made the test fixture was we didn't want to keep taking the intake manifold on and off to keep testing lifters.

I feel the quality of the aftermarket lifters today  is awful.

Dear LeMans,

         Initially, I thought that it had broken off.  Later, I looked more carefully and it had not broken off, but *worn* off due to the sub-standard hardness.  When I pulled all the other push rods, there was another one with similar abnormal wear.  Where the metal went, is through the oil system including the oil filter. The engine runs much more quietly and as strong as ever with sixteen fully functional and properly hardened push rods.

                      Warmest regards, Chuck Engles

There is a tradeoff on hardness.

I had a racing set of push rods from Crane. A brand that I never question the quality of.  Hardened for use with guide plates. I ran them a few miles and then all Hell broke loose.

I was only a mile from home so I was able to limp home.

When I took it apart I found that the tips on two had broken off near the lifters and many if not all had cracked through the dimple weld that held the tips on.

Crane refunded the purchase price and I wouldn't take another set from them.

The explanation was "a bad batch of metal", but in reality they had been over hardened to the level of what a good drill bit is.

You don't use a drill bit as a drift pin because it will shatter...badly.

Anyone who works with metals will tell you that in hardening or tempering it, at some point the metal gets brittle and will shatter like tempered glass will.

So really, there is a "sweet zone" for the hardness of the metal depending on the application intended.

The fact is that in many cases it is better to have it softer and bend then too hard and shatter. It is very easy to criticize this and basically what is happening is that once you get away from OEM parts, the aftermarket is a crap shoot regardless of how well meaning the MFG is.

Here is the culprit

I haven't dropped it off yet but it's certain the camshaft is pretty damaged too.

I know this has happened to at least one other person with the same camshaft and lifters. I'll message Bullet Racing and see how they explain it

@cengles posted:

Dear LeMans,

         Initially, I thought that it had broken off.  Later, I looked more carefully and it had not broken off, but *worn* off due to the sub-standard hardness.  When I pulled all the other push rods, there was another one with similar abnormal wear.  Where the metal went, is through the oil system including the oil filter. The engine runs much more quietly and as strong as ever with sixteen fully functional and properly hardened push rods.

                      Warmest regards, Chuck Engles

That’s bad.. did you stick a magnet on the new oil filter?

Dear Le Mans,

          I have a magnet on the oil filter of both Panteras and have had for quite some time.

                          Warmest regards, Chuck Engles

There have been many that have gone to the hydraulic roller camshaft. The vast majority seemingly have not had issues with it.

Apparently though enough have had this kind of issue with components to it.

There are many that scoff at what I do as, i.e., the component decisions that I make as "old hat from the 'old guy' ". Perhaps that is right but one thing that will never happen at my end is to have this kind of failure simply because I will never go to a roller lifter camshaft. It simply introduces an additional level of potential component failure in the valve train that ultimately can have catastrophic consequences.

The potential failure risk far out ways the small benefits of using a hydraulic lifter valve train.

I personally have seen this type of failure too often. The roller lifter solution simply is not a bulletproof one. Why risk it?

I'm sorry for your loss.

Doug, I tend to agree with you. Hydraulic roller lifters should be reliable. After all, they are OEM in 5.0L Mustangs where they do not have reliability issues, that I’m aware of. The problem is, the lifters are heavy, which creates the need for heavy valve springs to control the inertia they create. Solid roller lifters are better in this regard. These heavy springs create a very hard, short life for the tiny needle bearings that live inside the rollers. The only partial solution is to lower your max RPM expectations and fit the very lightest valve springs possible. That’s how Ford dealt with this issue in the 5.0L. Solid roller lifters are a bit lighter than hydraulic roller lifters, so they can get away with lighter valve springs. As a result, they are more reliable
As I mentioned in Marlin’s pilot bearing thread, Isky makes solid roller lifters that use the same style of bearing as his pilot bearings. No needle bearings! Unfortunately, they are expensive and so far unavailable as hydraulic lifters.

