KB HyperT's?

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340RULES

340RULES

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Hi all,

I'm in the process of exchanging my uncut J's to the RHS Heads stage 1 through Shady. I purchased the car after the bottom end was completed. After opening up the engine last eve I notice KB HyperT's with valve reliefs. Without miking it appears to be 005 positive deck. I'm familiar with the top ring gap problem with KB HT's, the engine had approx 3000 miles prior to tear down. Ran great, no detenation problems! Even hit 7200 rpms on occassion I just want more power if I can get away from stroking. I like the 340 .030 over aspect. I would like to run 10 1/2 to 1 or a little less on 91-93 pump. I have a 508 purple with an air gap and quick fuel 650DP. Any suggestions on head gasket thickness, or if I should can those pistons? Seems the KB Cast HT's have good and bad press!
 
I think if it were me and you did not have a written record fo the top ring gap - I'd take the pistons out and check. It's a pain - but it's that important. You should have more heat in the top ring with the RHS - there's less surface area and you're adding compression. So you want to make sure the top ring has a lot of gap. As far as the head gaskets - I'd go with any composition gasket that is .035-.045 compressed - the thinner the better.
 
Moper, I was thinking the same. the compress is in the low 10's. I would like to bump to 10.5 to 1. If I go that route why don't I just replace the pistons? any recommendations for pump gas.
 
I ran KB's (KB107) in a 360.
Lasted 5 years before one came apart, killing the cylinder & Eddy heads.
It had seen maybe 10 shots of NOS (125hp) over its lifetime, it had 925 passes on it.
I planned ahead on the NOS shots with a different tune.
The start of the 2012 season, I ran a leak-down (5%), all good.
The first race of the season, it ran as fast as it ever had & blew up after the run.
If I had it to do over again, I would have went with a Forged piston.
 
I agree with forged if I plan on shooting nitros, I'm just trying to improve an already sturdy and dependable engine.
 
I would not worry about the 1-2 point in compression. It's moot.
What con rods are in the engine now? If it is a factory rod, simply stay with a standard .039 Fel-Pro and be good with it. Unless the slugs are positive in height, you may want a little more room. No sense in pushing it with Hyper slugs. None what so ever.

You can find a little more power with a 750 carb a d different cam. Run a split duration cam in what ever style your going to run. (Hyd. Or solid or roller etc... )
 
Over 900 passes is nothing to flinch at.those pistons did they're job imo

If it has 3000 miles on it and already 10.1 comp...I would.t take it apart to check cause of half a point increase, it would have popped a ring land at 9.1 comp already if the gaps were too tight.imo

Leave it is my advice.
 
IMO - no reason to replace the pistons. Just run a quick cleaning pass with a light hone and toss a set of fresh file-to-fit rings in it at most. Set the top ring per KB's spec for high performance use (I think it's going to end up around .028-.030", run the 2nd gap at .024", and run whatever gasket you can find. If you take it apart and measure the top and it's big enough, you could just put it back together...
 
Guys, thanks a bunch for the advice, I believe if it was going to pop it would have long ago, especially spinning to 7200 plus. Factory rods rumble, going to perform a clay check and see what I have, spray some pam or non stick. I'm concerned about the Hyd lifters, solid would be my choice. Any suggestions on clearence?
 
Clearance on head to piston? I run KB-107's @ zero deck with a Fel-Pro .039 gasket. No problems. I have run tighter clearances. Sometimes the slug shows signs of pitting. "To close" so I run the thicker gasket. Fuel requirements are also concern at times. So running above "That point" can become problematic.
Also consider rod stretch. Older rods can have more stretch than a newer rod and a quality race rod has less stretch. Different materials stretch more than others. Play it safe and worry not!

For street rides, 10-1 iron headed and 11-1 aluminum headed is where I yield it at. I have run higher compression engines on pump gas before with a point plus in the ratio, but as I stated before, again, fuel can be an issue at times.

Figure a basic 3% increase in power from 1 full point of compression but your only going a 1-2 point at the edge now? Not worth the headache. You'll never feel the difference.
 
Oh crap, for got to mention that the valve to piston clearances are well written about from MoPar, piston manufacturers, valve makers and cam companies. Same with the valve spring bi d height and clearances.
 
tHANKS RUMBLE, AS ALWAYS I APPRECIATE YOUR KNOWLEDGE.. I WILL LET YOU KNOW WHAT THIS PROJECT IS COMPLETED.
 
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