[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

[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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[Singleton]

Originally Posted by shermanator2

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.

My point in bringing this up is that we should not be considering the lobe lift when determining if the oil band or oil hole relief notch come out of the top of the lifter bore. All proper cams should be the same and essentially the oil band should be inside the lifter bore when the roller is at the radius of the cam journal.

Thanks for posting this information. I must say, after reading this I was a little skeptical. So I measured an old 066 cam I had laying around. Placed a straight edge across the cam bearing journals, and the nose of the lobes were almost exactly the same height as the journals, (I could slip-in a .010 feeler gauge).

[tempest1964]

Pictures really do say a thousand words.

[68hotbird]

As some of you know the sealed power 2148 lifter causes the dog bones to rise up slightly at max lift which is not supposed to happen. Over time this could cause a failure of the spyder and could cause some small metal filings in your engine. I have attached a couple of pictures of how I machined the dogbones to get clearance. I took .035 off of the flat and that gave me good clearance at max lift. The dog bones are hardened I had to cut them on a mill with a 4 flute carbide cutter but not hard to do at all. Just wanted to share this modification in case anyone else needed the info.

[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.

[RH68]

So what would happen if the oil hole came slightly above the top of the lifter bore? I have a spare block and went out and bought one of these lifters to check. One of my lifter bores is chamfered. If the lobe is almost the same OD as the cam journal, it looks like the machined relief around the oil hole will be just above the chamfer by a few thousandths. Would this even matter? Seems like there will be oil leaking past the body of the lifter anyway due to the running clearance, so if a bit more leaked out through the relief would it matter?

I also took the lifter apart. The hole is drilled on about a 60 degree angle. If there was a way to plug the existing hole, a new hole could be drilled on a steeper angle which would move the hole further down towards the roller tip.

[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.

[P@blo]

Originally Posted by 68hotbird

As some of you know the sealed power 2148 lifter causes the dog bones to rise up slightly at max lift which is not supposed to happen. Over time this could cause a failure of the spyder and could cause some small metal filings in your engine. I have attached a couple of pictures of how I machined the dogbones to get clearance. I took .035 off of the flat and that gave me good clearance at max lift. The dog bones are hardened I had to cut them on a mill with a 4 flute carbide cutter but not hard to do at all. Just wanted to share this modification in case anyone else needed the info.

Great information thanks for posting. Looking at your modifications I noticed your dog bones are not the same ones shown in the video or on Summit Racing website. The dog bones on the Comp Cams 31-1000 Ferd kit has a taper to it starting from the leading edge.

Also, the video stated the modification would only require a belt sander to clearance the backside. Are the dog bones you used and ones offered by the Pontiac vendor the same as mentioned in the video?

[68hotbird]

They are the ford comp 31-1000 . They use a generic picture in the add. Ive bought 6 sets and none of them are tapered.

[P@blo]

Originally Posted by 68hotbird

They are the ford comp 31-1000 . They use a generic picture in the add. Ive bought 6 sets and none of them are tapered.

You are correct hotburd. There is no taper to the dog bones in the comp cams 31-1000 kit.

My curiosity has got me now so hopefully I'm on the right track. You previously established the highest point on the lobe is consistent across all cams. The problem is only with the small base circle cams so what is exactly going on because the lifter is not any higher in the liter bore on the larger base circle cams?

Looking at the 31-1000 dog bones and the pictures of your modifications appear to create more clearance for the lifter to travel higher in the bore but small base circle cams drop lower. The comments on the youtube video reccomend the comp XR88HR with the 1.65:1 rockers no carbide cutter modification necessary.

"Jim was saying that the max lift he’s personally used on one is .580” but others work the mod have claimed “.630” without issues.

So far the consensus is the oiling is improved I’ve the stock/retrofit lifters. I’d imagine you can monkey with the base circle for better or more consistent results. "

Seems the stock dog bone particle lobe lift limit is ~0.380 or so. Thanks again for your posts and passing your information along and look forward to learning more about this mod.

[JC455]

Hi all!
I just finished my latest video- Like the title says, it’s about retrofitting GM roller lifters into a Pontiac V8!
Check it out- see what you think.
If you like it, please give it a Thumbs Up... and subscribe!

https://youtu.be/50I58n4vD8U

[P@blo]

Great video JC thanks for taking the time to post. I posted a link to my thread about the better quality snap-rings you mentioned for reference. Hopefully you plan to do a video about the whole process.

http://forums.maxperformanceinc.com/...47#post2602747

Also, the original youtube video stated the comp XR88HR has the correct base circle and have many guys running them with the 1.65:1 rockers. Other larger cams may require additional dog bone modifications. The Comp Cams instructions state:

"Final Check Spin the engine over by hand at the crankshaft with a wrench and watch closely to movement of the lifters. As the lifters move up and down, the lifter guides should remain perfectly flat on the tops of the lifter bores. They should not be moved at all. If they do, the camshaft does not have the correct base circle size to be used with these retro-fit lifters in non-hydraulic roller cam engines. Stop here and replace the camshaft with the proper one before proceeding. Running the engine with this condition will surely result in major engine damage."

[JC455]

Thanks P@blo! I’ve been gathering info for the proper dimensions of the snap rings— that sure helps!
Also, glad you liked the video!

[JC455]

I was curious about the “remaining flat” part, so I did a little checking.
The Ford Windsor small block has some large, beefy lifter bosses that are flat on top.
The retainer sits on this lifter boss pad and is held by the spider.
Here’s a video of modding an aftermarket Ford block due to retainer issues:
https://youtu.be/OBsWxi54XIY

Since we are retrofitting stuff that was never intended for our engines, we just have to do our best not to over-stress the parts.
I think we’ll be okay ��

[JLMounce]

Great vid! Definitely helps illustrate some of the pitfalls here.

So the only thing that could possibly still be an issue is the height of the non-machined section of the lifter. It appears to be coming out of the lifter bore high enough to push on the dog bone. I believe that is why the other member here pointed out that he's notching the dog bones, to avoid that happening.

That said, considering the construction of the dog bone and have a ball and socket connection to the spider, I'm almost wondering if it's meant to pivot?

[Singleton]

Nice video. I guess I have the same question as JLMounce above about the dog bone and the lifter flats.
Also, at the 6:33 mark of the video I believe you might have misspoke about the base circle being larger for more cam lift. Smaller base circle would be more lift if lobe noses are the same height, right?