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Old 07-05-2022, 08:24 PM
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Default Crankshaft end play

New build with 4.25" stroke Eagle Crank and Clevite 77 bearings in 400 block. Setup dial indicator and measured about 0.010"-0.0105" end play. For a mild 461 street car, would there be any concern?

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Old 07-05-2022, 08:33 PM
74Grandville 74Grandville is offline
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Default Crankshaft end play

No

Spec is 6-11 thou

Sent from my iPhone using Tapatalk

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Old 07-05-2022, 08:59 PM
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Quote:
Originally Posted by 74Grandville View Post
No

Spec is 6-11 thou

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Thanks for the quick reply!

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Old 07-05-2022, 09:20 PM
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I think factory specs. through the 60's-early 70's is .003-.007". But I am fine with .010-.011. Did you check it before and after you torqued the #4 cap? Light oil only on the thrust faces, not thick assembly lube?. If it doesn't change more than ,0015-.002 max, not torqued/torqued, and just light oil on the thrust, you are fine. Also that should be free clearance, no prying pressure. Pry one direction, release, set dial to zero, pry other direction, release, read dial.

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Old 07-06-2022, 06:04 AM
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The concern here is the rod side play also.

If any of the pair of Rods has less side clearance then what you have for thrust clearance then that pair of Rods will be forced into acting as the thrust Bearing which is not good for a number or reasons and non of which will add to the longevity of the short block!

This excess front and rear motion also adds to the sawing action on the rear main seal.

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Old 07-06-2022, 09:07 AM
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That's a very important point, Steve. So if this crankshaft actually has .010" end play, then the rod side clearance needs to me .012-.013" minimum. You never want side clearance to be less than thrust clearance. When crankshaft true free play exceeds .012", some corrective action needs to be taken. I also won't run tighter than .005" on the thrust.

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Old 07-06-2022, 10:02 AM
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In an effort to give correct information, here are the end play, (thrust) clearance specs. from assorted Pontiac Chassis service manuals I had easily available here.
1961, 1962, 1965, 1966: .0035"- .0085". 1967, 1970, 1973, 1975: .003"- .009". Personally, I won't let anything leave here tighter than .005, looser than .011. Over .012" = trouble. (note: I had a small mistake on the specs. in post #4.)

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Old 07-06-2022, 10:24 PM
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Thanks for the additional input. Here's more info.
1. Checked play before torqueing the main caps with no grease on thrust bearing. Very slight "prying pressure" resulted in 0.010" measurement.
2. Rods have from 0.028"-0.032" side clearance measuring with calipers uninstalled.
3. Rods are Eagle H beam 6.800 with floating wrist pins.
4. Rear main is BOP one piece Viton.

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Old 07-06-2022, 11:41 PM
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Quote:
Originally Posted by pontiacmark View Post
... 2. Rods have from 0.028"-0.032" side clearance...
That will cause more oil "dumping" than is usually desired.

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Old 07-07-2022, 05:54 AM
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I guess I could live with that wide thrust clearance if you do not want to mess around with a few other thrust bearings , but Your going to need a tight fitting Crank scraper to deal with all of the oil windage that will be thrown off of those Rods.

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Old 07-07-2022, 10:25 AM
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That's allot of side clearance. Not ideal. But just for fun, even on the bench do this. Install a pair of rods on a crank pin in correct orientation. Then measure the side clearance directly between the pair with feeler gauges. IMO, that will give you a more direct, accurate measurement than using calipers. This is because the large fillet radius used by the aftermarket crank manufacturers is very hard to calculate and measure with calipers. Try a pair and get back with us. Good luck.

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Old 07-07-2022, 10:58 AM
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Quote:
Originally Posted by mgarblik View Post
Also that should be free clearance, no prying pressure. Pry one direction, release, set dial to zero, pry other direction, release, read dial.
This is great info - I had no idea

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Old 07-07-2022, 11:20 AM
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I've never understood how rod side clearance could greatly affect oil volume through the bearing. (i.e., excess oil throw-off, windage, oil on the cylinder wall leading to oil burning/overloading the rings, etc.)

The oil clearance itself limits the amount of oil that can flow through the bearing, not the side clearance. If the side clearance were unusually tight, I suppose it could restrict flow--but it'd take a considerable lack of side clearance. Excess side clearance merely allows whatever oil that can flow across the bearing, to be flung off. So it's the bearing clearance that limits oil throw, not side clearance.

Am I wrong?

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Old 07-07-2022, 11:54 AM
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"Am I wrong?"

I dont think your wrong another aspect is if more oil flows from a rod bearing that also means more oil going in and part of oils job is to cool, rod bearings are one of the most taxed surfaces in a engine

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Old 07-07-2022, 10:11 PM
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Updates:
1. Rechecked end play AFTER mains torqued down. 0.007-0.0075
2. Rechecked rod side clearance on one pair installed with feeler gage between rods. 0.029".

Not too worried about the larger side clearance. Bearing clearance is good so there is the right combination of flow and pressure. Have read where the aftermarket rods are a bit narrower than stock.

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Old 07-08-2022, 12:12 AM
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Quote:
Originally Posted by Schurkey View Post
... The oil clearance itself limits the amount of oil that can flow through the bearing, not the side clearance...
... Am I wrong?...
I believe you are wrong, although I've not tried to investigate it.

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Old 07-08-2022, 01:10 AM
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Every BBC rod I have used on a Pontiac crank has been .025-.030 side clearance.

If .029 sounds like a lot.one mopar I run on the street has a Billet crank out of a Top Fuel Hemi, and has .075 side clearance on the rods.. I would say excessive side clearance might be a issue if it wasnt for that engine, cause we have been mercilessly thrashing on it since 1994..still runs great.

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Old 07-08-2022, 03:38 AM
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Quote:
Originally Posted by Schurkey View Post
...So it's the bearing clearance that limits oil throw, not side clearance...Am I wrong?
No, we'd be screwed because of all that nasty oil escaping on #1, #2, #3 and #5 main bearings that don't have side clearances. As far as rods, we are looking at maybe .003" rod bearing clearance if really loose and side clearance is at least three to four times that or more. So again side bearing clearance is a moot point on oil control.

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Old 07-08-2022, 07:21 AM
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I don't see the making a A/B case for a street strip steel rod motor and a top fuel motor valid!

Seeing as a top fuel motor has Aluminum Rods with there greater expansion rate and they are acting as partial heat sinks for 8000 plus hp I can see having .070" for side clearance, especially since they run straight 50W oil.

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Old 07-08-2022, 08:03 AM
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I would agree with your post if that engine still was a Nitro Hemi with AL rods…and I am not suggesting anyone open the side clearances out that far, it is just an example to make that .029” feel warm and fuzzy. The example is a 550 HP 510 stroker street engine with stock factory steel rods in it, only the crank is from a Nitro car. It has a lot of street miles and passes down the strip. We built it back before people were building stroker engines, and after market forged stroker cranks did not exist any place at the time.


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