460 running rough - head gaskets?
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From: Cleveland, WI USA
460 running rough - head gaskets?
Greetings all,
I just replaced the lifters in my 74? 460 and it runs a little better. I'm still getting a ticking and missing. When I pulled the plugs, #1 was pretty mucked up, but the rest were clean and dry. I'm guessing the ticking might be an exhaust manifold-to-crossover pipe leak since that's been a problem before.
As for the missing, I'm not sure. Plugs, cap, & rotor all seem fine but I may replace them anyhow. I do see some grey smoke from the exhaust and it spits black drops all over the wal in the garage when I rev it up. The smoke isn't really thick, but it's noticable.
Could the black spatter, light grey smoke, and the missing all be as simple as a blown head gasket? I haven't done the compression test yet but will tonight.
Also, can you use RTV on head gaskets? My instincts tell me no.
Thanks for any advice.
Kevin K.
I just replaced the lifters in my 74? 460 and it runs a little better. I'm still getting a ticking and missing. When I pulled the plugs, #1 was pretty mucked up, but the rest were clean and dry. I'm guessing the ticking might be an exhaust manifold-to-crossover pipe leak since that's been a problem before.
As for the missing, I'm not sure. Plugs, cap, & rotor all seem fine but I may replace them anyhow. I do see some grey smoke from the exhaust and it spits black drops all over the wal in the garage when I rev it up. The smoke isn't really thick, but it's noticable.
Could the black spatter, light grey smoke, and the missing all be as simple as a blown head gasket? I haven't done the compression test yet but will tonight.
Also, can you use RTV on head gaskets? My instincts tell me no.
Thanks for any advice.
Kevin K.
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Posting Guru
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From: Cleveland, WI USA
460 running rough - head gaskets?
I did my compression test last night. The guage is a Craftsman, screw-in-the-plug-hole type and is supposed to be very accurate. The instructions say the difference between cyl's should be less than 5 or 10 psi.. Mine ranged from 70 to 115. That's a heck of a lot more than 5 or 10 apart.
Any idea what might cause such a variation?
Thanks in advance!
Kevin K.
Oh, and part of the reason it was running crappy after the lifters was because some idiot forgot to hook the vacuum advance back up.
Any idea what might cause such a variation?
Thanks in advance!
Kevin K.
Oh, and part of the reason it was running crappy after the lifters was because some idiot forgot to hook the vacuum advance back up.
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From: Cleveland, WI USA
460 running rough - head gaskets?
I was afraid of something like that.
I seem to recall that you could tell if it was the rings by squirting oil in the cylinder and checking the compression again. Is that a difinative test, and about how much oil do I put in.
Thanks!
Kevin K.
I seem to recall that you could tell if it was the rings by squirting oil in the cylinder and checking the compression again. Is that a difinative test, and about how much oil do I put in.
Thanks!
Kevin K.
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From: Cleveland, WI USA
460 running rough - head gaskets?
Ok. I did the shot-o-wd40 and rechecked the compression. It jumped about 10 psi after a small blast. Should it have gone up more, or is that enough of an indication that the rings are bad?
Now I realize I should do a full rebuild at this point, but that's not in the budget. I'd like to just replace the rings if I can.
Do I need oversized rings? Do I need to hone the cylinders? Is there an easy way to tell if the block's been bored out or not?
I guess for starters I should pull the heads and look at how big of a ridge I have at the top of the cylinders. That would indicate how much wear there is on the cyl. wall.
Any suggestions on the ring change would be greatly appreciated.
Thanks!
Kevin K.
Now I realize I should do a full rebuild at this point, but that's not in the budget. I'd like to just replace the rings if I can.
Do I need oversized rings? Do I need to hone the cylinders? Is there an easy way to tell if the block's been bored out or not?
I guess for starters I should pull the heads and look at how big of a ridge I have at the top of the cylinders. That would indicate how much wear there is on the cyl. wall.
Any suggestions on the ring change would be greatly appreciated.
Thanks!
Kevin K.
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Joined: Aug 2001
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From: Nevada
460 running rough - head gaskets?
Your compression is way too low and erratic to answer the question without the engine being stripped down. You need to measure cylinder wall taper to determine if it can be re-ringed. If the taper is OK, it's just a matter of cutting the ridge out. If the ring lands on the pistons haven't been damaged.
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Thread Starter
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Posting Guru
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From: Cleveland, WI USA
460 running rough - head gaskets?
Thanks for thereplies.
By taper, do you mean the difference in diameter between the top and bottom of the cylinder or the thickness of the ridge? What's an acceptable taper?
Sorry for all the dumb questions. I haven't rebuilt an engine since high school.
Kevin K.
By taper, do you mean the difference in diameter between the top and bottom of the cylinder or the thickness of the ridge? What's an acceptable taper?
Sorry for all the dumb questions. I haven't rebuilt an engine since high school.
Kevin K.
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Thread Starter
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Posting Guru
Joined: Feb 2002
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From: Cleveland, WI USA
460 running rough - head gaskets?
I think I found the problem with my "running rough" 460.
While I was replacing the rear main seal, I tried to rotate the crank to clean the shaft where the seal rides. I grabbed the crank by the connecting rods and felt some unusual play. I thought it was horizontal play but quickly learned it wasn't.
The bearings where the connecting rod rides on the crank have about 1/32" of play in them. I can actually see the piston slide up and down the cyl. without the crank moving. I'm guessing that's not good.
I haven't actually mic'ed the journals or the cyl's. yet, but I'm guessing a complete rebuild is just around the corner. Either that, or getting another engine.
Is it really worth it to have the engine rebuilt? Would it be cheaper to get a crate engine?
Any thoughts?
Kevin K.
While I was replacing the rear main seal, I tried to rotate the crank to clean the shaft where the seal rides. I grabbed the crank by the connecting rods and felt some unusual play. I thought it was horizontal play but quickly learned it wasn't.
The bearings where the connecting rod rides on the crank have about 1/32" of play in them. I can actually see the piston slide up and down the cyl. without the crank moving. I'm guessing that's not good.
I haven't actually mic'ed the journals or the cyl's. yet, but I'm guessing a complete rebuild is just around the corner. Either that, or getting another engine.
Is it really worth it to have the engine rebuilt? Would it be cheaper to get a crate engine?
Any thoughts?
Kevin K.
Postmaster
Joined: Aug 2001
Posts: 2,882
Likes: 0
From: Nevada
460 running rough - head gaskets?
I'm not a big fan of crate engines from hearing too many horror stories about them. If you have a local machine shop that can be trusted, talk to them about a rebuild. That way you can get in their face if something goes wrong.
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Posting Guru
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From: Cleveland, WI USA
460 running rough - head gaskets?
Thanks George!
I've had my doubts about crate engines too, but I never knew anyone that had one. Besides, for a long block 460, it was almost $1400. I know I can rebuild for less.
Kevin K.
I've had my doubts about crate engines too, but I never knew anyone that had one. Besides, for a long block 460, it was almost $1400. I know I can rebuild for less.
Kevin K.
