Author Topic: 400 Build Help  (Read 124 times)

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Offline tals225

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400 Build Help
« on: September 13, 2017, 07:24:26 PM »
OK. I'm you all get tired of answering engine build questions but the information that I see here on your forum is helpful.
I had a 76 400 built about 20 years ago now. I have put about 500 miles on it only. My concern is that it is mismatched because I seem to have never gotten great performance out of it.
Here is the current build:
Block: 1976 Pontiac 400 .030
Heads: 1976 6x-8 with 2.11 & 1.77 valves. Ported and polished. 1.5:1 roller rockers. Intake matched.
Crank: Stock .030
Pistons: TRWL2262F30
Intake Manifold: Edelbrock RPM Performer
Carb: Edelbrock 750
Camshaft: Lunati 07703, .534 .534, Installed straight up at TDC
Differentials: 3.73
Tranny: TH350
Stall convertor: 10"
Exhaust: Hooker SuperComp headers and dual exhaust with crossover pipe
Distributor: HEI

The throttle response is horrible. No instant response when you hit the pedal.
It's impossible to time and tune with the aggressive cam.

So, what do I need to do to start over and make this into a daily driver that can compete with today's sports cars and not sound like it is from the drag strip?
I assume it's the camshaft but I have no idea what to get or what else I need to consider.
I feel that the 3:73 gears are too much for a daily driver.
I am also annoyed with the fact that the header gaskets always crack and create the loud ticking sound. Just tired of the loud headers all together. Is there an alternative that would sacrifice the exhaust flow?
Sorry for all the questions. I'm a beginner when it comes to engine builds which is why I had someone build this 20 years ago.

Looking for guidance and a solid build to get me on the road everyday and allow me to pounce on today's sports cars when I want to.

Oh yeah. It's in a 1981 Trans Am. The 301 turbo was swapped with the 400 20 years ago.



Offline SA74SD

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Re: 400 Build Help
« Reply #1 on: September 14, 2017, 09:50:52 AM »
Unless your heads/block were cut, your compression is less than 8 to 1. Add that cam and it's no wonder it has no low speed response. Did you degree the cam when installed? I would consult with a professional engine builder about advancing the cam timing to try to help with low speed cylinder filling.

Invest in some d port ram air manifolds and you have no more headaches from header gaskets. You won't lose any appreciable power.

Offline tals225

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Re: 400 Build Help
« Reply #2 on: September 15, 2017, 11:19:56 PM »
Thank you. I will certainly talk to a local builder.
Do you think I should change the cam to something with a little less lift?

Offline SA74SD

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Re: 400 Build Help
« Reply #3 on: September 16, 2017, 08:33:44 AM »
No problem with the cam lift. It's the cam timing events along with lack of compression that is killing low speed cylinder filling. Be aware that advancing the cam is just a crutch.  To really wake up that motor, you need to increase the C.R. 1 1/2 to 2 points. Good Luck.