Tightest valve to piston clearance...

[1stBxMopar]

What's the tightest valve to piston clearance you have run with a HYDRAULIC CAM- (intake and exhaust)
Who has gone closest to the edge!!!!!!!

 

[Budnicks]

0.060" exhaust, I don't remember how close the intakes were, maybe 0.080", the problem is, the piston chases the exhaust valve back up to the seats, especially on our modern split duration camshafts, with wide lobe centers/lobe seperations... The intake valve is running away from the valve, as it opens... I wouldn't recommend it though, I had "no issues" but, I also never floated the valves either... 5800 rpm's or so max, cam & valve springs could go to 6200 rpm advertised easily, but didn't pull past 5800 rpm, w/hydraulic camshaft ballpark spec.'s of 0.525" gross valve lift & around 280*-ish advertised duration, w/1.6:1 roller rockers... I had lots of clearance before the 1.6:1 rockers added 0.045" lift = 0.560" gross vale lift...

 

[383man]

I have seen guys run them as tight as Budnicks says at .060 but I prefer .100 minimum to be safe. And you have to make sure you check it all thru the overlap period. Ron

 

[RustyRatRod]

.100 minimum has always been the standard. I'd say stick with it.

 

[Meep-Meep]

The key here is hydraulic cam. All you need is some pump up and not enough room and :violent1: I had plenty with HYD cam motors because my lift was never over .500". I want to say .100" +

You know 427 Fords had raised pads on the piston tops and raised dimples on the valves so if they were to meet the only contact would be in the center - thus not hitting the valve on edge and bending it. Interesting solution.

 

[RustyRatRod]

That's why I NEVER EVER EVER use hardened pushrods. I want to replace just pushrods. I don't want a grenaded engine. lol

 

[moparpoor]

0.090 on the intake and 0.120 on the exhaust any much tighter than that is a gamble.Especially with a sloppy hydraulic cam.Tight lash roller or solid,super light valvetrain,and spot geometry you may run tighter.Don't forget bottom end clearances along with piston to wall clearances.A little rod stretch and piston rock ooops You get the picture.

 

[Budnicks]

That's why I NEVER EVER EVER use hardened pushrods. I want to replace just pushrods. I don't want a grenaded engine. lol

I agree to a certain point, until you get any kind of valve spring pressure that won't work any longer, or over 0.550" lift or roller-cams or adjustable rockers of higher ratios even, it only works with smallish Hydraulic & Solid lifter flat tappet stuff maybe, where you don't need a ton of valve spring pressures & running stock type rockers... But I get your point...

 

[moparbob498]

Well.....i've always run .100 on exh. & .100 on int.--but this latest 440 my bro & i put together has around .068 on exh. & @ .085 on int.
And we've had it running..& free revved it good bit...if it was gonna grenade we wanted it to happen in our garage not at the track.. so far so good..& its only a .613 ultradyne tight lash solid (.026 lash) will give further update soon as she's about ready for her debut at Pittsburgh Raceway.....

 

[blue_stocker]

With a good amount of stock eliminator cams, we're lucky to have any so some builders rely on changing the rocker ratio as non-factory notches are not allowed. Personally I had one cam that allowed a whopping .030". As witnessed on my pistons something was dancing, not enough to damage anything but dimples were the norm for that engine and that with a .458" lift cam! Of course, the duration was in the 258/263 @ .050" range and the lobe ramp profiles were equal to that of some mechanical roller cams...but always fun and interesting playing with these parts. As a general rule, minimum .080" for both I/E, if you can control that figure by flycutting the pistons.

 

[moparbob498]

Thats nice to know.....im still paranoid....lol