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hey all

just wondering if anyone has the specs on the standard 99 models valves? in particular the length.

i have a set of over sized valves that i was going to get install on a head i was getting done but the guys
doing the valve job said that the replacements were too long by more than just a mm.

ive measured up the replacement valves but the standard vavles are now in the head ready to go.. bit dissapointing

replacements are
int 34mm x 5.94mm x 102.62mm

exh 29mm x 5.94mm x 102.62mm

anyone able to give respective figures on standard gear?

cheers

irwin

Standard is up to 102.31mm so that would make them 0.31mm above

thats out of the nb8a book too isnt it?

thats frustrating... i told them to measure them both before they decided not to use them.. i feel like ive been ripped off

the over size valves of 1mm make huge amounts of difference?

Interesting. This is from the '95 NA8 Technical Data. NA8 valves are shorter!

With the solid lifters I couldn’t say if the 0.31mm could be adjusted for with shims or not, it could be ok or just out of range, but at the worst you could get away with regrinding the cams with the required base circle diameter, then you would have an extra 0.31mm of lift.
(also maybe the reason they are longer, for more lift with custom cam setup)

With the flow, 1mm Oversize will increase the flow area by exactly 3%, which doesn’t mean 3% more power, probably more like 1-2%, but it’s the same as only increasing valve lift by 0.25mm, you can make up for it in the cam setup, but if the cams are already to the limit or planned to be, then it’s important as they work together and every % counts.

There’s other usefull things when redoing valves, one is the cut angles on the seat, if three angles are used the flow will be smoother and again improve overall flow.

Much easier to get it redone now though, if thats how you want it.

Rotary clearly is well informed. However the replacement valves that you had and which were not fitted are, according to the standard specs oversize. I could understand why the fitter would be reluctant to fit a valve out of spec. You also mentioned that you had measured the replacement valves. Unless you have some training and the right equipment it is possible to measure these incorrectly. In work situations one might only use quality calibrated equipment.

Mr Morlock wrote:Rotary clearly is well informed. However the replacement valves that you had and which were not fitted are, according to the standard specs oversize. I could understand why the fitter would be reluctant to fit a valve out of spec. You also mentioned that you had measured the replacement valves. Unless you have some training and the right equipment it is possible to measure these incorrectly. In work situations one might only use quality calibrated equipment.

the sizes i gave i got with a verner and cross refed them with the sizes i was told they were by the person that i bought them off.

im a fitter and turner by trade so i know how to use a g clamp (woops i mean mic)

Most after market valves are longer
You just grind the tips to suit the shims this is STD practice in an engine shop

Irwin as a F&T you will indeed know how to measure things. But plenty do not and use dodgy equipt. At work we had a largish toolroom working on injection moulding dies and complex jigs and fixtures., The work these guys did was fantastic but much was finally outsourced and the standard dropped.