Camshafts and Compression
- Thread starter Valman
- Start date
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I will contact Rhoads about the pushrod length. The lifters have been adjusted as per their instructions.
Yes. P’rod being to short also increases angular stresses - increased chance of bending. You don’t know anyone who does pushrods in Sydney do you?
BSB67
Well-Known Member
Is there more information on that than you posted? I only see a change in net lift but not duration and area under the curve.
Not Sydney but I've used Jet Engineering in Red Hill VIC multiple times for custom length stuff - excellent customer service & very fast turnaround. The last set I bought they had made up & delivered to me in QLD within 3 days.
I sent them an email today with the details, see how I go. Thanks for the recommendation.
I measured them today, original ones (Comp Cams) are 7.390’’. With the lifters adjusted I need 7.690-7.700’’.
Now, you should have a controlled maximum amount of lifter bleed down.
I'm curious how much lifter bleed down ( if any) you were getting before on a cranking compression test. Considering you couldn't get the springs to compress oil from the lifter. I guess we will find out when you repeat the cranking compression test.
PRH
Well-Known Member
If that picture is showing where the adjuster is, after the proper lifter preload has been set…….then yes…..they’re too short.
The picture does show the adjuster after setting the lifter. - I adjusted it to 0.012’’ as per the Rhoads instructions.
This should relieve the high compression condition, all being well!
I’m a bit concerned about the lifter ‘pumping up’ - towards the top circlip. Or am I overthinking it??
It honestly felt like the adjuster would strip the aluminium thread in the rocker doing it that way. I probably could’ve squeezed the lifter in a vice with soft jaws to bleed it, I wasn’t game for that.
BSB67, post #181.
The seat duration does not change with prod length.
Area under the curve does.....
D. Vizard measured a number of different rocker arms & ratios...........the numbers were all over the map.
The seat duration does not change with prod length.
Area under the curve does.....
D. Vizard measured a number of different rocker arms & ratios...........the numbers were all over the map.
I’ve found someone who can make them, not cheap but very good quality.
To lengthen them, do you mean making a press in insert under one end?
No. Prods are weakest halfway along their length. That is where they will bend unless in contact with some other part of the engine.
Put a spacer in the bottom of the prod, about 1" up from the bottom. Use a lathe for precise cuts & to keep the prod straight. Get some steel tube, 0.040-.060" wall thickness that is a neat fit over the prod. Slide the tube over the prod sections with spacer in place & equal amount of tube either side of the spacer. Silver solder the tube to each side of the prod. Sil sol will flow into the joint by capillary action, making a very strong joint. Black oxide prods will have to be wire brushed back to bare metal. As an example, if after cleaning up the the prod ends, you need a 1/4" spacer, I would make the tube 3/4" long. You can use an old prod to make the spacers. You are adding some weight, but it is minimal.
I would do some measuring first BEFORE going to longer prods to try & get an idea if longer prods are going to make a worthwhile difference.
Crane brought out quick lift rockers for the SBC. The idea was to get the valves open early to get the flow going. Crane did that by lowering the prod seat in the rocker...
Put a spacer in the bottom of the prod, about 1" up from the bottom. Use a lathe for precise cuts & to keep the prod straight. Get some steel tube, 0.040-.060" wall thickness that is a neat fit over the prod. Slide the tube over the prod sections with spacer in place & equal amount of tube either side of the spacer. Silver solder the tube to each side of the prod. Sil sol will flow into the joint by capillary action, making a very strong joint. Black oxide prods will have to be wire brushed back to bare metal. As an example, if after cleaning up the the prod ends, you need a 1/4" spacer, I would make the tube 3/4" long. You can use an old prod to make the spacers. You are adding some weight, but it is minimal.
I would do some measuring first BEFORE going to longer prods to try & get an idea if longer prods are going to make a worthwhile difference.
Crane brought out quick lift rockers for the SBC. The idea was to get the valves open early to get the flow going. Crane did that by lowering the prod seat in the rocker...
Could buy one 3/8’’ p’rod for the steel tube. Drill to 5/16’’ ID, that gives a 0.0312’’ wall thickness maybe a bit thin? Make the spacer insert out of the shank of a 5/16’’ bolt. I have silver brazing gear, that’s no problem.
I was just quoted $500 for the custom length pushrods. Mancini Racing has a cut to length set but out of stock.
Rhoads got back to me, no issue with the lifter adjustment. They didn’t seem too concerned about the p’rod being short. I still am!
I was just quoted $500 for the custom length pushrods. Mancini Racing has a cut to length set but out of stock.
Rhoads got back to me, no issue with the lifter adjustment. They didn’t seem too concerned about the p’rod being short. I still am!
PRH
Well-Known Member
The P/R being too short won’t bother the lifter any……..the adjuster screw may not love it though, and/or the P/R oiling may be compromised.
It would likely be okay for long enough to run the engine a bit and see if it improves the issues you’re hoping it does.
Just make sure the P/R doesn’t contact the head throughout its full travel.
It would likely be okay for long enough to run the engine a bit and see if it improves the issues you’re hoping it does.
Just make sure the P/R doesn’t contact the head throughout its full travel.
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That’s basically what I’m thinking. It’ll be ok to run and test. Can always replace the p’rods later if it comes to it.
I’m more worried about breaking the adjuster screw or the back off the rocker, but it should be ok. I can do a quick compression test before the intake goes back on & get a visual of the valvetrain at the same time. I’m getting the intake ceramic coated while it’s off, so a few days wait on that anyway.
Val,
If you are going to use old bolts as sleeves to lengthen the prods, I would use 7/16" bolts. Rocker geometry is quite complex. As far as loss of lift etc from too short/too long prods, you could take measurements with a dial gauge etc v crank position to see just how much lift/duration is affected. It is swings & roundabouts. There are different theories. B3 racing engines has rocker arm correction kits for Mopars. A couple of years back, I got roasted on this forum for daring to point out errors in the Tech section of that website.
If you are going to use old bolts as sleeves to lengthen the prods, I would use 7/16" bolts. Rocker geometry is quite complex. As far as loss of lift etc from too short/too long prods, you could take measurements with a dial gauge etc v crank position to see just how much lift/duration is affected. It is swings & roundabouts. There are different theories. B3 racing engines has rocker arm correction kits for Mopars. A couple of years back, I got roasted on this forum for daring to point out errors in the Tech section of that website.
I did do this when I built the engine, there was minimal loss on the exhaust valve only. Intake came out as advertised on the cam card. So geometry must’ve been pretty good. Got the roller tip centred well on the valve tip etc…
I don’t think I’ll lengthen the p’rods. I can convert to ball/ball rods & cup adjusters then use off the shelf p’rods. Oil through the rods, then block the oil squirter for the adjuster in the rocker. Just weighing it all up atm.
TT5.9mag
Two atmospheres are better than one
Centering the sweep is not nearly as important as the width of the sweep.
You got roasted because you were wrong.
TT5.9mag
Two atmospheres are better than one
Link to thread please.
I don’t know what thread it was, but it was full of DV this and DV that.
Mike has forgotten more about rocker geometry than most guys on here, myself being at the top of the list.
I’ve watched some pretty smart people argue with Mike and they were dead wrong.
It gets old repeating the same **** month after month and year after year.
I will say this. I’m smart enough to know you don’t fix a geometry issue with a valve spring.
That’s a fact.
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