@davidnunn posted:

Doug, I tend to agree with you. Hydraulic roller lifters should be reliable. After all, they are OEM in 5.0L Mustangs where they do not have reliability issues, that I’m aware of. The problem is, the lifters are heavy, which creates the need for heavy valve springs to control them. Solid roller lifters are better in this regard. These heavy springs create a very hard, short life for the tiny needle bearings that live inside the rollers. The only partial solution is to lower your max RPM expectations and fit the very lightest valve springs possible. That’s how Ford dealt with this issue in the 5.0L. Solid roller lifters are a bit lighter than hydraulic roller lifters, so they are more reliable.
As I mentioned in Marlin’s pilot bearing thread, Isky makes solid roller lifters that use the same style of bearing as his pilot bearings. No needle bearings! Unfortunately, they are expensive and so far unavailable as hydraulic lifters.

My solution is simple. I use a solid lifter cam and valve train.

They are the lightest of all, offer the greatest longevity and the highest rpm potential.

To me, they are also the easiest to maintain.

To me, when you find the answer, stop looking.

To me, "There ain't no Coupe DeVille at the bottom of a Cracker Jack Box". - Meatloaf is correct on this point.

Some folks are like the Conquistadors searching for the city of gold that never comes.

I had the same configuration of a Bullet cam and Morel (branded as Bullet) lifters.

What happened to me was one of the link bars came loose when one of the rivets popped off of the lifter pair.

That allowed the roller lifter to rotate in the lifter bore, which wore both the cam lobe and the lifter roller.

Once mine started wearing, it wore very fast, in about 200 miles.  Post-disassembly, appeared to be just the failure of the lifter pair (the rivet), but not an engine build issue.

Doug - I think you’re being a little harsh on people who choose different solutions?

If you recall – not that long ago, everybody was talking about how catastrophically solid lifters fail because of a lack of ZzZz ZzZzP.  

You pays your money and you takes your chances.  Everybody puts a lot of thought into these motors when you’re spending 10 grand or more to build one. It’s easy in retrospect look back and say “oh you shouldn’t have done that”.  

And like you said, lots of people have built this configuration motors and they have run well.

Anyway – good luck with the fix Rene.  I suspect you’re going to want to disassemble your engine and flush it out. I like the Bullet Cams spec, but I went with a different roller lifter manufacturer on the repair.

Rocky

With two clearly documented failures of the same part, people may consider not sourcing their roller lifters from Bullet, if that’s the path they choose!

I removed all the lifters and some have abnormal wear

Doug, you may be right, solid flat lifters may be a better solution but if I change now I will have to change all the lifters, pushrods and, to take advantage of the weight, all the springs. That is a lot of work and money.

I sent Bullet a message and am waiting for their response.

That’s interesting, Rene…

It would seem that the only way to get wear there is if the (or both) lifter body was / were  able to rotate in the bore(s).

As I recall, there’s a lot of gap on those link bars, so it would have to move a good distance to be able to touch there…

Let us know what they say…. How long did you run your engine since you’ve built it?

This is all about risk analysis. There should be enough data available to project a clear picture of the risks.

I don't tell anyone what to do and frankly while I am involved in building something I like to keep that secret incase it doesn't go so well. Plus, some, like my wife use me as a negative barometer and whisper, don't do what that jerk does.

As far as my personal success and failure rate goes, the bumps on my head should indicate that learning from failure should have made me a genius and sadly (to me) in has not.

As far as mixing in zddp as a preventative to failure, I've tried that and it mixes strangely with my Vodka. It hasn'nt made me any stupider but there is only so low you can go?

In actuality the lack of quality control of new components, particularly in the aftermarket ultimately is the culpret.

I would also theorize, right or wrong, that if you want the same dependability on these roller cams, then you should model OEM ones. Those have got thousands if not millions of test miles on THOSE solutions. Not some re-application of Pro Stock racing engine solutions that may or may not have the same dependability?

After seeing that simple failure of the retaining rivets, how comfortable are you going to feel with running one in YOUR car and exactly how many trouble free miles do you expect to put on those components?

For example, there are people running titanium valve train components on the street. NASCAR race cars change those out after every race.

How many miles are you going to put on those?

Yes Rocky. All food for thought. We can all share our various experiences here. When there is a reoccuring theme though, I would take those into consideration as to, what will I do if those break on me or maybe is it worth the risk for little gained.

...and OEM engines running roller lifter assemblies are designed for that, not added onto modified flat lifter cams.

