RabidStreetRacer

iTrader: (1)

So I am almost finished building my engine and have to order the last part, pushrods. I have a 1999/2000 5.3 with a comp cams Thumpr cam. I put in LS1 1.7 rockers, LS6 lifters and have had the heads milled 0.015". Comp recommends a 7.400" pushrod with unmilled heads. Subtracting the milled heads comes out to 7.385". I used a comp cams pushrod length checker and came out with 7.325", then i added 0.060" for lifter preload and matched the 7.385". So I am new at this and was wondering if I am right with the numbers. Also do I need specific pushrods besides 5/16 and both ends are balled? Do I have to have the exact 0.060 lifter preload or can i use 0.050" and go with 7.375 pushrods?

Will these work? http://www.summitracing.com/parts/su...s/media/images
Or http://www.jegs.com/i/Edelbrock/350/9646/10002/-1

JPH

iTrader: (2)

How much preload did you have with your 7.400 pushrods? You will want to run a hardened chrom-moly pushrod, .080-.083 wall, 1pc. design.

RabidStreetRacer

iTrader: (1)

I just ordered some chrom-moly 7.4"s used for $50. the preload will be 0.075

smws6ta

iTrader: (5)

save yourself some grief and $$$

Order a push rod checker for $20 (ws6store) and get the exact measurement.

I was told that I could use the same length with no problems.....now I'm having to wait for my checker to come in. I just did some work on my heads and threw in LS7 lifters with 7.4" CM PR's now I have noise unlike before.

JPH

iTrader: (2)

Ok. I probably would have told you to run a 7.375 length, knowing now you have .075 preload with 7.400s. I shoot for a .040-.060 range myself on builds, but it really depends on the lifter manufacture. You will be fine though.

RabidStreetRacer

iTrader: (1)

I have a comp push rod length checker and thats how I got the numbers. I just came up with a custom length and didn't know which way to go.

RabidStreetRacer

iTrader: (1)

I'm going to try out the 7.4"s and see if they work. Worse case is i'm out $50. If they don't work I will go with the 7.375's.

vettenuts

iTrader: (4)

7.385" is the stock length. Throw the originals back in there and see how it runs and how quiet it is. Go from there. Just don't go crazy with the motor while they are in there.

I would also recommend 11/32" OD pushrods rather than 5/16".

Tainted

iTrader: (9)

Another vote to measure.
Sometimes you may need several different length pushrods.

88Fbody6L

iTrader: (5)

I went with everyone telling me stock were 7.380-7.385 and that 7.400 were longer than stock. Wasn't true. They were .003 different. Ended up needing 7.425. Just be careful with everyones advice

JPH

iTrader: (2)

Cool.

vettenuts

iTrader: (4)

I assume you measured the gauge length on both and not overall length.

88Fbody6L

iTrader: (5)

I measured them tip to tip with a caliper. Granted, I know this is not gauge length, but the 7.400 measured exactly the same as my stock rods and everyone said the stocks are shorter than the 7.400. Not the case

vettenuts

iTrader: (4)

That measurement is OAL and not valid due to differences in end chamfer, wall thickness, etc. of any two given pushrods. I have measured several stock pushrod sets using gauge length and they all came out at 7.385". Even the parts houses like TSP will tell you the same, the 7.400" myth started with that being the aftermarket cam replacement part used to make up for the smaller diameter base circle on the cam.

88Fbody6L

iTrader: (5)

I understand that the end chamfer will skew the measurement, but my point is that everyone was telling me that stocks were 7.385 and that a 7.400 is longer and should be by .015. No matter how you measure them, whether gauge length or OAL, when you compare two things using the same measuring device and they measure the same, the lengths cannot be different regardless of chamfer or wall thickness.

vettenuts

iTrader: (4)

That's the point. I can take two identical pushrods of the exact same guage length and then bore a larger hole in one and the overall length measurement will indicate it is much shorter even though the gauge length has not changed.