what kinda sound would a ls1 with to large pushrods sound like . i have a checker and im readong 7.350 but im confused on the adjustment with a 7.350 fits except i when i rock the rocker arm back and forth i can fill the lifter cup giving

 

too long will usually not allow the motor to start. they hang the valve open and you get no compression. or if it's just barely too long, you may get popping thourgh the intake/exhaust system.

 

im not having any poping what should my compression be and ill run a checker on it . it just has a ticking abour 1200 rpm not at wide open or at idle

 

standard compression should be around 175ish. put a vacuum gauge on the car. if the needle bounces around, the intake valve(s) are hung open.

you should be able to push the rocker down more after they are tightened down. you don't want them bottomed out. stock lifters should be preloaded about .100-.120"

 

man ur a life saver with my stock 7.400s on the rocker arm will not evenbudge back and forth but when i put the 7.350 on the checker i have some give back and forth and can fill the cup on the lifter give but the 7.400s feel like ther bottom out

 

also im on comp oem style lifters

 

were the heads milled? i'm guessing you've done heads and cam.

 

no there just stock ls6 heads i got from gm i found a part number in this ls1 book i have that shows tips and parts on building them. someone said that the ls6 valves are bigger and that is why i need a shorter pushrod?

 

um no. LS6 valves are the same size. should still be running the stock 7.400" long pushrods as well.

 

it sounds like a lifter tapping but there all new so im gonna try the 7.350 what can it hurt?

 

Um, no Sir, you are incorrect, the LS6 valves ARE longer, the PR on all LSx motors are the same.

GM made the LS6 valves longer to compensate for the higher-lift cam (smaller base circles).

 

so in theory i need shorter pushrods then the stock 7.400

 

Yes, IF a stock block and IF stock heads and IF stock LS1 cam.. IF you are running a larger cam (and not much larger - think stock LS6 cam - and of course just because the lift of two cams are xxx doesn't mean both cams have identical base circles) then you should be in the ball park with 7.400"

If you are running the stock LS1 cam you MIGHT have an issue, but I would be suprised that the additional length would be so long as to bottom out the lifter.

Bottom line, IF you are using the PR checker properly (and it can be a bitch to use it correctly), then go with whatever it tells you.

 

well with a 7.350 i feel it is just right not to tight not to loose but im running ls6 cam and heads

 

So if using all stock components (LS6 cam and heads), stock PR's (7.400") should work just fine, as it has for tens of thousands of stock motors.

I'm wondering if you are confused about how to measure PR length.

The idea is to figure out the "no preload" value (barely touching the rocker arm seat with a closed valve / on base of cam lobe), then tighten the rocker and that new value will be the lifter preload. So to clarify, if you've tightend the rocker all the way down and you have "play" between the PR tip and rocker arm, then your PR's are too short.

 

i was refering to valve diameter. he did say bigger and not longer. but, i stand corrected on the valve stem length. either way, as you stated, the pushrods are still 7.400" long, because he is using the LS6 cam.

 

well im lost on the noise unless its just old rocker arms mine have over 100,000 on them

 

found this info on the LS6 valves

but, he's using the LS6 cam, so that should negate the need for shorter pushrods.

 

thanks man, i dunno where i stand now its all new up top when i done the head swap the rings was great and the sidewalls was smooth look like brand new. the only thing i havent put new was the rocker arms

 

I have read this whole thread and am still confused on what you are doing. Is the 7.350 measurement with an adjustable pushrod at zero lash with the rocker snugged down? If so, you are too short.

The stock rockers will have some side to side play. Don't move the rocker side to side when trying to use the adjustable pushrod, lift the rocker tip and listen/feel for the "tick tick" of a loose rocker with it snugged down. You lengthen the pushrod until you just eliminate the "tick tick" but gently lifting the tip of the rocker.