[rohrt]

I think this is the Delphi (ls1) compared to the Seal power (ls7). I found this discussion here.

https://ls1tech.com/forums/generatio...-length-2.html

[JLMounce]

It's my understanding that there were at least 2 variants of the "LS7" lifter. That engine's design parameters with it's offset rocker arms and higher operating rpms, would likely necessitate a different lifter design than your standard truck based LS.

The LS7 engines have known valvetrain issues, so it's not a surprise that there's likely different parts depending on year and revision.

I don't believe that anyone should spec LS7 specific lifters for this application. The HT2148's seem to cross reference to the 4.3 v6, 4.8 and 5.3 v8 LS engines specifically.

[Will]

Originally Posted by JLMounce

...

I don't believe that anyone should spec LS7 specific lifters for this application. The HT2148's seem to cross reference to the 4.3 v6, 4.8 and 5.3 v8 LS engines specifically.

Which brings up concerns of durability/usefulness in a high performance application. One of the reasons to go with an OE lifter is supposedly higher quality, but if GM didn't design these lifters with high lifts and high spring pressures in mind, then they may not be all that great after all.

[JLMounce]

Originally Posted by Will

Which brings up concerns of durability/usefulness in a high performance application. One of the reasons to go with an OE lifter is supposedly higher quality, but if GM didn't design these lifters with high lifts and high spring pressures in mind, then they may not be all that great after all.

Actually, if you look at the uses involved and the operating conditions you see those engines operating in, it’s not that different than what you see for a typical street Pontiac.

[Will]

Thanks VERY much for your input! I for one really appreciate it.

The talk in other circles that gets me concerned is everyone is talking about LS7 lifters, but it doesn't look like those will work.

My biggest concern is how well these lifters will work with aggressive cams. In larger engines, cams with 240+ duration and .377" lobes are just a starting point. Something like the "Road Paver" from SD Performance (246/252 dur @ .050" lift .608"/.608" lift with 1.52 ratio rockers) would seem to be too big. It would be a shame to have to use a heavier lifter in a higher RPM application.

[rohrt]

I know Buttler recommends the Johnson short travel and they are around $600 last I looked but currently not available. I have my motor out and really need to make a choice on roller lifters.
Seems they all have 1 of 4 issues.
1. Oil band in wrong spot that leads to...
2. Lifter not pumping up
3. breakage of roller or link
4. Improper bleed down rate
Then throw on top the fact that not all cams are ground the same. Some have a reduced base circle grind in order to increase the lift.
For every person that has claimed they put 1000s of miles on their brand of roller lifter there is one who has had catastrophic failure. I doesn't help that your never dealing with the same setup when it comes to lift or spring ratings.
I'm tending to lean in the direction of the LS7 lifters. The lifter weight, the GM tolerance they must adhere to and the cost are really compelling. However If the johnson short travel lifter is indeed the best I would go that direction without question, but how would you prove it?

[JLMounce]

What I don't understand about the lobe lift situation, is how the issue is showing regardless? The nose of the cam should not be any higher than the cam bearings. Increased lobe lift typically occurs by reducing the base circle. Compared to a stock camshaft, you would actually expect the opposite to be happening, with the oil band coming out of the bottom of the lifter bore, not the top.

Is it that some camshafts are doing a combination of both? Where a factory cam the nose is bellow the bearing enough that if gives room to increase it's height?

[shermanator2]

As I said in the one of the other threads on this same subject, any optimally designed cam will have the nose of the cam at the same height (radius from cam shaft centerline) regardless of lobe lift. The difference between a high lift cam and a low lift cam will be in the radius of the base circle, not the radius of the nose. The nose radius should be just less than the radius of the cam bearing journals (just allowing the cam to be installed down the tunnel). Sure, you can design a cam with a smaller base circle and smaller nose radius, but in doing so you are either increasing side loading on the lifter or reducing the ramp rate, or both. I want neither of these in a cam that I use.

