460 compression test

[BlowHo]

OK - I posted previously about my motor not starting, I went and bought a comression tester. I know it's getting spark and fuel. Hang on to your hats

#1 = 35psi (Went to 60 w/oil in the hole)
#2 = 80
#3 = 60
#4 = 45
#5 = 45
#6 = 60
#7 = 35
#8 = 60 (80 w/oil)

So, this means piston rings, right? Is there anything else it could be? Head gasket maybe? Is it better just to get a new motor or rebuild? I can defintely take stuff apart and put it back together, have done so many times.

Let me know your thoughts. Thanks

 

[Coors]

Re: 460 compression test

Could be rings;test the rest with oil and see if pressure rises.
I think you need to rebuild it.
After you get below 115; it is time.

 

[Reel Poor]

Re: 460 compression test

Looks like it's time to do a cylinder leak test to see what's wrong.

 

[whywhyzed]

Re: 460 compression test

maybe just quickly try that compression tester on your car or something before condemning the motor.....

 

[HT32BSX115]

460 compression test

It might be good to do a leak-down. This way you can isolate the leaks to intake/exhaust valves or the rings. You may just be able to pull the heads and have the valves done. I think it unlikely that ALL the valves are bad....

My 460 did 160+ psi on 7 cyls and 155 on the 8th..... Even with the flat cam..... It's gone now. I sold it to a guy in Puyallup.....He's going to put it in a truck.

You might just consider getting a long block. 410 Machine in Buckley quoted me $1795 to do mine last year.... Check around with some machine shops. They'll all probably have a similar deal.

The other thing you can do is check out Craigs list. You can probably find several 460's around here for around $150-300

Check this out: http://seattle.craigslist.org/see/pts/354420657.html


This would probably be a good deal since you could put a marine cam in it and have the machine shop finish it.

 

[Bondo]

Re: 460 compression test

Ayuh,........

With #s like those,.........
That motor is Way Past Tired......... She's Beat......

 

[BlowHo]

Re: 460 compression test

I started pullling it apart last night. I looked on craigs list too, RIck, this boat is becoming a nightmare.

The worst thing is that I was told this motor only had 63 hours on a rebuild. I am learning lessons I already knew all over again.

 

[Robj]

Re: 460 compression test

These numbers are so low that they don't make sense to me. With the exception of the 80, all the rest are below 50, unless the engine was thrashed. On a worn engine I would expect a few low holes, not the entire thing. A sitting engine will give innaccurate results because the cylinders are not lubricated properly and rings aren't sealing which can easily explain the variability. At least that is what I found on my engine. Regardless just for curiosity, when you are ripping it apart, check the alignment of the timing chain. Low numbers on all cylinders can be explained by an an incorrectly aligned chain. Just a shot in the dark, but I think it is worth looking at.

Have a great day,

Rob.

 

[HT32BSX115]

Re: 460 compression test

Yeah...........I was told that my old 460 only needed to be timed!!


I think something else may be wrong there.......When I checked my old 66 Marktwain (150 Mercruiser/6cyl chev), Comps were between 120 and 135 PSI.

This was on a nearly 40 year old engine that was not babied. It was getting tired but it still ran pretty good.


You'll know when you get the heads off. Look closely at the camshaft and cyl walls. It'll be pretty obvious when you get inside.


I am voting for your getting a long block. I wouldn't try to "fix" only 1 or 2 discovered specific problems.

 

[BlowHo]

Re: 460 compression test

Still tearing it apart, lots of corrosion. The guy I bought it from said the boat was outdoors through last winter. He said the cover tore from water weight nad it tore directly over the motor.

When I look down through the intake manifold I can see rust, one stubborn bolt to go and I'll have it off.

Riser and exhaust manifolds have build up in the jackets, it is breaking off easy and the walls look solid, the gaskets were obviously failing. There was also the nastiest, blackest water I have ever seen in the exhaust passages.

I had pulled valve covers before and the rods, springs and rockers look good.

I am wondering if the pistons and rings are just rusting apart. Oh well, I'll find out soon enough.




One damn thing is for sure, I WILL take my family out in this boat and when/if I sell it it's gonna be mechanically sound! (It might be 2010, but you get the point) Thanks for the suggestions and ideas.