3/8 or 7/16 pushrods?

At what point should a person look at upgradeing to the 7/16 pushrods? Spring pressure and or RPM?

lghting94 wrote:At what point should a person look at upgradeing to the 7/16 pushrods? Spring pressure and or RPM?

Both ...kind of. The high rpm requires stiff springs that require the better p. rods.

The stiffer the better.......

OK Here is my issue My engine is 495 cid with iron cj's turning 7000 RPM and has a seat pressure of 265 lbs I run the comp magnum 3/8 .080 pushrods. Last Fall when checking the engine and doing my preventitive maintenence we noticed some intake valves had been floating so we increased the seat pressure from 235 to the now 265 and i cant remember the open pressures but it increased dramatically. I am now wondering if this extra spring pressure could be causing my pushrods to flex at high RPM since my motor doesnt seem to react as quick as it used to and doesnt want to go as far up in rpm either horspower peak was 6900 now at 6700 on the dyno. I am running the Jomar stud girdles so i dont believe it is flexing the rocker studs.

The 7/16" stuff will a PITA to install (If you can get Guide Plates) and you may need to grind clearance. Try some .135 wall 3/8" stuff.

I'd also look in some other directions too, you shouldn;t be floating stuff at 7000 rpm, with a 2.24 valve at the pressures you have described. What the cam lobes?

The open pressure is the deal. Do you see any evidence of valve float.......fretting at the keepers or multi strike patterns on the valve tips?
A less flexable push rod is not only good for some power but also is easier on parts.....lifters etc.

Its a custom solid roller cam from Cam research 278/286 advertised duration 772 lift 110 lobe center. other than that i dont know, the valves are ferrea 2.25 stainless intakes 5000 series. retainers and locks are from comp cams and are steel.

We are seeing multiple strikes on the valve tips

Put a better p. rod in it.

try a Trend or CV products tappered pushrod fixes stuff pretty easily and not so much PITA.

some Titanium Retainers wouldn't hurt either.

studly wrote:try a Trend or CV products tappered pushrod fixes stuff pretty easily and not so much PITA.

Tappered rods can not be ran in a guide plate.

I am running .752/.771 276/286 with 350lb seat/850ishlb open Ti retainers. I use 3/8" Smith Bros .140 wall, and have used 3/8" .140 wall Manton with no problems so far. I should think the 3/8" in a .135-.140 wall in either of the above or a Trend p-rod would work well. Also you can custom order for length.

JMO Mark

I sent KY JELLY some .135" x 3/8" stuff for his P51 engine.........they are in the engine this year.

Lot's of good suggestions have been mentioned in the above posts. IMO the two most important suggestions are for you to use titanium retainers (proper fitting) and the thicker wall .135" X 3/8" pushrods. Also carefully check the length of your pushrods and make sure you have proper geometry.

Uncle Charlie

Thank You everyone for your suggestions, I will be dissasembling the engine for winter maintenence in the next couple weeks and will be looking at purchasing new p-rods for next season and will also be looking into the ti. retainers and locks. We did check for proper geometry when the engine was built and everything looked very good(I learned to check this by attending the winter tech seminar in owensboro a couple years ago), but I will check it all again to verify it is where it needs to be.

we run 7/16 tapered pushrods in our sbf turbo motor but we also have about 335# on the seat.

For a drop in the thick wall 3/8" stuff is easier. If you got it apart you go with the 7/16" with a little work.

richter69 wrote:For a drop in the thick wall 3/8" stuff is easier. If you got it apart you go with the 7/16" with a little work.

I agree. I saw the pushrod holes in a few different sets of BBF heads two weeks ago and there isn't as much room as I thought there would be.

I had more grinding on my street heads trying to get the Harland Sharp pos rockers to work with the short ass p rod they wanted than I did these P51's............. the p rod holes just need a slight touch up on the intake side at the very bottom. Took longer to make the guide plates.