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2016 race dates and car changes

Race 1, sorry no sound..



Race 2,

Flying through the field Dave, and that's approx 30 bhp down????

I think you may have the winning machine there. Is it at all possible that the bent push rod is simply the weakest part in that amazing package which needs to be stronger?
 
Flying through the field Dave, and that's approx 30 bhp down????

I think you may have the winning machine there. Is it at all possible that the bent push rod is simply the weakest part in that amazing package which needs to be stronger?

Yes Andy,back to back runs on the dyno with the machined rocker assembly suprised us all with the power loss.
I don't think it's the pushrods, we are only bending them on no4 which tells me somethings wrong there.
We had lots of interest at Brands as to the cause of the problem.
Spring seats on no 4, Spring going coil bound, pushrods touching head.
Will be checking all of these at the end of the season.



What are you revving to?

7000rpm Dave. At Brands we were coming out of Clearways when they went, not even high up the revs..
 
Yes Andy,back to back runs on the dyno with the machined rocker assembly suprised us all with the power loss.
I don't think it's the pushrods, we are only bending them on no4 which tells me somethings wrong there.
We had lots of interest at Brands as to the cause of the problem.
Spring seats on no 4, Spring going coil bound, pushrods touching head.
Will be checking all of these at the end of the season.





7000rpm Dave. At Brands we were coming out of Clearways when they went, not even high up the revs..
Peak torque then!
 
Im sure glens old setup was the same, big ramp of torque on turbo spool and bend the pushrods.

Did you try a custom pushrod ?
 
Maybe... but wouldn't the torque affect all the pushrods.
I would expect the weakest will go 1st - If it keeps doing just number 4 then I would suspect something other than 'just the weakest point' Has No 4 gone before? and if so, what did you replace it with?
 
Maybe... but wouldn't the torque affect all the pushrods.
How would engine torque affect the pushrods? All the pushrod does is compress the valve spring, in my head i'm thinking:

>RPM.... the faster the cam lobe comes around the bigger 'impact' it'll have trying to open the valve/compress the spring faster. Think of it as hitting the rod with a hammer harder and faster as the RPM rises.
>Sticking valve....Resistance against the rod overstresses it
>Coilbound spring.... as above
>Possible valve float? Are you running uprated springs Clarkey?
 
How would engine torque affect the pushrods? All the pushrod does is compress the valve spring, in my head i'm thinking:

>RPM.... the faster the cam lobe comes around the bigger 'impact' it'll have trying to open the valve/compress the spring faster. Think of it as hitting the rod with a hammer harder and faster as the RPM rises.
>Sticking valve....Resistance against the rod overstresses it
>Coilbound spring.... as above
>Possible valve float? Are you running uprated springs Clarkey?

Yes uprated springs, I was told.
What about somewhere like this ? Prob cost an arm and a leg but still http://www.mantonpushrods.com/Images/Manton_Catalog.pdf

Yes, emailed Manton and no reply,

I would expect the weakest will go 1st - If it keeps doing just number 4 then I would suspect something other than 'just the weakest point' Has No 4 gone before? and if so, what did you replace it with?

Always number 4, replaced the rocker assembly with one 3mm shorter at the pedestals. This works .....
 
Always number 4, replaced the rocker assembly with one 3mm shorter at the pedestals. This works .....
From what your describing, the other 3 rods are right on the limit, but the 4th seems to be going just past.
is the cam lobe a bit higher, the rocker assy just that bit bigger, is the valve stem just that bit longer. Or is it getting that bit hotter than the rest?
 
From what your describing, the other 3 rods are right on the limit, but the 4th seems to be going just past.
is the cam lobe a bit higher, the rocker assy just that bit bigger, is the valve stem just that bit longer. Or is it getting that bit hotter than the rest?

Not measured anything up personally, had lots of discussions with the engine builder who assures me , everything is correct !!!

Going to check everything before we go to Snetterton, will try and get some pics of the head.
 
Yes uprated springs, I was told.
I was always under the impression that uprated springs where needed for 'revvy' engines to stop 'coil bind' due to the lack of opposing force at higher rpm, therefore a stronger spring would speed up the relative rebound.

You might find that a less harsh spring may help???
 
Always number 4, replaced the rocker assembly with one 3mm shorter at the pedestals. This works .....
That has me puzzled, he height of the pedestals effects only the angle at which the the follower is pushed by the rod, and as this is less, if memory serves me right, the rod is not at 90 deg therefore there may be a slight reduction in travel for the valve. Maybe the cam lobe on 4 is slightly larger or the rocker assembly or seating is not true/ cam bearings worn.

I'd look in these areas also.
The fact that it's always 4 would lend me to look in this area 1st
 
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Not measured anything up personally, had lots of discussions with the engine builder who assures me , everything is correct !!!

Going to check everything before we go to Snetterton, will try and get some pics of the head.
CTM are normally very good and its not like they haven't built a 5 turbo lump before, but its defiantly not a coincidence that its always number 4 that lets go
 
I was always under the impression that uprated springs where needed for 'revvy' engines to stop 'coil bind' due to the lack of opposing force at higher rpm, therefore a stronger spring would speed up the relative rebound.

You might find that a less harsh spring may help???

Coil bind is pushing the spring down so far it wont compress any more.

Uprated springs are fitted to stop valve float (primarily), meaning the valve doesnt close as fast as the cam rotates off lobe, leaving the valve "floating" and at risk of a tap from the piston.
 
I think everything needs measuring very carefully.
The engine builders would have done this, but your right.
Turn it over by hand and measure everything and comparing to the other cylinders

Height of valve stem to top of head with out the rocker assy off

dimensions of rocker assy that cause the bent rod to another that hasn't been modified

push rod min to max travel

valve spring compression with rocker assy

Just another thought, have you got a temperature gun? does cylinder 4 get a lot hotter than the rest?
 
Thanks for the info @Andyquadra , way above my capabilities :)
This cam will be coming out at the end of the season, not worth the hassle.
I can count on one hand the pushrods we have bent in 7 years racing and developing the car. Looks like we did more at Snetterton as the car wouldn't rev over 5k.

Anyway heres a video from Snetterton with the big boys :)

 
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