Hey everyone. I'm looking for some advice. The motor is a stock LQ9 shortblock. New bearings and rings but factory bore, crank, rods and pistons. I'm using stock 243 heads with this build. So this is basically an iron LS2. I put in a Summit 8707 cam. The specs are:

226 int./238 exh.
0.600 int./0.600 exh.
113 LSA

This is a picture of what happened when I test fit the engine with two welded solid lifters and two test springs.






I guess I need a different cam. What do you guys think?

 

I wouldn't think you'd run into P-V issues with that camshaft.

 

Did you mock this up with the headgasket in place? Something seems off here...did you degree the camshaft?

 

I agree, something is off. You shouldn’t have PTV issues with that cam.

I would check the camshaft position with a degree wheel.

 

I used an old headgasket when I bolted the head down. To be honest I've never used a degree wheel. I just lined it up dot to dot. I thought of one thing but I have very low expectations. I did this test with factory pushrods. I was told that the cam would work fine with factory length pushrods, but that could be wrong. So I'm going to re-do the test with a checker and see what happens.

Also these are junkyard heads. Maybe they have been decked? I'll check that too before sending the cam back.

 

Your “test” pushrods are too long and opening the valves on the base circle. Grind down your pushrods and radius the ends to when you bolt the rockers down it’s not opening the valves.

 

I never thought of that. That sounds way less annoying then trying to use a push rod length checker one valve at a time. I'll try this when I get home. I still have low expectations. It didn't look like the valve was opening at all when I tightened the rocker down on base circle. But I wasn't looking for it either. So I guess I'll find out.

 

It's not as simple as claying the piston and lining up dot to dot to reach TDC and pushing the valves down into the clay.

 

I watched that video. Are you saying that the clay method doesn't work? Seems like a lot of people do it. Most of the tutorials I've seen on using clay show that it is as simple as putting clay on the piston and seeing how far the valve pushes it down. It's not as accurate as using a dial indicator but it seems like it will show you if your going to have an issue or not on a street car anyway.

 

Same basic concept but using clay instead of a dial indicator. Clay ***** onto the pistons, bolt heads and rocker arms down and then turn the engine over by hand so that both valve events occur. Remove the head and carefully cut a section away of each clay ball and measure them.

 

Ok. Sorry I misunderstood you. But yes this is exactly what I did. Later today I'll play around with it and see what I can find out.

 

Easiest way by far to measure P t V clearance right here imo.
Piston to Valve method

 

Ok so I have at least a little figured out. The stock length push rods are in fact too long. So to check this I threw out my welded lifters. Then I took a lifter apart and flipped the internal plunger around backwards. This basically makes a solid lifter. I found a video showing how this works on YouTube. I put my length checker in there with my new solid lifter and set zero lash. My checker says that I need a pushrod that is 7.324" long. The factory rods are 7.380. I did the clay test again with the checker instead of a real pushrod, but so far only on the exhaust side and got .180" PTVC. So my piston to valve clearance is good. But this raises a question. Were these heads decked or do Summit cams require shorter pushrods? I pulled the heads off a truck in a junk yard, so anything is possible. I need to figure this out because with stock heads it would put me at 10.9:1 compression. I don't want to go any higher.

Thanks guys for all the help. I was about to send the cam back to Summit. I never thought the pushrods would be too long.

 

You would need to CC the heads to see of they have been decked.

 

I believe stock un-milled heads should measure 1.625 inches from the surface to the bottom head bolt face.

 

Thank you for this. I just went out and put calipers on the heads. They ranged from 1.618 to 1.625.

 

Ok so something doesn't sound right. I'm completely lost here. So after messing with it for way too long last night this is what I found. If I put in a new set of LS7 lifters and check for pushrod length needed to get to zero lash I get 7.28-7.29 depending on the cylinder. If I set my pushrod length checker to 7.29 total length and remove my LS7 lifter and put in a solid lifter then put clay on the piston I get .140 clearance on the intake and .206 on exhaust. This was done with a lightweight test spring installed.

BUT this doesn't take into account for lifter preload. From my understanding with LS7 lifters I need .75 to .100 preload. So 7.29 + .100 = 7.39. 7.39 is a factory length push rod. If I put a factory length push rod in with the clay both valves just barley touch the piston. So do you take lifter preload into account when measuring PTVC? It seems to me like you would have to.

Also just to clarify I checked the zero lash measurement with both the LS7 lifter and my solid lifter. They both came out the same 7.29. All testing was done with an old clean head gasket. Also I tried taking a lifter apart and flipping the plunger around to make a solid lifter. It seemed to have a lot of play. So I went back to using a welded lifter. The end lash for the welded lifter was the exact same as the new LS7 lifter.

I feel like I'm doing something wrong. Every person on the internet on two different forums are telling me that this cam should be fine. But I'm not seeing it. What am I doing wrong?

 

You are over thinking this. With your solid lifters, set your pushrod to zero lash. The length of that pushrod doesn’t matter. Whatever it takes to get to zero lash. Check your p2v clearance and that’s what you have.

 

I guess what I'm trying to understand is if I do that and then account for lifter preload wouldn't the valve hit the piston?

 

Nope. The added length of the pr is accounted for in the lifter cup being pushed into the lifter bore by that preload dimension.