What would cause one header tube to be hotter than the others?

Joe Harrison · Apr 12, 2007

Take you reading direct from the lifter if possible using a long feeler for the dial. Most come with several leanghts. Pre-load it some and set to zero and do a full revolution about 3 times and compair readings. Then do a good cylinder and see what you have. Remember to compare intake to intake exhaust to exhaust.

Speaking of heads:

What casting number or type of heads are running? What type of intake? Some later castings are more prone to cracks than others. 882 heads for instance can crack but still are not a bad cracking head. Now 624 heads crack all the time. They crack between valves or from seats, intake and exhaust runners and from spark plug holes. All other heads can crack here also but 624's are the worst. I have seen all of the above on 882's and basicly any mid 70's heads up to current versions of vortecs. If you have a head with 7 bolt hole exhaust manifold bolts you have a light casting head.

Joe

mnm99 · Apr 12, 2007

I'm sorry I take that back. When I pulled the plugs just now to do the dial test they did look the same. I'll take a pic. I only dialed the 2 exhaust + 2 intake lobes on 4 and 6 so far and they are the same. What a pain! I'll go get the casting.

Here are the numbers I got.

Pass 8870128 or 8870123?

Drivers 8970126

I think they are 3970126 They are hard to read. If I had a bad lobe would I see it in the rocker movement? They all look the same at idle.

Sound right?

Joe Harrison · Apr 12, 2007

Need to dial it at the lifter. Hydraulic lifter is being pushed into the lifter by the spring tension and with the engine not runing it can be bleeding off as you rotate it. You want to do it similer to degreeing a cam. you would use a solid lifter for that but that's why I said to pre-load it and then zero your dial.

The casting number 3970126 comes back as 67-71 327/350 heads. if these heads do not have hard seats they could be having trouble. 71 or so is close to having factory induction hardened seats. Also old heads if they are hard seated can go to water around the seat when opening up for the new hard seat. They may not be cracked or crack when done but if thin can cause problems in a few miles or a few years it just depends how rusted they are from the water jacket out.

You might be left with only afew options if you can't find anything and that's to pull it apart. I would look at the cam first but then again heads are just as easy to pull when you get that far.

These heads could be cracked from the spark plug hole to the outside of the head. Each intake stroke it pulling air/vacume/leaking vacume to the cylinder. I have only ever seen one head cracked that bad in a spark plug hole. It was an angle plug 492 casting head. Pissed me off to!!! I had it welded and ran it anyway!!

Joe

Lonnie67 · Apr 12, 2007

mnm99 said:
Also I am noticeing , I may be going crazy because of all the test I've done, but right around that cylinder I hear a clacking sound. Not a loose rocker sound or a rod knock, kinda K K K K , EVER SO SLIGHT.

Exhaust leak at header gasket? They sound just like valvetrain clacks. This might cause the hot header, not your miss though.

I quickly read both post and didn't see anyone mention this, but maybe I missed it.

mnm99 · Apr 12, 2007

Joe Harrison said:
Need to dial it at the lifter. Hydraulic lifter is being pushed into the lifter by the spring tension and with the engine not runing it can be bleeding off as you rotate it. You want to do it similer to degreeing a cam. you would use a solid lifter for that but that's why I said to pre-load it and then zero your dial.

The casting number 3970126 comes back as 67-71 327/350 heads. if these heads do not have hard seats they could be having trouble. 71 or so is close to having factory induction hardened seats. Also old heads if they are hard seated can go to water around the seat when opening up for the new hard seat. They may not be cracked or crack when done but if thin can cause problems in a few miles or a few years it just depends how rusted they are from the water jacket out.

You might be left with only afew options if you can't find anything and that's to pull it apart. I would look at the cam first but then again heads are just as easy to pull when you get that far.

These heads could be cracked from the spark plug hole to the outside of the head. Each intake stroke it pulling air/vacume/leaking vacume to the cylinder. I have only ever seen one head cracked that bad in a spark plug hole. It was an angle plug 492 casting head. Pissed me off to!!! I had it welded and ran it anyway!!

Joe

Thanks. I did remove the rocker arm, brought the lobe to the lowest part and set my dial gauge right on top of the push rod and zeroed it out . Turned the engine by hand and saw the rod go up. I wasn't to sure how to read the gauge but it has a small dial thats 1-10 I would imagine 100th and the large dial thats 1000th. Both times it went to 3 on the small and 15 on the large. Anyway it was the same. I only did 6 and 4 though.

