Potential Group Purchase - Wiseco GS650 741cc pistons

[Old Colt]

That Athena gasket is not MLS. It's a regular composite gasket with a silver outer skin layer.

Thank you for stating that these are not MLS gaskets.
FWIW 1.3mm might be a bit thick for our needs. We really need to get a piston in an engine to check the setup height. Then the gasket thickness can be determined. Granted 95% of the setups will not really matter just what the squish area turns out to be but it would be nice to have it right.

[Chuck78]

I can get an OEM 650 gasket shipped off to Thailand asap & wait until after we have all received our pistons to order the MLS I suppose. We can have Mike sell the 25 year old Wiseco NOS gaskets to those who don't care enough to wait for a piston-in-hole deck height measurement. I generally always mill a skim coat off of the deck and the head to ensure trueness and an excellent mating surface, so 1.3mm may not be bad. The compressed thickness will be slightly less, fwiw.

Old Colt, I was hoping you would chime in a good bit on head gasket technical specifications, thank you. Please voice any other concerns or suggestions you have.

I could also send dimensions to Cometic for a composite quote, but I think they are around $80 each for a small batch if I recall correctly from forum posts from here a few years ago.

[Old Colt]

It would be nice to get a clay imprint between the head and piston just to see what the chamber looks like at TDC and what the true squish is.
At an estimate of $80 for Cometic the Gaskets to go might be very competitive, might be damn nice gaskets too and for me much less work than making an O-ringed copper gasket.

I am thinking I should get my azz in gear and assemble the bottom end of this motor. I am thinking I am glad I never contoured the chambers to fit the OEM 750 pistons.

[Chuck78]

Here ya go!

Hi Chuck,

Cost to make your gasket as a 1.3 or 1.4mm MLS head gasket would be as follows:

1-4 pcs: $119.95/ea.
5+ pcs: $79.95/ea.

Lead time is 3-4 weeks at the moment.

We can work from a scale scan you make (more info: www.gasketstogo.com/scans)

Or you can send your pattern to me (www.gasketstogo.com/mailing)

If you decide to order I would send you a PayPal invoice you can pay by credit card once we are ready to proceed.

I will attach an info sheet for MLS gaskets to this message.

Regards,

John



--
Regards,

John M. Baker
Owner

https://www.gasketstogo.com

I recall the gs750/850-920cc I built a few years ago having the piston about .016" in the hole @ TDC after a very light skimming of the block deck surface to mill it smooth. I was told that the GS1100G MLS gasket I was using had a compressed thickness of .040", and that would put me at an ideal quench height to help ward off any detonation (pre-ignition/"pinging").

In my hot rod/musclecar days with my GTO fanatic dad, I had learned in that community that in a water cooled small block chevy v8, .039"-.045" quench height was preferred to keep you clear of detonation concerns. Could be that these air cooled engines that run much hotter (270 degrees vs 210 water cooled) need more quench/squish band height due to different operating parameters? Heat of compression and latent heat combined is what causes detonation (like how a diesel operates intentionally).

I will research this more.

[Old Colt]

The engines I build which are considerably smaller than that old big iron are run considerably tighter clearance. Common practice is around 0.030 clearance. Most of my engines are in the 0.015 to .020 range.
With this piston setup the clearance up in the chamber needs to be checked as well as the outer squish area.
Those prices are good. Obviously there are other costs involved such as shipping in and out.

[Ace07]

Yeah those prices for those gaskets sound good to me. I have heard anything back from wiseco. I called them Friday and found out my contact, Ale, is gone until Tuesday. I always hate waiting. Ha ha ha

[tkent02]

Could be that these air cooled engines that run much hotter (270 degrees vs 210 water cooled) need more quench/squish band height due to different operating parameters? Heat of compression and latent heat combined is what causes detonation (like how a diesel operates intentionally).

I will research this more.

I think it's the opposite. To be able to be sold in places with very hot climates they need enough cooling fins to keep the engines from burning up in the hottest conditions they would encounter anywhere. These GS engines were fine going up steep hills in desert heat, were sold in tropical places for years and I don't recall them ever having problems from getting too hot. Mine were fine in Death Valley in summer, the Arizona desert, stuck in traffic in Phoenix, just never heard of problems from running too hot. The later 16 valve engines got hotter around the heads, some needed oil coolers, but the 8 valve engines were always fine. This gives them way more than enough cooling fins to stay cool in more normal temperatures. I bet if you were to measure the temperatures in more normal operating conditions you would find them quite cool compared to similar water cooled engines.

[Ace07]

Hey guys I think I messed up on grinding out my top case to make the 650 cyclinders fit. I was dumb enough to grind part of the case where the crank sits. If I found in half way will the case still work? I am such an idiot sometimes. I cut about a quarter into it.

[Nessism]

Post some good photos. Use photobucket or similar and post up the IMG code. Hopefully it's not too bad.

[Ace07]

I have never used photo bucket before, but I am sure it is not to hard. I will try to post some pictures. I just can't believe I did something that stupid. It was just one of those days for me

http://i1067.photobucket.com/albums/u429/Ace1500/IMG_21681_zpspvznxdrm.jpg

I also found some hair line cracks.

http://i1067.photobucket.com/albums/u429/Ace1500/IMG_21711_zpszzjgju51.jpg

http://i1067.photobucket.com/albums/u429/Ace1500/IMG_21691_zpsfefut13a.jpg

so I will probably just order a different case

[Charlie G]

I have never used photo bucket before, but I am sure it is not to hard. I will try to post some pictures. I just can't believe I did something that stupid. It was just one of those days for me

http://i1067.photobucket.com/albums/u429/Ace1500/IMG_21681_zpspvznxdrm.jpg

I also found some hair line cracks.

http://i1067.photobucket.com/albums/u429/Ace1500/IMG_21711_zpszzjgju51.jpg

http://i1067.photobucket.com/albums/u429/Ace1500/IMG_21691_zpsfefut13a.jpg

so I will probably just order a different case

Click on the image code, paste on the post and this will appear.

[Old Colt]

That will not hurt the engine. The lines you point to are casting flow, not cracks. You did grind one bearing saddle in pretty deep though.
Doing this type of work you are much better off to do trial assemblies and let the parts talk as to what is needed to be done. The areas you ground, neither the pistons nor the cylinders go there.

On my engine case the 650 cylinders fit, tightly but they fit the 550 case. I did clean up some casting flash a bit so the cylinders set down easier is all mine needed.

[Chuck78]

That will not hurt the engine. The lines you point to are casting flow, not cracks. You did grind one bearing saddle in pretty deep though.
Doing this type of work you are much better off to do trial assemblies and let the parts talk as to what is needed to be done. The areas you ground, neither the pistons nor the cylinders go there.

On my engine case the 650 cylinders fit, tightly but they fit the 550 case. I did clean up some casting flash a bit so the cylinders set down easier is all mine needed.

What he said. Grinding the bearing saddle down like that, I'd be a little concerned about however. That's pretty deep on one and looks like you cut into the side all the way to the bearing on another.

The "cracks" are just casting lines as said. Not cracks at all.

[tkent02]

Since it's a roller bearing engine I would agree it's OK, I might be concerned if it was going to be a highly stressed engine abused in racing or something but I bet for normal use it will be OK. Hell it's probably OK anyway, the 550s are extremely overbuilt, as indestructible as any engine ever made.

[tkent02]

On my engine case the 650 cylinders fit, tightly but they fit the 550 case. I did clean up some casting flash a bit so the cylinders set down easier is all mine needed.

That's very surprising, I had to grind away a ton of metal. What year 550 cases did you use?