Tell me about it Rob!! It seems way off, but we measured several times, and I even went ahead and bought the 6.881 rods, and checked it with those. I used your site for rocker arm adjustment proceedures FYI.

I don't think it is right either, but its hard to argue with what my eyes are seeing.

Here is the proceedure (although pretty common sence) I used maybe I am missing something.

I pulled off the rocker, removed the pushrod. I then adjusted my length checker put the rocker on and tightened it down, and turned over the engine. I adjust the length checker until the roller on the rocker tip was as centered as possible. Then got push rods to match that size.

Sorry to hijack your thread OP but I think the information is relevent.

 

When I measured the LS7's againest the stock LT1's there was about 0.100" difference in cup depth. I have 7.050"'s in my engine and I would probably be better off with 7.000"s. I think there may be a lot of people running without measuring assuming there fine when they aren't.

 

What other changes did you make when you went to the LS7 lifters? How did you measure the lifter to get that .1" figure?

 

I also used a different cam, thinner head gasket, different rockers, and the heads were milled. Every combination could be different which is why you should always check your vavle train geometery when you change any valvetrian part.

I used a ball in the cup and measured with a dial caliper, it was roughly 0.1" I did this over a year ago and don't remember the exact figure.

 

I do agree that "fine" may not mean the same thing to everyone. Bottom line, it should be measured.

 

Interesting. If I measured correctly I am having to use a .319 shorter pushrod vs. you having to use a .15 or .2 shorter rod. Im running the very thin .26" Victor Rienz gaskets. Are you running a thicker gasket? Where your heads milled 0.119 to 0.169?

If thats the case then I'm not as worried about the great difference.

 

I'm running the .027 Mr Gasket head gaskets. The difference maybe in the rockers, mine are Crane Aluminum RRs.

 

No cause Im using the GMPP Aluminum RRs which are identical to the Crane Golds. How much did you mill from your heads?

 

So on a stock setup are they fine? Or will I need different pushrods?

I'm debating buying a set for my hotcam swap (was planning on retaining stock pushrods)

 

No they are not. You will need shorter pushrods if you wish to keep proper valvetrain geometry. They are definaely not direct replacement for LT1s, and it would also seem they are even shallower (but not as much) then stock LS1 lifters.

 

As has already been said-measure!

 

If you didn't replace your valvespring with a weak spring before you checked, you are probably allowing the movement of the lifter piston and possibly flex of the adjustable PR (mine flexed noticeably under the load of a regular valvespring) to affect your measurements. Did you take note of either of these things while you turned it over?

 

I was curious about this myself. I did not use a check spring, nor solid lifter, but when I turn the engine over there is not enough pressure to collapse the lifter. There was also no flax in the length checker.

That is very good info though.

 

I'd be careful about thinking you were not collapsing the lifter. It is still somewhat easy to do. My ls7 lifters would collapse under the pressure of the beehive spring used by AI.

 

When I checked mine I used springs that were just barely strong enough to hold the valve closed.