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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 1976Scottsdale on November 20, 2006, 10:22:00 PM

Title: Terrible luck lately.
Post by: 1976Scottsdale on November 20, 2006, 10:22:00 PM

I finally got my 1976 K-20 all quieted down with some Thrush Turbo mufflers.(sounds good)  Now I hear the noise I hate the most... tapping.  I crawled under it to see if I could hear where it was coming from.  It had only one bolt in the torque converter.  So, added two and tightened the other.  Still taps.  So, I added an aftermarket oil pressure gauge.  32psi hot, 15-20 cold.  Figured okay, mud truck, 300 mile crate engine, change the oil.  Still no pressure difference.  have to start brush fire, so old oil goes on pile and the match never gets close before flaming up.  The oil was full of gas.  Long story short, that makes 3 now that have to get new bearings due to bad fuel pumps.

Does anyone reccomend a good brand to use for a new pump?

Are there any special steps to prolong pump life?

I am installing new rods and mains thas weekend and an electric fuel pump for now and will replace with a mechanical... maybe, later.

Title: Re: Terrible luck lately.
Post by: Lt.Del on November 20, 2006, 11:00:00 PM

Needless to say, something just isn't right to go through all those pumps.  Are you sure the pump rod is seated correctly?  Is the crank shaft of the engine the same in all cases---hitting it correctly?  Or, are all the pumps coming from the same batch (same store, etc.)

Are you sure it is your pump?  I am not sure, but will a crack in the intake do the same thing--put gas in the oil?  

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4

Title: Yes
Post by: VileZambonie on November 21, 2006, 03:41:00 PM

And it can be found very easily using a smoke machine.  

Title: not sure
Post by: 1976Scottsdale on November 25, 2006, 06:51:00 AM

I am not sure what the deal is.  I ripped the bottom end apart and found no real wear in the main bearings, the pushrod is seated.  They keep using junkyard pumps instead of new ones.  Forgot to mention that part.  Going to go ahead and pull the engine and get it inside to finish my work, since it is getting cold.  Then I will look at the rod bearings.  The new pump says to pack the cavity with heavy grease because if not, pump failure could occur.

Title: Re: not sure
Post by: Lt.Del on November 26, 2006, 11:18:00 AM

diaphrams dry out on pumps that haven't been used in months.  Just like carbs dry out.  All seals would need to be replaced.  

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4

Title: Grease
Post by: VileZambonie on November 26, 2006, 12:43:00 PM

A little bit of grease can help hold the pump pushrod in placebut you should not have to put any grease inside a mechanical fuel pump. You'd have to have quite a bit of gas in the oil for it to wipe out your bearings 3 times. Is the oil getting overfull? It might help you to pinpoint exactly where the noise is coming from before yanking apart then engine. A powerbalance test can help isolate a bad rod bearing. Are you sure that flexplate isn't cracked?

Title: Re: Grease
Post by: 1976Scottsdale on November 26, 2006, 07:23:00 PM

The flexplate appears to be fine.  The engine had low oil pressure anyway, so it had to come apart.  Also, these were three separate engines, had this happened to one engine three times, I would have junked the whole thing out of anger and started over.  I am going to check the flexplate more closely very soon.  I will be pulling the engine out to clean and paint it as soon as I have time.

Last but not least, a question.

What is a Power Balance test?  I have never heard of this.  I use a long bolt to hold the pushrod in place in the hole in the front of the block.