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I have hot rodding questions about a Pontiac 455 and 400.

SteveSS

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I know this is a Mopar forum and my Mopars are running pretty good. I just wanted to ask some basic questions about an American V8s. My son has the engine out of his 1973 Grand Am with a 400. Being the block is probably a mid seventies what's the easiest dirt cheap way to make lots of torque? He is not asking for help but I thought I might suggest something while the engine is torn down. He's a college student so he's really squeezing every dime.

My 1973 Grand Am came with a rebuilt 455. The previous owner said it was a very mild build which scares me since I don't want to put something in the car just to yank it back out because it's dog. Remember we live at 7,500 above sea level which is big power robber. One thing I thought of was to have the heads or the block shaved down to increase the compression, although I don't know how much that costs or if its even the right thing to do. Everything I see on the net is let's build a 750 hp Pontiac so it's not much help.
 
You didn't provide a lot of info. but you did say he was squeezing every dime, so I would suggest mainly focusing on a good choice of cam and proper tune for your altitude.
 
Don't know what the valve pockets look like on those but if they are anything like Mom's heads, it would be wise to do clean them up. I've done this and it really lets the engine breathe better and is well worth the money imo. I don't do a full on port job on street engines but do believe in blue printing one. IE, make sure the cam is degreed in and do NOT just install the cam using the dot method. Make sure the intake ports match the heads. It's not so bad if the ports in the heads are a hair larger than the intake ports but it's bad if it's the other way around. Do not go crazy with excessive bearing clearances. Over the years I've found that you can keep them on the minimum end of the tolerance and it works fine and you don't need to run heavier oil weights.
 
Well start with a set of 6X heads 455 's are expensive the 6X are the performance heads you can do slot with them watching gaskets and cleaning up the ports! Then I'd say cam ! These motors arnt very powerful .
To be honest the cheapest fastest thing would probably be a ls1 swap ...
 
Nitrous !! End of Story !!, get on C.L and pick one up used for 1/2 price.
 
Trouble is nothing you do will be cheap. Those motors have extremely low comp ratio. If you measured you would find less than 8-1. Not to mention 70's cam technology.
Doug
 
I know this is a Mopar forum and my Mopars are running pretty good. I just wanted to ask some basic questions about an American V8s. My son has the engine out of his 1973 Grand Am with a 400. Being the block is probably a mid seventies what's the easiest dirt cheap way to make lots of torque? He is not asking for help but I thought I might suggest something while the engine is torn down. He's a college student so he's really squeezing every dime.

My 1973 Grand Am came with a rebuilt 455. The previous owner said it was a very mild build which scares me since I don't want to put something in the car just to yank it back out because it's dog. Remember we live at 7,500 above sea level which is big power robber. One thing I thought of was to have the heads or the block shaved down to increase the compression, although I don't know how much that costs or if its even the right thing to do. Everything I see on the net is let's build a 750 hp Pontiac so it's not much help.

Sorry to say this, I agree with the above. 6.0 LS iron-block swap, with a very-mild camshaft upgrade. That's about the least expensive, dollar-for-dollar upgrade you could do at this point. With factory EFI, the difference will be dramatic. Pontiac engines are probably the -most- expensive builds you can have, upping the compression (increasing cylinder pressure) to build power back down on the low end, is not going to improve the engines performance dramatically.

Something like;
LQ4 6.0 with an LS9 (ZR1) camshaft ($149 @ summitracing) and uses a factory pushrod length. Upgrade the valve springs, such as the factory LS6 springs ($60-$80). Good to go, will last a lifetime and make great power.

Then in the future, when funding allows. Pick up a used Magnuson supercharger kit or similar. Forced induction is about the only way you'll make great power at that elevation.

If only we built Chevrolet's.. lol.
 
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The July 2016 Car Craft is dedicated solely to Pontiac.
It's a good and informative read and worthwhile if you can get your hands on it.
20171205_082241.jpg
 
Sorry to say this, I agree with the above. 6.0 LS iron-block swap, with a very-mild camshaft upgrade. That's about the least expensive, dollar-for-dollar upgrade you could do at this point. With factory EFI, the difference will be dramatic. Pontiac engines are probably the -most- expensive builds you can have, upping the compression (increasing cylinder pressure) to build power back down on the low end, is not going to improve the engines performance dramatically.

Something like;
LQ4 6.0 with an LS9 (ZR1) camshaft ($149 @ summitracing) and uses a factory pushrod length. Upgrade the valve springs, such as the factory LS6 springs ($60-$80). Good to go, will last a lifetime and make great power.
The $$$$ start when you buy mounts , pulleys , brackets, oil pan, that fit the old chassis, fuel system, and then the electronics to run it all. Now add it all up. Several friends done these swaps in Chevelle's. It's not near as cost effective as it's made out to be.
Doug
 
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