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valve chatter?

userbmx1315

userbmx1315

NAXJA Forum User
Location
Dallas, NC
well my stroker has been chattering since ive built it.
it'll rev up fine in park and sound great, but when i floor it in gear it has a bad top-end chatter. my father said it was low octain gas and its spark knocking. any other ideas?

stock h.o. cam
4.2 crank & rods
bored .04 over(cant remember .04 or .03)
bored throttle body
99+ intake
 
It sounds like it could be pinging as he said. What octane fuel are you running?

My 88 with a similar stoker will ping on anything less than 91, but as with any Renix the knock sensor retards the timing to stop it again. I just run 91 all the time.
 
throw some 91 in there to see if there is a difference, it should only run about $3 a tank more anyway.

In the winter I can get away with mid or low test, in the summer heat I have to switch back to premium.
 
Given what you just stated it will need premium.

Valve noise will sound like a sewing machine and have a rythm. Pinging will be like marbles in a can just shaken.. random tapping noises.
 
i'm not sure of the compression ratio.
i put 93 octain in it, we'll find out when the gas mixes
 
is she getting hot? do you run a carb. with this stroker or stock injectiors? check ur egt,an fuel air ratio. taller head gasket.rethink ur build? were did u skmp.:smoker:
 
Yes, what injectors? Its a 98 XJ so it is fuel injected. And changing the head gasket won't do anything beneficial because you will be increasing quench which helps combat detonation.
 
did you clarify if it actually pinging or is it just a steady valvetrain chatter.

My stroker valvetrain sounds like a sewing machine with a nice low resonance background rumble.
 
i dont think it has a rhythm. just under load it starts.
drove it today with 93 octain. didnt help. going to pull the valve cover and double check the valves, and rocker arms
 
userbmx1315 said:
i dont think it has a rhythm. just under load it starts.
drove it today with 93 octain. didnt help. going to pull the valve cover and double check the valves, and rocker arms
Click to expand...
The fact that it is happening under a load tells me it's not likely valve train noise. Drive it and put it under a load till it makes the noise for a few seconds, shut the engine down immediately and pull a couple of plugs and look at them. If they look kinda white and ashy you are pinging. You might get some results from some colder heat range plugs. You can try an octane booster or maybe a lead substitute and see if that helps. If not, you may need to see about getting the computer flashed to change the timing curve. As a last resort you could see about getting a head shim made to lower your compression.
 
think i'm running 25lb injectors, they are used (have my stock '98 ones in the building)
its bored .04 over, stock head, havent had anything shaved or dished

the tank was at 1/8 (87 octane) put it at little over 1/2 (93octane)



theres a gas station that has 100 oct, how would tht effect my motor?
 
would help more than likely, cant hurt anything but the wallet
 
actually I doubt it would help at all. Have we even decided if the motor is pinging or knocking? Adding a $50 tank of gas is just spending money for the hell of it.
 
userbmx1315 said:
think i'm running 25lb injectors, they are used (have my stock '98 ones in the building)
its bored .04 over, stock head, havent had anything shaved or dished

the tank was at 1/8 (87 octane) put it at little over 1/2 (93octane)



theres a gas station that has 100 oct, how would tht effect my motor?
Click to expand...
Your motor will be fine on 100 octane. If the noise goes away with the 100 octane then that proves it is pinging. The thing to do then is figure out how to change the timing or maybe use an adjustable MAP sensor to get the timing curve to change. I know there are some guys on here who know a bunch about that.
 
i think the "noise" went away. just gotta fix the rubber freeze plug that blew out the back of the head. then i'll find out.
 
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