by Old Skool Fri Jan 30, 2015 9:26 am
I have been building the V8 cross members and doing the V8 conversions for many years now and ALWAYS advise to put boxes under the seats. Even in Dave Grohls Falcon van with stock manifolds it was too tight without the boxes. There isn't enough room for breathing, for insulation and good luck changing a spark plug without them!!!!!!!!!!!! SO regardless of long tube or shorties,, the boxes are a better idea.
In regards to shorties versus long tube headers as well as primary tube size here is what my cylinder head porting company tells me.
Firstly,, shorty headers work well on a computer controlled engine as the computer can compensate for the camshaft grind and control the engine output. On a non computer controlled motor shorty headers strictly compromise the engines power output as it cannot control the variables with the camshaft grind and its performance.
On my aluminum heads, it has the dual exhaust bolt pattern and can run the 1 3/4" primaries instead of the standard 1 5/8" primary tubes. According to them, by running the larger tube size on any engine less than 600 hspwer and anything less than 7500 rpm up,, DONT DO IT as the larger size actually hurts the exhaust scavenging,, ESPECIALLY with shorty headers.....
SO,, with that,, I will be using headers on the aluminum heads that have a minimum of 3/8 flange thickness,,, will be using the wider exhaust bolt pattern as the issue with most of the headers are that the bolts are too close to the pipe. I just threw out a brand new set of the cheapies off of Ebay as the exhaust studs would not enter the holes with using a die grinder to oblong the holes,, and after that,, there is almost NO GASKET thickness left at those points!!!!!!!!!!! DONT BUY THE CHEAPIES OFF OF EBAY,,, THEY ARE JUNK!!!!!!!!!!!! if you want a set you can have these,,, LOL...
So,, IMO and the cylinder head builder,,, use LONG TUBE HEADERS with 1 5/8 primary tube size.....
I have four conversions in progress here right now and two motors that I am building for myself right now also. The cast iron 302 heads I will be using the narrow bolt pattern, 3/8th flange, long tube headers with bowl type connector flanges to the exhaust pipes.
On the big roller motor with the aluminum heads, I will be using 3/8th flange, long tube, wide exhaust port bolt pattern headers, ceramic coated inside and out..
Unfortunetely,,, whether or not I like it,,,, so far the header price is going to start at $450 if I am lucky????????????? but realistically expect about $650,,, unless I get lucky.
Old Skool
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