Inliners International Forums General Discussion Hi Performance Roller lifter for Jimmys

This came from I guy I know on the HAMB:-
For any really serious GMC guys out there, Crower is running off another batch of roller lifters for the 302's. They only make these once in a while so when they are gone, the're gone and you have to wait until they see enough interest to run another batch.

Part number for the lifters should be 66274T989-1. These are groove type lifters, not link type and require modification to the lifter bores to keep them properly oriented. The tool to modify the lifter bores is the drill jig 66575X989-1. Dave & Matt at Crower have been the ones dealing with this so they would be the ones to contact with questions.

I believe the Chevy 235 / 261 takes has the same lifter bore so I can't see a reason these wouldn't work for them too.

Anybody here that's an Inliner member can pass the word on.

John

Can anyone tell me if these lifters are interchangeable b/w Chev and Jimmy sixes?

Price? Also, can a stock cam shaft be ground with a roller profile? I am afraid I am not too up to speed on this conversion.

The .990" OD matches not only the stovebolt but also the Buick L8 IIRC.
However: the GMC doesn't have hydraulic tappets, but the 1958-63 Chevy uses the hydraulic "waist" to transfer oil pressure across the tappets front to rear. If this is missing or in the wrong place, the rockers get no oil.
Grooving the tappet bore works, but it's delicate machining (must be absolutely parallel to the bore, concentric and clocked to within 1°?). I'm not sure the Chevy has the same amount of material in the gallery.
They're also very heavy, which means really big springs (300+ lbs.), I'm not sure the cam drive will like this long-term.
Grinding the original cam to a roller may not work, the stock lobe is very short and "pointy", leaving little room for a new and much more "square" lobe.

A 7 years back I ran a set of the "new" Crowers in Joe Fontanas 12 Port GMC and they had tie bars. Bill Harris helped me get a set last year and they too have tie bars. Some of the rivets needed to be ground to miss the push rods.

My old set needed a bar mounted to the lifter gallery to keep them from turning and I liked that best. You need to spin the pushrod to break the oil suction on a tie bar or you can pull the lifter out and loose the tie bar...been there done that...not good.

I've never seen a "stock" cam be ground for a roller...They were all made from blanks with much fuller lobes...Good Luck

Hi, I'm new over here (to the forum). I just got a 261 I want to rebuild for my '52, have been reading (lurking?) a lot.


Has anyone put roller lifters in an 848 head on a 261?


[edit: I did join just to ask this question]

I'd rather see a fixed bar, rather than an attached link just to save reciprocating weight (those roller are heavy enough!), but there must still be something very definite on the lifter body to be restrained.
The original button or lug could be used, with a fixed plate slotted to allow the lug to travel vertically, but it's got to be pretty strong, absolutely straight/parallel, and hardened against wear. Since it doesn't move, the plate can be attached in several places. The height is obviously the lobe height + safety factor for strength, perhaps 1/4" on either end, so .500" lobe needs a 1" plate minimum, etc. Thickness: same as the lug is probably safe, but stiffer if it's solid behind the slot.
However: I'm not sure where to attach it. There are no flat vertical surfaces inside the pushrod compartment, no available threaded bosses, nothing substantial to tap. A single strap or plate could run the whole length and tie all 12 lifters together, but it's got to bolt somewhere.
If you had the nerve, you could just bolt it into the inside of the pushrod cover. "Hang" it in place on the lugs, its several studs protrude out beyond the gasket edge and through the wall of the modified cover. Slip machined spacers on the studs, put the cover on, put nuts and Stat-O-Seals on the studs.

Has anyone put roller lifters in an 848 head on a 261?

I assume you mean roller lifters in a 261 with an 848 head?
Or roller rockers in an 848 head on a 261?
Which head isn't relevant for a roller cam, and except for minor rocker oil changes any 235 or 261 should be the same for roller tappets.

This is a very, very expensive mod, and won't do anything useful (let alone cost-effective) for a street engine. With all the parts, you're not going to have much left of $1,000.

Clarification: there may be roller-compatible profiles that can be ground on an existing cam, but the result will be much too mild to justify the expense: short duration, limited choice of LSA (just a guess: 4° change maximum), and low lift. It's also got to be a steel cam: all 1937-54 with small journal, 1955 large journal, or any 1956-63 engine using a 1955 cam.

I arranged some of my thoughts on this on a separate page on my site, here: http://victorylibrary.com/mopar/roller-adapt.htm

OK, thanks.

With the stock rocker arms(1.35:1 ratio) it will be impossible to get anywhere near enough lift if you grind a stock cam. There isn't very much lobe to work with when you profile it for a roller lifter.

I had a stock cam ground for my 321" GMC and it had to be ground so the lobe base circle was clear down to the cam barrel. With the 1.85:1 roller rockers I built I got just over 0.600 lift at the valve with flat tappets. I needed that much lift so the engine would be able to use the intake flow at 0.600 lift.

Unless you have deep pockets or access to a "good" machine shop I'd suggest you build a 292.

Ron

I'll chime in again, I'm toying with the idea of not running the tiebars. I can remove the holders and turn around the lifters and use a bar...Actually 2 bars split in the middle. We always used aluminum bar stock about 1/4" thick and 1/2" wide. We "notched" it for each of the push rods and never had a problem. It's mounted on the outside and clears the side plate without problems. They are held down with 2 10-24 machine screws.

I need to look at the Crowers to see if it will work; always did with the Herberts. Still running a flat tappet since I rarely see 6000 RPM. With my home made rockers I have .615" lift on a cam ground from a stock steel GMC. Good Luck

The H-D tappets are guided by slots in the tappet bore, about 1/32" wider than the roller wheel, but that's only possible because the wheel OD (.855") is larger than the body (.731").

Assuming that some used but good (or rebuildable) tappets are available, rather than the "correct" .990" units, the obvious cheap install is to combine bushing down the tappet bores to the roller body OD, and slotting the bushing ID for a locating pin.
A GM .842" tappet leaves .074" of wall thickness. Also saves a few grams.
There may be GM tappets short enough that the original link button would be inside the tappet bore, which allows simply milling the button down to fit a bushing slot, like 1/16" deep by 3/16" wide. What's bad about this is that it uses only a single point of alignment taking all the load, and it's on the thrust axis where bushing wear is highest.