# Recommendation for low to mid RPM torque…



## 11th Indian (Feb 15, 2018)

Recommendation for low to mid RPM torque….

Stock 1972 400, low compression (8.2…) Engine spends most of its time in 5th gear (Running a Tremec TKO) between 1500 and 2500 on the highway. Surprised at how responsive it is in 5th gear, never lugs.
However I need to pull the engine soon due to a rear main seal leak. The engine was rebuilt before I bought the car, I put 7000 miles on it. Still takes close to 1000 miles for the oil to discolor and I am getting an average of 158psi in a compression test, with no more than a 5% variance.

I figure while the engine is out I would like to change the heads cam and exhaust. (rod bolts?) Not scared to rev it to 5000, I just don’t do that with this car, keep it generally below 4500 when I want to gun it.
Another 50 plus hp and some additional torque would be nice, and not to threatening to the existing bottom end….?? I usually fill it up with 93…


Any recommendations for heads and cam setup?
Thanks


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## Lemans guy (Oct 14, 2014)

How many miles on the engine?.....you may want to consider improving your PCV system to relieve crankcase pressure and it may stoop the rear main seal leak. Are you having any other oil leaks? Valveless cover gaskets? Or oil out the side of the breathers after a drive?...

if so you may just have too much crankcase pressure. Now you may want to pull it anyway to do all that other stuff, but it sounds like you are pulling it for the main seal.

why not check your PCV system and improve it if you can and it may fix the main seal leak for a lot less money and effort.
now if it works you won’t get to play with a new cam and such, but at least you will have a choice.


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## 11th Indian (Feb 15, 2018)

Lemans guy said:


> How many miles on the engine?.....you may want to consider improving your PCV system to relieve crankcase pressure and it may stoop the rear main seal leak. Are you having any other oil leaks? Valveless cover gaskets? Or oil out the side of the breathers after a drive?...
> 
> if so you may just have too much crankcase pressure. Now you may want to pull it anyway to do all that other stuff, but it sounds like you are pulling it for the main seal.
> 
> ...


I dont know how many miles are on the rebuild. I have replaced the PCV valve and installed valve covers with an open breather in each cover. No other oil leaks - just the rear main. Not sure how to measure crankcase pressure. The leak is significant.


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## Jim K (Nov 17, 2020)

Greetings 11th,
You pretty much have the same motor as my original 400 in my 71. I don't know what your budget is but I've heard decent things about Edelbrocks 87 CC D port aluminum heads. Your current heads should be 7K3's with 96cc chambers. Maybe you can achieve what you are after with the right cam change?
Since your have an overdrive and most of your engine RPM is in the lower range, you'll probably want a milder cam, BUT there is a lot of other factors that play into these kinds of selections (rear gear ratio, vehicle weight, altitude where you live, etc.. etc..) Best to talk with a cam manufacturer. They know all the right questions to ask.

As for your rear main leak, chances are when the engine was rebuilt they used a rope seal. There is nothing wrong with a rope seal (otherwise Pontiac wouldn't have made 1000's of engines with them) they can be a bit tricky on install and you have to know how best to install them. BOP engineering has a couple of rear viton seal options that are easy to install and work well, but the condition of your crank where the seal makes contact plays a big role in how well the seal works. I'd look at that closely at that when you get it out.
Jim K


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