I’m running the Crane “high-performance” Hydraulic Roller-Lifters with my Comp XFI-292 cam (lift in the .590s at the valve) in my LTX 396 stroker.

The Crane Tech department is telling me to use 1, to 1 ½ turns preload with their high-performance HR lifters. Specifically, their high-performance lifters require that additional preload (different from other HR lifters on the market). And that additional preload will give me the maximum performance and RPM from their HR lifters.

That is a lot of preload, considering the general assumption for performance HR applications is ¼ to one ½ turn preload, or less. However, I’m been having some high RPM issues with my engine (also just installed new PAC-1518s).

So, does everyone agree the Crane’s recommendation for 1 to 1 ½ turns of preload with these HR lifters?

WD

 

It is against what I have always done but I would at least try their recommendation. They did build them.

 

Wow, thats alot of preload. I agree with the above, I mean it is there lifter.

 

Here is the specific information on the Crane lifters.

Long travel design for 87-99 blocks originally equipped with hydraulic roller cam and lifters.

A necessity when camshafts have greater than stock lobe lift or reduced base circle diameter.

For use with standard GM alignment bars. 10535-16a

Again, I want to get some opinions here on the forum before I add a full-turn of preload.

WD

 

I would call back several times and talk to all the different "techs" to see if their opinion varies.

 

I know crane said they gained power by adding more preload to their lifters. On a side not I'm not sure how you expected the 1518's to fix your valvefloat problem since they have the same spring pressure and rate as your old 918's.

 

Thanks, that is the only Crane specific lifter info I’ve heard so far (from anyone).

Also, while the 918s and the PAC-1518s have the same basic specs, the 1518s are supposed to be a much better spring (general consensus from many articles). Also, a lot of the LS guys are using the 1518s. Additionally, PAC tells me they originally made the 918s for Comp and their 1218s are the same as the 918s.

WD

 

I know the 1518 is a far superior spring than the 918, but it has the same spring pressures so it won't do anything for curing valve float unless the 918's started losing pressure. I was under the impression thats why you changed them unless you just did it for peice of mind.

As far as the preload it can't hurt to try it.

 

The 1518 can be installed at 1.750" with your lift. That will give you some more pressure.

 

I've got the new PAC-1518s installed now and the installed heights are around 1.785 on my AFRs. Also, I used new titanium retainers with 10 degree locks.

On the lifter preload issue. I'm going with Crane's recommendation and placing the preload at "one full turn" to see if that improves the high RPM issue. I only need a slight improvement in the 6500+ RPM range (3rd gear as I approach the stripe).

Additionally, I never did get a conclusive post here (one way or the other)on Crane's recommendation for "one to one and a half turns" of preload. Possbily that additional lifter preload will also help the high RPM issue.

WD

 

The only way I see that much preload helping is if their lifter has a softer "push". As for the spring and the valve float there is so much more to it then just seat pressure. The pac's have a much higher rebound rate and allow a wider range of harmonics with out reducing the stability.

 

Sorry by "push" I mean that the firmness of a pumped lifter is softer then most other applications.

 

Rich, thanks for your input! I'm going to do one full-turn of preload this weekend, however, it will be some time in February before the track is open again and I can T-n-T to determine if it helped, or hurt the performance. Also, see if the new PAC-1518s help some.

WD

 

No problem. I seem to get ignored half the time due to my low post count. I am an admin on ls1lt1 and don't moonlight other places often.

 

The thing about 1 turn is if ya float the valves it will pump up and hold the valve open that much further.Possibly getting into a piston.
There will be no performance difference in 1/8 and 1 turn.
Too much spring is way better than not enough.