Dyno results - headers vs rams horn manifolds - Impala Tech
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post #1 of 4 (permalink) Old 02-04-2011, 12:19 PM Thread Starter
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Dyno results - headers vs rams horn manifolds

I had my newly built, mild 383 run on a dyno. It is going in my 64 Impala, so good torque was important as was keeping the idle civilized enough for power brakes and air conditioning. I also wanted it to look like a perfectly stock 327-300hp. Given those constraints with the stock block, heads and intake manifold to work with, it came out rather well.








One of the things I wanted to test was the headers vs stock rams horns exhaust manifold topic that seems to come up from time to time. Since this engine is made of stock castings, overall breathing ability is rather limited. So the headers never really get a chance to show much advantage at the extreme top end. The rams horns are reproduction 2.5 inch manifolds that have the correct casting numbers on them. They were mildly ported and the anti-reversion bumps removed.






I have to say, that in my test conditions, using the rams horns is a no brainer. Why deal the disadvantages of headers for such a small gain?






What made a bigger impact on performance was adding the 2.5 to 2 inch reducers to the pipes, to simulate what actually happens at the muffler on the stock exhaust system on the 64 Impala. It also points out that an all 2.5 inch exhaust system would be an advantage.






And just for fun I did a run with the stock air cleaner and filter in place, along with the 2.5 to 2 inch reducers on the exhaust (trying to simulate how it will be once installed in the Impala). On a 64 Impala the air cleaner horn has a remarkably small opening and I was expecting it to really cause a hit on the performance.





Surprisingly, the air cleaner/filter had little impact. This is probably highlighting how restricted the intake manifold is. I am thinking it might be worth porting the intake a bit to pick up some more power higher up the RPM range. I don’t think a mild port would have much if any effect on idle quality, since it is a 383 breathing through a 327’s intake.



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post #2 of 4 (permalink) Old 02-04-2011, 03:23 PM
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Great thread! Thanks so much for sharing your results.

How about going with a nice high flow aluminum intake, and massaging it with a dremel where needed to look like a factory piece, then painting it?

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post #3 of 4 (permalink) Old 02-04-2011, 04:50 PM Thread Starter
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My goal is to make this stock enough to pass judging for originality. I know, it is some sort of bi-polar disorder, wanting stock looks and more performance. I have not seen an aftermarket intake that comes close to the appearance of the stock manifold. There are things that are fairly plain to see, and often changed on aftermarket manifolds that would trip me up. Like the angle and location of the water temp 'idiot light' sensor, the “Firing Order” cast into the front runner. Small things perhaps, but if you are looking at a row of early 60’s Impalas, that will stick out. I think I will find another stock intake and see what kind of porting (grinding and or acid) that can be done to improve it without killing the idle quality. But I will put that on the "to do" list for after the restoration is complete and the urge to tinker with it starts to kick in.



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post #4 of 4 (permalink) Old 02-04-2011, 07:14 PM
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That's some really good info. My only question is the primary tubing size on the headers used. They look like they are on the big side for your application. I'm guessing a 1 3/4 or even a 1 5/8 primary would have been ideal.

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