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89FormulaLS2 · Posted: Tue Jun 14, 2005 9:42 am Post subject: P/V clearance question

As some of you may recall, I was going to put an LS1 with heads/cam into my 89 Formula, originally. Waited over a year, then fired the mechanic and took the car to Hawks Third Generation, since they have an established reputation for 3rd gen f-body LS1 swaps. THEN I decided to go with an SDPC LS2 402, instead.

Well, I still have my 91 Camaro RS, and this LS1 engine sitting here. Cool

So I was going through my extra parts yesterday, looking at what I might want to use, and what I could sell.

The mechanic I fired had done a piston/valve clearance check to see if the TR224 cam I bought would give me any problems, because my heads have been milled .055. He said the valve actually hit the piston when he hand-cranked it, and NO WAY would it work.

Well, in going through my things, I just realized something. HE USED THE STOCK SPRINGS. I have a brand new set of Crane dual blue stripes sitting here in the box that I bought with the cam.

Now I'm still something of a newb on a lot of this stuff, but these Crane springs are a full .200" longer than the stockers, and a lot stiffer to boot. I'm thinking that the P/V check needs to be done again, 'cause with the correct springs I might still be fine.

Anyone agree or disagree?

superls1 · Joined: 19 Apr 2005 Posts: 15

I don't think the spring height would impact P-to-V. If any of the following components changed: valve stem length, rocker ratio, pushrod length, or the cam, then I think you would impact how far down the valve is going to go. I am no expert either. Will you springs work with you valves? Wouldn't different installed heights greatly effect seat pressure. i.e. if the spring really is .100 longer, but you install at the same height as older springs, then isn't the spring already being compressed .100 when the valve is completely closed? Seems like you might hit coil bind sooner in this situation as well.

2000BlackHawk · Joined: 06 Jan 2005 Posts: 182

You may not have had a PtoV problem but you probably had a coil bind issue. So what he probably did was just install it then turn the motor over and the spring went into coil bind which he thought was the valve hitting the piston.

89FormulaLS2 · Posted: Tue Jun 14, 2005 8:54 pm Post subject:

On the advice of Thunder Racing, he put a layer of modeling clay on the piston. He showed me where the valve pressed all the way through the clay to actually hit the piston.

I don't know much about coil bind, so I guess I need to look into this a bit more, huh?

We DID use the 7.350" pushrods instead of the stock 7.4" ones.

BigJohn · Vendor Joined: 08 Jan 2004 Posts: 209 Location: Texas

Using the shorter pushrod is not a problem as that is a typical pushrod used with aftermarket cams due to the difference cam characteristics.

Do you know the Crane part #, and are you sure about the .200 difference? Also, are your heads milled .055? What is the CR?

2000BlackHawk · Joined: 06 Jan 2005 Posts: 182

Ah, well if you actually clayed the piston and then went all the way to the piston top you have no clearance. Did you make sure to use a solid lifter and a used gasket?

89FormulaLS2 · Posted: Fri Jun 17, 2005 9:30 pm Post subject: