Why grind the crank? & What wt. oil to use?

[1899]

Been looking for awile on the search engine, Im just curious. why do some builders grind the crank? Ive got a 455. Im currently running std. rod and main bearings. Also On the stand, im running 5W-30 and im getting 55Lbs cold. But when running hard on the water it could change things a bit.what weight oil should I run on a freshly built motor?

[beerjet]

I do not have freshly rebuilt engine but I've always been told to run straight 50 and it did make a diffrence from the 5-30
beerjets .02

[SmokinLowriderSS]

Mains on a 455 will often get ground because they are so large that at high RPM's the surface speed of the steel in the oil film at the bearing gets very high. Grinding that circle to a smaller diameter reduces the shear forces which reduces oil heating.
My taylor ran 10-40 oil for decades, no problem. I tended to run 20-50 castrol, still no problems, Big end bearings were worn out when I took her down last winter, but was 27 years old, no damage. She now runs 10-50 Syntech pure synthetic from Castrol. Modestly modded 454, about 400 genuine HP on the new headers over old logs.

[Oldsquirt]

...... Im just curious. why do some builders grind the crank? ....
It's pretty simple, really. The crank journals need to be round and need a smooth surface. Over time, the journals do go out of round and can develop taper. The surface of the journal can develop scratches and other blemishes. Would you want to put something like this back in your engine? The only way to correct any imperfections of this sort is to re-grind the crank down to the next size. Re-grinds are done in increments of .010".
Hopefully any "builder" who doesn't regrind a crank has documented that it has no physical defects.
Mains on a 455 will often get ground because they are so large that at high RPM's the surface speed of the steel in the oil film at the bearing gets very high. Grinding that circle to a smaller diameter reduces the shear forces which reduces oil heating.
A stock regrind isn't going to do anything to help that problem. The Olds455 has much larger main and rod journals than, say, a BBC at 3" and 2.5", respectively. The BBC is 2.75 and 2.2" for mains and rods. If you wanted to reduce ROD bearing speed you'd need to regrind to a much smaller size(like the BBC's 2.2"), necessitating the use of custom rods. Nothing you can reasonably do to reduce MAIN journal size.

[1899]

I thought you polished the crank to remove any imperfections. Ok got it.

[Oldsquirt]

In some cases you might get by with polishing, but those imperfections had better be very small. You can not polish a crank journal back to "round". Grinding cranks is a very common practice.

[H2OT TIMES]

I am told by more than one guy, who knows more about Olds than I, that it is critical to reharden the Olds crank after it is ground. Evidently there are several ways to do that and I'm told to use what ever methode you happen to prefer, but be sure you do it.

[SmokinLowriderSS]

Thx for the clarification Oldsquirt. I was just not thinking of the "clean-to-round" on a rebuild and was thinking of the journal size change work you described for the reason I posted. You covered both well.

[moneysucker]

I would not recomend 50 wt Olsd 455s are known for not being able to drain back into the pan fast enough already and starving the bottom end of oil. I used 20 50 in mine back in the day with a 10 qt pan. I would stick with 10 40 or 20 50 a multi wt oil is probably better in this application unless there are oiling mods done then your builder would have told you what oil you should use. Good luck with the boat.
Cy

[TIMINATOR]

***boat Mag. April issue. BIG OLDS ARTICLE. Answers all the questions. TIMINATOR

[396_WAYS_TO_SPIT]

I would not recomend 50 wt Olsd 455s are known for not being able to drain back into the pan fast enough already and starving the bottom end of oil. I used 20 50 in mine back in the day with a 10 qt pan. I would stick with 10 40 or 20 50 a multi wt oil is probably better in this application unless there are oiling mods done then your builder would have told you what oil you should use. Good luck with the boat.
Cy
I ran sae60 in my last olds and she ran hard every day. I also had oil restricted pushrods and a 10qt pan with a stock oil pump....