I did a compression check again for the heck of it while the plugs were out. This time the engine was warm and I got all 150's to 152's. I'm amazed how close they are.

Question.... What is accomplished by doing a compression check. What does it EXACTLY tell you. I hear leak downs are better, but what solid facts come from a compression? When I talked to comp cams they said if my compression is good the cam is good. How correct is that?

I want to bring it somewhere to verify my ignition is good before I start pulling heads. I know I verified this 2x but for a piece of mind I would like someone else that does this for a living to tell me.
Thanks.

zdld17 · Apr 12, 2007

Roughly, sounds like you got .315 lift before rocker arm , then x 1.5 = .470 valve lift? How big did you say your cam was?

Joe Harrison · Apr 12, 2007

A compression test will tell you if your even accross your cylinders. You want a variance of less than 10%.

If it's low and you squirt oil in the cylinder and the compression goes up you have a cylinder seating problem that is most likey rings or wear. If nothing happens it's a head gasket or stuck valve basicly something above the short block..........or a hole in the piston or some other major short block damage.

leak down tests make it easy to pin point the problem with the leaking air. both are good and complement each other. With both valves closed and not operating you may or may not get compression. You have to get air into the cylinder to get compression. if loosen the rocker complety off the valve so it's not touching the spring at all on both intake and exaust (heck remove them) bring the piston to TDC install the compression tester and turn it over you should have very little compression. If it gets the 150-160 or your normal reading, air is coming into the cylinder from someplace. Your valves may not be sealing to the seat, gasket bad around cylinder or cracks in head or block?

Some one correct me if I am wrong. but if you close it all off the reading should not be much, you can only compress the amount of air in the cylinder. With it at TDC that is not much. When the piston strokes and the reading goes to normal it would have to be getting air from some place other than the normal intake route correct??

Joe

mnm99 · Apr 12, 2007

zdld17 said:
Roughly, sounds like you got .315 lift before rocker arm , then x 1.5 = .470 valve lift? How big did you say your cam was?

280H comp cam. I would give or take a little since it's my first time.
Part Number 12-212-2
Engine 1955-1998 Chevrolet
262ci-400ci
8cyl.
Grind Number CS 280H-10
Description

--------------------------------------------------------------------------------

Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.48 0.48
Duration At 0.006 Tappet Lift 280 280

--------------------------------------------------------------------------------

Valve Timing At 0.006
Open Close
Intake 34 66
Exhaust 74 26

--------------------------------------------------------------------------------

These Specs Are For The Cam Installed At 106 Intake CL
Intake Exhaust
Duration At 0.05 230 230
Lobe Lift 0.32 0.32
Lobe Separation 110

--------------------------------------------------------------------------------

Joe Harrison · Apr 12, 2007

Hell I just thought of something. You might have a crack at the heated exhaust crossover to the #6 intake port. That port is under pressure with hot exhaust gases. It could also be in your intake if it's cast iron. If you pressureize the cylinder with the exuahst open in #6 and close up all the others intakes by loosening the rocker arms so the valves come all the way up. make sure your #6 intake valve is closed and the piston in #6 at BDC. put that 100 PSI on it and listen at the carb. If you hear something coming through the carb it can only be the intake valve not seating or a crack.

Joe

zdld17 · Apr 12, 2007

mnm99 said:
280H comp cam. I would give or take a little since it's my first time.
Part Number 12-212-2
Engine 1955-1998 Chevrolet
262ci-400ci
8cyl.
Grind Number CS 280H-10
Description

--------------------------------------------------------------------------------

Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.48 0.48
Duration At 0.006 Tappet Lift 280 280

--------------------------------------------------------------------------------

Valve Timing At 0.006
Open Close
Intake 34 66
Exhaust 74 26

--------------------------------------------------------------------------------

These Specs Are For The Cam Installed At 106 Intake CL
Intake Exhaust
Duration At 0.05 230 230
Lobe Lift 0.32 0.32
Lobe Separation 110

--------------------------------------------------------------------------------

Your cam advertised at .480, you measure about .470. Done deal, move on to something else , Wouldn't you guys say so? Sounds like Joe thought if something else.

Joe Harrison · Apr 12, 2007

I would say so Don. I don't think it can get any closer than that.

