460 compression test question

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Apr 3, 2008 | 10:54 AM

OldRacerGuy

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460 compression test question

Hello!

First post here after lurking and searching the last week.

I'm looking at a couple of F350s, one of them claims a Ford ReMan'd engine. A CARFAX search isn't showing any record of major work, so maybe the guy did it himself or had a small shop do the work. Or maybe not...

Here's my plan: Look over the truck for traces of an engine swap, like a clean engine and wrench marks on the proper bolts. If it passes that test, then I'll test the compression on 1 or 2 cyls. If the motor is fresh the the comp #s should be at the new level. Here's the question: What are the compression #s for a fresh 460?

I know to check the exhaust manifolds for broken bolts, etc. Any other common problem spots to look for?

Thanks

Apr 3, 2008 | 11:33 AM

merlynr

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My old hi mileage 460 still had 120+ psi, but don't know for sure for you. I used to see Ford reman'd engines with a tag on underside somewhere. Again, I don't know if they still do that.

Apr 3, 2008 | 03:19 PM

monsterbaby

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From: iowa

Honestly what the compression number actually is, really isn't that important (it will change with what cam it has, what heads it has, the static compression ratio, how good the battery is, barometric preasure, and how fast the starter turns the motor over) what matters is that all the cylinders are within about +/-5psi of each other across the board. Or in other words no more then a total of 10psi difference from the highest to the lowest (preferabley not one being 10 psi lower then the rest). But I would say if it has cylinders below 100psi run.

Apr 3, 2008 | 03:27 PM

Bear 45/70

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From: Union, Washington

Quote:

Originally Posted by monsterbaby

Actually the industry standard is the low number is within 15% of the high number. I never heard and rarely saw an engine that would meet your +/- 5 psi number in over 50 years of working on engines, 35 years of that as a professional. A lot of new or rebuilt engine won't meet your +/- 5 number.

Apr 3, 2008 | 03:39 PM

ATC Crazy

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From: SW VA

I would check the compression on EVERY cylinder! Look at the thread I started in this forum. On my engine, cylinders 1-4 showed between 150 and 160 psi. Cylinder 5 was 175 psi, #6 was 0 psi, and #8 was 125 psi. It started and ran just fine....I thought it just had a miss from a bad wire or plug.

Too bad I already committed to buying it before I checked it out...BUT, I have a solid, highly sought after engine that the drag racers would love to have (C9VE block, D0VE heads)

Apr 3, 2008 | 03:44 PM

Bear 45/70

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Quote:

Originally Posted by ATC Crazy

I agree, because a couple doesn't tell you enough. It's like checking to see if any bones are broken in your hands, and then assuming none are broken anywhere in your body.

Apr 7, 2008 | 01:34 PM

OldRacerGuy

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I bought the truck. Motor has been replaced, receipts and a phone call to the installing mechanic verified that. 92 F350 CrewCab longbed 4x4 in very good condition, almost perfectly stock. White, 173k on the truck, 6k on the engine. $4400. 460, auto trans, runs great. I've been driving Toyotas for the last 7-8 years, this thing is a big change. No more quick U-turns...

Thanks for the answers, looking forward to hanging out here.

ORGuy