SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: jayare92 on February 06, 2015, 05:40:48 PM
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Ok so i know this isnt about a boat but i need some advice. I have a 1998 gmc sierra with the 5.7 vortec. My question is i have access to a set of heads with a little work done to them and are basicly brand new id like to see if they will work on my truck. They are out of a 88 5.7 center bolt heads( just like mine). Will these be a direct fit onto my block?. The #'s stamped are 14096217 below it k256. Thanks for any advice!
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The vortec heads are the best production SBC head. They flow 238 CFM @ 28" vacuum and .450 valve lift. The '88 5.7 heads flow nowhere near what the vortec heads do. The vortec intake has an eight vertical bolt bolt-pattern compared to the twelve angled bolts of the earlier heads. You can redrill the intake bolt-pattern, but the ports don't line up as nice as the correct manifold. You will also need the correct rockers and push rods. You might run into issues if you ever have to go to a smog referee. Unless you are going to an aluminum aftermarket head, IMHO, your performance will drop compared to the vortecs.
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The vortec heads are the best production SBC head. They flow 238 CFM @ 28" vacuum and .450 valve lift. The '88 5.7 heads flow nowhere near what the vortec heads do. The vortec intake has an eight vertical bolt bolt-pattern compared to the twelve angled bolts of the earlier heads. You can redrill the intake bolt-pattern, but the ports don't line up as nice as the correct manifold. You will also need the correct rockers and push rods. You might run into issues if you ever have to go to a smog referee. Unless you are going to an aluminum aftermarket head, IMHO, your performance will drop compared to the vortecs.
ooh alright thanks. Yea i dont to lose power so il just look into some vortecs. These were a set basicly free and one of mine has a bad valve. I was told their 64cc 194valve. I just bought this truck and dont know much about the vortec motors. not sure what cc my current heads are.
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The vortec heads are 1.94 intake and 1.50 exhaust. They are very well shaped valves without the characteristic "ski jump" that most production valves have. I scrapped a few brand new sets learning how to port them and I am pretty sure I still have all the new out of them. They work really good with 2.02 and 1.60s, the low lift flow numbers pick up substantially.
Look around, I bet you can find some good used pull-offs cheap.
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The vortec heads are 1.94 intake and 1.50 exhaust. They are very well shaped valves without the characteristic "ski jump" that most production valves have. I scrapped a few brand new sets learning how to port them and I am pretty sure I still have all the new out of them. They work really good with 2.02 and 1.60s, the low lift flow numbers pick up substantially.
Look around, I bet you can find some good used pull-offs cheap.
ok cool maybe il take my heads off and send into the local machine shop and see what they can do. Maybe open them up a little. Its got a bad valve on the #6 cylinder