98TXFBODY

To all you guys with a 4 inch stroke....how high do you rev your engines? We just got my dads 427 running (4 1/8 bore x 4 inch stroke...C5R block).
How high can it go and be safe?

We had it on the dyno the other day and at 5800 rmps it blew the dipstick out. Anyone else had this happen? I figure some valve cover breathers will fix the problem.


Thanks for the help.

marco427

I've run my 427 to 6700 rpm, but due to the "old" intake setup (ported LS6 manifold, 78mm TB) it runs out of air much above 6000. The stock LS6 PCV system seems to handle crankcase pressure buildup well.

triumphman

the smart thing to do is ask the engine builder, he would know what parts were used and the safe rpm limit. it sounds like you may have a blow by issue.you may want to do a leakdown test.

LOnSLO

iTrader: (15)

I rev mine over 8000. I have a good valvetrain setup though. Your builder would be the best to ask, as stated above.

98TXFBODY

The guy who built it doesn't really want us to spin it over 6k....I builds alot of circle track motors and goes for low revs and lots of low and mid range power. He used to build some NASCAR motors and is not very into the ls1 market.


The motor has Crowler Rods & Crank. Jessle adjustable Rocker Arms, Manley duel springs (2.08/1.6 valves), CP pistons. I know the motor can handle it....my only question is with a long stroke is the rod angle at the bottome of the stroke to much to really spin the motor.....from what some of you have said I think we can spin it up higher.

11 Bravo

iTrader: (3)

I would fix the dipstick problem and get it running properly, then get it back on the dyno and see where it is making peak power. I'm sure you can rev it way higher than 6k with no worries.

strokedls1

iTrader: (1)

I spin my motor to 6500 on the regular. With your valve train you should be good to 7k no problem. You need to put it on a dyno to figure out where the power is to decide on the shifting. Much over 6k with an ls6 is starting to max out the intake. I have never had enough blowby to blow the dip stick. That sounds like a problem. I put some k&n breathers on the valve covers, and use an ls6 pcv with a catch can.

98TXFBODY

We have a FAST manifold with a 90 mm TB. The power curve was still on the rise when we cut it off.......Im kinda worried now that no one else has had the dip stick problem.....that would suck ***** if it had alot of blow-by