Does any one know what the recommended lifter preload should be? I have milled the heads and put on steel shim headgaskets so the pushrods are REALLY long. I have one adjustable pushrod so I measured the length at zero preload and got 8.550" The shortest pushrods I have are 8.670" I KNOW those won't work but what should I look for as far as length? Thanks
Proper lifter preload
- Thread starter fuzzyGN
- Start date
turbofabricator
Well-Known Member
- Joined
- Mar 7, 2004
Contact Smith Bros. in Oregon, and order up a set of adjustable push rods for your engine. I just ordered a set for a roller cam. They ship them out the next day. (usually)
- Joined
- May 26, 2001
This is for a car I just sold so I don't want to spend a ton on "fixing" this. I did find some shorter push rods and was able to get them to about .070" preload. The car sounds much better and idles better too. I told the kid to live with it for a while and see what it is like. Thanks for the help.
Just a Six??
OK! Who Farted??
- Joined
- Jul 4, 2003
Wouldnt 70 preload be close to bottoming out? If you dont want to spend the $100 then at least get the kid who just got the car from you to do it!
stock GN 231 GM lifters bottom out at about .190------but they are not designed to run anywhere close to that kind of range.....RC
.030-.040"
this thread got me motivated to do something that i have been wanting to do for years but just couldn't seem to find the time---------to date i have probably built nearly 40 turbo engines over a period of 15 years-------lifter preload is never mentioned in any GM literature (at least none that i can find) and I have always done things according to what others experienced builders have suggested---------for numerous engines i have used the range of .030 to .040 and it has always seemed to work fine--------but i have always wondered what GM did originally in our engines-------today i took one of the brand new crate long blocks that i have and checked the lifter preload-------it was a 0 mile engine assembled in oct 86-------very surprising results---------i checked one bank only-------driver side-----here is what i found---------pushrod lenghts were 8.677, 8.676, 8.672, 8.674, 8.671, 8.672 respectively------- i have normally considered that the median length of turbo pushrods to be 8.680 based on previous measurements of numerous engines-------i have removed them from used stock engines a long as 8.684--------i only checked the preload of lifters 1 3 4 & 5 since lifters 2 & 6 were sitting on the high side of a cam lobe and i didn't want to rotate a brand new 20 year old engine without doing some lubrication prep---------preload was .096, .078, .079, .093----------quite a surprise------a lot more than I expected but it appears that is how they were set up when new-------when I get another chance I intend to check a couple more engines to see what the overall variation is----------i also checked the plunger movement range in the lifter-------.196---------seems that GM chose to set preload just about midrange of the plunger travel--------that would allow for the greatest service life due to part wear since some wear surfaces increase preload and others decrease it........................RC
Now that....
Is very informative. Think I'll measure the one's I have out now.:smile:
Is very informative.
Think I'll measure the one's I have out now.:smile:What tool is it that you use too measure the length of the push rod with and where can you get one, just popped a headgasket and would like to do this since I have a set minus 1 of adj. push rods, I had a complete set and some one on this site needed one a few years back to borrow and never sent it back, even after numerous e-mails, so know I have 11, so I thought that I would measure each one and have Smith bros. or Nick and Mike make them
indidvidually for me, Nick can you do this for me?? Or does some one have the tool that I can borrow and I promise to send it back and not be like the person that borrowed 1 adj. and never sent it back, that just infuriates me when you try to help some one and the treat you like that, I might even dig his name up and post it here, I'm getting mad just thinking about it, ERRRR.
Ron
indidvidually for me, Nick can you do this for me?? Or does some one have the tool that I can borrow and I promise to send it back and not be like the person that borrowed 1 adj. and never sent it back, that just infuriates me when you try to help some one and the treat you like that, I might even dig his name up and post it here, I'm getting mad just thinking about it, ERRRR.
Ron
i've done lots of engines with preload in that range (with GM 5234485 lifters) and they have seemed to worked fine--------different lifter brands could make a difference--------and the engine would obviously be less tolerant to changes due to valve train wear compared to a stock engine but these days that is probably a non issue since most of us don't put thousands of miles a year on these cars like when they were new-----------i know a lot of lifters have different plunger ranges even though they are specified for the turbo engine and are considered correct replacements----------if you really want to borrow a length checker i could consider loaning mine to you---------it is custom built and quite superior to any i have ever seen for sale------i have an out of car checker and one for checking in the engine----------the one for the engine check iss a modified Starrett inside micrometer that has actual pushrod ends on it--------the out of car one is a special outside digital micrometer with actual lifter plungers on each end-------measures to 4 decimal places----------as for different length rods heres some useful info---------years ago i purchased every pushrod that TRW sells in the Advance Auto and Autozone catalogues for every kind of pushrod engine--------nearly 50 different pushrods------i then checked to see if they were compatible with our engines (oil feed hole, rod dia, correct ends etc) and organized them in order of length if all was ok--------these are always easy to find since these stores are everywhere--------heres the data-----nominal GM length 8.680---------TRW # RP-3252 is .066 shorter---------RP-3185 is .030 shorter--------RP-3164 is .005 longer (can be considered stock length for all practical purposes)--------RP-3213R is .010 longer--------RP-316435 is .033 longer--------RP-316460 is .062 longer---------RP-3102 is .089 longer-----------RP-3245 is .195 longer----------RP-3211 is .286 longer------------in building dozens of engines over the years i have never not been able to find what i needed in this assortment and most of them only cost a couple bucks except for 3213R and 3102 which are $9 and $5 respectively----------also note----------these numbers are the actual lengths of the rods and the numbers do not always agree with the lengths stated in the catalogue-----don't know why????....................RC
Any of you guys ever layed a straight edge across a OEM set of heads and seen the variance in valve stem heights?
i've worked on a few engines like you describe for guys that have come to my shop and have actually had to select different length rods for some locations to maintain preload within a tolerable range--------some head shops really do crummy work and don't seem to consider this at all--------its not just the lifter preload that is affected by this--------think about the spring variations caused by different valve heights not to mention different moving masses between valves-------go figure---------one thing i can say---------the new oem heads were straight as an arrow-----------and so are any quality heads and/or valve job.............RC
WOW, great info. The heads were fresh and the guy that does them is completely anal about valve stem heights so are all within a thou or two of each other. It sounds like the .070 would be OK. Again it could leave a little power on the table but this is a high school kid and I already hear him ripping up and down the street. Flowmasters on a V6 have a very distinctive sound. I don't really think he needs more power right now. I have saved and printed the pushrod lengths for future reference. Thanks for doing all that work. Great thread!