Now that I've removed the 3:90 ring and pinion and replaced it with a set of 3:38's, with all looking well,backlash,ring gear pattern etc. etc. My problem I have now is from 1800-1900 rpm's the engine is like a high pinging or wisthling in it. Once it gets to about 2200 rpm's it goes away, it is not the differential it is in the engine and have done nothing to the engine in over 6 months. I used to drag race for 22 years, and I called up my old engine,builder ,asked him and I think he's been drinking to much egg nog over the holidays. What do you inliners think it could be?

Whats the cranking compression of your engine & how much is the compression ratio?

MBHD

What engine is this?
What does it have for a distributor?
What carb and air cleaner?

Whistling? Vaccum leak maybe? Or is this at WOT?

The pinging sounds like detonation (as you describe it) but the whistle, I dunno.

Do you have video of it (with sound)?

We'll I'm back and glad to see you Inliners are here to help me. I'm going to try and answer these questions the best I can.It is the ol 235' 6 cyl. with 5500 miles on it. This engine I built about 2 years ago really runs good even with the wistle in it. The reason I'm saying wistle is because going to work today thats all I really heard, a wistle. The cranking compression at 3500 miles averaged 124 lbs per cylinder, comppresion ratio I don't really know, they are flat top pistons with an 848 head and ahydraulic camshaft.I'm running the ol stock 1 barrel rochester carb with fram air filter and a stock delco reyme distributer at 6 degrees advanced.We'll I appreciate all your help there inliners. Have a good 1.

Putting one of those small dry element filters on it is going to cause what could be described as a whistle. nothing to do about it other than try a different type of filter, usually a larger one. If you have an oil bath filter handy, you could try that to see if it changes the sound.

Checking the compression would be to see if you blew the head gasket between cylinders. This usually causes a ping under load, rather than a whistle, though.

If your timing was off, it would also cause more of a ping than a whistle as well.

It's possible you have a vac leak, but it would give you other symptoms as well, like a lean backfire on deceleration, or a rough idle, or surging, for example.

It sounds to me like you are leaning on it a little harder then you used to because you went from a 3:90 to a 3:36 gear, and the type of air cleaner you are using. I'm not sure I can pin it down any better without being there or at least hearing it.

Once I did a quick work on a cylinder head @ a local Junior College engine rebuilding class.

Cut new cast iron valve guides w/a hacksaw at all different angles,really choppy looking cuts.

Valve job & all,installed the cylinder head & bamm,,whistled all the time,turns out with the very crude cuts on the cast iron valve guides caused the whistleing LOL.

MBHD

Well been gone for while, now that I'm back I installed a stock oil bathe cleaner on the truck and guess what? It still whistles at about 1900 rpm's.. Like I said earlier I haven't done anything to the engine since I changed the gears and I don't know.

I had a 300 Ford six do it to me before and it was a worn throttle shaft on the carb. Since you changed gears, it probably changed your cruise RPM to the point, your carb shaft position stays at this point of were the excess wear is and is more noticeable than before the gear change....

get a buddy over and jack the truck up in the rear and one person bring the rpm up to that point while the other tries to determine where the wwhistling is coming from. Being you can hear the whistling from inside the car tells me it should be pretty easy to find as most engine noises like this arent usually noticable while driving. Being you can also hear this while driving I would also check any vacuum lines you may have in the truck that may go to the wiper motor if of coarse you do have vacuum wipers. Another possiblity is a T/O bearing or pilot bearings also will make this type of noise, I have also seen people leave a little extra on the cotter pin on the front wheel bearings that it will rub up against the fgrease cap and cause the same noise, as stated above being you had different gears the engine was considerably loader and you never noticed it.