[67elko]

hi all,

I have a GM 350 crate engine in my '67. I currently have 1 3/4" headers going back to dual 2 1/2" exhaust. I think I have too much flow, robbing me of low end torque/performance. Should I replace the headers with 1.5" shorties into dual 2" exhaust?

 

[67elko]

Thanks for the responses, guys!

The cam is what came with the GM/Goodwrench motor, I think it's pretty mild. Edelbrock dual-plane (2701) intake manifold, had an Edelbrock 600cfm (1406) carb but am replacing that next week with a Quadrajet 750cfm. Tranny is TH350.

I'm thinking 1.5" headers? Or should I wait until the QJet goes in to decide?

 

[67elko]

oh, and 3.18 rear

 

[67elko]

Okay, I just found my invoice for the engine build parts from Summit from 2005...they're actually 1 5/8" Summit headers...why would my low end torque be so anemic with 3.18 rear gearing?:dontknow:

 

[67elko]

TH350 tranny, had rear axles re-done a few years back and the guy said "3.18 rear," HEI distributor, cam/crank/heads which came standard with the Goodwrench 350/260.

Quadrajets were only made in 750 and 800cfm, right?

Can you give an example of a "ported source" to attach the vacuum to?

 

[67elko]

Got the quadrajet

Will be running Summit's SUM-G9001-9 1 5/8" headers. Not using the crappy paper gaskets so I ordered Mr Gasket copper header gaskets. The Jeg's guy told me to order the Mr Gasket 7152G with 1.63" round ports but then the Summit guys say I need the Mr Gasket 7150 with the 1.5" round ports...which is correct for these headers??:dontknow:

 

[67elko]

update: those Summit 1 5/8" headers work great with the Mr Gasket 7152G 1.63" gaskets!

The Qjet will NOT mount to the Edelbrock 2701 intake. There is NO adapter, their square bore carb to spread bore manifold adapter doesn't work if you flip it upside down (despite assurances from a local mechanic and a Jeg's tech that it would work.)

I'm waiting to see whether I can swap my QJet for a Holley 600cfm (the cheapest solution.) I don't really want to deal with an intake manifold swap but I may be able to justify the expense just in MPG savings alone (gas is $4.30/gallon here.) But I don't want to have to do that....

 

[67elko]

I'm already ahead of you

It turns out that Edelbrock does make a spread bore to square bore adapter...for single-plane intake. It'll end up being a 3/4" spacer, too. I'm going to try it since I don't want to deal with a manifold swap and another Edelbrock/squarebore carb is something I want to stay away from.

Thanks for the encouragement!