As JLMounce points out, with higher lifts we should be concerned with the oil band coming out the bottom, not the top. And 68hotbird, I appreciate all of the great information that you have been providing, but if you show me a cam with a nose that is significantly lower that the journal, I will call it a substandard cam.

Just for fun, I happened to have a Melling SPC-7 (068) on my bench. I measured the nose radius and found it to be 0.020" less than the journal radius. I am guessing that is typical with production tolerances.

[P@blo]

This topic is new to me but after reading up on it some things are starting to sink in. So based on journal size as lift increases the base circle radius becomes smaller. Either way I would be going in the right direction using a smaller lift cam on the same journal.

For educational purposes, are all higher lift cams on the same journal considered small base circle cams?

Secondly, is the cut-off point where there is so little surface area (higher loading) due such to a small base circle radii (high lift lobe) that a larger journal cam becomes necessary?

I still might be loose on a couple of the details but the way I read it the theoretical base circle diameter is reduced by the greater lobe lift desired which leaves us with the practice or actual reduced base circle radii. So a lobe with no lift, or perfectly round, would have the same theoretical and actual base circles thus making it round.

Sorry for my brain guys lol

[Singleton]

Originally Posted by shermanator2

As I said in the one of the other threads on this same subject, any optimally designed cam will have the nose of the cam at the same height (radius from cam shaft centerline) regardless of lobe lift. The difference between a high lift cam and a low lift cam will be in the radius of the base circle, not the radius of the nose. The nose radius should be just less than the radius of the cam bearing journals (just allowing the cam to be installed down the tunnel).

Here’s a pic illustrating what you’re describing. An Spc-4 cam (066 factory cam). A straight edge placed on the bearing journals, I can get a .010-.012 feeler gauge between the nose of lobe and the straight edge.

[Murf]

This is a great thread with lots of good input. I had never thought of lifter base circle question.
So I went out & did some checking. I hope this will help more than it hurts.

This is a comparison of the SP lifter to the old style Comp lifters.

Doesn’t look like uncovering the band at the bottom will be a problem.

Next I took a couple pics of the top. These are the cam specs.



The second pic has .040 feeler gauges between lobe & lifter.

The first pic has .060 worth of gauges and you can just see the oil hole starting to show.

Edited because the pics flopped on loading.
Hope this helps!
Murf




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[Murf]

Wouldn’t let me post in original post. This is just to give an idea of what the lifter bore looks like.



Murf


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[Scarebird]

Good luck drilling a hole in a lifter.

[RH68]

Originally Posted by Scarebird

Good luck drilling a hole in a lifter.

Carbide. I know the lifters are hardened.

[NeighborsComplaint]

I assume exposing the oil hole results in oil pressure losses and lifter collapse in addition to potential for the lifter to rock in the bore and potentially crack the block. With worn lifter bores, you would bush them, so why couldn't you just extend the bushing high enough above the casting to eliminate the possibility of exposing the oil hole? Even if the cost of this additional machining made the LS lifter swap a $ wash compared to retrofit lifters, you would still gain the reliability of an OEM spec lifter.

[boardog]

this is the you tube video
https://youtu.be/fAKTh3uWBrE

[Pete D]

It is interesting to use a comp cams Ford kit to put Chevy lifters in a Pontiac.

[shermanator2]

Look at these two screen shots that I grabbed from that video. It looks to me like the round main lifter body is coming out far enough to lift the dog bones. It also looks like the spider is contacting the lifters. I have no experience with dog bones like these, but are they upside down?

[242177P]

Originally Posted by shermanator2

I have no experience with dog bones like these, but are they upside down?

I was surprised to learn the flat side IS the top....



Thinking about how the ends are tapered leads me to suspect they're actually
supposed to teeter totter at times??

[tom s]

I have a 301 stroker engine going together right now.I asked the builder to order a pair is sealpower lifters to see how they would work in the 301 block,oil holes are diff from reg std deck blocks.Tom