Hi Guy's, I have a stock ZZ4. It runs great
up to 6,450 RPM. But at 6,450 it is starting to miss. It's not popping out the carb. or exhaust. Just starts cutting out. It could be
running itself out of fuel. Or the cam is not able to turn that kind of RPM's. Or valve float. I'm thinking about putting in a
LT4 Hot Cam Kit. I think this will help.
Any idea's of what valve springs I should use to get say 6,800-6,900 RPM,s out of my power plant? Thanks Carburetor Mike

Mike, I'm not familiar with the ZZ4 intimately but assume it runs a hyd roller. This is your problem. Hyd roller aren't desiged for over 6500. The lifters are way too heavy. If I am correct, you must go to a solid roller. Crane makes a nice one as does Comp ( one becuase I'd only recommend the smallest grinds).

I'm guessing that your current springs have the seat/opn pressure to handle the ligher solid liters to 7 as they are.

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Gene C.
67 Chevelle SS 427/L88 (http://www.chevelles.com/showroom/chaas00.jpg)

Thanks Gene, Yes it has hyd. roller lifters.
And the same springs as the ZZ430 which has been raced to 7,000 rpm. But I'm not sure if that raced engine had solids or not. The short block is the same so I know it can take the RPM's. The ZZ4 doesn't have the Fast Burn Heads or the LT4 Hot Cam Kit like the ZZ430. Which are the only differances.
Thats why I think the cam kit will help. I
just thought by going from 101# lbs at seat to 130# would be the answer. I'm just not crazy about the idea of the haveing to adjust the solids all the time. Not to mention the clatter that comes with them.
Thanks Carburetor Mike

Mike,

The zz430 also had 1.6 rockers. This may help on more rpms. Not get valve float so quickly.



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Jay 69 SS-350

it could be the distribtor you got some distributors only provide good spark up to 6500 like and HEI if you dont have this u should get a DUI distributor good look man

Hi Guys, Yes the LT4 Hot Cam Kit come with the 6 to 1 rockers just like the ZZ430 engines. I'm hopeing it will help. Also I have a Mallory Comp 9000 Dist. I've been told it is good enough to get to 7,000 RPM.
I'm also going with a larger fuel pump for next year. The Carter P4594 6-8 psi 72 gph.
Should do just fine. Thanks Guys, Knowledge is power and I need all I can get.

Mike, just so you know, I buzz my 427 to 7000 ( on the powershifts anyway) all the time and the only time I adjust my lifters is when I what to tune the engine power up or dowm. They dont move. Maybe once a year you check em. The revs are MESUREABLY better.

Also, I have a float problem. It can be one of 3 things, float ( i have new springs??), fuel , or distrib. I run a Pertronix and the ignition man ran the distrib up to 8000. I might try an MSD just so the Pertronix is used as a trigger. I am also going to replace my fuel pump or take the regulator off.

But hyd rollers just dont rev. I'd run a 288 Comp or SR238 Crane solid. You need more than 130 to keep those fat bastards down on the cam.

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Gene C.
67 Chevelle SS 427/L88 (http://www.chevelles.com/showroom/chaas00.jpg)

Thanks again Gene, I guess solids may be the answer then. How much clatter do they make?
I'll try the hot cam kit and fuel pump first. If that doesn't do it solids it is.
Any guess on how much seat pres. I'll need to keep those fat basterds on the cam. Ha Ha Ha? I guess I could go get a performance book and do some research. But I sure do appriecate all the reply's, Thanks Everyone.
Keep them comeing. Carburetor Mike

Mike,

AFR makes a Hydra-Rev kit for hydraulic roller cams. It's a rev kit designed for use with hydraulic roller cams. There are some buttons that fit on top of the lifters, then springs go on, and finally some aluminum plates which hold the springs in place under the heads. The kit is about $179. for aftermarket lifters and a few bucks more for factory lifters. It will stop valve float if that's what you're experiencing.

Jody