I plan on installing a comp cams 274XE. The lift figures are .487"/.490". I have the cast iron center bolt TPI heads. I will change the valve springs with the comp cams 981's. I'm more concerned with retainer to seal clearance.

While we're on the subject I might as well ask if I will have any valve to piston clearance problems?

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1986 CAMARO Z28 ->
151,000 original miles, 43,000 on 89' vette 350 block, Holley 650 DP, Weiand intake, 1.6 rockers, 1 5/8" headers, no cat, 2 1/2" Flowmaster catback, Mallory coil, March pulleys, B&M Ripper shifter, T5 with 3.35 1st gear and 0 miles, 90% Centerforce clutch, 3.73 posi, Eibach 1" drop springs, Spohn LCA's, Spohn adjustable panhard rod, Subframe connectors, all bushings are urethane, 2 12" Sound Streams, 2 Infinity 6X9's, 2 Pioneer 6X9's, 800 watt Lanzar Vibe amp. ET 13.32@ 106.4MPH 3300lbs less driver and speakers Next mods-> Extreme Energy 268 cam, Holley street dom intake, ported heads.

1987 TRANS AM ->
73,000 miles, 305TPI, auto, gutted air box, gutted cat.

 

Now I am not going to say that that could be a problem running, but if you have a standard
flat top piston (especially with no valve reliefs) you could be get into big problems.

As well you could used a thicker head gasket?
Most builders use a generic head gasket that is 40 thousandth's of an inch. If you experience valve to piston clearence problems you could go to a copper gasket. They are 20 thousandth's of an inch thicker yet.

Your springs I am sure you know can not be too strong or weak. You could use a stock spring but if you hit 4500 RPM - 5000 RPM you would smash that spring together so hard something would break. Probably a spring of about 100 lbs. with an internal dampener would be fabulous. Hopes that helps.

 

To give you a better idea. The engine I have is an 89' vette 350 block with roller cam and 4 bolt main. I think I might be ok with piston to valve, I was going to have the heads milled a bit too.

My friend works at a machine shop and I could have him machine them down so I don't have interferance with the valve guides and retainers.

Anybody else done this kind of cam swap? PLEASE HELP. I only have about 2 weeks.

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1986 CAMARO Z28 ->
151,000 original miles, 43,000 on 89' vette 350 block, Holley 650 DP, Weiand intake, 1.6 rockers, 1 5/8" headers, no cat, 2 1/2" Flowmaster catback, Mallory coil, March pulleys, B&M Ripper shifter, T5 with 3.35 1st gear and 0 miles, 90% Centerforce clutch, 3.73 posi, Eibach 1" drop springs, Spohn LCA's, Spohn adjustable panhard rod, Subframe connectors, all bushings are urethane, 2 12" Sound Streams, 2 Infinity 6X9's, 2 Pioneer 6X9's, 800 watt Lanzar Vibe amp. ET 13.32@ 106.4MPH 3300lbs less driver and speakers Next mods-> Extreme Energy 268 cam, Holley street dom intake, ported heads.

1987 TRANS AM ->
73,000 miles, 305TPI, auto, gutted air box, gutted cat.

 

I'm running .500 lift with flattop pistons. No problems at all.

 

im running a .555 lift cam with 1.6 rockes (total valve lift of .888),.275 dome pistons and .040 copper head gaskets with no valve clearance problems.

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85 IROC 350 11:1keith blacks,.555lift erson roller cam,1.5 crane roller rockers,edelbrock intake,holley 4150 750dbl pumper, nitrous oxide,full length heddman headers,true dual exhaust, 11"stall converter, 700R4, 3.73 locker

 

i check valve to piston clearance without head gasket (.040 usually) and you'd have to have about .650 lift before you start to get to the .100 minumin,(w/flat tops w/valve reliefs) most of the time. the only true way to know about the retainer to guide clearance is to check it for sure. if i were to take a guess i'd say you'll be fine.

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ICON Motorsports

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