# 400 Engine...Need Help



## mtgoat (May 28, 2013)

Hello All. I am new to the forum and am just getting into this so i dont know a whole lot yet. I recently bought a 65 gto with a 1970 400 block in it. It has 1975 5C heads, edelbrock 600 cfm carb, stock intake, manifolds, etc and it is pretty weak. I do have an edelbrock performer intake, but not sure how much that will help without addressing other issues. I have not had a compression done on it yet. I have a budget right around 4k right now and was wondering if it is possible to get a lot more power (around 450) with this budget and what I have to work with.

I have a friend that recommended edelbrock heads which are spendy, but figure that my budget would be shot as I would probably need to redo/replace everything. I have looded around at some other cast heads and am not sure which route to go. 

I want this car to be a daily driver with around 400-450 hp and be able to run on premium pump gas. 

I appreciate anyone and everyones help. Thanks.


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## mikea455 (Jun 1, 2013)

Much depends on how you are going to use your engine. 

$4K is a good start. With the heads you have, the compression will be low. Maybe 8.0 to 1. Not a good start for 450 HP. Next, are starting with a rebuild or are you bolting on things to make power? If the engine has lots of miles, most likely you won't see much return with bolt on speed equipment.

If you are going to rebuild, then you need to look at getting some aftermarket connecting rods as the cast ones are not very forgiving once you start making lots of power. In the old days before forged rods could be purchased easily, preparing cast rods took a lot of time, new rods bolts and other machining. Then, a lightweight wrist pin would be used to further lessen the load on the rods. For that much time and money, a few more dollars would get you a set of forged aftermarket connecting rods.

Block work such as boring and honing and deburring is a another expense you really can't leave out. Forged pistons would be a great investment. Stay away from "pop-up" type pistons as Pontiac combustion chambers do not work well with them. The crankshaft will need attention as well. Be prepared to have the rotating assembly balanced after you have all the parts and machine work done. 

Edelbrock heads are a good investment also. But if you could locate some earlier model stock performance heads where compression would be higher, you would definitely benefit from that choice and save a few dollars. The aluminum heads are more forgiving with high compression and are not as sensitive to pump gas with poor octane.

Camshaft selection is very important. Getting something that requires the engine to spin 7,000 RPM to make power isn't going to work well with the short block and the budget you have. There are some great hydraulic cams that are old time favorites with Pontiac engines. If you speak with a camshaft manufacturer, they can also recommend some great hydraulic roller cams for a Pontiac too. A cam for the street and a stock torque converter will be very different from something you are racing and have a high stall racing torque converter.

$4K will probably be on the low side for something you are going to race. Carb sizing, gear ratios, transmission selection all come into play. I usually tell people to purchase a carb sized to your needs and just tell people it's a bigger CFM carb. Something large will require a lot of displacement, compression, a bigger cam and a lot of gear in the car.

For the street, Pontiacs can dominate. A standard 1970 455 made 500 foot pounds of torque. Torque is what gets things moving. HP is what makes top end. 

Hope that helps.


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## jmt455 (Mar 26, 2012)

Welcome to the forum!

I recommend that you focus on maximizing the engine's torque as opposed to peak HP ratings as you go through your part selection decisions.

Pontiacs are great torque-makers; use that inherent strength to your advantage.


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