Using 7.350's or less pushrods on unmilled heads..
11-13-2003, 02:56 AM
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Using 7.350's or less pushrods on unmilled heads.. whats the deal here?? this is my situation! would that hurt performance like what I am thinking. it means valves won't open properly right? can someone comment in that please? I have GTP S2, they told me they were milled but after I showed them to my mechanic he said they were not milled 
11-13-2003, 07:17 AM
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My friend with GTP S2 LS1 heads & Pig cam put 7.4" pushrods in his motor when he did the H/C swap. His valvetrain was noisy and he didn't feel like he was getting all the 'power' he was supposed to. Trapping about 114 at the strip. Compression check revealed valves hanging open, 140-150 psi.
He put 7.35" pushrods in the motor. Compression jumps to 190, and he's trapping 119-120. Valvetrain quieted down too.
$90 in pushrods for 40 hp.
Talk about bang for your buck.
So yeah, it matters, but you may have either get a pushrod length check tool, or start with 7.35's and see where you go from there...
-Andrew
He put 7.35" pushrods in the motor. Compression jumps to 190, and he's trapping 119-120. Valvetrain quieted down too.
$90 in pushrods for 40 hp.
Talk about bang for your buck.So yeah, it matters, but you may have either get a pushrod length check tool, or start with 7.35's and see where you go from there...
-Andrew
11-13-2003, 08:18 AM
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We think his were milled .030, but only Craig knows for sure.
Honestly, I do not know how to tell the exact length of pushrod you'll need. To me, it does seem like a guess. There are pushrod length check tools available, but I've never used one, so I don't know how well it would work with the LS1.
He accidentally guessed on his motor. He ordered "735" pushrods from SDPC. Well, their guy interpreted this as the pushrod part number that ends in 735... Which was a 7.4" pushrod.
After looking around for his lost power (and valvetrain noise - sounded like my mom's 30 year old sewing machine!), we eventually found the long pushrods, and put the right ones in there. Power found, valvetrain quiet.
-Andrew
Honestly, I do not know how to tell the exact length of pushrod you'll need. To me, it does seem like a guess. There are pushrod length check tools available, but I've never used one, so I don't know how well it would work with the LS1.
He accidentally guessed on his motor. He ordered "735" pushrods from SDPC. Well, their guy interpreted this as the pushrod part number that ends in 735... Which was a 7.4" pushrod.
After looking around for his lost power (and valvetrain noise - sounded like my mom's 30 year old sewing machine!), we eventually found the long pushrods, and put the right ones in there. Power found, valvetrain quiet.-Andrew
11-13-2003, 08:27 AM
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If you get the proper lifter load with the rockers bolted down then the rod length should be correct. I would suspect with the 7.350 rods and unmilled heads you will not get enough load on the lifters and noise will occur.
Checking rod length is very easy with solid lifters and roller tip rockers. All you have to do is mark the valve tips with a marking pen, bolt up the valve train and roll the engine over. Remove the rockers and see if the roller tip is centered on the valve tip. The roller tips leave a mark where they made contact. With hydraulic and non roller tip I don't know how other than insuring proper lifter load.
Checking rod length is very easy with solid lifters and roller tip rockers. All you have to do is mark the valve tips with a marking pen, bolt up the valve train and roll the engine over. Remove the rockers and see if the roller tip is centered on the valve tip. The roller tips leave a mark where they made contact. With hydraulic and non roller tip I don't know how other than insuring proper lifter load.