[77poncho]

ok.. so with the advise of alot of research and q&a on here i had the following engine built.

71 400 block
Butler Rotating assembly 461
stock intake
6x-8 milled around 96-98 cc
stainless vales and valve job
Comp Cams 995-16 Dual Assemblies Valve Springs.
Competition Cams 740-16 Steel Retainers, 10 degree
COMP CAMS 10 DEGREE SUPER VALVE LOCKS
CompCams Roller tip 1.65 ratio rockers
compcams xe274 ( not my choice, builder did this)
rebuilt q-jet
distributor was recurved
new fuel pump
high volume oil pump
RARE 2 1/2 collector manifolds
2 1/2 pypes x-pipe with violators
3.08 motive gears with yukon carrier Posi
new performance built Transmission th350
probably forgetting to mention something that was done performane wise.. but with this combo it should roast the tires. i have had the car back just about a year and builder said in the beginning that the gearing ( 2.56 or 2.41 ) was what was really holding it back.. and after that would be a night and day difference .im really bummed about this as im out of money.. and originally went to this guy because he is a "Pontiac" guy. i am psychically limited as to what i can do. anyway results sucked on the dyno
peak HP was 170 and torque 279

with the combo it has i was expecting to see numbers at least 350hp+ and low to mid 400+ torque.

and it seems to run good.. but just no power. i have taken it on a few 200 mile trips and its good to go..

[Chief of the 60's]

Yep, that is dismal. Was that at the crank or the rear wheels? Rear gear is not good, neither is that carb, recheck that timing too. Also, building an engine on a forum, usually just does not end well. Just my

[RocktimusPryme]

There are more expert opinions on here than mine but something is wrong. Even the mildest 461 ever should be better than that. I just don’t see how you don’t make 400 ft lbs. it almost seems like you would have to try to not make it.

[pastry_chef]

What type of idle vacuum do you have?

How much ignition timing?

Would be interesting to see a cranking pressure test.

[77poncho]

the dyno was at the wheel.. i can do a cranking pressure test and see what those results are.

[77poncho]

Originally Posted by pastry_chef

What type of idle vacuum do you have?

How much ignition timing?

Would be interesting to see a cranking pressure test.

i dont know vac & timing degrees right now..

[Will]

Wheel or crank? I'm guessing wheel....

Engine sounds fine, no odd noises?

Whenever an engine is down on power like this it's time to get back to basics. That combo should have lots of lower midrange torque but be pretty much done by 5000 RPM.

What is the compression ratio? Time to check cranking compression.

What are the actual mechanical timing numbers. Initial advance and total mechanical and at what RPM? Get actual measurements from the running engine.

A/F ratios throughout the RPM range. Maybe a wideband O2 sensor is needed.

I would initially suspect an issue with timing or fuel delivery. Something weird in the valvetrain could be at play, also. Run a compression check and get a timing light on it. Easiest things to do first.

[77poncho]

Originally Posted by Chief of the 60's

Yep, that is dismal. Was that at the crank or the rear wheels? Rear gear is not good, neither is that carb, recheck that timing too. Also, building an engine on a forum, usually just does not end well. Just my

when you see soooo many positive results with similar combos to mine thats why the build went the direction it did. as far as the gearing.. your thoughts?? i want a semi friendly highway gear hence the 3.08.. with the 400+ torque i was expecting that should easily carry it.. and as far as the q-jet i want the shaker functional on my 78 Trans Am.

[ponjohn]

Stock fuel pump?

If so I would start there, need a good electric setup with return to supply these engines.
ESPECIALLY with a q-jet, has such a small bowl it needs volume to keep it supplied.

[Will]

your 3.08 gears have nothing to do with how much power the engine makes. TaMan is running 10s with 3.08s. Time to focus on real issues...

Is your Q-jet all stock? What year and model? A stock carb can't supply an engine like this, neither can a stock fuel pump.

But, I run the risk of getting ahead of things. As mentioned above, check off the easy stuff first. Timing and compression check. Once you know those are okay look into fuel delivery.

[77poncho]

Originally Posted by ponjohn

Stock fuel pump?

If so I would start there, need a good electric setup with return to supply these engines.
ESPECIALLY with a q-jet, has such a small bowl it needs volume to keep it supplied.

not stock, upgraded, dont know off hand what it is but is it mechanical. im pretty sure the i remember seeing guys easily getting mid 300 HP and using mechanical pumps. on the dyno run the AFR was between 11.9 - 13.4 for the entire run except when let off accelerator and it leaned a little, but while under power was in the target range.

