Whining... Er, screaming!

geekdaddy

geekdaddy

X1/9 Learner's Permit...
I just completed my first cylinder head replacement after purchasing a performance head from Matt. I tapped and plugged the coolant ports and attempted to follow his instructions to the letter.

Just finished the install. Good news is she fired right-up. Some stumbling while cold and I need to set the timing with a light but generally seems to be running ok, except for...

At approximately 1.2-1.5K, a fairly loud whine/scream/shreek emerges from the engine compartment. No idea where it's coming from and it fades away when RPMs drop back below ~900. Not sure what's causing it. I re-mounted the insert in my Allison Exhaust so that's one potential cause I suppose.

However, looking for suggestions from folks here about where to look for sources of the noise.
 
phillips82 said:
V-belts too loose or tight? Water pump bearings? Alternator bearings?
Click to expand...

Water pump is one year new and alternator was rebuilt two years ago. Both were ok before the new head went in. Belt tension seems ok and consistent with what I've experienced previously. Alternator is working well.
 
Greg, get a small tube or hose

Plug one end into yer ear and check for the location of the squeal.
Try not to blow out your ear drum in the process...
 
Greg... what we use here in SoCal...

http://www.harborfreight.com/mechanics-stethoscope-69913.html

image_22652.jpg


A broom stick or long screwdriver works great also. If you don't have a Harbor Freight nearby in New England, ask the Telephone Operator for a Haa-Baaa Freight and maybe that'll help...

BTW... has the SCREAM ever come back? Maybe just birthing pains...
 
I tried using a plastic tube to isolate the noise but still cannot determine where it's coming from. I don't think it's coming from the tensioner bearing based on using the tube to listen.

I inspected the cam area since this is a new head and it's bathed in oil so I don't think that's the problem.

It's definitely coming from the top of the engine area. Is less pronounced from underneath. I may have to try Tony's harbor freight tool approach...

And found my coolant leak is coming from the heater hose elbow that I transferred from my old head to the new one. I used some high-temp teflon sealant paste on the threads, tightened the elbow as much as I could while keeping it aligned with the hose (I could tighten another half turn but it would then be pointed at the exhaust manifolds) and then firmly tightened the collar nut. But it's still leaking a little. ARGH!!! :(
 
Hey Greg, did you use

Teflon tape on the threads? If so, maybe not enough.
You definitely don't want that to continue leaking.
 
Cam

Did the head have a reground cam? Was cam box shaved to get valve clearance. On my latest 1500 rebuild by Bearnie, we went with the 1300 tensioner bearing (larger diameter) to get belt tight
 
Deane said:
Did the head have a reground cam? Was cam box shaved to get valve clearance. On my latest 1500 rebuild by Bearnie, we went with the 1300 tensioner bearing (larger diameter) to get belt tight
Click to expand...

Hi Deane. Head and tower are shaved and Matt recommends a 1300 tensioner bearing and bracket which I have installed. Belt is snug. Can it be too tight? It's certainly not loose.
 
If so Greg... try loosening the cam tensioner a bit...

and see if there is a change...

At least it will eliminate or prove the belt or tensioner as the problem.
 
belt

I have my belt tensioned on the tighter side. Will give it a listen tomorrow after I replace my clutch slave hose (the dreaded clutch bleeding horrors), but that's another story, will get back on how belt sounds.
 
Inspect the timing belt

Look for wear on either edge - It is possible to get the tensioner installed slightly cocked so it can cause the timing belt to rub against the retaining ring on the pulley. You might also smell some burning rubber.
 
Whining

Ok finally got around to running engine. I do have belt whining at 1500 to 3000 rpm, more pronounced on throttle off. Not very loud and not screaming. As stated before I have belt GNT (good-n-tight). Above 3000 rpm too much exhaust noise to hear much else. As a note we did change out the old plastic cam pulley for a good condition metal one. 1979 1500cc carb.
 
UPDATE: Still screaming...

Had some back and forth discussions with Matt. He was concerned that my tentioner bearing had very little clearance with the face of the bracket. My 1500 bearing/bracket had much better clearance. The 1300 bearing also seemed to fit the 1500 bracket better with more clearance so I tried the 1300 bearing with the 1500 bracket.

Everything "looks" good and the belts align well. But still screaming. I followed Tony's recommendation and shelled out $3.19 for a stethoscope from my local HF and think I may have found something...

I probed the tensioner bearing hub, the cam pully bearing area, cam tower, air flow meter area and found nothing. However, I could hear the same pitch "scream" in the stethoscope when probing nearly anywhere on the plenum & intake runners. Now I just need to figure-out why.

I didn't modify anything on the plenum when I diassembled the cylinder head. I simply removed it and set it aside for a few months before reinstalling.

Will find some time during the next few days to pull the plenum (again) and inspect it along with the intake runners but would appreciate any ideas here. First things I will check are the intake manifold gasket edges (any overhang that could "flutter?") and the butterfly valve but appreciate any other recommendations for things to check...
 
Oh... Are you now insinuating that the scream is...

not a mechanical thing... but possibly some kind of vibration or harmonic cause by an air or vacuum leak?

HMMMMM!

This will be a first... and from what you have looked and and heard and tweaked so far... just may be a good possibility!

For the moment let us assume some kinda vacuum leak. Why not (make a mess) and use WD40 and squirt it all around the suspected area(s) while the engine is running and screaming. Hopefully you can do this at an idle or at a steady speed so you can hear and see the engine accelerate when the extra fuel (WD40) is sucked in.

Almost forgot... an UNLIT propane torch will work as well... The WD40 might find a mechanical problem though.

This resolution will be interesting to hear...
 
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