PIM 427 Hammer engine - Surging at cruise

Asajay, I’m surprised PIM doesn’t have this all figured out. Isn’t their 427 Hammer a standard engine package? Are you using the carb they recommend? If so, can’t they tell you what jet sizes work best?

The common denominator here is the camshaft timing.

I don't know what kind of an "animal" the "Hammer" is but just reacting to this data, it has to be the cam timing? There is nothing left to consider?

There should be a ton of vacuum with that many cubes. I would take an "educated guess" and say in general it sounds like too much duration? I acknowledge that this is very easy for me to say but I see no other factors that you have not looked at?

What rocker arm ratios is this engine running? I'm thinking that you could pull a SB Chevy deal and play with the rocker arm ratios? If you are at 1.6:1 now, it doesn't give you much to try since the next step would be 1.5 and you could just vary it into intake v. exhausts but ultimately I think you need to consult with a custom camshaft grinder.

You need to see the cam card.

The logic to me indicates that you cannot live with those lean numbers indefinitely? I would want to see the "dyno map" on that engine. You just can't build that and not have run it on a dyno before installing it. That makes no sense at all.

To me, that seems like some kind of an incompetence on the builders?

That is just my sense of where to concentrate your attention.

Thank you Doug, I believe others I've consulted on this are leaning similarly.  It just doesn't make sense to me as-is.

This is the engine build and all the details I can get out of PIM so far:
https://pim.net/crate.html

No cam card and no dyno sheet on the build in this owner's car.

The owner purchased it as a drop-in solution.  PIM did the install along with the rest of a restoration at PIM.  The owner eventually had to retrieve the car after it having spent an inordinate amout of time in their shop with no apparent forward progress.  The owner, understandably wanted to drive their car.  Now it's been in my shop for the better part of summer.  (I can only work on things in the after hours after I get off my day job)

The Demon carb came with this build; it's part of the package.  I just this morning got word back from Holley on this specific list number and was given the following specs:
https://www.holley.com/product...uct/parts/SDA-850-MS

The carb meets all those specs as I discovered when I took it apart, except it looks like this one has pump nozzles 33 instead of 32 (both primary and secondary).  The only change I've made was to install #86 primary jets to work out the lean surge at cruise, which didn't cure it completly.

I don't relish the idea of tearing into the engine to check valve timing.  However, I -can- look at the rockers, and hopefully they would have the ratio stamped on them.  Honestly I've been avoiding this step since I can clearly see cork gaskets were used... I dislike cork gaskets.

Any ideas on how I might check valve timing with the engine -in-?

Thank you,

Asa  Jay

...In My View, I have read what You have tried.

I know Surging is fuel, Not Ignition. You are correct there.

Have You checked the 'Fuel Pump Pressure'? Does the Exhaust Smell 'Over' RICH?

I think the Mixture screws are IN too tight, these are very sensitive to the Whole, and will cause Surging. They play a BIG part, 'Addition' in the 'Idle to Cruise' Transition 'Circuits'.

I would go to 1-1/2 Out, Start from there. I cut mine down to 1-1/4 Out on a 750, when the Idle Smelled rich, Yes! It was Only a 351C. Makes a Huge Difference! When those are too lean, you may be 'Trying' to make up for them, with Excessively RICH Jets. I would Think 76 Primaries, 82 Secondaries, in that 'Vicinity' would be more 'Crisp'. Try a 6.5 Power Valve, For cruising.

38 Degrees @ 3000 Is The Maximum, By 'The Books'. in My View, try cutting back to 36 @ 3100 RPM.

Tuning for 'Highest Vacuum' at Idel...Doesn't Always work.

Good Luck with It!

P.S. What was the CFM on that Carb?

Hi Marlin,

The exhaust does not smell rich.
The carb is an 850.
Starting at 1-1/2 out, the engine will idle and the vacuum is about 5.  At that point the AF is still in the mid to high 20's.  I can dial out the mixture screws to enrichen the idle more, but then it loses more vacuum and eventually dies, and I don't get below 20 on the AF gauge.

The surging felt "less" with the larger jets which is why I was thinking of a richer jet again.  I could try to lean the jets and richen the idle, but I know at idle, the main jets should not be a factor.

Will a 6.5 power valve be practical if the highest vacuum is 13-14?

I appreciate the input.

Asa  Jay

Website says the carb is an 850.

To get the timing on the cam, you would need to use the timing wheel procedure for "dialing in a cam".

