[unruhjonny]

Originally Posted by Skidmark

Id probably be happy with 275 hp. Sounds doable on a budget.

The (b)hp numbers published for the 1971-1972 Pontiac 400 were 300hp
1971 = #96 heads, 067 cam, log manifold, standard intake, 750cfm Qjet; full dual exhaust (2-1/4" pipes)
1972 = #7K3 heads, 067 cam, log manifold, standard intake, 750cfm Qjet; full dual exhaust (2-1/4" pipes)
The net-hp numbers were about 50 less - but that's still a substantial bump from the 1975 rating of 185hp.

I need to ask;
Does your car have a factory style exhaust?
(factory was a 'Y' pipe after the engine, to a catalytic converter, and single to muffler behind the rear axle - and dual after muffler.)

[Skidmark]

Originally Posted by b-man

Here you go:

https://forums.maxperformanceinc.com...1&postcount=22

Thanks, I'm saving that link.

[unruhjonny]

FYI - that build, although not fancy by any means, would (I'd wager a guess based on machining costs of late) absolutely blow through your $2,000 budget.

It's builds like that, which really attracted me to 'pure stock' stuff - you're essentially stock, with no trick parts - just there's careful attention paid to the assembly.

[steve25]

If your not doing anything to the short block and your looking to run something bigger then your stock 067 cam that will add some nice power And not detract from drivability then you must with a 400 cid motor get the compression up to 9.2 by hook or crook.

That’s why I posted go for rebuilding your 62 heads.
A needed valve job will add 1.2 CCs to the chamber volume and the use of a thicker then .039” head gasket should get you right there.

[Skidmark]

Originally Posted by steve25

If your not doing anything to the short block and your looking to run something bigger then your stock 067 cam that will add some nice power And not detract from drivability then you must with a 400 cid motor get the compression up to 9.2 by hook or crook.

That’s why I posted go for rebuilding your 62 heads.
A needed valve job will add 1.2 CCs to the chamber volume and the use of a thicker then .039” head gasket should get you right there.

Thanks for the explanation on the compression ratio.

[bobzdar]

I had a '77 400 (L78, so 6x-8 heads) t/a with 4 speed. Had the edelbrock 'performer' package - intake, cam and carb. It was a dog, ran 16's at 86mph in the 1/4. I swapped cam to a 744 clone, torker intake, qjet and 4 tube flowtech headers. Cost me about $500 at the time, now it'd be closer to a grand - current prices say melling spc-3, used torker and 1 5/8" flowtech headers come to around $700, add $100 for fluids and gaskets, but assume you already have a qjet. Car went high 14's at 98mph but had bad wheel hop and fuel delivery issues. Carter mech pump fixed the fuel issues and I rebuilt the suspension, which fixed the wheel hop, but I never ran it in the 1/4 again. I assumed I could have hit low 14's at around 100mph if I wanted to drag it, but built it more for road racing. 86mph to 98mph is around a 100hp gain without having to pull the heads. These cars are way undercammed at stock, keep in mind they have the same airflow in the heads as the ra1 and ra3 cars that came with either 068 (auto) or 744 (stick) cam in the '60's. Pontiac also used the 744 (originally 041) in the SD which only had 8.4 comp. It's about moving air in and out.

20k miles later, I swapped to high compression #16's with crower valve springs, along with a cast iron factory intake (per prevailing wisdom at the time, early 2000's) and it didn't get any faster though picked up low end - which was pretty much useless with a stick. It wiped a cam lobe likely due to the higher spring pressures, and cracked the pressure plate at the track, and I sold it in a fit of stupidity.

[Sirrotica]

The 455 SD is a classic example of why you don't gain a ton of power when you increase compression ratios a full point. As you say, moving air is another way to increase power, over raising compression. Moving more air doesn't have the possible drawbacks that increasing compression over your fuels ability to supress detonation does. More naturally aspirated air doesn't break pistons, or rings.

As I previously posted, on a late 2nd gen T/A I would go for full length headers over RA manifolds, because they have the ability to move more air. If you keep the low compression, you have to move more air to compensate.

I had a customer that actually managed to order a 73 SD 4 speed car, removed the RA manifolds and substituted Hooker super comp headers. The car noticably picked up with just that modification. No times, just butt meter readings.

Another customer car, 1976 455 T/A, cam, headers, H pipe, intake. it ran a 13.92 with 7.6 to 1, 455 D port engine, basically the same engine that came in a B body daily driver. The car would run out of gas just before shifted, due to the stock fuel lines. Probably would have run 2-3 tenths quicker without fuel delivery problems.

During the late 70s, early 80s, there was no premium pump gas, if you wanted a quick street car, you had to stay with low compression for the low octane fuel available.

