Thread: squeal from engine at idle (70 350 vette)

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Hello, just joined and thought I would jump right in with a question.

Thanks in advance for any thoughts.

I have a 70 corvette, 350 base 300hp(does not seem to have ever been removed from the car), ac, auto, 78,000 on the clock, and appears to be very stock with most every factory part there less some replaced rubber hoses, solid driver 3 on 1 to 5 scale (have only had the car 6 months).

At idle there is a fairly loud squeal from the engine (seems to be from the front).

This is what I did before posting::
•removed air cleaner checked for vacuum leaks and leaks in general (stock rochester 4brl) noLuck
•then removed AC belt noluck
•then removed power steering belt noluck
•then removed alt/water pump belt noluck
•then checked spark plugs (tight) noluck

Squeal continues with all belts off (I would only run the engine a minute or two with the water pump belt off)

Squeal starts a few momments after starting. Sometimes it does not squeal till the engine idle is increased but then stops if engine speed continues to increase (never reving above 1,800 - 2,000rpm while testing.

At first the squeal would only happen if it was cold (cold for southern california!) maybe 55 or 60 degrees out.

Once the engine reaches 180 for 10 minutes (water pump belt on) the squeal would stop, however that is changing and the squeal is not going away.

The engine starts and idles very smooth after cranking over a few times (very quickly actually).
The car seems to rev quick and clean and runs out quite strong for an older (stock) car.

I have run several tanks of 91 unleaded with some NOS octane/lead boost added (never more than the package suggest)

The car sat covered for two months (jan-feb) and the problem become more common after that.

I can work metal/fiberglass and paint but engines are not my thing. If anyone out there could shed light on this situation I would really appreciate it.

Best wishes and thanks in advance.

russ,

Originally posted by socalstreetrods
Hello, just joined and thought I would jump right in with a question.

Thanks in advance for any thoughts.

I have a 70 corvette, 350 base 300hp(does not seem to have ever been removed from the car), ac, auto, 78,000 on the clock, and appears to be very stock with most every factory part there less some replaced rubber hoses, solid driver 3 on 1 to 5 scale (have only had the car 6 months).

At idle there is a fairly loud squeal from the engine (seems to be from the front).

This is what I did before posting::
•removed air cleaner checked for vacuum leaks and leaks in general (stock rochester 4brl) noLuck
•then removed AC belt noluck
•then removed power steering belt noluck
•then removed alt/water pump belt noluck
•then checked spark plugs (tight) noluck

Squeal continues with all belts off (I would only run the engine a minute or two with the water pump belt off)

Squeal starts a few momments after starting. Sometimes it does not squeal till the engine idle is increased but then stops if engine speed continues to increase (never reving above 1,800 - 2,000rpm while testing.

At first the squeal would only happen if it was cold (cold for southern california!) maybe 55 or 60 degrees out.

Once the engine reaches 180 for 10 minutes (water pump belt on) the squeal would stop, however that is changing and the squeal is not going away.


The engine starts and idles very smooth after cranking over a few times (very quickly actually).
The car seems to rev quick and clean and runs out quite strong for an older (stock) car.

I have run several tanks of 91 unleaded with some NOS octane/lead boost added (never more than the package suggest)

The car sat covered for two months (jan-feb) and the problem become more common after that.

I can work metal/fiberglass and paint but engines are not my thing. If anyone out there could shed light on this situation I would really appreciate it.

Best wishes and thanks in advance.

russ,

on most of the GM cars the heater fan motor turns all of the time and the bearings will go bad sometimes or something in the heater box. check that. if its a straight shift check the pilot bushings and throw-out bearing. other wise its not much turning with the belts off. sounds like it something to do with the vac. pinch off all of the vac. hoses with motor running and see if it changes anything. that heater fan motor will make all kinds of noise to.

If it is a 4 speed, check the throw out bearing.

Mike,
thank you - I will remove the fuse/power to the heater then address each vacuum hose as suggested (man-oh-man are there a lot of vacuum hoses on a corvette!)

Can a mechanical fuel pump make a noise (squeal)?

russ,

Originally posted by socalstreetrods
Mike,
thank you - I will remove the fuse/power to the heater then address each vacuum hose as suggested (man-oh-man are there a lot of vacuum hoses on a corvette!)

Can a mechanical fuel pump make a noise (squeal)?

russ,

never heard one squeal, they can click like a bad lifter. don't pull all of the hoses off , take a pair of needle noise pliers and pinch them off one at a time.