38 replies to this topic

[dotmatrix]

hello

The car in question is only used for hill climbing, some of you may know it from other questions I have asked. It has a kent 296sp cam, double valve springs, 1.5:1 alloy roller tip rockers, standard pushrods, lightened followers.

 

1. Does 1.5:1 rockers even provide any significant increase in flow with this cam and setup or would the engine produce as much with standard rockers?

2. I have been searching a bit on how to lighten the valve train, and have there for been searching for answers on which rocker arms are the lightest?

3. Are titanium pushrods or something simularly light and strong available? I don't like the carbon pushrods or the minispares alloy centre pushrod as it is larger in diameter and my pushrod holes are sleeved.

[nicklouse]

no idea never bothered with "standard" ratio rockers so cant comment on 1.

the spring caps can be changed out. 2

I just use the standard push rods.

 

and don't forget the cam followers. there are some light ones out there.

Edited by nicklouse, 13 June 2018 - 08:58 AM.

[Spider]

In regards to 1. that will largely depend on your head, and also carbs and exhaust headers.

[InnoCooperExport]

I thought all the hot Kent cams were designed with 1.5 rockers in mind? I think I remember reading that in the big yellow Bible. I'll have to dig it out.

[dotmatrix]

no idea never bothered with "standard" ratio rockers so cant comment on 1.

the spring caps can be changed out. 2

I just use the standard push rods.

 

and don't forget the cam followers. there are some light ones out there.

 

yes. I did see titanium spring caps somewhere

 

as far as I remember I have the C-AEG580 followers from minispares. are there any lighter out there? what are you using?

Edited by dotmatrix, 13 June 2018 - 09:24 AM.

[nicklouse]

 

no idea never bothered with "standard" ratio rockers so cant comment on 1.

the spring caps can be changed out. 2

I just use the standard push rods.

 

and don't forget the cam followers. there are some light ones out there.

 

yes. I did see titanium spring caps somewhere

 

as far as I remember I have the C-AEG580 followers from minispares. are there any lighter out there? what are you using?

 

the ones that cam with the cam.

[dotmatrix]

In regards to 1. that will largely depend on your head, and also carbs and exhaust headers.

 

the head probably could be better, but I am having difficulty finding out which of the many £1000 performance head manufactures makes the best head, but thats a question for an other thread :)

 

regarding carburettors i have dual hif44's on an old heavily ported log manifold. I am considering changing the manifold for the maniflow one although expensive.

[nicklouse]

 

In regards to 1. that will largely depend on your head, and also carbs and exhaust headers.

 

the head probably could be better, but I am having difficulty finding out which of the many £1000 performance head manufactures makes the best head, but thats a question for an other thread :)

 

regarding carburettors i have dual hif44's on an old heavily ported log manifold. I am considering changing the manifold for the maniflow one although expensive.

 

the one that builds your engine. or one that produces a head to suit your engine.

[dotmatrix]

 

 

In regards to 1. that will largely depend on your head, and also carbs and exhaust headers.

 

the head probably could be better, but I am having difficulty finding out which of the many £1000 performance head manufactures makes the best head, but thats a question for an other thread :)

 

regarding carburettors i have dual hif44's on an old heavily ported log manifold. I am considering changing the manifold for the maniflow one although expensive.

 

the one that builds your engine. or one that produces a head to suit your engine.

 

can you elaborate a bit, I am not sure I understand what you mean?

[nicklouse]

you can not build a good engine by buying bits and hoping they work.

 

buying the best of everything does not mean you will have a good engine. for example to get the CR for the cam/lift where are you going to remove the material from the head or the block? what CC dish in the pistons? is it actually going to be a dish or......

 

or you can do what I did had a good head, decided on a cam and carb. Knew what events I was mainly doing. knew what CC I needed. left it all with the engine builder to machine and assemble. in the end both the block and the head were skimmed put pistons where he wanted and the CR to what was needed.

[GraemeC]

I have a Maniflow manifold if you’d be interested

[dotmatrix]

 

you can not build a good engine by buying bits and hoping they work.
 
buying the best of everything does not mean you will have a good engine. for example to get the CR for the cam/lift where are you going to remove the material from the head or the block? what CC dish in the pistons? is it actually going to be a dish or......
 
or you can do what I did had a good head, decided on a cam and carb. Knew what events I was mainly doing. knew what CC I needed. left it all with the engine builder to machine and assemble. in the end both the block and the head were skimmed put pistons where he wanted and the CR to what was needed.

 
aah right. well I am my engine builder and have been for some years. a lot of lessons learned some of them expensive, but great fun:)
I know how many cc's I want the head to be and also what compression ratio I want.
 
the engine is assembled and running well, but lacking a bit of power and rpm as you noted in one of my other threads, so what I will be looking for at some point is a good, professionally ported head that flows well that I can have skimmed down to the chamber volume I want. my problem with cylinder heads is that there are so many to choose from at relatively the same price, and all I have to compare is prices and company names as no one states flow numbers and even if they did they would probably not be comparable.

Edited by dotmatrix, 13 June 2018 - 12:32 PM.

[Cooperman]

In general valve train inertia is usually only a problem at over around 7500 rpm.
It was an issue on the 970 S where 9000 rpm was available and on the one I built for historic motor-sport my son and I lightened a set of original S rockers and also lightened the cam followers. That worked. An alternative would be to use original 850 pressed steel rockers with a line of weld to prevent separation.
Of course, lightening the valve train enables lower-rate valve springs to be used which means lees valve train wear and an unmeasurable increase in power.

[GraemeC]

I would go with someone like TurboPhil for a head - he’ll work with you to give you the head you want and can prove the figures with his flow bench. He’s busy though.

[hhhh]

In general valve train inertia is usually only a problem at over around 7500 rpm.
It was an issue on the 970 S where 9000 rpm was available and on the one I built for historic motor-sport my son and I lightened a set of original S rockers and also lightened the cam followers. That worked. An alternative would be to use original 850 pressed steel rockers with a line of weld to prevent separation.
Of course, lightening the valve train enables lower-rate valve springs to be used which means lees valve train wear and an unmeasurable increase in power.

In general I agree with all this, but there are exceptions that have been demonstrated with modern vibrational analysis where additional valve train mass has prevented vibrational modes which cause valve bounce. High speed photography can show some very strange things going on that are sometimes quite unexpected and contrary to previous assumptions.