I also noticed that in Medical experiments, there is always one person that gets the placebo that winds up with a miracle cure! So some notice that it simply defies logic yet there it is in black and white. I think that happens in these automotive experiments sometimes also?

I was only pointing out my train of thought on selecting a valve train and everyone should have as much information as they can get in order to make their own decision of which way to go.

Here is Bullet's first response:

Hello Rene,

for the lifter to have that much damage to the wheel the problem started from the beginning of running the engine.
The tie bar of the lifter should not have any stress on it unless something hits it or the camshaft is improperly installed.
What type of damage do the other lifters have? If the tie bars have similar wear it could be an installation issue.
What damage does the camshaft have?

Chris

They are in bad faith!
I told them I knew this happened to Rocky a few years ago and I'm waiting for their second response

I have run about 1600 miles since the engine rebuild.

It is true that the tie bar do not have any stress but I think that it undergoes heat treatment to harden it and if this treatment is poorly done, it becomes fragile and breaks with vibrations.

HA! IN THEORY the bar has no stress on it however if the rollers are not perfectly square, flat and parallel it will induce an inertia to make the lifter turn.

That will make the bar act as a pry bar and pull the rivet out.

Also if the lobe of the cam is not perfectly "square" to the center line it will induce the lifter to turn.

That is all irrelevant. The question is really, "are you going to warranty the kit or not"?

Exactly WTF could you have screwed up in the cam installation? You put it in backwards, sideways or upside down?

I got the same "crap" from Compcams when I opened the box and the distributor drive gears crumbled off of the camshaft.

They told me, "that is not covered by our warranty BUT to maintain good customer relations, we will replace the cam FOR FREE!"

Here is the actual truth about camshafts. They only spot check them for quality and accuracy. The big companies have like five slave machines all grinding the same profile together and the operator just loads the blanks in and runs the system.

They don't check every cam and every lobe. They don't check every cam blank before the load it. That is too time consuming and therefore too expensive.

Don't let them shovel BS on you.

here is my response to Bullet

If the problem had started right from the beginning, the clicking noise would have appeared very quickly, which is not the case. I have only driven about 40 miles to home since the noise started and it has increased in intensity quite quickly.

Doug sez:

“In actuality the lack of quality control of new components, particularly in the aftermarket ultimately is the culprit.”

This is absolutely correct in these modern times!

These are not OEM roller lifter cams and lifters. They are aftermarket.

You can't rely on a near 100% dependability. All you can do is simplify the valve train and/or keep changing out the breaking components.

Rene, you don't need to change out the valve springs. New push rods with stock flat lifter cams should be stock, not custom.

You are going to change out the lifters and cam anyway.  This isn't as complicated as you think if you go to a flat lifter cam.

If you switch, you can get a cam kit. Cam, lifters and matching springs.

So I don't understand the issue some have with adding ZDDP to the oil? You are just returning that oil mix to the original formula that the car was designed with.

The issue now with ZDDP is that it has the tendency to foul catalitic converters. There are none on Panteras to foul.

US law requires OEM manufacturers to warranty the emission systems for 100,000 miles. Cats are expensive to replace.

Current OEM manufacturers went to roller lifter cams for that reason and because they are aiming at a Fleet fuel consumption average and the roller lifters help that Fleet number. There is no other reason.

A roller lifter camshaft can be ground with a steeper lobe ramp then a flat lifter cam can. So that permits a more radical cam timing with better everyday manners BUT the cams you are selecting are too mild to take advantage of that, so then what is the advantage of a roller lifter cam?

Simplify. It is the best course of action.

Incidentally, what does the lifter bore in the block look like? Aren't you risking damaging those in the block with another lifter failure?

I have installed bronze sleeves in the tappet housings and they appear to be in good condition but they are certainly not designed to operate with faulty tappets.

When I say replacing the springs, I mean to put in softer ones to take advantage of the weight reduction of mechanical flat tappets over hydraulic roller tappets

The weight of the higher spring rates will not matter much at all except to give your valve train more rpm potential.

I would guess that it is highly unlikely that you will put 100,000 miles on your car.

It should have no issues with those springs in the normal usage of a very high performance vehicle.

