Question for the pros

[Gelcoater]

Been reading a little and im kinda bored so I figure I'll throw this out there.

Whats the deal with lifter bores? Im talking older 60s-80s engines. GM seems to all be a .875 while Chryslers are .904, small or big block,Ford....well i dont care:D but i want to say smallish.

The Mopar fans claim greater valve train stability from a larger lifter,and the ability to run a cam with a bit more velocity of open/close event, to the point that some cam mfgs make Mopar specific cams to take advantage of the .904.The GM guys seem to argue the bigger lifter is heavier,adding to upper rpm instability. If this is the case why do many aftermarket GM blocks list a .904 lifter bore as an option?

As far as new tech,whats in an LS block,.875, .904 or something else?

I know,I know,talk about an obscure detail.........:D


Whats the opinion of those here who build high performance engines for a living?

[rivermobster]

Both trains of thought are correct.

:D

But...

If your gonna build a REAL race engine, your gonna run a roller cam. So at that point this argument becomes moot.

[Gelcoater]

Both trains of thought are correct.

:D

But...

If your gonna build a REAL race engine, your gonna run a roller cam. So at that point this argument becomes moot.I guess if one assumes you want to build a REAL race engine? The majority of boaters and hot street people do not. Nor do most want to dump another 1K plus on all the roller goodies. Me? Im sold on a solid lifter cam setup if for nothing else simplicity and cost effectiveness. It doesnt get much more simple than a piece of metal carved into a cylindrical shape.

[obnoxious001]

Better not try buying .875" lifters for an early Chevy block, not going to fit, they are .842"

If you plan to run a flat tappet cam for simplicity and cost, then you don't even want to start thinking of boring and bushing the lifter bores, not a cheap deal. I paid $1000 to have a Dart Iron Eagle block bored and bushed for Jesel keyed roller lifters, and the lifters themselves were another $3000. This was for a junior fuel A nostalgia dragster, lots of cam lift and rpm involved!

[Gelcoater]

Better not try buying .875" lifters for an early Chevy block, not going to fit, they are .842"

If you plan to run a flat tappet cam for simplicity and cost, then you don't even want to start thinking of boring and bushing the lifter bores, not a cheap deal. I paid $1000 to have a Dart Iron Eagle block bored and bushed for Jesel keyed roller lifters, and the lifters themselves were another $3000. This was for a junior fuel A nostalgia dragster, lots of cam lift and rpm involved!Yep,sorry my mistake,.842"

Like i said,not everyone wants a "race" engine,nevermind a nitro engine.Looks like im not going to get a strait answer.

And when you had this Dart block bushed,were they .904 or .842?:cool:

[obnoxious001]

Yep,sorry my mistake,.842"

Like i said,not everyone wants a "race" engine,nevermind a nitro engine.Looks like im not going to get a strait answer.

And when you had this Dart block bushed,were they .904 or .842?:cool:

That was a straight answer. It's expensive and not necessary if you are not building a race engine, unless you have a problem with worn lifter bores, or bad lifter bore alignment. To me it would make more sense to spend the money on a roller cam than spend the money on bushing lifter bores.

That particular block was set up for .937 lifters.

[rivermobster]

Yep,sorry my mistake,.842"

Like i said,not everyone wants a "race" engine,nevermind a nitro engine.Looks like im not going to get a strait answer.

And when you had this Dart block bushed,were they .904 or .842?:cool:

See how you are? My answer WAS a straight answer in every way. :D

Both trains of thought ARE correct. The wider base gives you the ability to use more agessive ramps. The smaller base (lifter diamater) makes for a lighter valve train.

Whats best for you?

If you want a high rpm engine, the lighter the weight the better. If you want a engine that pulls like a train, your gonna want a high valve lift, so the wider base would help you in that respect. Big block or small block? 5k or 10k red line? Jet, v-drive or i/o? Every set up has different needs.

"Whats better" depends on what you are building said engine for.

Both set-ups have there pros and cons.

:)

[Dave Wettlaufer]

I think by better, we're talking design theory for said usage....being production car engines.

You can smooth it all out with the "pros and cons" bs, but the fact is, for old v-8's turning the rpm that they do, the bigger lifter bore is the way to go. Why wouldn't you want your valves open wider sooner? A hot mopar flat tappet initially beats a roller in valve acceleration off the seat.
If you were to run the hotter mopar profiles with a smaller lifter, it would die quick. Maybe thats why Ford and Chevy were so quick to jump on the roller hydraulic bandwagon.

For a 7500 rpm small block mopar 318/340 all that is needed is 10-1 comp, stock 2.02 1.60 heads, the right flat tappet solid cam, some Crane (or similar quality) roller rockers, RPM Airgap intake, and headers. Nothing "trick"...

What do ya need to do to a small block chevy to accomplish the same goal?:cool:

[blowncat 509]

I think by better, we're talking design theory for said usage....being production car engines.

You can smooth it all out with the "pros and cons" bs, but the fact is, for old v-8's turning the rpm that they do, the bigger lifter bore is the way to go. Why wouldn't you want your valves open wider sooner? A hot mopar flat tappet initially beats a roller in valve acceleration off the seat.
If you were to run the hotter mopar profiles with a smaller lifter, it would die quick. Maybe thats why Ford and Chevy were so quick to jump on the roller hydraulic bandwagon.

For a 7500 rpm small block mopar 318/340 all that is needed is 10-1 comp, stock 2.02 1.60 heads, the right flat tappet solid cam, some Crane (or similar quality) roller rockers, RPM Airgap intake, and headers. Nothing "trick"...

What do ya need to do to a small block chevy to accomplish the same goal?:cool:

for a small block chevy? are you joking? 327/350? the same chit you just
listed:rolleyes: