Valve bounce
Turbo Mini Forums

Hiya fella's

Not technically a turbo problem, but you guys seem more technically minded than other forums.

My NA 1100 is getting what sounds like valve bounce at around 7000rpm. That was on fast road springs, I swapped them out for isky 330lb ones but the problem still pursues. Could be the compressed hight of the spring is wrong. It sounds the most obvious to me.

So does anyone know what the compressed height of an isky spring should be? and an accurate way to measure it?

Apart from that is there anything else that would contribute to valve bounce? or anything that may sound like valve bounce which im overlooking?

The rest of the valvetrain looks like this.. cooper s size valves with waisted stems on the inlet, isky 330lb springs, titanium valve caps, 1.3 roller rockers (clearance set to 15 thou), standard pushrods, bp300 cam.

Your thoughts please? :)

Thanks, Dan

Edited by apbellamy on 23rd Sep, 2009.

It's a short stroke big bore Andy. With those springs it should be good for 8K+ if the bottom end is well prepped.

If something is worth doing, it's worth doing half of.

the south African 1100 is a destroke 1275 but the uk spec 1100 is a over stroked 998

there is a thread titled something like rev limit .. bla bla quite recent where it was calculated 7000rpm on a 'uk' 1100 is pushing it basically...

Yes i moved to the darkside

Instagram @jdm_brett

edit: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=304197

my clubby hits valve bounce in 3rd at 6300 it just hits a wall and sounds aufull, i just stay below that

my last turbo engine could pull to 7000 in every gear no problem.. double valve springs + ph2 cam

Yes i moved to the darkside

Instagram @jdm_brett

I forget the fitted length of Isky springs but there should be a minimum of 30 thou between the coils at full lift, check this.

Paul

I seriously doubt it!

What does valve bounce sound like?
(ill accept bang bang bang)

My 998 revs quite hard, but no tacho and no sound deadening i cant really go by ear.

In boost we trust

Yes i moved to the darkside

Instagram @jdm_brett

On 23rd Sep, 2009 Brett said:

On 23rd Sep, 2009 best_stig said:
What does valve bounce sound like?

i would describe it as sounding like the valves being opened with a hammer!!

In boost we trust

My 1100 would rev past 6k and not bounce. Looking at your set up I would say its your rocker gear and duration of valve travel at 7k thats no compatible.

You may have to try double valve springs.

Own the day

How old are your Iskys?
I found mine weakened after about 5,000 miles so changed for a set of Swiftune ones with their steel top caps. Theyre very good to well over 9,000rpm and theyre cheap too

Paul

I seriously doubt it!

They're brand new from minispares, only been to MITP and back with them, plus a bit of driving locally, 200 miles at the absolute most. :(

You need to check the fitted height of them then, if they are bouncing they will be set too tall and probably floating aswell

Paul

I seriously doubt it!

When you need an engine or components of the highest quality you need to talk to HRE. I highly doubt you are getting valve bounce at 7000 rpm with 330lb springs my race motors run 260lb they are Reving to 7650rpm at shift light and no sign of valve bounce of valve float, what is the valve guide Clarence set at ?

Is there a huge loss of power when the noise Accrues

On 23rd Sep, 2009 JetBLICK said:



And finally, Josh, iskys are double valve springs

Ta

Own the day

Dan.

What did you do to get a decent compression ratio on your engine? Did you deck the block? or use longer rods?

Edited by John on 24th Sep, 2009.

If something is worth doing, it's worth doing half of.

Paul W, the coils have well over 30 thou clearance at full lift. I think you may be right that they're set too tall, the titanium caps look like they hold the spring noticeably higher than standard caps.

Paul H, i thought similar too, i used to have a 998 that went up to 8000rpm no sweat on kent double springs, which is why i think somethings not right.

I never really noticed if there was a severe loss of power, so i took it out today to check. This may sound risky but i kept my foot buried in first, and it actually reved up through the valve bounce and then cleaned up a bit. There is a drop in power thats noticeable, but its not too dramatic, just noisy.

The valve clearances are 15 thou.

m.m.m.m 225 thou was skimmed off the block for the pistons to be level, then the head was skimmed as appropriate for 11-1 CR. You have to use 998 pushrods with the shorter block too.

Dan

from old ISKY catalog, for Sprites:

Installed height 1.187"
Seat pressure 115lb.
Coil bind height 0.720"
Spring rate 320lb/in.

Parts:
VWE-005 outer spring
SP-116 inner spring
SP-007 retainer

From Des Hammill 1275 book:
He says Isky coil bind height is 0.750"
Stock 1275 installed height of 1.390" is too high for Isky springs, gives only 60lb seat pressure. Use .070" shim. Standard retainers need machining to fit Isky springs.

And what pistons & rods were they?

Is this an A+ block?

Edited by John on 24th Sep, 2009.

If something is worth doing, it's worth doing half of.

Cheers fella.

Not that am interested in building a short stroke turbo screamer or anything

If something is worth doing, it's worth doing half of.

here is a link to the valve spring page in Hammill's book...

http://books.google.com/books?id=oqqhmgbXZ...page&q=&f=false