My bud with the screwed up lifter update. Turns out I/We were right, the new Comp cam was toast. I must say that Jegs is being very good about it, and is covering the cam kit and some labor, even though I still think it was installed wrong. Now he's going nutz with aluminum heads and a full Lunati roller set up. Q. the front boss on the block shows old damage from the cam gear wearing away about a 3/32's groove around the cam hole. I say previous because the cam bearing is mounted properly and sticks out the same distance, from a previous rebuild. I know it can be built up, but that would mean a complete strip down. I can't see that this would cause a problem if the gears and chain, and everything is new. Does the cam try to screw itself in or out in a big block? In, then it will ruin the cam bearing in short order, out then he could use those teflon buttons inside the cover. What do you think????

 

the cam goes in when running( with the dizzy installed)....if there is damage on the block thrust face where the gear rides, i would fix it...if you run a button be sure there is around .010 clearance from the front cover....a lot of builders run a torrington at the rear of the gear which should be done on a gear drive but i never do with a chain set up and a button on rollers..he should speak with lunati and see what they require for the cam warranty....jmo robbie.....

 

You need to fix the grooved area. You're talking about at least .090-.100" wear. That wear surface is what positions the cam properly with respect to the lifters and the cam lobes. A flat tappet is naturally pulled back into the block because the lifters actually ride off center on the lobe. This is what makes the lifters spin and cuts wear. The bad lobe could have been caused because the lifters weren't spinning properly and the cam was moving around.

I've seen more than one motor wasted because of this. It does not get better and the metal ends up wiping out the bearings, scuffing the walls and pistons etc.

There are gears that include a torrington bearing but you need to have block correct first. There are repair plates available but again the surface needs to be machined to correct depth. I saw one last year where someone tried to stuff the repair gear setup in there with a cam button to hold it all in place. Totally trashed the engine with all the metal flying around in there.

I'm sad to say it but there is only one way to fix this right.

You *might* be able to do something with a Gen VI style cam with the stepped nose and the retainer plate with the 2 bolts if your block has the provisions.


For reference...for motors that aren'd this damaged yet, drilling this hole in the thrust face provides pressurized oil directly to the cam thrust area and eliminates the problem. This is on my 540 after 10+ years of running (and I like LOTS of oil pressure). You can still see the factory machine marks. My 30 year old 427 looks just as nice.

JIM

 

Wow, Jim where you have an out-ie, this one has an in-ie. I have a question and a favor to ask you. First how deep and what diameter bit for the hole, and it is at 12 o'clock right? Second can you tell me how far does that surface stick out from the surrounding surface of the block? thanks.

 

Looks like 6 o'clock to me---That block is upside down !!! The hole is drilled into the oil feed passageway for the front cam bearing.

 

Thanks Ron, figured that out after I posted. I remembered looking at the cam oiling hole today on the bottom, and for a second wondered what oil galley runs at the top.....? None! Doh.

 

Sorry I'm late....but you guys figured it out. That is a Merlin block but should be awful similar. Some GM blocks have a larger surface with two bolt holes to hold retainer plates. Even older ones.

The size of the hole isn't critical. 1/16-1/8" is fine. It doesn't lose much oil pressure since gear is up against it. You drill all the way through into the oil passage. But this is to be done while the motor is apart. Otherwise you'll have metal shavings going right to the crank when it starts.

Those cam bearings in that picture are 10 years old also even with near 800" roller cams and the springs to go along with it.

JIM

 

Jim, if you're running solid rollers, how do you keep them from failing, or do you just throw them away periodically.

I would have gone solid roller with my 427, but I hear way too many horror stories.

 

We're going to run a gen6 cam and a retainer plate across the front for the gear to run against, since the block has the mount holes for it. Anybody know the GM part# for it. Thanks to Frank (midyear) and Bob Profitt at Performance Research in Columbus, and Les at Jegs for the help. Saved a complete teardown.

 

Thanks to JIM as well. TTT

 

I just keep an eye on them. First you make sure you get the type with pressurized oiling to them. Comp, Lunati, Isky....most have them. Makes a big difference.

You can also step up to the Isky EZX style with no needles and just bushings. Costs more....but *if* something happens they don't spread needles and junk through your motor.

I just completed a 2500 mile road trip with a .774 lift cam (serious springs!) with a set of Lunati lifters (made by Morel..some of the best out there by far). I've since put about 400 hundred additional miles on them on the street and the valves haven't moved in adjustment a bit.

Depending on how much I drive it each year...I usually pull them and rebuild them every couple of years. I've been primarily using Comps until this last set. They are relatively inexpensive and they can rebuild them for a lot less than replacement.

The biggest trick is to never ignore a loose valve. Many people hear one start ticking and think * Oh..I must have mis-adjusted it last time I set them*. WRONG! If you had...it would have been noisy as soon as you cranked it. If one is looser than the others something is wearing. Cam, lifter, pushrod, rocker, valve....something. If you check it quickly and fix it you can 99% of the time catch it before serious damage is done to the cam. When I say quickly...I mean don't drive it the last 40 miles home. Check it then before going further.


Solid rollers are great..but they ARE a wear item. Just like anything else....the more aggressive the parts the more it wears. Many folks get many many miles on solid rollers with milder street roller type cams. The horror stories are form folks like me that like to run around with .800" or more on the street! We just have to be more careful!

Look into the tight lash street roller type lobes....they do pretty well. My current/favorite cam in my motor is over 10 years old! It's no baby...but it's not *crazy* and is very easy on parts despite the big lift.

JIM

 

I agree with Jim. I run solid rollers in both my cars. The blown, injected 532 has Crower Severe duty lifters in it, but are not HIPPO lifters, as I built the engine before they were popular way back when. The 395 Dart uses Crower Severe Duty HIPPO lifters.

The 532 has mild springs and the 395 has rather heavy springs. I use the same policy with both engines:

Avoid idling. Avoid idling. Avoid idling.
Never cruise below 2000 rpm. Yes, I have an overdrive that can do 75 at 1200.