ATTENTION Engine builder's!

[Guest]

Now that I have most of you checking out this post, I need some professional advice on checking piston to valve clearance,

78 750 bottom end, 78 750 cams, 83 850 cylinders ( stock bore, de-glazed on sunnen machine), 83 850 head surface milled 0.020"

Engine is completely dis-assembled, going to be checking piston to valve clearance with degree wheel and dial indicator. (no play-dough, lol)

Questions are...


Does anyone's know the stock, or acceptable piston to valve clearance on an 83 850? (no info in FSM)

Does anyone know the compressed thickness of the OEM GS 850 headgasket? (do not have the old one to re-assemble, only the stock 750 one)

Are their any other metal head gasket's available for the 850 with different thickness's? (i.e. cometic, wiseco, etc.)

At what degrees's should I check (and be worried about) for intake valve ATDC and exhaust valve BTDC contact?



Cheer's everyone,

Darren

[phydeauxmutt]

Rapidray would be the one that would know those numbers for you.

[one_civic]

sorry, 0.020" was taken off

[bwringer]

So, ummmmmmm, what's wrong with the Play-Doh approach?

[GregT]

Without knowing what the lift and duration figures are for the cams you're using and what lobe centers you intend putting them on, we're just guessing.

If they're dead stock cams on dead stock timing you should still plasticine the valve cutaways and do a trial assembly anyway.
Others may differ but for a street 8V motor, I'd look for a minimum of .080in valve to piston both sides.

[stetracer]

.050 intake side and .075 exhaust side are the minimums

[phydeauxmutt]

.050 intake side and .075 exhaust side are the minimums

Is that in inches or sillymeters?

[rapidray]

That is inches, as in THOUSANDTHS, 50 thousandths & 75 thousandths.
Ray.

[phydeauxmutt]

Thanks, Ray. I understood the "thousandths" part, just wanted clarification on the units.

Some people still think in American units, others insist on "it's built to metric standards, you MUST measure everything in metric".

[mikerophone]

Is that in inches or sillymeters?

Some people still think in American units, others insist on "it's built to metric standards, you MUST measure everything in metric".

I'd say you can measure it in whatever units you prefer and convert as needed based on the unit spec provided but I'm curious, as this seems like a bit of a self contradiction - do you prefer American units (decimals and fractions) or "sillymeters"?

I am a proud American citizen but to me, the imperial system has always been my second choice over metric. Linear vs. math...when my son wanted to help and grab me a couple of wrenches or sockets that vary around a certain size, like say 1/2" when working on an old dodge pickup, even he would comment at a young age how complicated it was hard to know if 7/16" was bigger or smaller than 5/8" until be visually compared the openings one day. Grabbing the 11, 12 and 13 when working on a metric bike or car just seems easier.

Not to stray off topic but I really wish we could standardize worldwide, I'd vote English and Metric

[Who Dat?]

... do you prefer American units (decimals and fractions) or "sillymeters"?

I, for one, use both.

Yes, I know the bike was built to metric specs, but I have never gotten around to getting a set of metric feeler gauges. Knowing that 0.0015" (usually the thinnest feeler) is within the metric spec of 0.03-0.08mm, as is 0.003", I will probably just keep using my Imperial-spec feelers. I will actually go up to 0.004", knowing that it's 0.010mm. I know it's not specified by Suzuki, but it works so well on the street.

As far as wrenches and sockets for the rest of the bike, about the only ones that cross easily are the 8mm (close to 5/16") and 14mm (close to 9/16"). Oh, yeah, there's also the 17mm (close to 3/4") and the 24mm axle nut (close to 15/16"). I don't have any metric sockets larger than 21mm, so I do use my 15/16" socket on the axle nut. Everything else gets what it's supposed to.

I have no problems with either measurement system. What bothers me is when you see both systems on the same vehicle.

[mikerophone]

What bothers me is when you see both systems on the same vehicle.

^^ This! My daughters Saturn Vue (Saturn was GM, influenced heavily by Opel, but is now defunct for those that aren't aware) has a Honda J35 engine and 5 speed transmission in it. So I use both metric and standard when I work on it. Mostly metric though, likely due to the Opel influence.

Here's a photo of the day I had her engine out and the engine out of my 850:

[one_civic]

[IMG][/IMG]


So here are the specs I have measured on P2V clearance on overlap, Please keep in mind this is my first time doing this and their may be some inconsistencies, I used the cheap Vesrah head and base gaskets for measuring, base measured 0.019" uncompressed and head gasket uncompressed 0.047" fibre material, 0.057 sealing gasket uncompressed,

BTW, never use these cheap gaskets for your head and base, heres's why,

[IMG][/IMG]

Exhaust with 2.60mm shim, 0.005 clearance
10 degree's BTDC 0.200"
5 degrees's BTDC 0.190"
TDC 0.188"
5 degree's ATDC 0.194"
10 degree's ATDC 0.210"

Intake with 2.60mm shim and less than 0.002" clearance
10 degree's BTDC 0.220"
5 degree's BTDC 0.203"
TDC 0.190"
5 degree's ATDC 0.175"
10 degree's ATDC 0.180"

[IMG][/IMG]

[one_civic]

And I measured the P2V clearance with stock 78 750 cams and stock timing,

I guess I had nothing to worry about, and yes I know my degree wheel is on the wrong side of the engine, that's what the green masking tape is for,

[one_civic]

Sorry, dis-regard the exhaust #'s, they were not measured on Valve overlap, here are the new number's, Like I said earlier, this is my first time measuring P2V clearance. Looks like I'm going to need The larger cometic 0.059" head gasket and base gasket. That would give me 0.047" - 0.059" = at least 0.012" more clearance, giving my smallest exhaust clearance at 10 degree's BTDC 0.085" + 0.012" = 0.097" new minimum exhaust clearance,

Am I right or am I completely screwing this up?

New Exhaust measurement's

20 degree's BDTC 0.105"
15 degree's BTDC 0.088
10 degree's BTDC 0.085"
5 degree's BTDC 0.090"
TDC 0.105"
5 degree's ATDC 0.130"
10 degree's ATDC 0.165"