[73Ventura]

My big block wont rev passed 5500. It's like a rev limiter is cutting in but I know its not that.
It has a comp cams ex274h cam 110*, [email protected]"lift and .55 valve lift, 2200 stall, Holley 780vc on an older performer 2 manifold, th350 and 10 bolt with 3.55 gears.
Not to sure where to start looking, could be carbie leaning out? plugs giving up? manifold limitations?
No other problems at all with the engine. Runs strong just runs out at 5500.

Any Ideas? thanks.

 

[mdw66nova]

More intake & more carb is needed would be my two cents. Running out of air and fuel.

 

[dje74nova]

What distributer/ignition system do u have?

 

[73Ventura]

Mallory distributor with an MSD ignition module with adjustable rev limiter set at 6000. Nothing fancy. I've tried the original Mallory module with no change.

 

[Professor Fate]

Big blocks are notorious for valve control issues. Might check valve springs.

 

[kennethraywil]

rev

I would say its the intake,the performer is idle to 5500 rpm if its the performer rpm the issue might be valve springs

 

[73Ventura]

I wonder if its worth playing around with the manifold? putting a 1" spacer under the carb? or is the performer 2 just not capable of any more than 5500rpm? ultimately I want to put an rpm airgap on but moneys tight at the moment.

 

[wskaiser]

If it sounds like a rev limiter, I place my bet on weak valve springs allowing valve float.

 

[MBZTECH]

Have you checked to see if it's getting full throttle? RICK

 

[sbc1320]

I wonder if its worth playing around with the manifold? putting a 1" spacer under the carb? or is the performer 2 just not capable of any more than 5500rpm? ultimately I want to put an rpm airgap on but moneys tight at the moment.

I run the 1" open wooden spacer along with the regular Performer RPM. :yes::yes::yes:

 

[sbc1320]

If it sounds like a rev limiter, I place my bet on weak valve springs allowing valve float.

X2, if all the your tune up checks out.

 

[RPM Nova]

If it sounds like a rev limiter, I place my bet on weak valve springs allowing valve float.

:yes:

Doesn't matter if it's a Performer (idle-5500) manifold, all that means is that the intake isn't optimal nor designed for peak power above 5500, not that it will be completely unable to rev past that rpm.

Like said above, if the ignition checks out with no issues, and the actual rev limiter isn't cutting in early (you said it's set for 6,000) then my next guess would be valve springs getting weak.

 

[ccvair]

Ive learned big blocks need some stiff spring to controll valve float because the valve train is heavy!!! Single springs will work at that lift provided seat pressure open is enough and the installed hight is correct. Im chasing the same trouble and will need to replace the springs for a better matched set. Unlike a small block,big blocks need a pretty healthy sping to keep away from valve float at higher rpm.

 

[73Ventura]

I hope it's not a problem with the valve springs giving up. Its a new rebuild with about 3000mls on it. It was built by a very good engine builder and has the recommended springs in it.
http://www.compperformancegroupstor...Store_Code=CC&Screen=PROD&Product_Code=924-16

We originally fitted these but found they were way too heavy.
http://www.compperformancegroupstor...Store_Code=CC&Screen=PROD&Product_Code=930-16

 

[Ryan V64SS]

PUt a bigger chip in it and try again. Rev limiter could be cutting in early or your tach is out of calibration.

 

[73Ventura]

PUt a bigger chip in it and try again. Rev limiter could be cutting in early or your tach is out of calibration.

Thanks for all your input.

I've eliminated the rev limiter as a problem.
I doubt very much its a valve train problem, were only
Talking 5500. If it was happening at 6500 then maybe.
I'm thinking its more carb/manifold.

I'd like to here Big Al's thoughts. You out there Al?

 

[RPM Nova]

I'm thinking its more carb/manifold.

Carb maybe, if it's not opening far enough. But I think looking at the manifold isn't going to help you any. Again, even if the manifold is designed for idle-5500, that doesn't mean that you'll hit a sudden and complete brick wall exactly at 5500 like a rev limiter. Also, has it always been this way since the engine was built? If not, then that would automatically rule out the intake anyway.

Sounds much more like valve springs or ignition related to me.

 

[WildBillyT]

Have you checked to see if it's getting full throttle? RICK

Just to rule this out, check and make sure you are getting full throttle. Stranger things have happened.

 

[73Ventura]

Throttle is opening all the way, have only discovered this problem after taking it to the track. On the street it never sees anything past 5k, no need to.

I have found this interesting.

http://www.youtube.com/watch?v=i2DvnoHWagk&feature=youtu.be

the part about spacing the carb and the cut out in the divider wall.
The top of my Performer is the same as the Performer RPM and have made an adapter out of sheet steel to cover the gaps when the Holley is bolted down. I don't use the correct 1/2" adapter plate made for this because of height restrictions but when I get time I'll throw one on and see what happens.

 

[ccvair]

Whats it doing when it hits 5500? is it acting like it bouncing off a rev limiter or just nosing over? mine would hit that rpm and act like it was on a limiter. did the same thing as you started sputtering at 5500. The guy I had bought the car from said it always did that. when I asked him about it He said the springs were matched to the cam. Im running a crane cam with 533 lift and it has single springs with a dampner.So I ordered some springs that have 354 lbs open pressure still a single spring. Im going to test mine and see where they are at. I had a good friend whos built race engines the last 40 years tell me it was springs also. Im running a performer 2 and a 750 holley,I have had engine both starve for fuel and go into valve float and mine deffently has the signs of float.It pulls like a bear till that rpm and its game over.