new 400 build making Pinto numbers on dyno
 

Had a local pro build a 400 for pump gas street driving that after 8k investment it came off the dyno at 191 hp, 262 tq. Didnt get much of an answer other than the quadrajet is a junk carb and should use something else.

Here's what they put together..
1971 YS 400, .060 pistons, crank .010 with factory rods.
#96 heads with new seats, surfaced and .065 head gaskets. Comp checked out to be 155 psi.
Bullet hyd roller camshaft 215/220 dur at .050, 106 degree, hyd roller lifters with new pushrods. Springs, studs and retainers in the cam kit. 1.56 roller rockers.
Factory cast iron intake, Ram Air manifolds, new HEI dist plugs and wires.

Not sure where cam was degreed in at or total timing.
Now maybe its just the carb I supplied that was junk and need to find a better quadrajet.
Big question is in my head, was this cam a good match for the compression?
Thanks in advance for any thoughts!

Verify a full 34* ADV at 2500 rpm.

Verify Quadrajet Secondaries open completely with gas pedal. Wheel dyno or engine dyno?


Time to rejet?

Were you there when they dyno'd it?

Something is wrong I'd say, a 2bbl would probably make more than that?
Are you mechanically inclined?

I'd check timing and full throttle as said. Also check valve adjustment.

:confused:

It should be making a good 300 HP. I would not have used a .065 head gasket though, but that did not cost you all that power.
Stock they were 300 HP and you have a bigger cam.

At what RPM was peak torque and peak HP?

Stan

Thanks guys for the replies. I wasnt there during the dyno session, was on a engine dyno, pulled rocker covers to check out lash (maybe one or 2 were out?) but even though cold engine none were over .003. peak hp was at 4300, tq was at 3600. I dont have the gasket they used under the carb, was suspicious bout that it didnt clear the secondary butterflies but surely they would have caught that.

why the .065 head gaskets? did you ask how far if any in the hole the pistons were? i been afraid to run a .038 gasket with mine .020 in the hole. i cant imagine a .065 gasket being a good idea even at 0 deck

i think your compression was not a good fit for your build.

Your lower than stock 2bbl HP sounds like you’re running on the primaries only, which on a quadrajet are actually smaller than a 2bbl Rochester. Verify the secondaries are actually opening.

A competent dyno operator would have noticed this and tried a different carburetor.

Tripower Motors built for street performance and using 67 and up heads, running off of just the center carb have made over 300 hp.

I say that the carbs secondary’s were not opening.

Does your dyno sheet for the motor have a vacuum column or at least a BSFC read out on it?

Did the builder check if different length push rods
Where needed considering the valve job and those ridiculous thick head gaskets?

Find a new builder/dyno... Something is way off for those numbers with that combo.

A 400 with 96 heads, .065 head gasket, typical 6cc pistons .010 down in the hole is going to be about 7.94 compression. That's with good TRW forgings. Please tell me they didn't use the cast 8-eyebrow monsters? If that's the case, the compression is in the 6s. Put it in your lawn tractor and run it on kerosene, LOL.

250-320 HP would be the expected output if properly tuned.

The tune was WAY off or the secondaries didn't open. Hyd cams don't have lash. Were the valves set correctly?

Low compression heads AND a thick headgasket? WTF is the builder thinking? Some builders don't care about engines that aren't SBC or LS, or don't know the gotchas on other makes.

Did you tell him you wanted it to run on 87 octane? What is the application, a tractor?

I am by no means as engine smart as alot of the minds on this forum but even I would definitely say something is not doing it's job (carb etc...) as this is the Dyno numbers from my stock (bored .030) 350 H.O. so I would think at minimum you should be in this ball park.
Hope you find your issue and it's an easy fix!

With the engine being run on an engine dyno. Could you please post the printouts of the dyno pulls? I would like to see the air consumption numbers, the fuel consumption numbers and the vacuum numbers. That would tell us quite a bit about the "junk quadrajet" Any carburetor can be "junk" if it has a problem, is not jetted properly, or isn't opening most of the way. When I know the engine has been built properly, but the student/customer supplies his own carburetor. If the engine way under performs, we have a "shop carburetor that always works well on anything we put it on". We remove the suspect carb and install the shop carb. I have personally witnessed a 50 HP increase vs a really messed up or mis-matched carb. I am in NO WAY saying Quadrajets are junk. You may have one with serious issues though. I have had many more Edelbrock AFB clones that were much worse before extensive tuning than any Q-jet.

