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5 GT Turbo c1j pushrods thread.

Clarkey

Well-Known Member
If I were doing a big power C1J, I would use a billet cam, not a recut, to reduce the pushrod length problems.

We need a new thread for pushrods.....
Some good points there Dave, I have some longer adjusters but not needed yet as still have the longer pushrods.
Been back to standard length this year due to reducing the pedestal height on the rocker assembly, which brings the pushrods away from head.
I thought we had solved the problem until Donington where we bent a few.


keep the wife happy.
That's the main thing, then you can play cars :)

All of my pushrods have witness marks on where they have caught the head so the hole definitely needs opening up. Still all these years and i have not actually managed to bend one yet

Your not trying hard enough :)
 
My piper285 is ground from a billet a
When I say billet I don't mean ground from an OE blank casting. Mine was cut from a big massive bit of bar, not a blank casting, to get me the profile I wanted. Thats why had to sell a kidney to fund it. You start from absolute scratch and a big block of metal, that way you can spec everything from lift (difference between the back of the lobe and front, and you control what level the back of the lobe sits at), duration, overlap etc etc. I spent hours and hours trying to understand it all, its a minefield.
www.rbracing_rsr.com_turbo_camshaft_diagram.webp
ETA: Watch out with lift, I nearly tripped up there, you need to be clear on whether lift is specced as per the diagram, or at the valve. Catcams listed by valve lift, which is cam lift * rocker ratio.
Loads of info on the web, but the rules (eg cylinder scavenging) change NA to turbo so be careful, the rules change again when using Nitrous too so be careful there as well. You also have to weigh up the cam design to your inlet and exhaust systems, and end use. No point in designing a wild-ass cam if you need it to drive on the street, or vice versa. I read so much, tried to suck it all up and got to the point I produced a viable cam spec, but i'm still an absolute beginner/amateur by comparison.

I personally think they lose their strength once bent but others disagree.
They will do, yes.
 
So can someone educate me on push rods and which ones are available ? It's been mentioned to me about Ka ones being usable and potentially tougher? Also Chris mentioned the yanks being able to sort some uprated ones. @Fordy @Clarkey - Where have you guy's got up to with this?
 
Came to a dead end on the custom Titanium Mark.
They will only make 5/16 which is 8mm, was after 6mm ideally after I spoke to someone who got them for Glen Robson.

Are there marks on the head ? maybe as simple just opening up the pushrod holes.
I'm sure you will be fine with a nice straight rod in there...
There are some ford ones which are 6mm, I've not found them yet :)
 
I found this quite interesting.

This is also worth a read http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.843.9155&rep=rep1&type=pdf

So I did a few calcs with some educated guesses of the cylinder pressure of around 25 - 35bar at opening of the exhaust valve (Ø26mm) with a rocker ratio of 1.5 and spring seat pressure of 120lbs.

= Pushrod load of 3.2kn (26mm valve)
= Pushrod load of 3.7kn (29mm valve)
Load at which a 6mm steel push rod buckles comes out at 4.1Kn.

There are a few assumptions in here but it looks like your right at the limit of the push rod and this assumes an axial force. (if the push rod is even slightly bent the max loading drops massively.)

Going up 1mm in diameter would increase the buckling force to 7.5Kn.

I'm sure there others on here who can do the calcs and point out any mistakes!!.
 
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Would you like me to contact the firm that made my Nimonic 80-A exhaust valves and ask them about making some porn star pushrods out of unobtanium?

Yes please Dave, worth getting a price .
Is it worth starting a new thread about all this as some good info on here and clogging up Marks thread...

I found this quite interesting.

This is also worth a read http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.843.9155&rep=rep1&type=pdf

So I did a few calcs with some educated guesses of the cylinder pressure of around 25 - 35bar at opening of the exhaust valve (Ø26mm) with a rocker ratio of 1.5 and spring seat pressure of 120lbs.

= Pushrod load of 3.2kn (26mm valve)
= Pushrod load of 3.7kn (29mm valve)
Load at which a 6mm steel push rod buckles comes out at 4.1Kn.

There are a few assumptions in here but it looks like your right at the limit of the push rod and this assumes an axial force. (if the push rod is even slightly bent the max loading drops massively.)

Going up 1mm in diameter would increase the buckling force to 7.5Kn.

I'm sure there others on here who can do the calcs and point out any mistakes!!.

Absolute legend..........love all this tech stuff.
How you even start to calculate pushrod forces amazes me but this is the detail that goes missing.
 
You need to increase the diameter.

A material change isn't going to help as the Modulus of elasticity is already 200Gpa for steel which is higher than most materials.
Titianium =115Gpa,
Aluminium = 70Gpa

Just a 1mm increase would dramatically increase the maximum load carrying abilities of the push rod.

The Americans are using anything upto 9/16in (14.3mm) Probably worth contacting a company in the states the cost of 16 starts at about $150 and alot of places will make custom ones.

Trend Performance - High Performance Pushrods, Wristpin, and Valve Train components
Pushrods : ISKY Racing Cams, Do It Right, Race With The Legend
 
Good find, and good price, it would save a lot of work and cost! I used Isky double springs in my head, looks to be decent quality kit.

Clarkey, coming at it from a different angle, what would stop you padding out the bottom of the bucket so the bottom of the pushrod sits up by 5mm? So making the bucket base 5mm thicker, basically.
 
Clarkey, coming at it from a different angle, what would stop you padding out the bottom of the bucket so the bottom of the pushrod sits up by 5mm? So making the bucket base 5mm thicker, basically.

I spoke to Charlie at CTM about doing just that Dave.
He didn't think it was worth it because you could get different size followers, which would do the same.
Nothing came of it though

The longer pushrods work well so stuck with them. I have longer adjusters for standard rods also.
 
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