First off, sorry I've been away so long. I have no excuse.

Now, on to my question/observation/issue:

A few years ago I had an H95 "Small Oval, Shrouded-Port" head ported within an inch of its life. It is beautiful. It flows ridiculous numbers. It is totally worthless for a street engine. Last week I decided to remove it and put on a "stock" oval port head to try and make the car driveable. My plan was to pull the valves and springs from the super hot rod head (aka $1,000.00 Albatross) and put them in the unmolested oval port head. (Sorry, I don't have casting numbers at hand.) Well, to my surprise, the H95 "Small Oval, Shrouded-Port" head appears to use a much shorter valve and spring package than other A-series heads. Like 1/4" (0.250" or 6.35mm) shorter! Do I have some weird bastard of a head or or has anyone else come across this situation? Is it possible that, since the ports are so badly shrouded, NO ONE has ever done anything with this head?

Fortunately, in all my hoards of junk... I mean spare parts, I did find a full set of "long" valves and springs and will be able to build a decent stock head for this engine.

Unfortunately I didn't discover the valve issue until the head was installed on the block and we went to install the rockers. (Hint, if your valve lash is 0.250" [6.35mm] instead of 0.010" [0.254mm] you may have the short, H95 "Small Oval, Shrouded-Port" valves in another head.)

That's normal -- H95 heads have closed chambers with the valves up higher in the head, so the valves are shorter. They did this to induce high-swirl which is good for HP. See H95.


Quote:Is that because the ports are now too big, needs very high RPM?
How would it work on a 1608 engine? Or an A15?

by the way, the H95 valves are only 3.8 mm shorter...

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Yes... well, we hope that is the issue. We think the ports are just so huge now that they don't have any gas velocity until the revs are way up there. I know who built this bottom end and don't really want to grenade the thing. Not to mention, I don't like sounding like I'm flogging it for all it is worth just to keep up with a Subaru Justy.

The engine is a 1400 so I'm not sure if another 100/200cc would help all that much.

I am glad to know that I'm not crazy and that the valves ARE in fact shorter. I just wish I'd known it before we assembled everything.

An addendum to the tech wiki might be in order. I'd do that but I'm just barely computer literate, as y'all may remember.

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Oh, I see that in the tech wiki now. Ok, to be perfectly honest, that 1/4" (6.35mm) was a wild-ass guess, based on observation from across the shop, while being held back from smashing the crap out of something.

This is to go in your hicost? You can get new double-valve springs from Isky, Bprojects, Kameairi, etc.

The stock Nissan ones are the best since they are for 7000 RPM. The aftermarket ones are for 9000 RPM so wear the guides out faster.

peterzekert.com might still have some. Bproject is $100/set.

Can you please post up some pics of this rare head, I really like the super deep tub chambers they are like some of the Harley aftermarket head combustion chambers focusing the charge in the centre of the piston with little wasted on the bore walls of the engine.

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Hicost! Funny. No I took it out of the Seven when it was too loud, buzzy, high-strung, and generally annoying. It is now in a B-210 called Lil' Wiggly... and proved to be too loud, buzzy, high-strung, and generally annoying.

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I have run the double valve springs before. I feel I should run them again in this engine but... um, well, I guess I don't have an excuse why not.

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I will see what I can do... which translates into asking Tensandtwenties to do it for me since I am just barely computer literate.