Piston-valve problem with TR230 cam
12-18-2003, 11:56 PM
#1
Piston-valve problem with TR230 cam I'm looking for some input on an interference problem I've never encountered before.
01 C5 Stock bottom end
JPR stage 2 241 castings milled .060
TR230/224 .575/563 111
Pistons Flycut .100
The valves are still hitting the notches in a few spots. .020 clearance on others I then assumed the cam timing must have been off a tooth. I've done this scores of times without issue, but you never know. So I tore the front back down and the cam is right on the dot. I even switched out the Rollmaster chain and sprockets for the stock 19K mile pieces and still the same problem.
There's got to be some issue with the cam, but what? The cam was a secondhand cam that obviously didn't bend valves on the engine it came from, Heads milled .060 shoudn't cause THIS big an interference.
???
01 C5 Stock bottom end
JPR stage 2 241 castings milled .060
TR230/224 .575/563 111
Pistons Flycut .100
The valves are still hitting the notches in a few spots. .020 clearance on others I then assumed the cam timing must have been off a tooth. I've done this scores of times without issue, but you never know. So I tore the front back down and the cam is right on the dot. I even switched out the Rollmaster chain and sprockets for the stock 19K mile pieces and still the same problem.
There's got to be some issue with the cam, but what? The cam was a secondhand cam that obviously didn't bend valves on the engine it came from, Heads milled .060 shoudn't cause THIS big an interference.
???
12-19-2003, 01:56 AM
#2
I can shift faster than you.
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I would degree the cam in and check the intake centerline. Dot-to-dot, this should result in a 111* ICL (assuming the cam was not special ordered).
You could also retard the cam a couple degrees. Retarding the cam opens the exhaust valve earlier and the intake valve later. This will give you a few thousandths more clearance on the intake side, and pretty much the same amount less on the exhaust.
I ran GTP heads milled .050" with a TR230 cam and the pistons had to be notched when I rebuilt the shortblock.
You could also retard the cam a couple degrees. Retarding the cam opens the exhaust valve earlier and the intake valve later. This will give you a few thousandths more clearance on the intake side, and pretty much the same amount less on the exhaust.
I ran GTP heads milled .050" with a TR230 cam and the pistons had to be notched when I rebuilt the shortblock.
12-19-2003, 11:36 AM
#4
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That cam should have ~.080 clearance intake & .110 exhaust on a stock longblock. With the heads milled .060 & larger valves....well, you obviously see the problem.
Are you checking P2V with the lifters at 'zero' prelaod?
Are you hitting the piston on BOTH intake & exhaust? If you have plenty of clearance on one side & none on the other you can move the cam a few degrees (advance or retard depending) & get a little more clearance. However, this should only be used for that extra .010-.020 clearance needed as more then this would move the cam too much.
Are you checking P2V with the lifters at 'zero' prelaod?
Are you hitting the piston on BOTH intake & exhaust? If you have plenty of clearance on one side & none on the other you can move the cam a few degrees (advance or retard depending) & get a little more clearance. However, this should only be used for that extra .010-.020 clearance needed as more then this would move the cam too much.
12-19-2003, 12:31 PM
#5
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...i have heads milled .055 and my cam is 220/220, 564/564, 112 (it just fit!)
...I asked about using bigger cams before I bought anything and was told clearence issues would result...
...I would not go nuts with the flycutting since if you go too far you will have a real mess ....just get a smaller cam...
...I asked about using bigger cams before I bought anything and was told clearence issues would result...
...I would not go nuts with the flycutting since if you go too far you will have a real mess ....just get a smaller cam...
