Mine has started making more noise than I think is permissable, so I've got to build myself a new shortblock... So I have some questions:

Does the slant six like full groove mains?

How badly balanced are factory builds?

Is there significant weakening issues to going undersize on the crank?

How much boring is ok before the blocks need to be verified?

I'm intending to get a large hub forged crank shortblock to replace what I'm sure is a cast crank engine in my truck. ( not quite sure of the definitive ID means... but I have to build another while I keep driving this one)

Thanks for any info...

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'81 W150 on Propane... Oversize valves, Oregon Camshaft cam, 10:5 static CR, Distributorless ignition, megajolt timing controller, PowerTrax lockers.

Fully grooved main bearings I wouldn't bother with in your RPM range. The crank is plenty strong even with the smallest bearing available. The balance isn't great, but it doesn't have to be either. So long as your pistons and rods are all reasonably close, run it. There's this one guy I talked to a couple years ago. He quit having blocks sonic checked before he'd bore them +.100" because they all came back OK. Definitive block ID is here: http://www.slantsix.org/articles/dutra- ... blocks.htm More casting numbers and info: http://www.slantsix.org/articles/parts-matrix/jpg.htm

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Joshua

+++ on all that Josh said. You can grind and bore to your heart's content on a forged crank 225. I have run std 1/2 groove mains in all my builds, routinely running 6000 RPM. I run loose clearances - 0.002" on rods and mains.

Lou

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Home of Slant6-powered fun machines since 1988

Any particular reason you like to run the rod bearings on the loose side?

As for rpm, I don't run past 4000 (I have it set up with an rpm limiter), but it also will get run at 2500 to 3600 at WOT (or nearly so) for long periods. To propel a full size 4x4 down the freeway at 75 requires at least 60 to 80 percent of it's maximum torque at over 3000 rpm.

Mind you, the truck runs down the freeway feeling like you have a small block under the hood, but the limitations are kinda obvious when you hit a 5.5 to 6 percent grade and gradually slows to 45 at WOT. ( I have 3.55 gears)

I'm hoping a little more tweaking with timing, the addition of the headers, and a few other improvements will increase the torque enough to keep it up to speed, rather than slowing down. Even though I'm running propane, this is the strongest running (torquey) slant six I've ever owned or driven.

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'81 W150 on Propane... Oversize valves, Oregon Camshaft cam, 10:5 static CR, Distributorless ignition, megajolt timing controller, PowerTrax lockers.

Yes, looser clearances for high RPM oiling.

I have run my engines at times for 3200-3800 RPM all day on cross country trips. This was before the advent of overdrives for me... Now, I usually cruise at 2200-2900 (70 - 90 MPH).

Put a turbo on that thing and you will have no more slowing down on the fwy... Nice thing about propane is no fuel suspension or wet manifold issues.

Lou

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Home of Slant6-powered fun machines since 1988

Cut some off head or block to get compression up, you will notice a lot of difference.

Richard

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Part of Tyrde-Browne Racing