696/796 valves in 695/800 heads

[suzyj]

I'm getting ready to order a bunch of parts for my ongoing 695 project, and thought I'd get some valves.

I'd really like to go 1mm oversize on the inlet, to 44mm. I need valves with 7mm stems, so all the oversize ones available for 900 heads are not applicable.

However I note the 696 has 44mm intakes and 7mm stems. Collets and opening/closing shims appear to be common for all the 7mm valves, so does that mean they're interchangeable?

I guess the specific question is how long are they? My 695 intake valves measure 98.4mm... Anyone have one handy to measure?

[Speeddog]

 

<sorry, no info>

[Raux]

Let me see if the spare head i have still has the valves to measure

[brad black]

you need the overall length and the groove to tip measurement.  I have neither.

[DarkMonster620]

Part #s:

M695: 211.1.066.1A Exhaust valve / 210.1.070.1A Intake valve
M696: 211.1.075.2B Exhaust valve / 210.1.075.2B Intake valve
M796: 211.1.075.2C Exhaust valve / 210.1.075.2B Intake valve

hope this helps . . . I've seen the same part having different part numbers on different models . ..  dunno why

[suzyj]

They have different part numbers because they're different diameters. 695 intake is 43 and 696 intake is 44.

That extra millimetre should give moar powah though, assuming other dimensions (notably length) are the same, and of course assuming the seat is cut to fit.

[Raux]

98
Possibly same as i have shoddy calipers

[suzyj]

Awesome Raux, thanks for that.

I reckon that's close enough that I can make it work, even if it's not exact. I can fanangle (see, I'm using technical terms!) things a little with how deep I cut the seats. Now to get ordering!

[ducpainter]

Awesome Raux, thanks for that.

I reckon that's close enough that I can make it work, even if it's not exact. I can fanangle (see, I'm using technical terms!) things a little with how deep I cut the seats. Now to get ordering!

You can also play with shims.

If you cut the seats too deep you'll shroud the valve and lose the size increase advantage.

[caperix]

Would it be more cost effective to source 696 heads? You will have to run 696 cylinders as well due to them using a head gasket, but that would get you the larger valves & the better cams.

[suzyj]

That's certainly an option, but would also require custom exhaust headers, as the 696 heads have a very different exhaust header mount, and I can't see 696 headers fitting on a 695.

[brad black]

generally I use a 44mm inlet valve to allow the porters to change the shape of the under seat area, std they often have a recess under the seat (or a step in the actual seat itself) and to give a proper transition from the bowl.  it's not for the valve size as such.

i'd say a 695 has enough inlet valve, and that, looking at the 696 dyno curves, they're possibly over valved to some extent as is.

[Speeddog]

Probably a bit late to the party, but found some info on 796 valves, about halfway down the page:

http://www.av-v.com/extreme_duty_valves3.htm   

[Raux]

generally I use a 44mm inlet valve to allow the porters to change the shape of the under seat area, std they often have a recess under the seat (or a step in the actual seat itself) and to give a proper transition from the bowl.  it's not for the valve size as such.

i'd say a 695 has enough inlet valve, and that, looking at the 696 dyno curves, they're possibly over valved to some extent as is.

the 696 are on the limit of valve sizing according to Bruce Meyers.
A clean port and polish will perk it up very nicely

[suzyj]

So to close this off, the answer is a definitive no.

I bought a 696 valve to try (part no. 2101075B). They're different from 695 intake valves in three important respects.

Firstly, the diameter (44 vs 43) - like d'uh, this is the reason I was keen on them.

Secondly, the distance from the end of the stem to the collet groove is much shorter on the 696 valve. A picture shows the difference well. The 695 valve is on the left, and the 696 valve is on the right.



Distance from tip to the tip side of the groove is 16.3 for the 695 valve, vs 10.4 for the 696 valve. So a show stopper.

The third reason makes me not want the valve even if I could get it to fit. The tulip shape is considerably different. Again, a picture, with 695 valve pn the left and 696 valve on the right:



The recess in the 696 valve is much more pronounced than the 695 valve. If you look at the back of the valve (first pic) you can see the back of the valve is taller on the 696 valve. This probably improves gas flow, but it would make the valve more likely to clobber the valve guide, and the big hole in the front of the valve would also decrease compression if used with a 695 piston.

Oh well, it was a nice idea, but wasn't to be.