The added load on the lifters and cam lobes with the heavier springs really doesn't matter  with correct lubrication.

The concern is that you need to be sure of the capacity of the push rods and if you go to a flat lifter camshaft, that you use a sufficient amount of ZDDP.

IF you are going to look around in considering valve train changes, you might come across the term "shell lifters".

Those were used by Ford in the 427's for higher rpm potential. Essentially what they are, are lightened lifters, i.e., lower mass.

Those typically were used with the sodium filled valve stems.

The combination put the 427 into 8,000 rpm capability EXCEPT for the valve springs which were limited at the time strictly to 7,000 rpm.

There is an entire side discussion about that with the development of the MkII GT40's for Lemans. There Ford did a 24hour crash test and determined that the maximum safe rpm of the engine for that race was 6,200 rpm.

So yes, there is a contradiction there in why would you put in 8,000 rpm components if at most it is safe for 7,000 rpm because of the valve springs, etc.

I can only envision a scenario in which different components were assigned to different engineering teams for development and the spring technology people just could not keep up within the given time frame?

The spring issue has been resolved. It was in the alloy of the spring steel which we now have.

incidentally, when NASCAR outlawed the big block Fords and the racers went to the 351c, there was issue of valve spring failure early on.

The racers solution was to submerge the valve springs in oil within the valve covers. I'm not sure of the exact procedure to accomplish this but it did involve restricting the oil return to the oil pan in a way that the valve covers would fill up with enough oil.

The submerging in oil was "cooling" the springs so they would not loose temper.

I know I can keep my springs since they are designed for a "heavy" valve train, but if I install much lighter lifters, these springs will be oversized and will create an unnecessarily high pressure at the cam/lifter contact.

For now I am waiting for Bullet's second answer

@rene4406 posted:

I know I can keep my springs since they are designed for a "heavy" valve train, but if I install much lighter lifters, these springs will be oversized and will create an unnecessarily high pressure at the cam/lifter contact.

For now I am waiting for Bullet's second answer

Best of luck with that. I hope this all ends well for you.

Isky does offer a hydraulic roller lifter with a bushing for a Windsor block.   I have been thinking about replacing my hydraulic roller lifters with the ones offered by Isky but haven’t done it yet because my motor doesn’t have too many miles on it.  It would be more for piece of mind and prevention.

I sent another message to Bullet:

and here is their response

@jimmym posted:

Isky does offer a hydraulic roller lifter with a bushing for a Windsor block.   I have been thinking about replacing my hydraulic roller lifters with the ones offered by Isky but haven’t done it yet because my motor doesn’t have too many miles on it.  It would be more for piece of mind and prevention.

Jesel too but they are very very expensive:

https://www.jesel.com/keyway-roller-lifters

They are just being cheap. I think that they should send you a complete new set up.

To me this is predictable but their reaction may simply be that they have so many complaints it puts their buisness in jeopardy if they replace all of them for free.

Some companies just have no integrity. Some do.

I have a 2003 Audi Turbo TT. I installed long ago, a Forge intercooler on it. It is specific to the car and not a universal fit.

In addition, I put a "Monster Turbo" on it.

Now at some point, some how I blew up the intercooler. It split at the seams in several places. The specs on the intercooler say it is good for 100psi. I only was at 28psi.

This was just before the Covid thing, so roughly 4 years ago. So I call up Forge and they tell me to send an email to customer relations since Forge USA no longer carries them.

I do it and in less then an hour, I get a message back for a picture of the failure. I oblige and really expect the run around?

Wrong.

I get a phone call from someone "up' in the company. He apologises for the failure. They no longer have these as stock items. What do they do?

THEY BUILD ME ANOTHER IMMEDIATELY from the original blue prints, run it to the airport in LONDON, ENGLAND, ship it out OVERNIGHT! It is here in NEW YORK THE NEXT DAY BY 10AM BY UPS RED LABEL!

What did this cost me? NOTHING! NADA! ZILCH! There is a personal letter in the box signed by the President of the company apologizing and saying that their products ARE GUARANTEED FOREVER!

That is a $1,100, intercooler and the shipping from London overnight was just under $700.

I literally had tears in my eyes, and do as I write this. This is what you call INTEGRITY!