There are allot of things a "Chevy shop" can do to ruin a Pontiac engine build. Did the shop you chose have at least 1 person on staff that had some specific knowledge about Pontiac engines? I ask this because you mentioned they installed new valve seats. All 16? Is there a chance they converted the intake seats to 45 degrees? That can hurt the power. Also, as mentioned, the compression may be really low which will allow any fuel to be used but kill the power. A cam ground on a 106 centerline for this build is not optimal IMO. Lots and lots of little things that may have been done in the Chevy world can conspire to make it run like a Chevy, unfortunately. Low torque and the Pontiac can't make the HP because of the low RPM limits. A little surprised an 8K engine build did not include some form of aftermarket connecting rods. Although that is not costing you any power in this build.

BTW, your reference to Pinto numbers on the dyno is just spot on. We build a 2300 Pinto engine for a student racing a spec. racer hydroplane. It made 235 HP @ 5800 RPM.

Agree that any carburetor can be "junk." When someone says that a Quadrajet is "junk", they usually do not know how to rebuild one, tune one, or make one function correctly. I would be willing to bet that the back barrels were not opening. Something is terribly wrong for that combination to not make over 200 horsepower. Even with close to an 8:1 compression ratio (assuming flat top pistons), I would think that it should make in the 300-325 HP range.

Other than cam timing being way out, I also suspect no secondary opening.

Or just flat out not getting full throttle. I’ve seen that story more than once with some dyno operators saying that’s the first thing they check.

Isn’t that super common with qudrajets or any vac secondary carb on an engine dyno? I know I’ve seen engine masters zip tie secondaries open.

BIG thanks for all the replies!! A few minutes ago I flipped the carb over to look at secondaries and WHOA BOY! Sure looks to me like the linkage on the secondaries is bent horribly, linkage wide open and that is as far as they open up, maybe half way

I've always been a Pinto guy, love them lil ponies! ( my niece says I'm a dork cause of it)

sorry for the poor pics of the sheet, camera is bout to konk out

Cleared it up some.


Lots of stuff looks suspect to me?

Judging by those numbers the carb was flooding out.

The first thing I would do is change your oil and filter.

I'm no dyno (or any other kind of) expert, but I would think the engine should use more fuel at higher rpm (4600) than lower rpm ( 3400).

Was everything hooked up during the dyno to where those numbers can be trusted? The BSFC numbers are frighteningly high. To the point that I'm not sure how they even kept the thing running.

That carp needs a serious overhaul and while QJets in general are not junk, the one you have probably is; in it's current state.

Yes, but not always. What may be going on with this graph is that the throttle was snapped open at the start of the run and there is a rich tip-in event happening.

If you lob off the first couple rows and the last couple rows, the engine's fuel consumption from a trend perspective seems okay, outside of the fact that it shows to be incredibly rich.

It is possible though that certain engine combinations could use less fuel at higher rpm's than lower rpm's. Peak Volumetric Efficiency typically occurs at the same time as peak torque. If VE falls off significantly after peak torque, it's possible to need less fuel at that point, even with more revs.

I'm surprised it made what it did if the AF data is correct. Get the air fuel straightened out by fixing or replacing the carburetor, get the timing where it needs to be, and see how it runs. That's what the dyno is for, finding an resolving issues. Don't go crazy over dyno numbers, I've never pulled into the staging beams and seen a dyno in the other lane.

The only numbers that look right are the oil pressure numbers.

With a Q-jet, Fuel A should show all the fuel being used. Fuel B should show 0 and be plugged off. The BSFC is crazy high. The fuel B numbers are contributing to this. The one page printout does not show any air flow numbers. Did they have an air hat on the carb? If not, that's another reason the numbers are so weird. Allot of wrong stuff going on with that printout. It's a computer . Garbage in, garbage out. As mentioned, the only usable data is the oil pressure. Spark plugs should be coal black. If not, the data is completely useless.

I'm surprised they even bothered with the pull with it being so rich.

All of the BSFC numbers are at least 2.5 times higher than they should be at a minimum.

The only two good things I see on that sheet is that the oil pressure is good , and that judging by the torque and hp numbers at 5000 rpm is that at least the dyno correction factor used on that day was not set to make the motor a paper / print out hero.

That being said I would have preferred that the pull went to 5400.

Maybe one other good thing is running that rich the motor was not pinging or knocking.


Was that hopefully the only pull that was made?

OK lets do some math. The dyno sheet is hard to read so I may have gotten a number wrong. Lets look at peak Hp - 4300 RPM.

Using Fuel A plus Fuel B and the shown BSFC we get 181.95 Un Corrected HP

Using Fuel A plus Fuel B and the shown A/F ratio we 2036.9 lbs/hr Air or roughly 445 SCFM

Using 181.95 Un Corrected HP and Fuel A we get a BSFC of 1.14097

Using Fuel A and the shown A/F ratio we 1712.7 lbs/hr Air or roughly 374 SCFM

I get a 1.053 Correction Factor

Stan

Thanks for doing the thinking, {math} for me. Made some sense out of that mess. I am a little puzzled by that fuel B. It should be zero and blocked off 100%. A Q-jet only has one inlet/fuel bowl. Certainly has some problems there. Some dyno, some carburetor, some engine? I think it's all because it's a Pontiac!!

