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I want to adjust my rockers on my 468 BBC, but I don't know what the cam specs are, or even what manufacturer. It is a solid flat tappet cam, roller rockers. thats all I know. It has a small lope at idle-I was told it was a "mild" cam. I guess I could check the lift with a dial indicater, if that makes any difference. What is a safe setting for the valve lash? How about a cold lash setting to get them in the ballpark before I set them hot? Right now they seem to be at about 22 cold, which seems like a lot to me. The heads are iron 049s. Any opinions?
 

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All iron isn't going to grow nearly as much as aluminum, so the numbers should be close hot vs cold. .024 intake/ .026 exhaust are really common hot numbers, I wouldn't go much under that. Im just guessing here but I would think all iron would expand .004 to .006, I wouldn't cold lash it under .018 myself intake or exhaust.
 

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steelcomp was here
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I want to adjust my rockers on my 468 BBC, but I don't know what the cam specs are, or even what manufacturer. It is a solid flat tappet cam, roller rockers. thats all I know. It has a small lope at idle-I was told it was a "mild" cam. I guess I could check the lift with a dial indicater, if that makes any difference. What is a safe setting for the valve lash? How about a cold lash setting to get them in the ballpark before I set them hot? Right now they seem to be at about 22 cold, which seems like a lot to me. The heads are iron 049s. Any opinions?
If they're irons, chances are they're not going to change much at all. The ex valves may tighten up a little depending on the valve material, but I'd start at .018"-.020" int and .022" -.024" ex.
 

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All iron isn't going to grow nearly as much as aluminum, so the numbers should be close hot vs cold. .024 intake/ .026 exhaust are really common hot numbers, I wouldn't go much under that. Im just guessing here but I would think all iron would expand .004 to .006, I wouldn't cold lash it under .018 myself intake or exhaust.
If they're irons, chances are they're not going to change much at all. The ex valves may tighten up a little depending on the valve material, but I'd start at .018"-.020" int and .022" -.024" ex.
What, are you guys sitting together sharing a sundae???...:D

You ever recomend + .001 on the exhaust?

GT
 

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O O. If you have a tight lash cam and it is running .020 or more you will beat it to death. They run .010-.014 normally. How does it sound at its current adjustment? If correctly adjusted you wont hear much noise. If it is fairly quite at that .020 I would set them at .022 and .024. See how that sounds. If it is quite you might be ok. Without the cam card it is just experience. Sorry I can't help anymore then that. And I would set those hot. .022 intake and .024 exhaust. If it rattles all to hell try .012 and .014. You can destroy your valve train if not set up right.
 

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Discussion Starter #9
O O. If you have a tight lash cam and it is running .020 or more you will beat it to death. They run .010-.014 normally. How does it sound at its current adjustment? If correctly adjusted you wont hear much noise. If it is fairly quite at that .020 I would set them at .022 and .024. See how that sounds. If it is quite you might be ok. Without the cam card it is just experience. Sorry I can't help anymore then that. And I would set those hot. .022 intake and .024 exhaust. If it rattles all to hell try .012 and .014. You can destroy your valve train if not set up right.
I don't notice any valvetrain noise,but it's pretty loud, so it's hard to tell for sure.
 

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I don't notice any valvetrain noise,but it's pretty loud, so it's hard to tell for sure.
Well if it is a tight lash cam and you are running it at 22 and 24 you will hear it. Put something on the valve cover and it will be hammering. Odds are it is a normal cam.
 

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Dig up the thread in here about flattened cams and oil & additives. A high quality oil will reduce the valvetrain noise.
 

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steelcomp was here
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What, are you guys sitting together sharing a sundae???...:D

You ever recomend + .001 on the exhaust?

GT
Guess I'll give the kid the cherry...probably never had one....:D

Two things to consider on lash. Heat and expansion (or the lack there of) and the lobe design. One we know, the other we don't in this case. It's always better to be on the tight side of recommended...as long as the valve closes and there's enough seat time for heat transfer, the rest is academic. Most of the time tighter lash will settle down valve train harmonics and reduce valve bounce which most people mistake for thinking you need a bigger cam. Too much lash, like the guy with the fat broads in his avatar said, can destroy a tight-lash cam, and cause unneeded noise and harmonics in a normal cam. The .002" added to the ex side typically allows for the extra expansion of the ex valve from seeing more heat, so .001" probably isn't enough. I am definitely not a fan of excessive lash.
What's most important than the actual lash setting is consistency from valve to valve. If you;re off a few thou from recommended, that's OK, but they all need to be consistent, whatever numbers you choose.
 

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Discussion Starter #14
OK, how hot is "hot" when adjusting the valves? I can recerculate water with a bucket and bring the temp up to whatever I need, but I only have temp guages on my heads. I fried the normal temp guage but thats another story. What is a good temp for the heads to read for adjusting? Also what would be a normal running "in the water" head temp ?
 

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OK, how hot is "hot" when adjusting the valves? I can recerculate water with a bucket and bring the temp up to whatever I need, but I only have temp guages on my heads. I fried the normal temp guage but thats another story. What is a good temp for the heads to read for adjusting? Also what would be a normal running "in the water" head temp ?
That's always the $64.00 question, but with iron heads, I wouldn't worry about it. Are you going to run the engine long enough to heat everything up?
You can run it long enough to heat up the water, but iof you don't have a good heat soak going, the engine will cool as you check the lash, and by the time you're done, the first valves won't be the same as the last ones. OR- run it long enough to get everything up to temp, get a good heat soak, (which is really hard to do without putting a load on everything) and then check one head. Then do it all over before you check the other one.:)bulb
Is that really necessary? Hmmm. Depends on how accurate you think your lash needs to be.
 

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I like to see 180* min, 200* is better. At that point youv'e been running near 5 minutes, the motor has a good heat soak. Let stand for 5 to 10 minutes, until the headers won't burn you, than lash like the wind!!!

P.S. Thanks for the cherry Professor!!!
 

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Discussion Starter #17
I like to see 180* min, 200* is better. At that point youv'e been running near 5 minutes, the motor has a good heat soak. Let stand for 5 to 10 minutes, until the headers won't burn you, than lash like the wind!!!

P.S. Thanks for the cherry Professor!!!
And that is temp at the head? I have a guage on the end of each head.
 

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i always check/adjust mine cold, between every race weekend. i do it that way because expansion will (should) be the same, and also because i have a stud girdle, which takes more time to get an adjustment exactly where you want it. then, get it hot and do a "quick check" to validate that everything is where i want it, trying to complete the check before it cools too much.
 

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i always check/adjust mine cold, between every race weekend. i do it that way because expansion will (should) be the same, and also because i have a stud girdle, which takes more time to get an adjustment exactly where you want it. then, get it hot and do a "quick check" to validate that everything is where i want it, trying to complete the check before it cools too much.
Crane cams used to have a tech article with cold lash ±'s on their site that said: +002 for iron heads on iron block, -.006 for aluminum heads on iron block and -.012 for aluminum heads on an aluminum block

They should still be checked hot like bp said, but that should get you in the ball park.
 
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