To this day I still find this amazing.

So Bullet won't even offer you a new lifter? Maybe they just can't get hold of the President because he is out playing on his boat with a "do not disturb"  order?

FYI: Forge sells the world's best hose clamps!

I didn’t want a new set of Morel lifters from them…

I was happy to get my cam reground.

Rocky

@davidnunn posted:

FYI: Forge sells the world's best hose clamps!

I would highly recommend them to anyone regardless of what you are buying from them.

I will FOREVER judge EVERY OTHER COMPANY IN THE WORLD by the standard that they set.

It really comes down to put up or shut up. Period. End of story.

The big kids on the block are saying you're afraid to come out and play now. What's it gonna' be boy?

I plan to do like Doug and go back to flat and mechanical lifters.
But with which camshaft? I need a minimum 75° ABDC closed intake, a lift of about 0.60'' and a maximum speed of at least 6500 rpm.

Any suggestions?

I would recommend this one.

https://www.compcams.com/magnu...-351c-351m-400m.html

That is just the cam. They offer it with a complete matched kit of cam, lifters and springs also.

Other then it sounds like a marching band at idle, the only negative that I see with it is the 110° centerline. That is basically an issue with the iron heads because of the  restriction in the exhaust ports very similar to what the FE series is limited by and struggle with.

It won't cost you any power as a result, it just won't maximize the exhaust gain that you would get with a better exhaust port like on the Motorsport aluminum head series.

I'm using this cam along with the first head in that series, the A3. Those have 60cc chambers and the largest intake ports of the series but have a raised exhaust port. That change is good for around 25-30 hp over the iron heads.

I'm running the combination with 180° 2" primary headers. So there is much less restriction in my set up. A 110° centerline makes sense there.

The most popular head in that series seems to be the C302B head but if you look at a set of those that has been raced prepared, the intake ports have been opened up to the point of closely resembling the stock as cast A3 intake ports.

That series of heads is where all of a sudden you go from a 500hp engine to something like 700-750hp.

What you do to match the induction is significant with that as well. I went to an 8 stack Weber system, then switched over to an 8 stack EFI to clean up the heavy Weber idle.

The combination does change the character of the car from a "gentleman's GT" into something more closely resembling a GT40. It all depends on your "tastes" I suppose? Personally, I don't have issue with it.

Others seem to though. It's just too nasty for them. To each his own?

I do not know where the upper rpm limit is going to be with the springs in that kit but it would tend to answer the criteria that you posted. I would inquire with Compcams about the rpm's with it? You may have better springs then those in the kit already installed in your heads?

I had seen this cam and also this one,

https://www.compcams.com/magnu...-351c-351m-400m.html

but I fear that the second one is a bit too "radical" for road use.

I have these springs:
https://www.manleyperformance....sional/MAN_22441-16/

which gives 146 lbs valves closed and 434 lbs at max lift for the intake and 164/461 for the exhaust.

I have cast iron cylinder heads and have no plans to change them.

Compcams say that you absolutely have to remove the internal spring for the break-in of the camshaft and the lifters, then put it back afterwards. I could make a tool to compress the springs with the cylinder heads in place and the engine in the car, but perhaps there are tools available commercially?

Cams:

I think that the second cam, as you have listed is too much for a street car.

What will tell you the nature of a cam is the "Advertised Duration". 294° is the advertised duration on the cam that I recommend to you. It is about as hot as you want to go in a street car.

What 294° is telling you here is that it is hot but not quite a dedicated racing cam and streetable. That is what Compcams is telling you with that number.

The second one that you list has an advertised duration of 306°. The "rule of thumb" on this is 300° or more is too much for a street driven vehicle.

The Advertised Duration doesn't mean too much other then tell you the nature of the cam. The duration @.050" lift is the significant number.

There is so much duration in the over 300's that you will actually hear the engine spitting through the exhausts. I know street cars that use them but they are more race car then street car and a bear to handle on the street. Basically Drag Race set ups.

294° advertised in this case is going to be 248° @ .050" lift.  I can tell you from experience that is a TREMENDOUS open track camshaft. It may seem at times a little much on the street but it loves an open track. It will outrun most of the ORIGINAL 1960's "factory road race cars".

