i cant answer those Q's, but remember that the dynatech headers are a slip fit collector............even from the mouth of dynatech themselves, a slip fit collector is almost impossible (well very very difficult) to get a 100% seal, and they recommend them for race only, where you arent relying on downstream O2's to properly read.

although im pretty sure you could have the collectors welded on properly so they wont leak ever.

 

1 3/4 should work fine, you wouldnt see much gain bettween them and 1 7/8 may 1-2 hp on the top end.

 

1 3/4 header will not bolt to my exhaust port,my port is too big. 1 3/4 header will not properly support my normally aspirated goals.
Engine analyzer Pro also supports the need for a bigger header in my case, as well as it would in Daves case also.


David

 

okay??? thats for your application. Not his, I didnt read anything in his post that say his ports are oversized. Primary size only helps a little up top, if your looking to twist to 7000 then primary length is a important factor. I dont know if this will help any but below is a link that tell the functions of the header, maybe it will help you decide which are best.

http://www.grapeaperacing.com/GrapeA...ustheaders.cfm

 

his car would definetly benefit from the 1 7/8 primaries........its obviously a race car (392 solid roller spraying 300!!!) and could care less about losing some low rpm power........the car will spend all its time at the high rpm anyway.

btw, the LS1's are kicking *** with 1 7/8 stepped headers on cars that probably dont put out as much power as his.

 

They will NOT clear the headers on the drivers side without giving the primary a good dent to fit around the Canton PIECE OF SH*T pan. The low oil sender will also not clear then, but you can remove the sender and use a low profile oil plug and they will BARELY clear that. Other then that, have the slip on collectors welded up, they leak like hell no matter what I did and caused a lean condition. Welded they are fine. But plug changing is a bitch on the passenger side unless you drop the starter. Then you can reach right up and get the rears. They are good headers, but they arent perfect for fittment with CANTONS JUNK PANS.

Q