I can't argue with what Marlin suggested either on the carb.

The entire "lean thing" makes no sense. To put things in perspective. a real 427 Ford will use somewhere in the 67 to 72 range.

86 and lean is from another Galaxie where the laws of physics do not apply.

MANY street Holleys will run much better with 28 pump jet nozzles. 32-33 is big but look at the pump jet arm and make sure that it is clearanced correctly using the feeler gauge.

Even on Webers I can get 12-14 inches at idle. The difficulty there isn't the carbs it is the IR manifold.

Is this engine using a Tunnel Ram of some type? That would mostly matter if you were a four corner idle.

I've heard remarks that new carbs have the wrong emulsion tubes or are missing them to begin with.

LOTS or reasons to be suspicious of a carb with symptoms like this.

You might want to try another carb before you go into the cam timing?

I only suggested a lower rocker arm ratio in order to in effect reduce the lift and duration of the built in cam timing.

You would be reducing the lift and the duration by around 16 degrees which will help.

Racers do this often, largely on the exhaust side but not knowing the cam timing is part of the issue in diagnosing the issue accurately at the moment?

Using the timing wheel is a real PITA. I always avoid it as much as I can. I've found that MAYBE the cam will be off 1 degree once in a millennium. It's hardly worth the effort unless you are really an unlucky person.

OH...it should be mentioned...if the diaphram in the power brake booster is shot, it will bleed off vacuum like this and because it is so remote to the engine compartment it is often over looked.

Hi Doug,

Good stuff.  Yes, I’m currently living in an alternate reality struggling to find my way back.

I have all the necessary tools for dialing in a cam (degree wheel, dial indicators, etc.), it’s just real hard to do with the engine assembled in the car.  

The vacuum brake booster is on its own isolated electric vacuum pump.  That was to compensate for the low vacuum and “no brakes at low speeds” complaint.  I did test the vacuum booster and check valve originally and found both to be operating normally.  Thank you for pointing out that possibility.

Zero degree on damper is TDC on #1; I did check that.  Compression testing shows about 180 give or take on all cylinders.  Firing order has been verified (also no backfiring anywhere.  All plugs are firing.

The intake is a single plane high rise as you can see from the photos on PIM’s web site.  The carb uses four corner idle.

The accelerator pumps work fine, no real stumbling on acceleration, only surging at cruise.  They -may- be oversized for the application.

86 jets gets me 13 AF under moderate load, that’s not the lean problem.  The lean problem is at idle and at cruise (lean surge).

I have an older Holley 850 DP that needs a kit run through it and I was looking to use it.  I was heading down that road last night and then found the fuel bowl connections were larger than the Demon.  I could just swap the fuel bowls from the Demon as I know they are already tuned for proper float height and should fit the Holley.

A lot more troubleshooting to do here.  Unfortunately the owner wishes to pick it up tomorrow for a short period before I can work on it again.  Carb tune is about the only thing I can fit in.  Once back in my shop I can look at the lifter/rocker/valve action

Right now my suspects are:

Carb Tune

Cam Timing off

Vacuum leak under intake.

Asa Jay

Has the engine always had this problem or something that has cropped up? Can a smoke test be done to test for vacuum leak?

@asajay posted:

Hi Doug,

Good stuff.  Yes, I’m currently living in an alternate reality struggling to find my way back.

I have all the necessary tools for dialing in a cam (degree wheel, dial indicators, etc.), it’s just real hard to do with the engine assembled in the car.  

The vacuum brake booster is on its own isolated electric vacuum pump.  That was to compensate for the low vacuum and “no brakes at low speeds” complaint.  I did test the vacuum booster and check valve originally and found both to be operating normally.  Thank you for pointing out that possibility.

Zero degree on damper is TDC on #1; I did check that.  Compression testing shows about 180 give or take on all cylinders.  Firing order has been verified (also no backfiring anywhere.  All plugs are firing.

The intake is a single plane high rise as you can see from the photos on PIM’s web site.  The carb uses four corner idle.

The accelerator pumps work fine, no real stumbling on acceleration, only surging at cruise.  They -may- be oversized for the application.

86 jets gets me 13 AF under moderate load, that’s not the lean problem.  The lean problem is at idle and at cruise (lean surge).

I have an older Holley 850 DP that needs a kit run through it and I was looking to use it.  I was heading down that road last night and then found the fuel bowl connections were larger than the Demon.  I could just swap the fuel bowls from the Demon as I know they are already tuned for proper float height and should fit the Holley.

