The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - have some questions about 350 performance parts

Winola73 · 07-03-2011, 05:53 PM

You've received some really good advice and keep in mind that your truck has the SM420 trans (or did). It's a great "truck" transmission, a lousy performance transmission and you'll break it if you can actually shift it fast enough to make use of 350HP. If you can't you'll eventually miss a gear and hurt your engine.

If I were in your shoes and mileage is a concern first thing I'd do is look into an overdrive trans to replace the 4 speed in it now. Personally I'd go with a 700R4, most of the affordable manual OD trannies won't hold up to much abuse. Then if you have enough left get a set of headers and at least dual exhaust and HEI ignition. If it's in good shape the Q-Jet is going to give you good performance and about the best MPG you can hope for with a carb.

After that you can think about cams but stay on the mild side. I like the Performer cam and it 2 dozen or so clones for daily drivers. It won't sound racy but it works.

07-03-2011, 05:53 PM	#10
Winola73 Registered User Join Date: Jan 2007 Location: Midwest Posts: 262	Re: have some questions about 350 performance parts You've received some really good advice and keep in mind that your truck has the SM420 trans (or did). It's a great "truck" transmission, a lousy performance transmission and you'll break it if you can actually shift it fast enough to make use of 350HP. If you can't you'll eventually miss a gear and hurt your engine. If I were in your shoes and mileage is a concern first thing I'd do is look into an overdrive trans to replace the 4 speed in it now. Personally I'd go with a 700R4, most of the affordable manual OD trannies won't hold up to much abuse. Then if you have enough left get a set of headers and at least dual exhaust and HEI ignition. If it's in good shape the Q-Jet is going to give you good performance and about the best MPG you can hope for with a carb. After that you can think about cams but stay on the mild side. I like the Performer cam and it 2 dozen or so clones for daily drivers. It won't sound racy but it works.