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Questions on valve/piston clearance...

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Old Mar 28, 2006 | 12:36 PM
  #1  
ResurrectingZ's Avatar
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Car: 1987 IROC 1991 RS
Engine: 5.7 TPI 5.0 TBI
Transmission: T-5 , 700R4
Axle/Gears: 2.73 twice
Questions on valve/piston clearance...

Ok here is the story: I got my 88 vette' heads, a 2 bolt main vortec 350 block (would be zz4 block if it was 4 ) just need to know if there are any clearance issues with the valves and pistons and max lift that can be achieved without floating the valves.

Comp Cams always gives the same answer, to use 08-503-8 cam, the flat top pistons have the 4 valve reliefs, replacing the springs to work with whatever cam, just need some input. Thanks.
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Old Mar 28, 2006 | 10:57 PM
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ResurrectingZ's Avatar
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Car: 1987 IROC 1991 RS
Engine: 5.7 TPI 5.0 TBI
Transmission: T-5 , 700R4
Axle/Gears: 2.73 twice
Also just wanted to note, the cam has been removed, cannot find any numbers except on the end 155 WB and 166 95r, its a roller cam, google does not have anything in that area. Any expertise?
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Old Mar 29, 2006 | 10:11 AM
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From: St. Augustine, FL
Car: 89 GTA
Engine: 383
Transmission: 4L80E
Axle/Gears: 12 bolt-3.73
You can use a dial caliper and measure the lobe lift then multiply it by 1.5 to get the total cam lift, then look through the internet to find the comparable gm roller cam.

Assuming you have the usual .025 deck height and will run a .015 head gasket, you should be fine to .625 lift, but measure it yourself to find out for sure.

With my .015 deck height and 58cc chambers with .026 gasket, I still had .100 clearance on both intake and exhaust valves with .604-.608 lift and 230-236 duration.
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Old Mar 29, 2006 | 11:25 PM
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ResurrectingZ's Avatar
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Car: 1987 IROC 1991 RS
Engine: 5.7 TPI 5.0 TBI
Transmission: T-5 , 700R4
Axle/Gears: 2.73 twice
Originally Posted by 89gta383
You can use a dial caliper and measure the lobe lift then multiply it by 1.5 to get the total cam lift, then look through the internet to find the comparable gm roller cam.

Assuming you have the usual .025 deck height and will run a .015 head gasket, you should be fine to .625 lift, but measure it yourself to find out for sure.

With my .015 deck height and 58cc chambers with .026 gasket, I still had .100 clearance on both intake and exhaust valves with .604-.608 lift and 230-236 duration.
I am assuming that you are running the 88j+ D exhaust port heads then, atm looking up the head gasket thickness fel-pro 7733, what cam would best complement this head set, in an educated opinion, getting anxious to send off the hooker super comp shorties to get air tubes chopped off and collector opened up a little more.
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Old Mar 30, 2006 | 08:12 AM
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From: St. Augustine, FL
Car: 89 GTA
Engine: 383
Transmission: 4L80E
Axle/Gears: 12 bolt-3.73
My heads are ported AFR 190's with the D port. I had to send my headers off to get the ports opened up to match, but the problem is trying to trim the fel-pro 1406 header gasket, that material is hard to trim.

I am assuming it is fel-pro 7733pt2? With your .025 in the hole and .039 head gasket you will have no problems with lift.
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Old Mar 30, 2006 | 12:52 PM
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ResurrectingZ's Avatar
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Car: 1987 IROC 1991 RS
Engine: 5.7 TPI 5.0 TBI
Transmission: T-5 , 700R4
Axle/Gears: 2.73 twice
Yea it is the 7733pt2, my headers need to be opened up a bit for the D port, usin 88 vette heads (113) should be interesting. Thanks for the replies.

With the valve reliefs on the piston ~4.6cc (correct me if I am wrong) I should reach my target compression of 10.45, didnt want anything over 10.5.

Last edited by ResurrectingZ; Mar 30, 2006 at 12:56 PM.
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