[sleekcrafter]

Been looking for awile on the search engine, Im just curious. why do some builders grind the crank? Ive got a 455. Im currently running std. rod and main bearings. Also On the stand, im running 5W-30 and im getting 55Lbs cold. But when running hard on the water it could change things a bit.what weight oil should I run on a freshly built motor?
For the OLDS guru's try www.442.com Lots of car guys as well a boat guy's. The trick to the engine is to make it more boat freindly, for extended high rpm operation. Sleek

[malcolm]

I've been studying my 455s oil system before I do the final cleanup on the block to put it together. What a wild oil path in that block!
The oil comes from the pump thru the rear main cap (like a Chevy). It then runs thru the filter and goes back in and Ts to the rear main, rear cam brg, and the right side lifter rail. The front 4 mains are drilled into that rail and T to the other cam brgs. The front main web has another drilling that feeds oil to the left side lifter rail with a little T in the front to feed the sender port on top of the block.
:boxed:

[sleekcrafter]

I've been studying my 455s oil system before I do the final cleanup on the block to put it together. What a wild oil path in that block!
The oil comes from the pump thru the rear main cap (like a Chevy). It then runs thru the filter and goes back in and Ts to the rear main, rear cam brg, and the right side lifter rail. The front 4 mains are drilled into that rail and T to the other cam brgs. The front main web has another drilling that feeds oil to the left side lifter rail with a little T in the front to feed the sender port on top of the block.
:boxed:
It's more the return path with the oil issues, and the fact there are massive
crank and rod journals. Cutting the crank .020/.020 slows the bearing speed down, helping reduce heat buildup, and require less oil on the bearing surface. The oil has problems finding it's way back to the pan, in jet boats sustaining higher rpm's. The heads have restricted drain passages, heads are drilled and tapped, for pipe fittings to help drain the oil back to the pan, external of the engine. Other things include, opening up the drain passages witha die grinder, the heads, and block area above the cam in the lifter valley, have casting slag blocking, a fair amount of the drain passages. Restricting the oil to the top end also helps, control oil flow, through out the engine. There are a whole host of oiling tricks with the Olds motors.
Sleek

[malcolm]

It's more the return path with the oil issues, and the fact there are massive
crank and rod journals. Cutting the crank .020/.020 slows the bearing speed down, helping reduce heat buildup, and require less oil on the bearing surface. The oil has problems finding it's way back to the pan, in jet boats sustaining higher rpm's. The heads have restricted drain passages, heads are drilled and tapped, for pipe fittings to help drain the oil back to the pan, external of the engine. Other things include, opening up the drain passages witha die grinder, the heads, and block area above the cam in the lifter valley, have casting slag blocking, a fair amount of the drain passages. Restricting the oil to the top end also helps, control oil flow, through out the engine. There are a whole host of oiling tricks with the Olds motors.
Sleek
Actually cutting the crank a few thous. isn't going do anything for slowing bearing speeds in an Olds as Oldsquirt has already mentioned. And the drainbacks are just part of the problem. There are some common misconceptions about Olds "oiling problems" and how to fix them. The biggest one is that restricting the cam bearings keeps oil from building up in the "top end". All it does is make sure more of the oil goes to the crank. That in conjuction with loose clearances and slotted rods are the only way to cool down the bearings in an Olds. Ok, I'll get off my soap box now.

[1899]

Ok, im thinking more of 40wt oil because I have not ground the crank and the engine came out of a car, standard bearings and all. Im shure im going to end up making the drainback mods on the valve covers sooner or later.
Would you use Lucas oil additive or will that just make things just too think?

[malcolm]

I was running some cheap Chevron 30w in mine and had the pressure drop to 20 pounds while I was gassing it up the river. I had to back off an ease it to the sandbar. I put in a qt of that red bottle Hyperlube and tried it again, it gained 50 rpm. Not bad for $6. :)

[1978 Rogers]

I was running some cheap Chevron 30w in mine and had the pressure drop to 20 pounds while I was gassing it up the river. I had to back off an ease it to the sandbar. I put in a qt of that red bottle Hyperlube and tried it again, it gained 50 rpm. Not bad for $6. :)
Think what you could do with some Slick 50. :rollside: