Just picked up 72 7a heads....hit or miss?
November 14th, 2012, 05:52 PM
#1
Just A BaBy {:
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Just picked up 72 7a heads....hit or miss?
i just got these head for $150, i was told they had a valve job but i dont know if it does at all. casting # 409 147, 64cc chamber.
so i think i did good.
so i think i did good.
November 14th, 2012, 05:56 PM
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November 14th, 2012, 06:16 PM
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Looks nice. 150 for a complete valve job seems pretty cheap. I thought most shops doing a valve job would also install new valve guide seals, pivots, rocker arms, springs and keepers.
November 14th, 2012, 06:41 PM
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November 14th, 2012, 06:44 PM
#7
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nope that is what the guy told me,an what was in the add. but im going to take them to a head shop to make sure.
November 14th, 2012, 06:53 PM
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IMO, valve train components have nothing to do with the valve job. Seals, springs, keepers, usually, but without knowing the cam specs, it is kinda hard to set spring pressures and check coil bind, especially for $150. Rockers are never included. I bet you find a WIDE single angle seat.
Last edited by captjim; November 14th, 2012 at 06:55 PM.
November 14th, 2012, 10:22 PM
#9
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IMO, valve train components have nothing to do with the valve job. Seals, springs, keepers, usually, but without knowing the cam specs, it is kinda hard to set spring pressures and check coil bind, especially for $150. Rockers are never included. I bet you find a WIDE single angle seat.
November 15th, 2012, 03:40 AM
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November 15th, 2012, 09:48 AM
#11
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well looks like im going to need help picking the right cam,all im doing to the engine is rebuilding the top end being intake heads exhaust manifold an the cam/kit,of course i will be upgrading some pieces as i go through it but thats the plan for this engine .
November 15th, 2012, 10:13 AM
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Jim's right, get the rest of the combo sorted out first, then get your cam, springs etc.
November 15th, 2012, 03:53 PM
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OK, I did not see where that was posted. So, you have 14 cc dished pistons that should sit down .020 in the hole. Use .028 head gaskets and mill the heads down to 64 and you will have 9 to 1 CR. Mill to 60 cc and you are at 9.5 to 1. Also, 79 350s have 1/2" head bolts and the older 350 heads are 7/16" so you will need them drilled to 17/32" No biggie.
Last edited by captjim; November 15th, 2012 at 03:56 PM.
November 16th, 2012, 08:35 AM
#17
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OK, I did not see where that was posted. So, you have 14 cc dished pistons that should sit down .020 in the hole. Use .028 head gaskets and mill the heads down to 64 and you will have 9 to 1 CR. Mill to 60 cc and you are at 9.5 to 1. Also, 79 350s have 1/2" head bolts and the older 350 heads are 7/16" so you will need them drilled to 17/32" No biggie.
ty bud i just picked up a compression tester to see what kind of psi i'm sitting on just to see if my hopes of getting 350 or so out of this engine would be possible.
November 16th, 2012, 08:45 AM
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You are mixing up static compression with cranking compression. Static compression ratio is a combination of bore, stroke, and volumes. Cranking compression is variable depending on many factors. You need to know the static Cr to properly build the engine combo.
November 17th, 2012, 08:36 AM
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November 17th, 2012, 08:41 AM
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He needs to know the compression ratio. You can take a 10 to 1 engine and have 220 psi cranking or 120 psi cranking, depending on the cam.
November 27th, 2012, 03:21 PM
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How much have the heads been milled?
It usually takes at least .030"+ to get the chambers down to the mid 60cc range.
Get them measured to be sure what you have so you can calculate true compression ratio. Most of these will be between 68 and 72cc's before the first valve job.
Good luck.
It usually takes at least .030"+ to get the chambers down to the mid 60cc range.
Get them measured to be sure what you have so you can calculate true compression ratio. Most of these will be between 68 and 72cc's before the first valve job.
Good luck.
November 27th, 2012, 07:02 PM
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