Are the 2 1/8" dia primary of the stellings gray headers too much for a 620 hp 502 ? I believe the cmi sport tubes are 1 7/8".
Jeff

Wags - I believe we have a mutual friend, who may suggest that 2 1/8 ID primary is too big.

I'm doing a build similar to yours, and I'll be bolting on KE's, with 1 7/8 ID runners. I was told that the 1 7/8 KE's will do quite nicely

What is the difference between the regular sport tubes and the sport tubes that come on the 525EFI'S? I have been looking at upgrading for a long time. I have about 650 hp 540 afr 315 and a 1000cfm 4150 carb. could i expect about 80 hp over the gills?

The Sport Tubes that come with the 525 efi:

1. has a different flange for the Edelbrock head. It won't fit a standard BBC head. Nor will a standard header fit the 525.

2. The collector to tailpipe flange is different. It's a Mercury flange.

3. The header length is different on the Merc version allowing equal length tailpipes on both sides.

4. The Merc 525 version has welded stainless steel distribution tubes.

5. Price. The Merc 525 version is only available through Mercury and is expensive to replace.

There may be additional differences.......

I have a pair of lightening headers if you prefer. They have been run about 8 hours total time, and are powder coated red.

send me some pics [email protected]

Still time for a great deal on Etops as we have several sets in stock with stock tails. Let us know if we can help or provide pricing.

Kirk
Ateco Engine and Dyno Shop - YOUR CMI SOURCE in the Midwest, South and East Coast!!

how much are e-tops? do you lose your silent choice with them (going from gils)?

i would stay away from anything but stainless marine and stelling.....Just my opinon but i have had bad luck with cmi......i run a stainless marine gen iii on my 572 and it fixed a lot of problems i had ie water, dont risk it engines are too exspensive,,,,,,believe me i put 4 in my mag last season two of which were water related problems

Sorry to hear that Nocig. Was it a reversion issue or other? Nobody makes a product with the intent of it not performing properly.

I don't know about staying away...Merc installs them on every one of their performance engines, Illmor installs them on all of their engines and just about every race boat uses them. Must be something about them.