PIM 427 Hammer engine - Surging at cruise

Another way to check for a vacuum leak on the bottom of the intake manifold:

1.  Remove the pcv valve from the valve cover and plug the grommet in the valve cover.  Make sure that it is sealed.

2.  Remove the breather cap from the other valve cover and set it aside.

3.  Start the engine and place a business card over the valve cover opening where the breather cap was just removed.  If there is a vacuum leak on the under side of the intake manifold or gasket, you will feel a suction when trying to remove the business card.

With the above configuration, you can also increase the engine RPM to 3,000 and then let the throttle plates close quickly, which will momentarily increase engine vacuum.

The above assumes that the engine doesn't have excessive blow-by.

John

Very clever, John! I'm officially 'borrowing' that tip for later (with your name attached). Thanks!

J DeRyke

Owner picked up the Pantera last night.  He trailered it home and will be driving it to a car show on Sunday.  I'll know more when he has time to drive it a little.

Fuel economy?  Ha!  No way.

I fillled up the tank to the top and after just a few days of troubleshooting, test drives, jet changes and more test drives, the tank was nearing half.  Either I did a lot more high-speed runs than I'm recallling, or it's using a -lot- of fuel.  I honestly think the pump squirters are oversized and need to be leaned out too.

I do appreciate all the inputs from the folks here on this thread.  If/when I get the car back in my shop, I'll see what else may be up.

Asa  Jay

Hi,

as an old grumbler (is that even a useable word in english?):

I don't think a carbureted engine can even run at AFR >20.

For example the BMW direct injection stratified charge engines n43/n53 could run at an overall AFR >20.

Do you trust your AFR gauge?

Does it measure fresh air in the exhaust at low engine speeds (reversion)?

Is there an exhaust leak present?

You say that the engine consumes a lot of fuel, so my suspicion is, that the engine runs richer than it shows on the gauge.

Spontaneously I can think of 2 things I would try:

1.

You posted the jets but wrote nothing about the air bleeds. The Demon carb in the link has changeable air bleeds.

One of the most common things to cure a lean stumble is to change the low speed air bleeds to a smaller size.

https://www.camaros.net/thread...ed-air-bleeds.56963/

2.

I fully agree that the cam specs are a vital info you need, but 18° initial is quite a lot. In my 408 Cleveland with GeorgeP inspired cam the vacuum at idle drops at more than 14°, so I set it at 13°.

Perhaps put it at 10° initial and work your way back to 18° and see what happens.

Hope this helps and as always: sorry for my bad english

Actually, GeorgS makes a good point…. I have a wideband O2 sensor in my Jensen.  I had been long fighting what I called “intermittent lean spikes” on my O2 meter indications.

What finally turned out to be the cause was that the ignition (distributor) was intermittently cutting out.  This sent a burst of unburied fuel into the exhaust- what was showing on the gauge as “lean” was actually very rich with unburned hydrocarbons.

The distributor was doing this all the time.  When it happened at Idle, the car would stall, like at a stop sign.  When it happened at speed, the engine would power through, and then pick back up.  When this happened, I’d see the “intermittent lean spikes” on my A/F ratio gauge.

I found the problem when distributor eventually failed completely, and I replaced it.  After that, I had no more intermittent stalls, and no more high speed “intermittent lean spikes”.

Somewhere in my troubleshoot, I read that the O2 sensors show lean in cases like this.  I’ll try and find the article.

Rocky

To summarize, I leaned the jets and got rid of the surge (for the most part).  Yes, reversion in the exhaust stationary it idle is a problem and after leaning the jets and driving, I’m sure that’s a contributor.

Thank you for the note.

Asa  Jay

...Have You checked the Adjustment of the Secondary Butterflies? The Blade Should be open enough to Make the Fuel Transfer SLOT Resemble a 'Square', No More, No Less. This Can Only Be adjusted with carb off the Manifold...unless you have made TINY Screw Drivers Bent at a 90 Degree angle, to reach the Slotted set screw from under the Carb, when it is mounted. I had replaced that set screw with a 'Allen Head' so it could be adjusted while the Engine was running. The Sec's being Open too far will kill Vacuum.

...Last Ignition was mentioned, Could be #'s 5 and 6 Plug Wires, Intermittently Arcing Over, together (Too Close), Or Any Plug Wire Arcing to a Ground!

A TEST!! In a Pitch Dark Garage, Pop the Decklid open, and while a Helper 'Lightly' Revs the Engine...You're Looking for a 'ARCing' to Ground. If one exists, You'll see it!!

Secondaries we’re set to Demon spec of 0.020 transfer slot open when carb was off manifold.

Dark garage plug wire arcing test.  Thanks!  I totally forgot about that one.  I’ll do that the next time the car is in my shop.

Thank you,

Asa Jay

Not only could this be an issue with cam timing, but it may also be that the cam was installed intentionally, not straight up?

You really need to see the cam specs and unfortunately need to see the timing gears.

In my view, it is next to impossible for that particular intake manifold to have any kind of a vacuum leak. You are chasing a ghost.

