Christmas Build, 3.2 Short Stroke, 10.1 CR

[Dpmulvan]

Originally Posted by icarp

Mike, after the oil ring scratched the Nicasil liners we ran an 800 grit aluminum oxide Hone and we’re able to do a fairly good job but the scratches still remained. We put the engine together with the understanding it would be less than perfect
That’s not to say that we didn’t add a pinch of hope for the possible outcome

I use the same 800 grit hone from brush research, it’s great for deglazing takes about 2 seconds per cylinder and leaves a perfect finish with a low RA. I thought about making a post about it but didn’t feel like starting an argument over it and red scotchbrite.

[snbush67]

Originally Posted by 911 tweaks

Nice project…
Q any specs and or parts changing since you are back in there…?
You guys got this…!
This will be another eye opener build…!
Carry on…

We are taking a pause until the heads arrive from being ported. We think they’ll be ready and arrive within two weeks.

I think that this build is going to squeeze everything possible out of a 3.2 short stroke.

Increasing CR from 9.8 , Mahle 10.1 CR pistons cylinders. We may be doing dual plugs.

The heads are being ported with Icarp specs, Iconel valves, titanium keepers, drilled for dual plugs etc.,

Keeping the Knightrace75 Camshafts.

The main and rod bearings are coated. Rockers faces, cam lobes and other surfaces have been Izumi treated.

Keeping the PMO 46’s with 42 Chokes.

Keeping the M&K headers and muffler.

[911 tweaks]

Very nice “tweaks” Shane….!! Thanks for sharing…
I anxiously await how this goes…
Go get em’….!

[Old H2S]

Did Ian tell you I'm running 200 PSI static compression with the M1 , no problem..
Nikkies cylinders with 9.5 CP pistons without the bottom shim.
Deck was -.067 with shim, -.027 without shim. The valve relief cuts left me plenty of room for the M1 cam so I let the shim out.
Zoom Zoom

[icarp]

Originally Posted by Old H2S

Did Ian tell you I'm running 200 PSI static compression with the M1 , no problem..
Nikkies cylinders with 9.5 CP pistons without the bottom shim.
Deck was -.067 with shim, -.027 without shim. The valve relief cuts left me plenty of room for the M1 cam so I let the shim out.
Zoom Zoom

Not static but cranking psi numbers .
The compression test was also done @10ft above sea level

ian

[snbush67]

This mornings deck height with base gasket is at -0.047”.

[911 tweaks]

Nice… !
When you get back the heads, can you post pics of where you may of had them tweaked…?
Are you staying with carbs?
Carry on…
Happy New Year to all involved in this Christmas build project…
Bob

[PeteKz]

Originally Posted by Old H2S

Did Ian tell you I'm running 200 PSI static compression with the M1 , no problem..
Nikkies cylinders with 9.5 CP pistons without the bottom shim.
Deck was -.067 with shim, -.027 without shim. The valve relief cuts left me plenty of room for the M1 cam so I let the shim out.
Zoom Zoom

That's slightly below the .030"/.75mm minimum rule of thumb. I've run pistons in other engines with this tight of piston clearance, but the pistons were fairly tight in the bore so they didn't rock much. What piston to cylinder clearance are you using?

[Jeff Alton]

What does "fairly tight in the bore" mean? What were the actual measurements for those and what Pistons/Material?

[PeteKz]

These were engines with iron cylinders and cast hypereutectic pistons. 4" bore, clearance .002".

[snbush67]

Better results with .010” base gaskets. - .037”’deck.

[snbush67]

[snbush67]

That looks about right.

[snbush67]

Decision time.

.037” deck = 10.47 CR
.047” deck = 10.16 CR

[snbush67]

Installed the inboard ramps.

[PeteKz]

Shane, you're using twin plug heads, right? If so, I would go for the tighter squish--.037". I'm at .030", using Mahle pistons with the Carrera domes on them.

IMO, you get more reduction in tendency to detonation with reduced squish/quench clearance than the increase in CR tends towards detonation (but I wouldn't swear to it, because it also depends on combustion chamber shape). Nevertheless, it's a tight balance. If you have the capability, I would consider shaving the piston dome down a bit to get the CR back to 10:1.

David Vizard has some excellent videos on YouTube about quench (he prefers that term), as well as all his other videos. I came across this info initially reading one of his books about 40 years ago, and I have strived to include it in all my types of engine builds since.

[snbush67]

Pete, yes twin plug heads. With the head torqued, deck came out to 0.040”, CR comes in around 10.1.

[snbush67]

I went with the .50 mm base gaskets. Pistons and cylinders are clipped in.

[G450X]

Looks like a great build. I have a similar build pending - early SC heads & CIS, Max Moritz P&C’s, M1 cams, SSI’s, M&K 2/1, etc..

I am having trouble finding Mahle rings for my build (1.2/1.2/3.0) and due to the hit or miss quality of Total Seal and Goetze rings, I’d really like Mahle rings.

If your rings are original 1.2/1.2/3.0, where did you find them? Were they NOS?

Thanks,

Mark

[snbush67]

Originally Posted by G450X

Looks like a great build. I have a similar build pending - early SC heads & CIS, Max Moritz P&C’s, M1 cams, SSI’s, M&K 2/1, etc..

I am having trouble finding Mahle rings for my build (1.2/1.2/3.0) and due to the hit or miss quality of Total Seal and Goetze rings, I’d really like Mahle rings.

If your rings are original 1.2/1.2/3.0, where did you find them? Were they NOS?

Thanks,

Mark

Mark,

I bought the Mahle Motorsports kit, it came with the ring pack.