spring maintenance.... (what has jewels be up to this week?).....

[jewels.]

pic H

[bucket]

glad to see you got it back together.....................

how about a KC area board meet and parts swap?????

[jewels.]

Originally posted by bucket
glad to see you got it back together.....................

how about a KC area board meet and parts swap?????

i'm all for it! do ya know of any around here? unfortunately, i'm in an apt, otherwise, i'd volunteer to host....

i'll check the local truck board, and see if anyone knows of anything happenin soon...

jewels.

[Terry Peerson]

There's a local truck board?

[jewels.]

Originally posted by Terry Peerson
There's a local truck board?

yes, Terry, or what you might call the closest thing to it.... it probably doesnt get as active as this board, but its a good place to meet the local people....

in fact, i should start being more active on it...

here is the site:

http://www.chevygmcofkc.org/

i hope josh wont be too upset about my posting another board html location on here

jewels.

[Terry Peerson]

Thanks,

Checked it out. Not much activity over there though. I would think there would be a few more KC people around. This site is hands-down the best site for 72 Truck info!

[jewels.]

hmmm - this is just an update with the manifolds.....

myself and a fellow board member have been having a PM (private message) conversation about the original cause of the cracks in the manifolds.... the conversation is really good, and offers a lot of info, so i thought i would post it here....

i know that chickenwing (another board member) has a thread (click here) right now about manifolds, which is why i'm returning to this thread and posting this information here....

hope this helps, chickenwing!

jewels.

PRIVATE MESSAGE CONVERSATION:

(anonymous board member) wrote on 03-31-2004 01:54 PM:
I read your posts about your exhaust manifolds! Good job!!!!!! One thing really concerns me though, have you ever wondered what made the manifolds crack in the first place? One manifold cracking is not uncommon, but 2 at the same time is definately a little odd. I have about 2 decades of experience on these trucks, and for the most part they are pretty good.
The cast iron manifolds are just that. Cast iron, and the older they are the more brittle they get! Typically what happens in Chevrolet's & GMC's is the motor mounts get very soft, oil soaked, deteriorate, and finally break (with age). The engine is still secure on the frame, but now when you rev it up with the gas pedal it rocks (a rolling motion) to the right. So what does all this have to do with the manifolds? Well, when the engine rocks, the right manifold is being forced down, and the left manifold is being forced up. If the engine and exhaust is hot and the exhaust system is mounted rigidly all the way back to the bumper something has to give, and in about 90% of the cases it's the manifold cracking just like your pictures depict.
There also could be one other reason that you sort of mentioned in your post. When mounting up your exhaust pipe to the manifold it should be a slip fit. By that I mean the parts should fit together without pulling or prying, or using the bolts or studs to pull the two assemblies together with their nuts. The manifolds work good, but if they are under any tension they crack. If you have any of those conditions then spend some time and adjust your exhaust system to releive the tension. Also check those motor mounts.... especially if they are more than a few years old, oil soaked, or you have a heavy foot on the gas pedal. I'm sure you don't want to go through this whole thing again!!!!! Hope this helps, and if you have any questions I'll be more than glad to assist. ...... (signed)
PS There are a couple of ways to check motor mounts, this is the way I do it. Do this in an open area and be CAREFUL. Open the hood, start it up, and have an observer watch the engine (standing off to the side). Put your foot on the brake pedal firmly and shift into low. Step on the gas a little, but hold it with the brake, then let off of the gas. If your engine rolls significantly when you apply power (gas) then you need to change the mounts. Be very careful doing this!

jewels. wrote on 03-31-2004 03:34 PM:
hmm - this is a great point.... i enjoyed your whole explanation.... as a mechanical engineer, i can fully understand what you are describing here....

hmmm, the cracks i have are not that big... there are cracks on both sides.... but the one on the pass side was larger.... no more than an inch long.... the one on the driver side was only about a centimeter...

i assumed that the cracks occurred because the manifolds were old and used when placed on the engine, and that the cracks developed over time from excessive heating and cooling of the cast iron....

my cab mounts look fairly decent, but i will try to run the test that you suggest the next time i have the opportunity....

i also think i will go out and oil and lube up the exhaust system to ensure that there is a lot of give in the exhaust pipes, to allow for any torque that might occur....

thanks for the advice!
jewels.

(anonymous board member) wrote on 04-01-2004 02:54 PM:

OK, Sounds good! We're not talking cab mounts though, what you want to check are engine mounts. You mentioned using 6 cylinder mounts and turning them around backwards etc. You would be checking these to make sure that they are adequately holding that small block Chevy as they should be. Just a simple check that hopefully is OK. But if your engine rocks then you'll have to look at a few other things.
If you ever go to drag races where cars race down the 1/4 mile track you'll see some interesting things. Your smaller cars (I'll pick my favorite: the 69 Camaro) when they launch at the starting line typically will lift the front wheel off the ground (at the start) as they accelerate down the track. That's engine torque, twisting the whole car frame. They usually strap the leftb side of the engine to the frame because the high horsepower engines will rip out the engine mounts. Take a look some time if you get a chance.
Let's talk about the cracks. This should be a good one for your mechanical engineering!!!!!!!!!! Are the cracks short or long? Where are they located (I couldn't see in the picture), and what caused them? If the cracks were around the bolt holes where it mounts to the engine then it could have been over torqued. If the cracks were located around the periphery of the donut mounting flanged where the studs are then it also could have been over-torqued, or under tension from the rest of the exhaust system. If the manifold cracked in the radius of the curved portion of the manifold (in the middle where it turns downward) and on the back side: that sort of crack is caused by the exhaust system under tension (more specifically: the exhaust system putting high tension on the exhaust manifold) Check it out and let me know what you come up with. If you suspect the exhaust system being the culprit lubricating the points where it's secured is not the correct approach (the hangars) although it may offer a short term remedy. Repositioning the hangars, or installing new ones with the rubber mounts is definately the way to go. Trust me, I speak with experience. I've been all over helicopters (crew cheif) and fixed wing jets, with over 22 years experience. I manage "NASA-ONE", which is the head honcho's corporate jet that's based here in Washington D.C. I'm a mechanic/flight engineer/private pilot. Let me know what you find!
(signed)

[bigskiohio]

I got my broken studs out by dropping a nut over stud then mig weld center of nut to bolt, fill up the nut hole . should turn right out , heat manifold if you want, but mig loosens them up pretty good

[jewels.]

Originally posted by bigskiohio
I got my broken studs out by dropping a nut over stud then mig weld center of nut to bolt, fill up the nut hole . should turn right out , heat manifold if you want, but mig loosens them up pretty good

yes - i did these a while back, but when i did them, i did it the hard way..... it is much easier to do it the way you specify.... and i have learned that this is the way most people would remove the studs....

he he... oh well.... ya have to learn somehow!

jewels.