Engine and Transmission Tech

Dropped in the cam and lifters today in the 3.5 Rover that is a rebuild and it appears that there is less than desired clearance as listed for the tolerances in the engine specs. What do you do if this is the case? To my understanding it is more usual to have too much clearance and have to shim the rocker stands. My lifters are made by Isky and are an older set, but when comparing them to another lifter from a Buick set the difference of the position of the retaining clip is really noticeable as the Isky ones have the position deeper into the lifter where the Buick set are at about middle the distance which left way too much clearance. If the tolerance isn't in the range desired would that cause extreme chatter when running or not? I was curious if they would possibly relax a bit or not. Thanks~~



Edited 1 time(s). Last edit at 05/11/2010 08:48PM by mabie1978.

How much less, Michelle?

You should have a usable range in the lifters of at least .060" although hitting the "sweet spot" will keep lifter noise down while avoiding high rpm pump up. Clearance is typically lost by milling heads and deck and by grinding valves and seats if the stems are not shortened. Shims can be used under the pedestals but custom length pushrods are a better solution. Accurate and correct measurements are a necessity to determine proper pushrod length.

JB

The smallest gauge we had to use for measuring was a 22 and some of the lifters were close that while others were even tighter. We couldn't find anything to use for measuring beyond the gauge Bernie had so we were figuring it to be less than the 20 needed. I am going to run out to the local machine shop today and see if they can get out a set for the early small block Chevy so I can see what they look like as the couple of Buick ones provide way too much clearance. Do you think new push rods would be a good solution? Right now I am using the original stock shafts and push rods in conjunction with the new set of Isky Lifters.

Adjustable pushrods for solid cams can be made to work,

Michelle and clan. I think what your describing ,lifter clearance, and what your seeking,lifter preload, are one and the same ? Assuming you had heads rebuilt, machine shop,(worth keeping), would have, ground/matched, all of the valve tips/ends, to same height. This way, your much closer to having similar lifter preload, assuming rockers, shafts and push rods have minimal wear. 03" min. preload is usually enough to prevent,"ticking", if your engine has adequate oil pressure.Unless your running excessively high oil pressure or rpm., "pump-up should not be a problem. If valve train is otherwise fine, assuming you, did'nt use a "re-ground" cam, and "still" not enough preload, suggest "carefully" machining bottoms of rocker stands. Remembering that say, .010",(example), removed from stands, will preload lifter approx. .015",(1.5/1 rocker ratio).Good Luck, roverman.



Edited 1 time(s). Last edit at 05/12/2010 02:27PM by roverman.

Thanks for the info Art, it seems to match what we found out today from the machine shop and from Mark at D&D. We did more measuring and it seems about half came out at .020 and the others close to .015. So we are a go for that issue :). I did find however that when we used the Olds block I have for test fitting that pulley alignment on it did not guarantee it would align on the Rover block. Luckily Bernie had another fan pulley that put us back in alignment. So we are moving forward and almost done with the engine itself and then on to the trans/clutch and HTOB. So I am sure I will be back.

Michelle,

.015 is not enough preload and the lifters will not pump up properly, for a 215 engine you need a mimimum of .020 and if it's not going to rev much over 5500 RPM anything up to .060 is acceptable with decent quality lifters.

I prefer to set mine at approx .030 as the engine seems to rum quieter but that may be my imagination.

Kevin.

This just in... .015" not enough? Don't want "custom" push rods or machine the stands? Don't want much ehh ? How bout "lash caps" on the the valve tips, say .03" thick, should get additional pre-load. Just drop-em on, and motor on down the road. Happy Trails, roverman.