The Leaky Head Thread
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
Okay, so I went back and checked.
9.45:1 compression and a #6 plug is about mid way on a scale of hot 2--> 11 cold.
We would run BP7ES in air cooled twin motorcycles, like a Norton Combat.
If it seemed okay in that, I can't imagine a #6 plug would be a problem in a water cooled engine.
9.45:1 compression and a #6 plug is about mid way on a scale of hot 2--> 11 cold.
We would run BP7ES in air cooled twin motorcycles, like a Norton Combat.
If it seemed okay in that, I can't imagine a #6 plug would be a problem in a water cooled engine.
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
We didn't polish anything, but there were no sharp edges. I looked. And, we are at 6˚ BTDC as Bruno said. In fact, we checked the timing indicator against the balancer using a dial indicator to find TDC and it is dead-on.
Another symptom is the way it cranks. Or, maybe I should say the way it kicks back. Today when Bruno first cranked it the engine spun nicely. Just as he let off the starter it fired a bit but didn't catch. When he hit it again it went UGH and stopped spinning for an instant and then spun and started. Keep in mind that he has MSD (sounds like a disease) and I doubt it has any retard built in for starting.
Another symptom is the way it cranks. Or, maybe I should say the way it kicks back. Today when Bruno first cranked it the engine spun nicely. Just as he let off the starter it fired a bit but didn't catch. When he hit it again it went UGH and stopped spinning for an instant and then spun and started. Keep in mind that he has MSD (sounds like a disease) and I doubt it has any retard built in for starting.
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Postmaster
Joined: Nov 2009
Posts: 4,575
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From: Broken Arrow , OK
I am not sure. A good machinist has had his hands on these heads twice now them all the way apart and nobody said anything about places needing polishing. The odd thing is that I cant remember the truck acting this way the first time it ran before the head gasket failure. Now I can hear something like back fires or something when I flog it down low. I am writing it off as plug wire issues for now, but I hope I am not having detonation issues and I hope that wasn't what caused the head gasket failure the first time.
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Postmaster
Joined: Nov 2009
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Likes: 5
From: Broken Arrow , OK
Okay, so I went back and checked.
9.45:1 compression and a #6 plug is about mid way on a scale of hot 2--> 11 cold.
We would run BP7ES in air cooled twin motorcycles, like a Norton Combat.
If it seemed okay in that, I can;t imagine a #6 plug would be a problem in a water cooled engine.
9.45:1 compression and a #6 plug is about mid way on a scale of hot 2--> 11 cold.
We would run BP7ES in air cooled twin motorcycles, like a Norton Combat.
If it seemed okay in that, I can;t imagine a #6 plug would be a problem in a water cooled engine.
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
The only way you could be having detonation is if those heads are much smaller than we think. We should have CC'd them to make sure, but they don't look small. And, you haven't driven it long enough for it to get completely hot. Further, you don't have anywhere near full throttle (it'll only go 35 MPH) and it usually takes lots of throttle to get detonation on an engine with no vacuum advance.
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Postmaster
Joined: Nov 2009
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From: Broken Arrow , OK
The only way you could be having detonation is if those heads are much smaller than we think. We should have CC'd them to make sure, but they don't look small. And, you haven't driven it long enough for it to get completely hot. Further, you don't have anywhere near full throttle (it'll only go 35 MPH) and it usually takes lots of throttle to get detonation on an engine with no vacuum advance.
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pedant
Joined: Jan 2008
Posts: 23,576
Likes: 40
From: EXTREME southwest CT
Bruno, That 276s plug crosses to a heat range 6 in NGK.
I don't think that is the issue... unless you sealed them with silicone and the heat can't get out of the plug and into the head!
Maybe you're just jetted too lean?
I don't think that is the issue... unless you sealed them with silicone and the heat can't get out of the plug and into the head!
Maybe you're just jetted too lean?
FTE Legend
Joined: Jul 2010
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From: Northeast, OK
You mean the bed I should have kept? No. He just doesn't like slang like "throw the engine in" or "throw the Bronco on the trailer". Would rather we be more precise and take 8 pages to explain how we will first start it up, put it in 4lo, ........ and finally secure it tightly to the trailer in 6 places.
Moderator
Joined: Nov 2007
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From: Denver Metro Area, CO
That is correct. 
Euphemisms such as "throw it on" imply a lack of professionalism, concern for correctness & quality, and can suggest unsafe procedures and end results.
Just my opinion.
That's a bit much but be verbose if you need to, I certainly am sometimes. However, I didn't earn the title of King of the 8-page microanalysis, so....
Euphemisms such as "throw it on" imply a lack of professionalism, concern for correctness & quality, and can suggest unsafe procedures and end results.Just my opinion.
and take 8 pages to explain how we will first start it up, put it in 4lo, ........ and finally secure it tightly to the trailer in 6 places.