The secondaries in that pic definitely arent fully open... but they look to be at least 3/4 open and I doubt that is the cause of the low numbers. The internal set up/tune could be the cause.

If you have the money/time for another dyno session, would try different carb or have that gone through by a pro. Surprised they didnt swap on a different known good carb if it was that bad.

Yeah that's pig rich. That mixture, low air flow and low compression will yield inaccurate dyno numbers. As more experienced members said, the dyno cell setup looks suspect.
I'd go so far as to say negligence by the dyno operator. With numbers that far off, they should abort the test and regroup with another carb, or tell the customer to bring another carb. That's time and money wasted making pulls like that.

[QUOTE=78w72;6611969 Surprised they didnt swap on a different known good carb if it was that bad.[/QUOTE]

Thats what I was thinking. Even if it used a spread to square spacer that would kill a little power by itself it would at least let the engine run reasoanably well to identify the carb as the issue or not.

Are we actually surprised by this? I've never known anybody that makes a blanket statement like "QJets are crap" to be arbiters of knowledge and attention to details.

The carburetor here is at least partially, if not completely to blame for sure, but the dyno operator (same as the engine builder?) didn't care enough to do anything other than shift any and all blame.

Had a shop carb been put in place and the engine only made 5-10 more hp, that person may have more explaining to do.

This build to me is a bit off the rockers in general. The compression is anemic, the cam choice is suspect, why it needs a a .060+ head gasket is beyond my comprehension.

This has the hallmark of a lazy build that somebody didn't really want to take seriously. Who wants to wager it's got 8 eyebrow pistons in it?

At any rate, at least the engine makes good oil pressure. If this was me in this situation, the engine would never go back to that particular builder. My process would then be the following:

-Remove heads and check to see how far in the hole the pistons are. Calculate compression with a FelPro 8516 head gasket, reinstall heads with new head gaskets
-Pick a new cam that is appropriate for the compression (probably a Butler 067 or 068 hyd roller)
-Have the QJet professionally rebuilt by somebody like CRK performance, or rebuild it myself per Cliff R's book.

Then I'd reinstall the engine and go have fun.

Im not above being lazy, heck my little YT channel is at least half about getting solid results for low effort inputs with a bunch of little paint projects I do. But I cant imagine wanting my name anywhere near that dyno sheet. There is no way I wouldnt have put a shop carb on it just to prove the engine I built wouldnt run reasonably well. If im on record as saying the carb is junk, you can bet Im going to put a working carb on it so I could spike the football about it.


I agree, if it were me I would evaluate swapping to a thinner head gasket if not the gasket and cam. Its just not that much extra work with the engine out of the car. That said, if you put a functional carb on it and it runs fine......dont be above just running it and enjoying your car. Would you be maximizing the engines potential? No. But dont let great be the enemy of good if it gets your car going down the road.

This. Not trying to upset the OP, but this whole build sounds like a DGAF special. Somebody who doesn't know better would run this engine until he got tired of it. It's like a 2.8L V6, it'll run forever because it's not going to make enough power to hurt itself. Maybe the shop is used to big Mopar? Those put the pistons way down the hole to lower compression.

Seriously though, if it's got good pistons in it, you've got a fighting chance. Swap on a set of heads with 75 to 85CC chambers, a Summit 2802 cam and let it eat. 370-410 HP like falling off a log.

Ideas.... Re Dyno someplace else.... change your oil and filter,,, re prime.... And im sure things are going to BETTER

Thanks so much fellas for alllll the info and thoughts on this. I too was surprised when I got the call it was done only to show up with it sitting on a stand ready to load and with those dyno sheets as they were, no prior call as to a potential carb problem or issues in general hence why it is now in my shop instead and asking here for better assistance.
First and foremost the carb problem, Ive contacted several places to see if they had something on hand but looks like I'll be sending this one out and waiting several weeks.
As far as the camshaft goes, I really thought I was getting a roller very close to the 068, when I saw the 106 seperation I wasnt sure why they went with that.
I am not opposed to a cam swap to get back on track of where I was initially wanting to get.
As far as a fresh dyno shop I do believe there is one very close that also has a wheel dyno in his shop, warrants a call on Wednesday!
Thanks again, I will keep adding pics as its opened up and some details what I find along the way

Do you have the cam card? If so can you post it?

Stan

its a small cam...but i dont think id swap it yet. if it were me....id get some 6x4 heads and sell the heads you have. replace those head gaskets with stock head gaakets. i bet that and the carb problems addressed will be like awhole different animal. at 8k hopefully you find it has decent pistons but 6x4s will still be better if theyre the cast rebuilder pistons.

im sure the 77 transams were slightly underated but your dyno numbers arent too much lower than the low compression 400s of the time. and your compresdion may very well be lower than those.