Dang only problem with what I posted above is. You need to plug the exhaust at the header/manifold. Or close off all exhaust valves on that bank 2,4,and 8 by loosening rockers to them also. Still have the problem of air going out exhaust though....Dang it.

Any ideas guys??

Joe

77wolf10.85 · Apr 13, 2007

Pull the heads and be done with it.

But I think I would put the left bank head on the right bank and vice versa if I didn't see a problem. And see if the problem switches banks. Whether or not you buy new gaskets is up to you.:noway:
You can leak test your intake valves with water and the head on it's side, older heads will trickle a teeny bit from intakes because they get crap in the seats.
You can do the same to the exhaust but the crossover port loses all your water on the center exhausts. Stuff a rag in it and you'll get a quick test.

TMessick · Apr 13, 2007

I'm coming from EFI and distributorless ignition land, but if you had an odd retarded spark on one cyl it would also raise EGT significantly. Not sure how this would happen with a distributor (problem with the cap?) But it might be worth clocking the distributor and moving your plug wires just to verify. Kind of a long shot, but thought I'd throw it out there...

mnm99 · Apr 13, 2007

TMessick said:
I'm coming from EFI and distributorless ignition land, but if you had an odd retarded spark on one cyl it would also raise EGT significantly. Not sure how this would happen with a distributor (problem with the cap?) But it might be worth clocking the distributor and moving your plug wires just to verify. Kind of a long shot, but thought I'd throw it out there...

Thanks. I tried that too.

mnm99 · Apr 13, 2007

77wolf10.85 said:
Pull the heads and be done with it.

But I think I would put the left bank head on the right bank and vice versa if I didn't see a problem. And see if the problem switches banks. Whether or not you buy new gaskets is up to you.:noway:
You can leak test your intake valves with water and the head on it's side, older heads will trickle a teeny bit from intakes because they get crap in the seats.
You can do the same to the exhaust but the crossover port loses all your water on the center exhausts. Stuff a rag in it and you'll get a quick test.

Like I said, once I verify the ignition and do a leak down I think I'm pulling the heads. It would make me feel better kinda knowing whats wrong before I do that.

Everett#2390 · Apr 13, 2007

Marc has done the air supply test to the cylinder and reported he did not hear any leakage at the tailpipe(s) and no bubbles in the coolant. But, he did say he heard an air leak. I would have placed a balloons over the tailpipe, or small condoms..........LOL

Marc has ruled out camshaft, valvetrain, short block, and most other maladies. gaskets are the only items left.

Joe Harrison · Apr 13, 2007

The one place that can not rule out is the exhuast cross over in the head. It could be cracked and leaking to the intake runner side of #6. The exhaust cross over shares a casting wall with the #6 intake port, also #4. On the right bank #3 and #5.

Joe

mnm99 · Apr 13, 2007

Joe Harrison said:
The one place that can not rule out is the exhuast cross over in the head. It could be cracked and leaking to the intake runner side of #6. The exhaust cross over shares a casting wall with the #6 intake port, also #4. On the right bank #3 and #5.

Joe

I hear ya. My intake doesn't have the crossover and the gasket blocket the heads off. I can see if it's cracked on the head. We'll see. I've been looking at the Brodix IK200 and the Sportsman II heads.

What piece of test equiptment could tell 100% that the ignition is good? Could the ignition even do that to temps?

Joe Harrison · Apr 14, 2007

Scope on the ignition. The old school test!! So to test you cross over all you need to do is disconnect your header/exhaust manifold. Block the exhaust port Put the piston at BDC. and remove the rockers from the intake and exhaust on #6. Run pressure in from the spark plug hole. If your getting pressure or air coming out the carb it has to be one of two things. Intake valve not sealing because it's burnt, cracked, bad seat stuck in a guide and not closing all the way or there is a crack going to the intake side via exhaust cross over etc. Basily will narrow it down to a head problem of some sort.

Joe

jaguareats · Apr 14, 2007

:beers: mnm lol cheers told you sell me car thought you had a weird problem with car.when i talked to you. it is getting weirder by the minute.for a tach install hhhhmmm.

What would cause one header tube to be hotter than the others?

Joe Harrison

mnm99

Joe Harrison

Lonnie67

mnm99

zdld17

Joe Harrison

mnm99

Joe Harrison

zdld17

Joe Harrison

77wolf10.85

TMessick

mnm99

mnm99

Everett#2390

Joe Harrison

mnm99

Joe Harrison

jaguareats

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