Engine has no power

[David McIntyre]

I have a 67 firebird with from what I was told a 413 pontiac engine that ran a 7.30 in a 72 ventura in the eigth, so figured that it should have enought power for a 3" exaust and I added hooker competition long tube headers with 1 3/4" primaries, I have a 750 holley double pumper carb. It has a 400 auto trans and a 2.73 rear gear, no posi, and it won't even spin the one tire, it has no power at all. any Ideas

 

[David McIntyre]

also, I tried a different carb and timing is at 15* and vacumm advance seems to be working properly. The compression is around 120 on all cylinders and I have the 6X heads which I was told are good heads. Oh and the way he told me he came to a 413 is with a 350 pontiac block 455 crank and 400 rods.

 

[nightroddersp]

also, I tried a different carb and timing is at 15* and vacumm advance seems to be working properly. The compression is around 120 on all cylinders and I have the 6X heads which I was told are good heads. Oh and the way he told me he came to a 413 is with a 350 pontiac block 455 crank and 400 rods.

i did not know there was a 350 big block... the 455 is a big block ans the 400 is either small block or a big block... sounds like they through an engine together and don't really know where the parts came from... i would tear the engine down and find out what exactly you have and put it together correctly with compatible part...this is just my opinion and never been a professional...

 

[melsg5]

Unlike Chevrolet, true Pontiac engines have only one basic block all the way from 350 to 400 to 455. They use different cranks, pistons, etc., no big block versus small block. The combination of a double pumper, a stock transmission and a 2.73 rear is a problem. You say you have 15 degrees initial timing, more important is what is your total timing, checked with a dial back timing light, and at what RPM does it occur. I would get rid of the double pumper and install either a quadrajet or a Holley with vacuum secondaries. Do you have any idea what cam is in the engine?

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[68firebird400]

I'm pretty sure that even if they put a 455 crank in a 350, you still have a 350 cubic inch displacement (unless someone bored it out). Personally i've never heard of that combination of parts. Sounds more than a little strange. I agree with others that a dbl pumper is to big. How's it run other than not burning the tires? If it idles good, revs up without missing then that's probably all that engine has in it. Especially with your rear end gears. 3" exhaust is also to big, not going to hurt all that much, but you really need more back pressure. 2.5" is more than big enough. Check your plugs and see if that carb. has flooded them out, If they're covered in black or wet, throw them away put new ones in. Maybe try it without the carb secondaries hooked up and see if there's a difference. Just my thoughts...

 

[David McIntyre]

according to the guy that built the engine, it ran a 7.01 in the eighth in a ventura, the only thing I'm running different is the exaust and carb, and of coarse the trans and rear which I know kills it as far as speed. I guess I may need to tear apart and start over, it has good compression and the plugs look good when I pulled them

 

[melsg5]

If you still have that 600 CFM carb and it's vacuum secondary, use that carburetor and if it needs a rebuild do it. Once you get some more agressive gears in the rear you can go back to the 750 dp.

 

[72firebirdguy]

There are no pontiac Big Blocks and small blocks. there is only a 30 pound difference between 326 and 455. all blocks have the same dimmensions. 10.24 deck height 6.625 inch rods

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