I would live with that Cam for now as long as it’s installed at least straight up.

On a 106 it’s really not going to make peak power above 5K especially with stock 96 heads, but on a 106 it will sound heathy if nothing else.

Get the motor running right first.

I dug into the boxes and did not see the cam card, think I'll give the builder a call to see if they still have it, would be super nice to have the specs on everything they put into this but I guess I'll learn all that as I dive into it this weekend.

After a phone call to a buddy pulled one cylinder head and started taking measurements. Double relief pistons that are .020 down in the cyl.
Looks like 1 of the water jackets in the head is plugged with a very old mess.
That .065 head gasket crushed down to approx .045
He recommended to just stick with the shortblock I have for now and he'll help redo topside.

Appearance wise you have 4 different valves, some with a recess other's without. What do the rest of them look like? Did you supply the parts or did your shop? I can't believe a shop would release this engine without questioning the output. What's the story behind the engine and what was the discussion with the shop prior to building it?

It looks like all of your valves , at least in that photo are the same size, there’s just a difference in the coloration of them due to how the motor was running.

Of concern to me is that it looks like antiseize was used on the head bolts and that’s not good since the bolts will not torque up right without a light coat of oil only on them.
Wash off the bolts and roll the motor over upside down and flush out all of those 20 head bolt holes with CRC electromotive cleaner if it is antiseize and not misplaced sealer.

Unlike other brands Pontiac head bolt holes are blind and so no sealer is needed if it turns out that crap was not antiseize.

Either way the bolt holes need to be clean enough that each bolt threads in easily with just two fingers.

Whatever that crap is in the heads you want to get out fully, so while the heads are off I would pop out the freeze out plugs on each end of the head to do that 100%.

Those .060” over 8 notch pistons also have a chamfer around there perimeter to keep the compression stock besides being .020” in the hole.

I would run a Fel Pro 8518 or 1016 gasket to get down to a crush of less than.045”.

While the heads are off take those lifters out and wash all of the oil out of them until they are bone dry roller wise.

Then spin them to check that they all roll smoothly with no stops and starts in the noise which would also indicate that they are going bad.

If they pass dip them in oil and roll them to lube them back up nice.

If your running the stock rocker studs now is the time to upgrade them to full 7/16” if your budget allows.

This is not an $8000.00 rebuild. Full stop.

To get to that type of figure requires an amount of machining and parts that this engine doesn't have. What, if anything you want to do about that, is your call.

I'd run the Felpro 1016 on this to tighten up the quench as much as possible. If the pistons are .020 in the whole you'd end up with about .060 quench, which is not great, but still better. My calculations would put you right at about 8:1 compression with that change. That's probably okay considering those pistons are notorious for creating detonation problems. The lower compression widens your tuning window.

I agree with everyone else, it's built and it's probably best to simply fix the visible problem spots while it's apart.

Yep $8,000 for those pistons that deep in the hole plus those head gaskets tells me that A-the shop knows nothing about Pontiacs or is the local auto parts machine shop and B- you must have high labor and parts rates in your neck of the woods or C- you got charged the Pontiac premium because a lot of shops don’t do many Pontiac builds or want too.

Now, regardless you have what you have and you want to make the best of it so looking at your valves and the potential for sloppy machine work it might be time to buy a cheap set of used castings with much smaller combustion chambers and have another shop swap over all of your (hopefully) new valve train components to get that compression up there for a little more HP.

This pisses me off.
Seen stuff like this at my buddies home shop 40 yrs building performance engines.
2-3 local commercial shops wont use even for machine work. Not just pontiacs. All makes.

First off sorry TinRabbit.

I'll say it.
Maybe a good machine shop but not a good engineer. Either cant or didn't bother to calculate CCs for final CR.
Wrong type pistons .020 down with .065 gaskets(maybe go to on all stock type builds?)
Kinda stuck with them unless have $ replace while engine out. Need rebalanced(if was)cant find same weight.
As Steve said is that antisize on head bolt threads? No oil? And if did go into water jackets would use thread sealer. Not antisize.
Gunked up water passage in head?
Least used quality lifters. But whats that discoloration around push rod seats? Some kind of break in paste?

Worst of all.
Didn't use requested cam profile without consulting you 1st. What the....
Besides everyone else rec-'s I'd make sure has correct spring height. Just saying...
Maybe try get him pay some for correct replacement cam.
Either way id look for a different shop if need anything you can't handle.

Finally.
A dyno operation/operator can't tune?
At 13 could tune with just a dwell meter an vacuum gauge.
Someone needs get a new job.
Like Walmart greeter...

Best of luck.
Looking forward see you get satisfied.