SCREECH in motor

[Print Dad 59]

Hello All,

I know this is NOT a Mustang - -BUT I need help in trying to help a friend.

 

Car is a 70 Torino - 429 - motor rebuilt last year. The car was stumbling and

POOR idle. Had a 600 Holley - no external adjustments and sight screws.

I am pretty certain the idle circuit was messed.

 

Today I put on a new Holley from Summit. 750 dual feed single pump (vac sec).

 

So I put the carb on - start the car and a LOAD screech. Sounds like a bad

alternator bearing. Can't tell where the noise is coming from.

 

I pulled off the belts to eliminate the pumps and pulleys etc on front - NO LUCK

 

I then checked the bolts on the flex plate - -look OK - I was hoping one had loosened. NOPE

I drained the oil and filled the oil even though it recently had an oil change.

 

The owner said he had the screech before BUt I had not heard it when I was trying to adjust he OLD carb

 

I checked for vac leak - found nothing. All ports capped etc.

 

I was gonna pull the vlave covers BUT noticed - cork and it was getting late.

 

My ONLY thoughts now are pull the covers check rockers

Then - pull the dizzy and look at the gear and shaft.

 

If still no luck - - before I pull the pan = = - any suggestions.

 

I do NOT think this is a vacuum leak or anything like that.

When I let it gently idle the noise went away fro about 20 seconds and then came back. It sounds like something is turning DRY

 

I would appreciate any ideas and suggestions - to be honest I have several

projects I have been neglecting on my MACH so I need to try and figure this out pretty quick

 

Thanks - -Print Dad

[Must1969 10]

Don't know anything about 429's but my 302 had a screech in my newly rebuilt motor. It did not appear at first but after about 100 miles on the motor it started. Sounded like it was comming from the back of the motor. I checked all the things you did, only difference I found some light metal shaving in oil pan. Pulled the motor......(not happy) and I found when it was rebuilt they put in a cam plug that was too deep and it was pushing everything forward. The cam was rubbing on the plug and making the noise. I did a complete rebuild again since it wore out the timing chain cover to and I am almost ready to drive again. I really hope that was the only problem if not I may be selling an engine pretty cheap... Not sure if this is the same as yours but just my 2cents.

[miketyler 15]

Can you tell what area its coming from?

 

After a timing chain replacement, a friend had left bolts loose on cam gear. Shortly after first startup the screeching began. We could see a circular area protruding slightly from the timing cover. (This was a cheby) Once we pulled the timing cover it was evident what had happened.

 

Other than something like that, I would guess maybe distributor?

Edited September 23, 2012 by miketyler

[Print Dad 59]

Hello All,

Thanks for the suggestions and ideas.

 

I forgot to mention a few things. The car has good oil pressure

running around 45-50 at idle. I did change the oil.

 

Today - he went to move the car and he got a back-fire through

the carb. Sounds like an intake valve issue to me BUT can't tell

till I pull the valve covers.

 

I can NOT determine where the noise is coming from. At times

it sounds like the #3 are and then you think around #6.

Really ODD - - one friend that knows motors thought it was coming from the

bell housing area. This is a REAl strange noise.

 

Thanks again - p Dad

[miketyler 15]

You are going to think this is crazy but try a stethescope. I have seen old schoolers use them for years and it might help you zero in on this thing. HF has them for a whopping $3.00

 

http://toolmonger.com/2009/09/02/stethoscopes/

 

http://www.harborfreight.com/mechanics-stethoscope-41966.html

Edited September 23, 2012 by miketyler

[maxum96 32]

Today - he went to move the car and he got a back-fire through

the carb. Sounds like an intake valve issue to me BUT can't tell

till I pull the valve covers.

 

I don't have any ideas on the screech. I would guess that it's something that probably rotates and it's rubbing on something. Backfire out the carb can be a number of things. Lean mixture, timing, bad intake valve are just a few.

[etel64 10]

starter?

[69RavenConv 307]

You are going to think this is crazy but try a stethescope. I have seen old schoolers use them for years and it might help you zero in on this thing. HF has them for a whopping $3.00

 

If you don't have a stethoscope, take the biggest screwdriver you own, put the blade on the spot you think the noise is coming from and your ear on the handle.

[LindenBruce 27]

Confirming the noise is worse after the carb change? It's possible a base plate gasket is installed wrong or is of the wrong application. I had this problem on a 351W 4v after a carb change back in the day. I used the wrong gasket and it was squealing like a harmonica. Bruce

[DRASTiK 22]

+1

 

Also, an incorrect base plate gasket that is sucking in outside air could not only cause a whistle or screech, but it could also cause a backfire through the carb. This is definitely worth a close look.

[1969 Mach1 14]

I'm not familiar with a 429. But, I have had a 351w make a strange whine/screech noise. It ended up the distributor gear being installed in slightly the wrong position on the distributor shaft. Just 0.004"-0.005" out of position. The tooth contact between the dist. gear and cam gear was incorrect and the distributor gear was getting damaged. For the rare and random backfire through the carb, the A/F mixture may just be too lean.

[Phils69 27]

Did you find out what was causing the screech?