db's Nats report

V8 Sam · Post by **V8 Sam** » Sat Aug 03, 13 2:41 pm

nice to meet you db!

i belive out first conversation went something like this.

'sam, this is db off the MMA'

'Hello sam, check out this pushrod..Bananarama! aint it?'

.

had no idea about the other trouble though!

db · Post by db » Sun Aug 04, 13 9:06 am

Yeah, Over the weekend I introduced myself to a lot of people like that

It was good to meet you mate!

db · Post by db » Sun Aug 04, 13 10:59 pm

This is the 2nd time I'm writing this cos my stupid goddam computer lost it

Possible stupid question-time...

Valve size - did I measure right- the full width of the head edge to edge?

Pushrods - Measure from the bottom of the adjuster recess to the bottom of the ball?

Pushrod adjuster - Two threads visible BELOW the rocker?

Rocker ratio - how do you tell if your rockers are 5:1 or 6:1?

I've looked at dozens of valves and have yet to fine ONE with the same 2-groove pattern as mine. I'm thinking this will be a problem...

Pete · Post by **Pete** » Sun Aug 04, 13 11:45 pm

TWO threads below the Rocker.

You are more dsylexic than me - its 1.5:1 or 1.6:1.
You can measure this and work it out. I bet they are 1.5:1....

Pete

db · Post by db » Mon Aug 05, 13 8:05 am

ta mate.

db · Post by db » Tue Aug 06, 13 12:10 am

Yup, 1.5:1 rockers.

The original 7 7/16"pushrods were obviously correct, but the one's from Dave Bishop I installed before the fatal run were 7 3/8" so 1/16" shorter.
This meant instead of the 2 threads, there were about 5.

There's a good chance that if I'd had this knowledge then... hindsight, etc blah blah whatever

Anyhow, this has been the demolition thread which I'm gonna leave now, the rebuild will be back on the Belve thread

Dave-R · Post by **Dave-R** » Tue Aug 06, 13 8:36 am

db wrote:The original 7 7/16"pushrods were obviously correct, but the one's from Dave Bishop I installed before the fatal run were 7 3/8" so 1/16" shorter.
This meant instead of the 2 threads, there were about 5.

Not a big deal and not what caused your problems.

db · Post by db » Tue Aug 06, 13 10:16 am

If it's not important, why did Pete buy very expensive custom length ones? Although he had replaced 3 with 1/16" LONGER ones

Pete- I never did ask- why did those 3 get replaced?
Did they mysteriously snap like the 2 on my way to the Pod?

Just how important is pushrod length?

Dave-R · Post by **Dave-R** » Tue Aug 06, 13 11:31 am

You don't want too much adjuster through the rocker as it becomes a weak point on a high lift cam. It ends up at a sharp angle to the pushrod cup. Pushing the pushrod away.

But not enough adjuster through the rocker and the cup can hit the underside of the rocker at full lift.

A couple of threads showing is just a ballpark guide and best practice. Not a critical issue until you get to extremes. And I have seen people using pushrods that were WAY too short or too long. Too long always ends in tears as the Bananarama! the rockers and either the cup or the rocker breaks.

db · Post by db » Tue Aug 06, 13 12:43 pm

Got it, ta

It was obvious when we fitted the shorter rods that there was a difference in the way the adjusters sat on them. With the valve fully shut (no load on the parts) there was probably a 25 degree deflection between pushrod and adjuster. We turned the motor over by hand and saw that the angle reduced to what looked ok as as the pushrod was loaded up with the spring pressure and crossed to 5-10 degrees the other way at fully open.
We felt as the deflection was least when the most pressure was applied that it would be ok.

Some of the adjusters came loose though, so maybe that's a sign they were over-stressed?