I don't wish this on anyone.

PIM has not been forthcoming with the engine build sheet, cam specs, or dyno sheet.  I’ll ask again.

Asa Jay

@asajay posted:

PIM has not been forthcoming with the engine build sheet, cam specs, or dyno sheet.  I’ll ask again.

Asa Jay

They have definitely sold more then just a few of those to Pantera owners.

It seems strange that others with a "Hammer" didn't join in with at least the cam specs in their engines?

I find it difficult to believe that would be proprietary information? People just buy these engines blindly? That I find amazing.

@panteradoug posted:

They have definitely sold more then just a few of those to Pantera owners.

Perhaps they haven't sold as many as one might think they have.

@davidnunn posted:

Perhaps they haven't sold as many as one might think they have.

The mind boggles. I would wager that they sold more then just one.

I asked PIM for specs on my 427 Hammer when I bought it circa 2005, but Jerry was not forthcoming. I got the sense that he felt it was proprietary information and I was not entitled to it.

For what it is worth, the setup he was using at that time did not cause the surging at issue here. The engine ran well.

@peterh posted:

I asked PIM for specs on my 427 Hammer when I bought it circa 2005, but Jerry was not forthcoming. I got the sense that he felt it was proprietary information and I was not entitled to it.

For what it is worth, the setup he was using at that time did not cause the surging at issue here. The engine ran well.

None of this speaks well for PIM.

@asajay posted:

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

here’s your vacuum leak!

Hammer engines have their PVC hose hooked up to the air cleaner(or just breath into the atmosphere)… you hook it up after the butterflies… lean …. (I assume you got it like that and somebody was “working “ on The car previously)

The other thing is that those engines run at 28°ish advance not 38° at 3000!

I looked into this engines if I wanted one for my car and -  no I don’t-!

You cannot use data from a 427 running in whatever car with the engine in the front!

That engine sits back there in a very hot box sucking in the hot air around  …. cooking itself! this engine has to run rich or it will melt! It’s a 427 with 500 - 600HP (depends how much money you spend ) at 6000 rpm with Hardly any air flowing around!

If you attempt to get a proper air fuel ratio To get maximum power… The maximum power will be there for a very short time! If you’re looking for fuel economy - Wrong engine! Wrong car!

Camshaft specs and rocker arm ratios are not the issue… I’m gonna bet the farm on that!

The engine I’m gonna go for my car is gonna be a little bit more sensible, less displacement less hassle less horsepower less heat…

I gotta go… I’m late for my anger management class…

Jerry from PIM asked me to call him.  I didn’t have time today but should be able to tomorrow.

LeMans850i, I appreciate the input.  The engine made about 5” vacuum or less until I increased timing and put the carb back to factory specs .  And it ran better.  It ran even better at about 13:1 AF when I leaned the jets.  Are you saying that is too lean for that engine at near full rpm under load?  ( my test conditions ).

I installed the PCV to the carb flange.  Prior to that both breathers (no pcv) were plumbed to the air cleaner, which was wet with oil and the hoses were soaked with oil ( leaked all over when disconnected ).  Now there is no oil residue in the air cleaner and oddly enough not in the PCV hose either.  It’s easily reversible and I don’t think that it’s causing a vacuum leak.  Vacuum was low before I ever made that mod.  I’m open to understanding this better and can easily reverse it back to two breathers plumbed to the air cleaner.

One of the reasons I’d like the cam specs is to better understand the maximum rpm.  The owner wants to spin it to 7,000 which I have STRONGLY ADVISED AGAINST.  The MSD currently has a 6,000 rpm pill in it.  Your comments lead me to believe it should stay at 6,000.  I find that a little concerning only because engines I’ve built in the past ( Cleveland’s ) could spin to 6,500 easily before valve float and I usually rpm limited them ( right or wrong ) to 6,300.  

in the end, you’re recommending putting everything back to the way it came.  That is easy enough to do.  And then we can evaluate it and start again.  I won’t see the car again for two weeks but I’ll be prepared to reverse all the changes.

FWIW, I don’t think the rockers were changed.  There was an idea that maybe the rocker ratio could be changed but I didn’t want to ho down that road. I want to know cam specs and the associated parts to better understand max rpm.

What is your opinion of airflow through the dogbone air cleaner?  I’ve been given data that shows it can rob horsepower on a 427 stroked Windsor.  It can’t get enough air which could explain the wet air cleaner or it could have been blow by but it doesn’t seem to exhibit blow by.  We were planning on replacing the air cleaner with something that flowed more.  Just curious your opinion on that part as well.

Thank you for your comments,

Asa  Jay

@asajay posted:

Jerry from PIM asked me to call him.  I didn’t have time today but should be able to tomorrow.

LeMans850i, I appreciate the input.  The engine made about 5” vacuum or less until I increased timing and put the carb back to factory specs .  And it ran better.  It ran even better at about 13:1 AF when I leaned the jets.  Are you saying that is too lean for that engine at near full rpm under load?  ( my test conditions ).

