Valve float issues on dyno

[Casper393W]

I think a more stable valve train is more important than a few more hp. I'm guessing a smaller cam would actually make more power, or at worse, about the same. Also, a 2.10 valve doesn't flow much more past .600" lift.

Are you serious dude?

I believe he is! Lol

Wow...

[drifter]

Did anyone measure the valve guide clearance ? We had an engine on the dyno and after a few pulls it had a hard time getting past a certain rpm after many checks we could not find anything externaly wrong and after more pulls the engine tagged a valve once the heads were taken off you could see signs of not enuf guide clearance

[user-9274568]

.600 318/228
.700 327/237
.800 332/243
.900 335/247
1.00 338/249

I had the engine at 723/571 in nitrous trim.

Pushrods were rubbing a touch at the top. No worries IMO..

[CamKing]

Pushrods were rubbing a touch at the top. No worries IMO..

If they're rubbing from flex, that flex could be causing valve loft, and seat bounce, and the more spring pressure you throw at it, the worse it'll get.

[Warp Speed]

Shows a little shaft fretting on the stand also?

[BLstangin]

Did anyone measure the valve guide clearance ? We had an engine on the dyno and after a few pulls it had a hard time getting past a certain rpm after many checks we could not find anything externaly wrong and after more pulls the engine tagged a valve once the heads were taken off you could see signs of not enuf guide clearance

I had this happen on a 383 chevy boat motor once. It ran good on the dyno for like 16 pulls then it started missing at like 5500 rpm, do another pull and it would miss with less rpm. Let it sit for like an hour while we scratched our heads and pulled the efi and put a carb on it, and it pulled clean to 6,000 again. Figured it was the efi, called it a day. Got it in the boat and ran for about 20 minutes with a different efi and was running perfect, cranked it up to 4,200 rpm cruise and about 10 seconds later a huge metal rattle sound and shut it off and on restart, dead miss and horrid knock, yup stuck a exhaust valve. Bet that was our problem on dyno also, but while changing things it cooled down enough that it didn't stick on the last pull.

[user-9274568]

It had .0012 intake and .0015 exhaust.

[R.Brown]

while you are doing that i would at least take 1 intake spring off and look real good at the locks, retainer, valve stem and spring
Tom

^^ Agreed!! ^^

That is the best advise so far and that is an easy thing for you to do now that it is off the dyno. Take (at least) an intake and exhaust spring off and apart, when you pull the rockers off, look at the valve tip pattern. Assuming there was enough run time, personally I've never seen a happy valve train that had the "star" pattern on the valve tips, and/or galled locks / retainers / spring tails.

I found Dynoing engines for the general public is many times torture regarding mis-matched combinations that need to be sorted, so I've seen a lot that need help. Not saying this is the case here, but the way that noses over, I would not be surprised if you found an issue.

If you go back to the dyno, always mount a timing light so you can monitor what's going on during the pull... it is a quick way to rule out an ignition trigger issue.

[maxracesoftware]

the Dyno Air Turbine ( if they have one ?? )
will immediately tell you if its really Valve Float issue

[andyf]

Yeah that power curve looks really nasty on the top end. Hard to say without some more details, could be a bunch of things. If it was me I'd swap the old cam back in to see if the problem goes away. If it doesn't then perhaps it is the ignition system or something else. Those springs should be fine for that application but you could have cam flex or pushrod flex or maybe the cam wasn't ground correctly or who knows what else. Lots of things can go wrong with a new combination!

I just did some dyno testing with the dual conical valve springs from Comp. We used a very aggressive QRI lobe from Comp and the engine pulled nice and smooth the whole way. That was with a much heavier intake valve than what you have (BB Mopar engine) and the seat load on the dual conical springs was only 200 lbs. Sometimes less is more.........

[user-17438]

the Dyno Air Turbine ( if they have one ?? )
will immediately tell you if its really Valve Float issue

I mentioned that yesterday. It appears the only data they have is a graph.

Maybe he should go back to a more equipped facility.

[user-17438]

Was you valve lash huge? Or moving all around?

[af2]

Did I miss what push rods are in there?

[hoffman900]

the Dyno Air Turbine ( if they have one ?? )
will immediately tell you if its really Valve Float issue

Larry, Jay, or anyone,

What metric would you be looking for to distinguish timing vs. say valve float?

[statsystems]

Did I miss what push rods are in there?

I think that was asked but not answered yet. I'd like to know what pushrods are in it.