I know it has been posted before but I cannot find a definite answer. I have GM MLS gaskets, unmilled 799 heads, TSP 233/239 cam, Patriot gold valve springs, LS7 lifters, stock LS1 rockers, and 7.4 pushrods. ARE 7.4" PUSHRODS TOO LONG??? I know some will say use a length checker but someone must have ran into the same issue and figured it out. I'm down about 25rwhp so I'm trying to figure this all out...

 

7.4 pushrods will be to long for you. You need to measure, there is no way around it. Its better safe then sorry. You will get excessive valvetrain noise as well as possible mechanical failures if your pushrods are to long. This is the tool you need.http://www.speedinc.com/cont.cfm?cid=C0000549

 

Why exactly would they be too long? If that were true, and my valves wouldnt seal completely, wouldn't I be down a lot on power? Also, wouldn't that make the idle sound like ****?

 

The easiest way to put it OS that ls7 have a shorter cup where your pushed sits on it. There are countless threads on it.

 

The ls7 lifter cup sits .050 higher than the ls1.. the proper preload specifications for the ls7 lifters need to be taken into account here. Look up the proper preload for the ls7 lifters and see if ur 7.4 pr's will work. I had milled 243s 62cc chambers, gm mls gaskets, stock rockers, and a cam, and I measured 7.3 zero lash and used my 7.4s giving me .100 preload which is a little on the high side but it worked well and wasn't that noisy.

 

You have been given the correct answer twice already.
MEASURE.
Every motor is different, what works on someone else setup might not do so in YOUR motor.
Do it right, do it once, Measure.

 

That is def true because I have LS7 lifters/EPS cam/stock unmilled 243 heads and 7.425" length PRs. I've checked, and all of my valves fully open and close.

And I might add, no sewing machine noise.