236° @ .050" is what most "street machine owners" are happy with NOW. I have that cam in two of my other cars and it is very driveable on the street but no fun in bumper to bumper traffic.

Springs:

I didn't look for the spring load specifications in the cam kit but as I remember they are at least dual springs. They may be triple. You need to look at that.

The 460 pounds that you have now is not really necessary with solid lifters. About 360 pounds is what you need. There is a factor of valve guide wear with higher rates especially if you are not using a "roller bearing" rocker arm.

Depending on the weight of the valves, your potential rpm normally with the cam kit that Compcams supplies is about 7,200 rpm. Titanium valves will turn a bit more. 7,500rpm given the same other components but the stems are softer and wear faster then chrome molly stems.

I honestly can't tell you the maximum of the cam since I have never looked for it. Generally the car is "tuned" to max out about 6,500 to 6,700 rpm. Certainly that is where the headers were built to max out at and with the Webers that is complimentary to their power range.

I am aware of their recommendations for breaking in the cam.

So far, "knock on wood...knock, knock, knock", I have yet to wipe out a brand new camshaft.

I did not follow their break in procedure but yes you can change the springs while the heads are on the engine. It is not fun to do on any car and worse on a Pantera.

Spring tools:

Yes there are kits for changing the springs on the car. They actually are common since it is not unusual for racers at the track to have to do maintenance on the valve train with minimal amounts of time expended.

The Compcams with .587 lift is one step down and would be 236° @ .050" duration.

It will idle hot at about 850-950rpm. You CAN get it down to 800 ish but that's about it.

Most people would not go hotter then that.

Frankly, in "the old days" it wasn't unusual to try the hottest cam first, then step down one at a time until you find the one that you want.

Compcams timing events on their cams are almost identical from engine series to engine series in many cases.

You need to remember also that the actual valve lift is not the cam lift. You need to deduct the "valve clearance" from that which I think in this case is going to be either .022" or .028" (I forget at this moment and would need to look at the cam card to verify that).

What you need to match though is the valve flow numbers from the heads to the lift of the valves to maximize the potential. But the flow of the intake manifold runners is also involved in that and unless you go to an IR intake manifold with equal runners, that is difficult to get them all completely in balance.

The carbs are involved in that as well and Weber 48ida's with 42mm chokes are maxed out at 2400cfm total divided by 8 =  300cfm intake per cylinder. So anything that is going to give you more flow then that is really wasted effort.

That's why with Webers the engine at 5.7L max's out at about 6500 to 6700 rpm.

So you need to know the flow numbers of your heads from flow bench testing to tell you the maximum flow and at what lift to be completely scientific about the entire thing.

With a single 4v intake, it is very difficult to balance flow that closely because normally you have 4 runners that flow high and 4 runners that flow lower.

You COULD do that on something like a Boss 302 inline carb along with a matching IR manifold but the results may not be worth the additional cost and time involved.

It all depends on how crazy you want to get with this?

Incidentally, you can take some of the effect of long duration cams out with efi.

Those are just my experiences and I have no doubt that others will feel very differently. To say that I am crazy is as the "Brits" would say, "in Doug's case that's a bit redundant".

With stock Iron Heads and the big Flow Difference between Intake and Exhaust Port a Split pattern Camshaft seems more logical. If you want to go mech flat tappet why not something like this:

https://crower.com/camshafts/f...ppet-camshaft-3.html

It doesn't have .600 lift but seems to be in the range you would liek to have.

There is this one too:

https://crower.com/camshafts/f...ppet-camshaft-4.html

@rene4406 posted:

There is this one too:

https://crower.com/camshafts/f...ppet-camshaft-4.html

That cam requires a static compression ratio of 10.25:1. I am running with under 10 with the Compcams 294.

In the US, pump gas of a 93 octane is only good for under 9.9:1 or so.

You will need to run racing gas with it.

I have found here that even SUNOCO unleaded racing gas will not handle that compression ratio. It needs the old purple 106 leaded racing gas.

Something to consider.

With the Cleveland I find that lift is more important then the duration is.

That cam is also a 112° centerline so it is not giving you the opportunity to benefit from exhaust improvements that a 110° can.

Look at the rpm range on it. It is done by 5750.