A lot more troubleshooting to do here.  Unfortunately the owner wishes to pick it up tomorrow for a short period before I can work on it again.  Carb tune is about the only thing I can fit in.  Once back in my shop I can look at the lifter/rocker/valve action

Right now my suspects are:

Carb Tune

Cam Timing off

Vacuum leak under intake.

Asa Jay

You certainly like a challenge. I'm feeling the stress from here and I have no dog in the hunt.

Don't forget to verify the balancer hasn't slipped.

Change the carb. Don't be surprised if it fixes the issue.  I like the ugly old Holleys. I understand them the best or better stated, I can figure out what they are doing...MOST of the time. Best of luck!

...oh...remember to keep the fuel pressure at 5 psi max. A higher pressure COULD make it surge at cruise because of a rising fuel level. The current pump gas is better suited to EFI. I'm having strange issues with a white substance building up on the inlet valves and making them stick CLOSED and I can't get the float levels where I want them. The fuel expands with heat and changes the floats.

I'm enjoying how most of the recommendations are hitting on things I've checked; it tells me I've at least been doing some of the right things.

Fuel pressure is right at 5 psi.  In an odd twist I do -not- understand, PIM installed a nice electric Holley fuel pump that maxes at 6 psi, and then put a regulator after it.  I guess that's just good insurance?  Fuel level in the bowls is right where it should be; nice to have sight glasses on both sides.

Balancer slipping... mmmm, doubt it. I got Cylinder #1 to TDC (plug out, depth-checker in) and the timing marks were right on.  Good thought.  It's a shiny new balancer and I doubt it would have slipped this early in it's life, but hey... I'm in some twilight zone anyway right?

I do -not- have a smoke tester, but after reading up on it a little this afternoon, I'll have one in a few days.  Not soon enough for my friend picking up his car, but I'll have it when we pick this all up again.

I'm going to try the Holley first thing tonight when I get out to the shop.

Thank you all for the suggestions.

Asa Jay

Years ago (35) when I was associated with "the street rodders", one suggested to use their method of troubleshooting.

What they would do is have the "friend" work on their car. The theory was that the primary (owner) would get blind to the issue and the new guy would see it.

Apparently it worked out to some extent but I learned not to leave a car with anyone after I came to pick up my GT350 from the alignment shop and found the mechanic doing burnouts with it in the parking lot.

If anyone is going to blow up my car, it's going to be me.

Funny, not so funny.

I can't do alignments, and this Pantera needed an alignment.  I took it to that shop yesterday, and sat while they worked on it.  They've been pretty good.  I've had three different Panteras there and no issues.

I get the being blind to the issue.  I feel that way right now. 

Asa  Jay

Sometimes I have to walk away for a couple of weeks. Two things will happen when I return.

1) I can't believe what a stupid thing I had done or 2) I see the issue right away and can't believe how stupid I was not to see it to begin with?

When someone wants to drive my car I say yes but on condition. Leave a cash deposit of $150,000, and then have a good time AND anything you break, YOU fix.

When you are going to go 150mph in the Silver State, do you feel better that you did the work or someone else? Either way it has to be a leap of faith?

I'm thinking of the scene in "To Catch a Thief".  The French cop is on the phone saying "poulet, poulet", trying to explain to his Captain how the car got wrecked. At 150 hitting a prairie chicken can do a lot of damage?

What a mystery!  

I have not seen anything about the PIM “Hammer” motors since PI stopped publishing their glossy magazine….  I’m guessing that was in 2005?

How long had the car been in the shop?

Seems that it’s pretty much the same as specified in the PIM description.  Is there anyone else running these engines that might provide their own experience?

Too bad there’s no dyno data…

Good Luck!

Rocky

Quick recap of tonight.

Put a Holley DP on it that has 76 primaries and 83 secondaries with 4.5 power valves.

It ran about the same; could not dial in idle to get anything less than 20-22 on the AF meter.  But it ran -better-.

Cruise felt better except AF now showed lean during mild acceleration.

I came back and rejetted the Demon way lean.  It ran better, but too lean in throttle.  Yanked it again and upped the jets two sizes.  Right or wrong it now puts the AF back where I like it around 13.  Idle is okay but still around 22 on the AF gauge.  Vacuum is hovering at 7-8.

The engine comes alive about 2,500 rpm.

Next up (when I get the materials together)  is smoke testing for vacuum leaks.

