[68WarDog]

For guys racing before the 90s(?) lifter bore brace, how were you addressing lifter bore destruction running high spring pressures (>600 open) with solid roller cams lobes( > .200@ .020).

[PAUL K]

We made lifter bore braces. Some folks (Butlers) shaped a piece of metal that would support the bottom of the bores and welded them in.

[racegto65]

Never ran one. Still don't. .750" lift and 300-pound springs.

[68WarDog]

Originally Posted by racegto65

Never ran one. Still don't. .750" lift and 300-pound springs.

Is that seat or open pressure? Serious solid roller race cams are 600 open.

[Elarson]

The issue is more related to an aggressive opening ramp; which creates a lot of side load on the lifter. Once you're farther open and the load is more vertical, it's not a problem.

When we first ran the Grocery Getter in the mid 90's, we used 455 stock blocks without lifter bore braces. We talked to Butler and got advice on what opening rate limit to adhere to. (nope...I don't remember what that was....). We ran roller cams with typical high spring loads and never broke a lifter bore.

Hope this helps...

Eric

[PAUL K]

I don't think the cause for broken lifter bores can be blamed on lobe aggressiveness alone. IMO the main reason is probably casting quality or uncontrolled valve train, then I'd consider lobe aggressiveness. I've talked with several Super Stock racers whom have always run the more aggressive lobes (that are supposed to break lifter bores) and most of them have never had an issue, even though they didn't use bore braces. One thing they all agreed on is, if the lifter bore broke it was almost always during the burn out..... Fwiw

I've seen a lot of mid to late 60's lifter bores that look weak. They have very little material on the open side of the lifter bore.

I posted a picture from a 70 400 block that has a lot of core shift and a 69 428 block that has a military grade lifter bores.

To answer for RaceGTO I'm sure he is referring to 300 lbs. seat pressire.

Also keep in mind folks have broke lifter bores while using braces.

[Sirrotica]

Just put in my 2 cents, in 1970 I worked at a Pontiac dealer. In their pile of warranty parts there was a RA IV engine , with a broken lifter bore. Now this car was running as Pontiac hydraulic cam that came in the engine.

Was it abused? More than likely, people that bought a GTO in that time frame with a RA IV engine didn't buy it to drive to the grocery store, and to church on Sundays.

I looked at the block, and the piece that broke off of it to see if there was any way I could piece it back together. There didn't look as though it was a faulty casting, that caused the break, it just let go.

BTW, the factory rep made sure no one could use that engine, by having an employee hit the side of the block with a sledge hammer. That's what they did back then to make sure it could never be resurrected, and be used again. Tough to be a 17 YO Pontiac fan, and see a RA IV block further rendered useless scrap metal....

I attended a Vo Tech in my last 2 years of high school, and we had an awesome welding instructor, that I had visions of him being able to "fix that block" with his awesome skill set. That dream never happened.....LOL

That block was the only block in my long automotive career that I actually saw with a broken Pontiac lifter bore. I also have run solid roller cams without a lifter brace, but have been lucky, and never broken a block either. Also never used 600 lb springs, my cams had rev kits with them.

[racegto65]

Originally Posted by 68WarDog

Is that seat or open pressure? Serious solid roller race cams are 600 open.

.300 seat