[77poncho]

Originally Posted by Will

your 3.08 gears have nothing to do with how much power the engine makes. TaMan is running 10s with 3.08s. Time to focus on real issues...

Is your Q-jet all stock? What year and model? A stock carb can't supply an engine like this, neither can a stock fuel pump.

But, I run the risk of getting ahead of things. As mentioned above, check off the easy stuff first. Timing and compression check. Once you know those are okay look into fuel delivery.

im with you on the gears.. 78 q-jet that was rebuilt with kit from cliff. i know bigger metering rods etc.. i believe the some work also done to allow more fuel flow.

[77poncho]

i will try to get a real good number on the timing and a compression check..

[77poncho]

Originally Posted by Will

Wheel or crank? I'm guessing wheel....

Engine sounds fine, no odd noises?

Whenever an engine is down on power like this it's time to get back to basics. That combo should have lots of lower midrange torque but be pretty much done by 5000 RPM.

What is the compression ratio? Time to check cranking compression.

What are the actual mechanical timing numbers. Initial advance and total mechanical and at what RPM? Get actual measurements from the running engine.

A/F ratios throughout the RPM range. Maybe a wideband O2 sensor is needed.

I would initially suspect an issue with timing or fuel delivery. Something weird in the valvetrain could be at play, also. Run a compression check and get a timing light on it. Easiest things to do first.

yes seems to run good.. i drove it today about 100 miles and 3000 rpm pretty much the whole way. AFR on the dyno was between 11.9-13.4. i do have bungs in the exhaust and can get sensors and monitor them.. valve train sounds healthy.. could be a timing issue, but just seems WAY off on power.. and looking at the rpm range on the data sheet it just noses over at 3700-4000 rpm ranger.. i should be still pulling hard at that point.

[ta man]

What does the builder think have you asked him? If he is truly a Pontiac guy he should know something is up. Was he at the chassis dyno? Was TDC confirmed on the balancer. What is the total timing? Cranking compression? Was cam degreed? Missing a couple sparkplug wires? Fuel restriction? Air intake restriction. ?

[Dick Boneske]

You didn't mention if the cam was degreed. Incorrect cam timing can kill HP big time.

Also, with 98 cc on a 461, compression ratio is really low. You need around 88 cc or smaller.

The deck height (top of piston to deck) needs to be zero or close to zero for a Pontiac to make good HP.

You spent a lot of money without getting some of the basics right.

[ta man]

What convertor?

[Chief of the 60's]

Originally Posted by Dick Boneske

You didn't mention if the cam was degreed. Incorrect cam timing can kill HP big time.

That was my first thought. But then I went on to read that the builder was a "Pontiac" builder so I dismissed that thought. Any good builder at all degrees a cam. However I will admit, this engine is a dog.

Hey OP, how do the plugs look?

[Sirrotica]

I guess only Holley carbs can make power?...……….LOL
I think that fallacy has already been disproven over and over...……...

This is a street driven car probably never going to exceed 450 flywheel HP. A Q jet is plenty capable of supporting this kind of power.

I had a friend that put a RA IV 400 in his 68 Firebird (4 speed, 3:31 gear, aluminum RA IV intake, and a Q Jet) that had very poor performance. The main problem was the tune was all screwed up. After going through the valves, re-jetting the carb, changing metering rods, adjusting the advance curve in the distributor, re-setting the timing the car was like a different car. No dyno figures back in the 70s, but it was quite impressive to drive.

The main thing is, having 1 or 2 items off, can kill the power level, even if it runs smoothly doesn't mean everything is at it's optimum. I'm guessing that if someone was to optimize everything in the tune up the engine is going to run 100% better. The other thing that can cause these same symptoms is a screw up in cam timing, it's not that hard to mess this up, and cause these exact symptoms.

Even a car with tall gears can smoke street tires when everything set up correctly. Just look at all the big Pontiac 455 cars with highway gears that can roast the tires for 150-200 ft. There's a problem/problems that so far has been missed, find it and you'll have a car to be proud of.

[RocktimusPryme]

Even with tame compression you should still anihilate those numbers. I mean I’m running 87 cc chambers on aluminum so 96 on iron isn’t that crazy. Now if your piston is way down in the cylinder that would suck but I still don’t think that is your primary culprit.