Inliners International Forums General Discussion Hi Performance First Start Chevy 250

I have fired up my '73 250 with Langdon's cast headers, Offy intake and Holly 390. After some tuning it is running ok but I have 2 issues to address. One is water seeping from the Langdon's Heat plate around the gasket. It is scary tight and I was careful to get it tightened down even but it still seeps. I used the stock gasket used to seal the exhaust heated manifold and I think is not suitable for H20 use maybe?

The 2nd problem is a weird one. All the time the engine is running it emits this piercing incredibly loud shreiking whistle. Sounds like a teakettle on full boil. Or several tea kettles. It's not the alternator, water pump, or power steering pump. The sound seems to be coming from the area just above the intake manifold and the front half of the engine.

I could use some advice on this one.

Some pics of the project are below in my sig.

I have the same setup with the heat plate on the Offy. No problems at all. I made a gasket from gasket material from a local auto parts store; common stuff. I had called Langdon for advice on installation and was cautioned not to tighten too much as that could cause the plate to warp. It sounds like that could be your problem. I can't comment on the noise you're hearing.

You might have a vacuum leak.

It sounds like you have exhaust leaking. Checking your project photos, it looks like your head had AIR, I would pull the plugs and check that they have a copper 'o' ring or other means to seal them from the exhaust pressure. Someone may have just put bolts in the ports.

On the water leak, I think you are right about the stock gasket, make a new one and maybe use some hi-temp RTV.

Tim

The last time I had this problem it was the damper delaminating and allowing the pulley to scrape the timing gear housing! Hope it's something simple! Herb

Thank you all for chiming in.

New discoveries:
I used a length of heater hose held to my ear to try to pinpoint the whistle/shreik and discovered it is loudest just above the center siamesed intake port. Real screaming Mimi.

I tried the old pull the spark plug wire off at idle trick to see if the rpm's decreased and the 2 center plugs had NO EFFECT at all. (I did get the P shocked out of me though)1,2,5,6 had an rpm drop.
Then:
compression test shows 130psi - 135psi cold and dry cyl 1 thru 6
Compression test shows 160psi - 165 psi with 2 squirts of 10-30 in each spark plug hole cyl 1 thru 6.
I used 5 rotations of the engine each test. The gage quit climbing on rotation 4.

So the compression is good as I see it.

Ohm test of the used autolite plug wires shows about 3K Ohms per foot. The Bosch platinums have about 2000 miles on them.

I'm thinking vacuum leak at the center siamesed port.

Please weigh in with any thoughts. I welcome the input. I been messing with these contraptions since 1968 but I will never be too old to learn something no matter how common or weird.

Correct. It is a 1973 engine. I used the stock plug to seal the AIR holes. I sliced each one off the air distibution tubing and removed the stub that was left. I then tapped the hole that remained in the center of each fitting to accept a 1/4-20 set screw which I installed with JB weld. I also excluded the tube that sticks down into the exhaust port. I screwed this assembly into each A.I.R. port. I'm thinking that one of those two items I removed is what created the seal you speak of. Good observation. I will do some measuring and fabricate 6 copper O rings and see if that makes a difference.

I have some gasket material from another project that worked well sealing cooling system coolant and pressure. I will fabricate a new gasket from that and replace the stock metal based one on the heat plate.
Lurching towards success one step at a time.

I'm thinking you might be right. See other posts for details. And thanks!

Vacuum leak.

Ron

The dissection will happen tomorrow. I got a new Felpro gasket and I'll try this again.

Definately vacuum leak. But not where I thought it was. I bought a very inexpensive automotive stethoscope and attached an extra length of tubing to it, Then while the engine idled I went hunting for the whistle. It was loudest around the center intake port but then as I probed around I discovered it was ear splittingly loud at the carb baseplate area right below the floatbowl.

I have a 3/8" aluminum 4 hole spacer. The loudest whistle was at the carb and spacer plate interface. I used the very thin black paper gaskets that I have always used with success with the V things I have fiddled with in the past. I'm suspecting these gaskets.

I took the carb and spacer plate off and replaced both gaskets with new ones that I had in my spare holley parts box. The vacuum leak is still there, only worse, and is still at the spacer but in a different spot. Evidently the spacer, or manifold flange, or carb base is not flat and the black thin paper gasket is not doing the job.

Felpro makes a thicker gasket and I will get a couple of those to try. I will also check my spacer for flatness as well as the carb baseplate.

I will get this.

Youtube link
http://www.youtube.com/watch?v=i91fw1OA96o

spray your carb sapcer with some lay out dye Then use a peice of sand paper on a GOOD flat surface. and run the spacer over it a few time and you will see any low spots.You can keep doing this till all low spots are gone.

Good suggestion and I plan on doing just that. Now where did I put my can of Dye-Chem....

You can use a permanant marker or other types of markers.

MBHD

You can also use a very lite/mist of Paint.Or pretty much any lite coat of color.Will do the same as all of the above.

Success! Fixed.

I got a pair of Mr. Gasket part#55 .063" thick 4 hole gaskets and that did the trick. Started up and idled. No bucking or thrashing or whistling. Dang that feels good. I set the idle speed, mixture and set the timing and it just purrs.

Now I can get on to finishing the car and maybe see some road time this summer.

Thank you all for your assitance.

Sound byte of the dual exhaust.

http://www.youtube.com/watch?v=mAxWGBr5wKA

Sounds nice! You have to do something about those legs.

Let's see some more once it is on the road. Tom

Something that I noticed while I was running the engine is a whirring/rattling sound that is evident whenever the clutch is engaged. Once I got over the excitement of fianally having it running I noticed it. Coming from the transmission in neutral or in gear with the clutch engaged. Push in the clutch and the noise goes away. In the video I posted the sound comes and goes with the rear tire rotation. Just before the end of the video the sound appears just as the tires start turning again.

I suspected a bad input bearing in the Saginaw 4-speed. Today I pulled out the Saginaw and checked it out and the input bearing is shot. Gritty and noisy when turned even by hand. I swapped in another Saginaw that felt smooth and quiet and the noise is gone. Video is pending.