During this time there were tons of older high compression factory heads available, cheap too. If you bolted GTO heads on your late smogger T/A you couldn't get fuel for it. At this time all the premium fuel engines left over from the late 60s were blowing up due to broken pistons, and rings. I wasted a good 65 Bonneville 389 this way.

[Skidmark]

Originally Posted by Skidmark

Car already has true duals no cats. Everything else is stock.

I think it's only 7.6:1 compression to ratio.

I know it is a 557 block.

I think 3:23 rear gears, not positive.

Cam, Carb rebuild, headers, different iron heads??

185 hp now.

2000. Budget.

Got lucky not 557 block early 75 build date. 988 block hell yeah.! 3:08 rear.

[Skidmark]

Thinking about what Steve said about the 62 heads sounds like the way to go to raise compression.

[Lee]

A set of quality 4-tube headers, or a set of used tri-Y's if you can find them. Have an O2 bung welded into the exhaust, when you take the car to a muffler shop. Then get a wideband oxygen sensor, and learn to tune your motor. Rent a chassis dyno for a few hours, and see how the O2 sensor readings relate to actual power.

If you have some money left over, get a torque converter that stalls around 2500 or so. Those changes should knock over a second off of your e.t. at the track.

[Baron Von Zeppelin]

Skid's car has RA manifolds and a transverse muffler.
Don't know the pipe size , or if an H pipe.
Fairly new exhaust system by previous owner , front to back.

3.08 gears is a big surprise though
Would have expected 3.23 or 3.42 in a 4spd car

[Baron Von Zeppelin]

I'd do the 62 heads with a thicker gasket
Cam ,,, or 1.65 rockers on the stock cam.
Your 75 intake will work , you can put later intakes on earlier heads - no mods.

Also this is an ultra low mileage survivor car.
Engine should be pretty snug still.

[HWYSTR455]

A TKO-600 has a lower 1st gear, that seems it would be a good upgrade for the money. Won't be able to do it for $2k, but you're pretty close. Maybe just save a little longer?

You can leave current engine intact and grab a better block for a better build down the road as another option.

The 2 biggest things that stress 557s is stroke & slicks. But in general, they are usually good to @ 500hp. Still, personally, I wouldn't throw money at it and just build something else.

Tax returns are right around the corner....


.

[Baron Von Zeppelin]

Oh and forgot to double stress what Steve said about opening the shaker scoop.
My 73 SD had a removable plate held with 3 Allen head screws.
If you don't see a provision for that - buy another used shaker and cut it.

World of difference

On my 79 I had a rectangle piece of dense foam rubber I kept stuffed in it when not driving , or while washing it.

[unruhjonny]

AFAIK, the 73-76 shaker scoops are all the same.
They were molded closed starting with 1977.

[pontiacstogo]

Originally Posted by unruhjonny

AFAIK, the 73-76 shaker scoops are all the same.

Pretty sure this is the case. On my 74 the block off plate was 'epoxied' on to the shaker. It was easy enough to remove the block off plate and replace it with a functional flapper.

https://www.ebay.com/itm/256181333556

Not sure about the performance increase, but definitely improved the intake noise (plus I kept the block off plate so it's reversable if needed).

[Baron Von Zeppelin]

The foam rubber I had for my 79 was a real tight squeeze.
Left it in place once after a wash and was going down the road , decided to punch it and remind how it felt with closed scoop .

It immediately sucked the piece down into the breather pan when I punched it.
So they like the extra air versus just the snorkel on the breather pan.

[Baron Von Zeppelin]

On the 73 , I guess the original owner did that mod himself.
Flap was held with an allen head in top center , then one at each lower corner.
It was a clean install.
The interior ridge that held the flap in place was blacked out (white car) .
He probably did all that

[HWYSTR455]

Restore a Musclecar has grates that can go in place of the block off plate or door, just to say:

https://store.restoreamusclecar.com/custom-parts.aspx

You can put a piece of foam in from the outside and it won't get sucked in.



.

[Skidmark]

Originally Posted by Baron Von Zeppelin

I'd do the 62 heads with a thicker gasket
Cam ,,, or 1.65 rockers on the stock cam.
Your 75 intake will work , you can put later intakes on earlier heads - no mods.

Also this is an ultra low mileage survivor car.
Engine should be pretty snug still.

The only mods so far were done by the previous owner. He did the exhaust(no cats), Installed a 72 factory intake and put 1.65 rockers on it.

I drove the car 125 miles yesterday and it runs great. I'll do the shaker modification and leave it alone for awhile while I work on my lemans I never realized how rich the lemans was running until I had the 75 TA to compare it to. After driving the TA and arriving at my destination and not smelling like fumes and exhaust I realized I've got some work to do with the lemans.

Previous owner told me the TA had a 3.08 rear. I haven't confirmed yet and PHS didn't list rear end either, unless I just didn't see it in the PHS packet.

One day I'll put the 62 heads on the TA as suggested by members.