The owner is interested in fuel injection too.  I’ll start researching that but need to make sure there are no vacuum leaks first.

Funny story for the night:

On the next to last drive my AF was off the scale lean and rpm was way high.  I didn’t go much further than the next intersection and came back.  I was thinking putting in 76 jets was way too lean.  I open the hood to check throttle position and maybe mixture and I hear a whistling.

Duh….  I forgot to hook up the PCV to the carb base.  The next drive was much better.  The good part is it showed how different in running it could be with a big enough vacuum leak.

Asa Jay

@rocky posted:

What a mystery!  

I have not seen anything about the PIM “Hammer” motors since PI stopped publishing their glossy magazine….  I’m guessing that was in 2005?

How long had the car been in the shop?

Seems that it’s pretty much the same as specified in the PIM description.  Is there anyone else running these engines that might provide their own experience?

Too bad there’s no dyno data…

Good Luck!

Rocky

In their description, PIM states that the "engine" is dyno tested. At this point I presume that they mean in general, since the specs are all the same, and not specifically each engine that they build? I have not seen a print out anywhere of the dyno results though?

Strange that this information from them would not be readily forth coming?

Ditto on the cam timing?

I'm thinking that there are only two items left to eliminate? A smoke test is a necessity and then when all else is eliminated, cam timing?

As far as a PCV system goes, until I worked on my Webers in an attempt to make them more street friendly, I never considered that a PCV system was a controlled vacuum leak before hand?

When plumbing the "Weber 'eight-stack' " together, that becomes readily apparent. In the case of the Webers, it amounts to about a 2 inch loss in vacuum in the system.

After much tinkering with the system, that was all I could reduce the loss to.

So in retrospect I could get a PCV system to work with the carbs but to get power brakes in the Pantera with Weber carbs, a vacuum pump was necessary.

As an interesting aside, originally when I "interviewed" Gary Hall about the PB issue, he said all I needed to do was get vacuum from one cylinder and that was how his intake manifold was made, i.e., with one cylinder drilled for a vacuum port? I'm not sure how he came to that conclusion but I do know that he would change the carb auxiliary venturi (chokes) to 32mm. Stock they were 37's.

Maybe with that change the vacuum characteristics change? I never tried that though?

I think right now though in your case switching to an EFI is essentially just enabling you to tune everything with the computer? I don't think that is a solution, just an aid in centralizing your thinking and simplifying changes and saving time in making them.

If this is a vacuum leak, it's big, just like the disconnected pcv is, like one of the port runners is cracked underneath somewhere. While on that subject, why not completely block the pcv system and retest?

I found that there are no good "off the shelf" pcv valves and the only thing to use was the adjustable pcv system, by ME Wagner.

Still no word back from PIM on the cam specs.  I wrote over the weekend so it's been a couple of days.  Maybe they need more time to dig them up?

Smoke test, valve train inspection and cam timing, all on the list.  The owner is supposed to be picking it up today but I've not heard from him.  If he does, all that testing will have to wait.

I did a test run using the Holley which had zero provisions for any vacuum accessory of any type; no port for vacuum advance, no port for brake booster or pcv.  And the Intake has no provisions for vacuum accessories.  The Demon carb has a base plate with three ports, one large (pcv and/or brake booster), one ported and one manifold. The Holley got the same/similar idle results and lean stumble on cruise.  Good question though.

I agree with the idea that EFI won't fix it.  That's what I told the owner to start with; if it won't run right with a properly tuned carb, it won't run right with EFI.  Though to be honest, I do think whatever is amiss might be hidden easier with EFI.  We don't want to hide problems, we want to fix them.  In any case, it's not currently on the table, and would take a large amount of time to install and get working properly.

Thank you for all the input.

Asa  Jay

By its nature a digital system is more precise and forth coming/informative,  then an analog approach.

Seemingly anything from pure stock in a Pantera is a challenge to some degree at any level.

Both the FAST and the Holley are pretty simple systems once you get the handle on them. FAST being simpler because of the batch fire approach, not needing a cam position sensor.

Just finding room for that in the Pantera with the balancer right up against your elbow needs a magicians touch.

I don't think that anyone needs the individual injector control of the Holley in a non-emissions controlled car? You are never going to need that complexity unless you intend to install an oxygen sensor into each header exhaust tube?

If your customer is satisfied with the way the car runs now, why go any further?

The only thing now is with 86 mains and 427 cubes, the fuel consumption is going to come close to gallons per mile.

As always...'Best of Luck'.