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Old 12-04-2010, 12:09 PM
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Cam Degree with heads off

I picked up a short block 383. Last night I got a set of heads 3973487. The block was decked and the guy last night told me the heads were also decked. Its clear, if the heads were done it was a while ago. There are brand new 2.08/1.60 SI Portflow S/S valves (+100) and springs installed. I just got a Summit G1056 Degree kit off Craigslist. I printed off the instructions but they are for if the heads are installed. I want to check the valve to piston clearance with the heads off so I dont screw anything up. Does anyone know how with that kit? Also if anyone is in Temecula and wants to teach me how to use it properly, come on over!

I have a Scat crank, not sure what pistons, Comp Cams roller rockers, LSM cam, Team G manifold and a Holley 750 to top off this build.

I also have Jegs 1.6 rollers to install on the heads. The heads have pressed in studs (with a tack weld), and no guide plates. Do I need guide plates or anyhting wlse to run these rockers?

Possibly a dumber question, but when I read the articles of these guys swapping heads and manifolds for Dyno runs, are they putting on new gaskets every time? I assume they get torqued down each time, so I think they would get a different reading ( P2V clearance) each time.

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Old 12-04-2010, 01:24 PM
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There is no way to check valve to piston clearance with the heads off, there are just a couple ways to do it.

One is to put clay in the valve reliefs, place the head on the block with the gasket, install 2 or 3 head bolts just lightly snug around the cylinder you are checking(you don't want to crush the gasket at this time). Set up the valvetrain in that cylinder - lifter, pushrod, rocker, and adjust it to zero lash(if you have a hydraulic cam you will have to bottom out the plunger or use a single solid lifter for this check). Roll the engine over through a complete cam cycle(2 crank revolutions) CAREFULLY, you want to be able to feel if there is NO piston to valve clearance and the valve has hit the piston so you don't bend anything. If it rolls through without incident - remove the valvetrain and the head and measure the thickness of the clay where the valve has impressed into it. Slice the impression in several places with a razor blade so you can see how close the valve edge is to the eyebrow in the piston.

Second method is to set the head up with two light checking springs on one cylinders valves, install head (lightly again as above) with one cylinders valvetrain, then set up a dial indicator to read off the valvespring retainer and then check clearance at about 3-5 intervals 20 either side of TDC overlap, using the indicator to check actual clearance at each point by pushing the valve down be hand until it touches the piston(no clay this time).

Tack welded studs is a problem, they WILL fail, that was done by a hack mechanic I'm sorry to say. You'll need to have them cut off, drilled out, and then the bosses milled for screw-in studs and guideplates.

Gaskets get replaced any time they are run and then removed, unless they are a reusable type like solid copper or MLS. Gasket crush will only vary by .001-.002" at the most, not enough to change anything, they are very consistent. to change piston to valve clearance you would have to change the style of gasket to a thicker or thinner version, and still you are only looking at .010-.015" in almost all cases.
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Old 12-04-2010, 01:44 PM
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Just curious, how do I know what length pushrods to get? I have the tool, but again wasn't sure about the whole torqued down thing.

If I get the rocker studs pulled and drilled/tapped, when I put in screw-in studs, should I get guideplates?
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Old 12-04-2010, 02:00 PM
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Rocker tip sweep across the valve tip will determine pushrod length. Set up the valvetrain on one cylinder using light checking springs, take a black marker and color the tip of the valve so the roller wheel will leave a track mark, then cycle the valvetrain through a couple rotations. You want to set pushrod length for the smallest pattern on the valve tip.

I would have guideplates installed when the studs are done.
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Old 12-04-2010, 02:16 PM
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Here's the tutorial from CompCams concerning pushrod length....
http://www.compcams.com/Products/CC-'Pushrods'-0.aspx

I can't seem to get this to work as a link, so copy and paste it into the address bar....
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Old 12-04-2010, 03:50 PM
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Awesome. I can't get the pushrod tool into the spot to measure the distance. I have some that say 8.400 3006 that came with the motor. They barely fit in the hole in the head but are way too long.
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Old 12-04-2010, 04:55 PM
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8.400" will be too long for any 23 head on a standard deck height SBC. Will usually be somewhere between 7.800"(stock length) and 8.100" depending on lifters cup position in the lifter body and length of valvestem(std, +.100" or +.200").
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