I installed the PCV to the carb flange.  Prior to that both breathers (no pcv) were plumbed to the air cleaner, which was wet with oil and the hoses were soaked with oil ( leaked all over when disconnected ).  Now there is no oil residue in the air cleaner and oddly enough not in the PCV hose either.  It’s easily reversible and I don’t think that it’s causing a vacuum leak.  Vacuum was low before I ever made that mod.  I’m open to understanding this better and can easily reverse it back to two breathers plumbed to the air cleaner.

One of the reasons I’d like the cam specs is to better understand the maximum rpm.  The owner wants to spin it to 7,000 which I have STRONGLY ADVISED AGAINST.  The MSD currently has a 6,000 rpm pill in it.  Your comments lead me to believe it should stay at 6,000.  I find that a little concerning only because engines I’ve built in the past ( Cleveland’s ) could spin to 6,500 easily before valve float and I usually rpm limited them ( right or wrong ) to 6,300.  

in the end, you’re recommending putting everything back to the way it came.  That is easy enough to do.  And then we can evaluate it and start again.  I won’t see the car again for two weeks but I’ll be prepared to reverse all the changes.

FWIW, I don’t think the rockers were changed.  There was an idea that maybe the rocker ratio could be changed but I didn’t want to ho down that road. I want to know cam specs and the associated parts to better understand max rpm.

What is your opinion of airflow through the dogbone air cleaner?  I’ve been given data that shows it can rob horsepower on a 427 stroked Windsor.  It can’t get enough air which could explain the wet air cleaner or it could have been blow by but it doesn’t seem to exhibit blow by.  We were planning on replacing the air cleaner with something that flowed more.  Just curious your opinion on that part as well.

Thank you for your comments,

Asa  Jay

Hammer is a 6k redline engine..  For my car I’m looking to do something more rev friendly.. 363 - short stroke big bore… now that would do 7k if properly build to do so!

4.030 bore and 4.170 stroke doesn’t sound like a rever to me… at least not as a lasting and reliable machine (unless you dump ungodly amount of money into it ) This engine is build for torque and to last… bringing it up to 6k is almost pointless, well, it is pointless! Torque comes down around 5k so shifting at 5k would get you around where the Torque is coming in hard again! It’s just the wrong engine for what’s asked for .. in my unprofessional opinion! (and you create more heat at higher rpm)
Its  like you asking a fat guy to sprint … he might do it a few times, He won’t be good at it, and he will be dead  after a while!
but if you take the same guy for a tug-of-war… Different story…

The second problem you may encounter is that this engine has a hydraulic roller cam and I don’t think those do not like to rev that high.. So you would have to convert to solid lifters! -The squeeze is not worth the juice 🥤Also, as you said, the valves… those huge intake valves are quite heavy and to persuade them to close in time….. that would take some springs (or titanium valves) !! And the hydraulic roller lifters Will complain!

just put breather caps on the valve covers and plug the port on the carburetor.. That’s what I’m doing! You definitely know when you have excessive blow by… Lol

if you want to do something good with the air filter… Get cold air into the intake!! That helps more than anything else! Right now it’s just sucks the hot air in! But to achieve that you have to build something… There’s nothing on the market that does the job!

There are many dog bone air cleaners on the market, but they’re not all the same… Be aware! Whatever you build the distance between carburetor and the upper deck of the air filter housing should be tall as possible, which creates the next problem on the Pantera because you can’t see out the rear window anymore.. and hopefully you have a high-quality balancer on the engine… and I’m not sure what the water pump will do…

I would make the engine run nicely, put the AFR gauge on the shelf, drive the car for a while and then read the spark plugs….. this will tell you a lot more! Not all cylinders get the same AF filling necessarily (it’s carbureted !!!) and you want to know if you have a lean cylinder.. and that’s  the one you want to keep happy!

As I said, this is just my unprofessional opinion….🤪

(Sorry for rambling on so long)

All good.  I do appreciate your insights.  This particular Pantera is owned by someone who doesn’t know engines very well and I believe was more sold on the flashy sales pitch and photos about the engine.  I don’t know it’s putting out 500 hp for certain without getting it in a dyno.  That may be in its future.  I think the owner feels disappointed that it doesn’t “feel” like 500.

it sounds like you did some comprehensive research. I can respect that.  I don’t normally work with Windsor strokers so I don’t have experience with them.

FWIW, the last Cleveland I built used a hydraulic roller cam, roller rockers , etc. and it would rev to the spec of 6,500 with the recommended valve train components.  I had planned on a solid roller for my next project but that’s been stalled quite a few years now.  So I’m living vicariously through other’s projects.

Asa  Jay

Please see my follow up post later

I do sincerely thank all of you who did reply and gave advice and experience to the situation especially as I was much less familiar with the type of buiI’m told the car is running better than ever and I think I got the owner talked out of the rpm limiter change they wanted to do.  Thanks to LeMans850i.

Thank you all,

Asa  Jay