Tripower update
Thread Starter
Racer
Joined: Aug 2005
Posts: 347
Likes: 0
From: Pace FL
Tripower update
I have torn into the motor to investigate the carnage from the track. First and only pass with this car so far. I had to depend on it as a daily driver for a month or so. It will be a winter project due to finances.
Needs:
2-3 new pistons and rings
all new valves (culprit to begin with)
Sleeve
1 new Head (slight chance of economical repair)
gaskets
I did find several areas where I was leaving power on the table and can fine tune it on reassembly to get a few more hp.
Needs:
2-3 new pistons and rings
all new valves (culprit to begin with)
Sleeve
1 new Head (slight chance of economical repair)
gaskets
I did find several areas where I was leaving power on the table and can fine tune it on reassembly to get a few more hp.
Thread Starter
Racer
Joined: Aug 2005
Posts: 347
Likes: 0
From: Pace FL
The intake valve broke at about 5000rpm. It appears that it was a tensile break at the transition point of the valve head to stem. The broken surface was pretty granular. It just dropped the head of the valve into the cylinder. The valves were from Howard's Cams brand11/32" with under cut stems.
I plan on going back with ferrea 11/32" straight stem competition valves. Thoughts?
I plan on going back with ferrea 11/32" straight stem competition valves. Thoughts?
Race Director
Joined: Jan 2000
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From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
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Got any close up pics of the piston valve pockets...maybe some that aren't torn up too bad?
JIM
JIM
Thread Starter
Racer
Joined: Aug 2005
Posts: 347
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From: Pace FL
Race Director
Joined: Sep 1999
Posts: 11,361
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From: Plano TX
Hmmm... I would look very carefully to why the valve broke. One possibility is a lifter too tight in its bore. At high rpm it can stick hanging the valve open. Piston smacks it->carnage. Happened to an unfortunate forum member...
Safety Car
Joined: Oct 1999
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From: NorCal
Hans
Thread Starter
Racer
Joined: Aug 2005
Posts: 347
Likes: 0
From: Pace FL
Update:
I have torn it down to the bare block. I found a couple more broken pieces to add to the list. I found one slightly bent connecting rod from the destroyed cylinder. And the porcelein from the sparkplug tip got into the intake then to a couple other cylinders and scratched up the cylinder walls. It will have to be bored 0.010", so I will be buying a new rotating assembly. The crank and all bearings at least were in wonderful shape. 0.070 over and 4.25" stroke would be a 498 I guess...
I have torn it down to the bare block. I found a couple more broken pieces to add to the list. I found one slightly bent connecting rod from the destroyed cylinder. And the porcelein from the sparkplug tip got into the intake then to a couple other cylinders and scratched up the cylinder walls. It will have to be bored 0.010", so I will be buying a new rotating assembly. The crank and all bearings at least were in wonderful shape. 0.070 over and 4.25" stroke would be a 498 I guess...
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Thread Starter
Racer
Joined: Aug 2005
Posts: 347
Likes: 0
From: Pace FL
There appears to be ~.080" clearance. Therewas no evidence of any contact in other cylinders or near contact (no rubbed carbon). It appears that the 11/32" with undercut valves just weren't strong enough. I am going with straight stem ferreas.
Thread Starter
Racer
Joined: Aug 2005
Posts: 347
Likes: 0
From: Pace FL