327 340HP Corvette

William Malik

Active Member
Supporting Member 2
I have transplanted this 1962 Corvette engine and close ratio T-10 with a 3.70 posi into my 62 Impala SS. The car is an original 327 300hp so I am running the original 2.5 inch rams horn full exhaust. Runs great!! I am just looking for opinions on adding the Headman elite long tube headers for a little more torque on the low end. Just thinking that the heavier Impala might benefit with headers. The engine is rebuilt bone stock from carb to oil pan, 11.25 CR, Duntov 097 solid lifter cam, 461x double hump heads, Carter 3269 AFB, 397 aluminum intake. I know there is a lot of performance experience on this site and all suggestions and comments are greatly appreciated. Thanks....Bill
 

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Don Jacks

Well Seasoned Member
Supporting Member 3
I think that the headers will make a good addition for this combination.Just be aware that the engine will likely need some jetting changes ,and a good recurve of the advance curve will likely help as well.Another low end boost would be a wide ratio trans in place of the close ratio unit that's in there now for such a heavy car.
 

4speedman

Well Known Member
Supporting Member 2
I am with Don on this a wide ratio trans will help the low end more than anything else you can do.The close ratio trans might be ok for a lightweight corvette but not for a full size car.The headers will help the top end a little that's when you will need more exhaust flow but those 2.5 exhaust manifolds are not that bad and are easy to live with.
 

La Hot Rods

Well Seasoned Member
Supporting Member 15
You could drop the gear in the rear end if you don't do a bunch of highway driving.
 

Don Jacks

Well Seasoned Member
Supporting Member 3
It's been my experience that a long tube header will pick up as well as broaden the engines torque band.The longer the primary tube,the better the results at the lower end of the band.Yes ,too long can effect the very top end,but that's not where this engine is expected to run.I suggest both the header addition,and the transmission change.You won't believe the difference until you experience it for your self.
 
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1958 delivery

Well Known Member
Supporting Member 2
It's been my experience that a long tube header will pick up as well as broaden the engines torque band.The longer the primary tube,the better the results at the lower end of the band.Yes ,too long can effect the very top end,but that's not where this engine is expected to run.I suggest both the header addition,and the transmission change.You won't believe the difference until you experience it for your self.


Good full length headers will add real horsepower to that puppy. Trans swap works also. BUT the best thing you could have done for that engine was change to a modern profile cam such as something in the Extreme series from Comp. I too like to build older engines with old, original profile cams BUT the modern grinds are head and shoulders better.
 

William Malik

Active Member
Supporting Member 2
Hi everyone. Thanks so much for your replies. I really am a person that likes to keep things original or at least original looking. My brother and I have had this engine and transmission that was pulled out of 62 Corvette in 1965 from a wrecking yard in Flint, Michigan. We have always looked for a home for this pair and so I finally bought this Impala with his help. The car did not have the original drive-line in it anyway. I thought of a lot of newer better components for the engine build, but stuck with originality. You are right about the transmission gear ratio, a wide box would work better. That would be something for future consideration. I have an oppertunity to purchase those Headman headers at a great price from the company that coats them for Headman with full warranty , thought that would improve performance with that day-2 look. I do not want to lower the rear end because I like to drive this car everywhere. I did think of selling this combo and look for a 409. But I am at the end of my budget LOL.
 

425/409ER

Well Known Member
If you are going to get headers, use the Headman ones, all the rest of the others fit like crap with a SB Chevy. Shorty's would work but I don't know how much hp you would lose over long tubes. I have some Sanderson Cast headers that worked pretty good when we had the 400 on the car. The Sanderson's are supposed to make more power than the GM 2.5 dumps.
 

William Malik

Active Member
Supporting Member 2
I have recently installed the Headman headers. They fit and tuck up in there really nice. No problem with ground clearances at all. I now feel the car pulls a little harder through the gears. Not sure but the car sounds a lot better, but not really louder. I have also modified the original air cleaner to draw more air.
 

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El Rat

Well Known Member
Very nice your work is neat!
Change the trans gearing leave everything else alone. It will make a bunch of difference. The 097 is just fine. I won over 100 races with that cam (I know along time ago)
As an aside I changed the trans the tires and the rear end ...the car slowed down!
 

425/409ER

Well Known Member
The headers will help over the Rams Horn manifolds. I had the Sanderson manifolds on my kids car when it had the 350 in it and the car did slow down, we could both feel it when I got on the throttle. The Headman's are the nicest SB headers for a 58-64 car. I had the old Cyclone ones on the car and they sucked big time. Be sure to rejet the carb as it might be a little lean after the header install.
 
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