another pushrod length question
Thread Starter
On The Tree
Joined: Oct 2009
Posts: 106
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From: Northern VA
another pushrod length question So i've read all the posts I can find and I understand how to measure pushrod length or so i thought.... I have the comp 6.80 pushrod checker tool, I have a tr224 cam (which I read has a smaller base circle) and the comp behive springs with comp hardened 7.40 pushrods. I have the terrible sewing machine noise and have had for the last 2.5 years I've had the cam in the car.
Decided it was probably my pushrod length so pulled it apart again, got #1 cyl on base circle, turned the tool out 9 turns and had lash with the rocker just snugged, so I turned it 10 turns and bam 0 lash. Well, my concern is that that would equate to 7.30 pushrods, adding in .50 preload that takes me to 7.35. Everything i've read says the pushrods with tr224 should be longer. So i'm confused
any input would be appreciated. ---- stock 806 heads.
Decided it was probably my pushrod length so pulled it apart again, got #1 cyl on base circle, turned the tool out 9 turns and had lash with the rocker just snugged, so I turned it 10 turns and bam 0 lash. Well, my concern is that that would equate to 7.30 pushrods, adding in .50 preload that takes me to 7.35. Everything i've read says the pushrods with tr224 should be longer. So i'm confused
any input would be appreciated. ---- stock 806 heads. The 7.400" pushrod was originally used to make up the difference in base circle between the stock cam and aftermarket while not changing the lifter preload from stock. (The stock pushrod is slightly shorter than 7.400") Most stock setups I have measured come in at around 0.100" preload. So your measurements appear to be reasonable, its just a question if you want to lower preload to 0.050". Some have reported a quieter setup with less preload but I have no personal experience with it.
I have a 226/228 with heads milled ~.021. I ended up with 7.3 pushrods. It's only been running a few days and I do notice some valvetrain nose. Not really more than it was stock, just different sounding. Time will tell, I have a tune scheduled in a couple weeks.
Thread Starter
On The Tree
Joined: Oct 2009
Posts: 106
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From: Northern VA
i wish i still had a stock pushrod to compare it too. I didn't realize they were shorter than the 740's. I thought the "correct" preload on the 98 lifters was .050. It would make sense to me that a higher pre-load would cause the lifter to act more like a solid lifter and thus be noiser. I'm just a shady tree mech though and am not schooled in such ways and arts.
So do you guys think the 7.35's would quite me down? Anyone done it with a tr224?
224/224/ 563/563 114 lsa on stock 806 heads with comp behhives
So do you guys think the 7.35's would quite me down? Anyone done it with a tr224?
224/224/ 563/563 114 lsa on stock 806 heads with comp behhives
Yeah, I am by no means an expert either.
I would test a couple cylinders and be sure you are on the cam base circle. However many turns gets you to zero lash with the checker + desired preload should be your correct length.
I obsessed over this for three days. I kept coming up with varying lengths to get zero lash on different valves. I finally ended up averaging all my zero lash measurements from the front four cylinders to get my final result. My preload may be anywhere from .050 to .100 depending on the valve. As long as it doesn't fly apart or destroy anything I'll be happy.
I would test a couple cylinders and be sure you are on the cam base circle. However many turns gets you to zero lash with the checker + desired preload should be your correct length.
I obsessed over this for three days. I kept coming up with varying lengths to get zero lash on different valves. I finally ended up averaging all my zero lash measurements from the front four cylinders to get my final result. My preload may be anywhere from .050 to .100 depending on the valve. As long as it doesn't fly apart or destroy anything I'll be happy.
Thread Starter
On The Tree
Joined: Oct 2009
Posts: 106
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From: Northern VA
Yeah I'm debating if I should just leave the 7.40s in there as I've been running it a while with them. Would just love to get rid of the noise from them. It's very pronounced in the cabin
I used a dial indicator on top of the rocker and torqued it down to spec using a 7.4 rod I had. Measure how much travel you get til it torques down. I found I was just short so I went with a 7.425 and my preload is .080. Still have a little noise but liveable. This is stock headed lq9 with ms3 cam
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The stock pushrods I have measured in the past come in at 7.385" (gauge length). So the 7.400" is the next closest size with the smaller base circle.
Have you called Trend pushrod, you can probably get a set of 5/16" pusrhods for a fairly reasonable price from them since they make them for Comp and others. If they don't work out, sell them. You might a few bucks. I am just not sure how much it wil quiet things down, if at all.
Have you called Trend pushrod, you can probably get a set of 5/16" pusrhods for a fairly reasonable price from them since they make them for Comp and others. If they don't work out, sell them. You might a few bucks. I am just not sure how much it wil quiet things down, if at all.
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