Piston Questions

[82 sportsc]

A couple of questions re pistons
# 1 - am told that pistons made for a cast iron cylinders can be coated/processed to function normally with aluminum cylinders
#2- also can pistons or rods made for a 66mm rods/crank be machined or reworked for a 70.4 crank/rods

Thanks, I know these are strange questions but have access to these pistons for a crazy cheap price
Regards
Frank

[Flat6pac]

You need to trim the piston skirt to clear the counterweights of the crank.
The 2.4 crank has a much smaller circumference on the rod journals so you need 2.4/2.7 rods for the crank
Bruce

[targa72e]

I would say the Aluminum cylinders can be coated to work with standard pistons. You can send the cylinders off to Millennium and get them nikasil coated. Once coated you can use standard pistons. Proper piston to cylinder clearance may be difficult to determined as its usually based on piston aluminum alloy used and design.

john

[Henry Schmidt]

Originally Posted by 82 sportsc

A couple of questions re pistons
# 1 - am told that pistons made for a cast iron cylinders can be coated/processed to function normally with aluminum cylinders
#2- also can pistons or rods made for a 66mm rods/crank be machined or reworked for a 70.4 crank/rods

Thanks, I know these are strange questions but have access to these pistons for a crazy cheap price
Regards
Frank

It sounds like you have either 2.0/ 2.2 "T" pistons [80/84mm]. The cylinders are indeed cast iron. If when you say "aluminum" cylinder you mean early Biral barrels [aluminum fins attached to cast iron liners] the pistons with be compatible.
Information you have so far about crank and rods is accurate. Skirt length is definitely a consideration. The longer skirt can hit the flyweights and the case at the base of the cylinder.

[82 sportsc]

Thanks guys….but a little confused on next steps …
The problem was my engine builder passed away unexpectedly last December ..
We had been accumulating parts for the rebuild as follows …
-LN 87.5mm cylinder set
-CP 87.5x9.5 2.2r pistons
- piston tops and skirts were coated
- we used a 2.4 / 70.4 crank
- original 2.2 rods reconditioned

EBS provided the the above and all engine related new components for the build
We spent over a year getting parts together and waited to fit the build into his schedule
Which was last year ….Took 6 months to find a new local builder and he was the first to open parts and begin the build….
He called to say the pistons were for a cast iron block and would not work with the billet aluminum cylinders
As per an email EBS did send the LN cylinders to CP to make sure they were mated together …but were not mfg’d correctly admitted by both EBS and CP
However their position was its been 4 years and therefore no warranty and no effort other than coating the pistons to work with cylinders ? Just doesnit seem right as were never opened and were in fact made wrong

Need solution of least additional cost …
Seems rods must go as been mentioned …….or change crank 66mm ? Cost decides
Seems piston skirts will need machined as has been mentioned ? Cost

Sorry for lengthy overview but decisions must be made to more forward with engine build
Appreciate all input, knowledge assistance and advise

Regards
Frank

[Henry Schmidt]

Originally Posted by 82 sportsc

Thanks guys….but a little confused on next steps …
The problem was my engine builder passed away unexpectedly last December ..
We had been accumulating parts for the rebuild as follows …
-LN 87.5mm cylinder set
-CP 87.5x9.5 2.2r pistons
- piston tops and skirts were coated
- we used a 2.4 / 70.4 crank
- original 2.2 rods reconditioned

EBS provided the the above and all engine related new components for the build
We spent over a year getting parts together and waited to fit the build into his schedule
Which was last year ….Took 6 months to find a new local builder and he was the first to open parts and begin the build….
He called to say the pistons were for a cast iron block and would not work with the billet aluminum cylinders
As per an email EBS did send the LN cylinders to CP to make sure they were mated together …but were not mfg’d correctly admitted by both EBS and CP
However their position was its been 4 years and therefore no warranty and no effort other than coating the pistons to work with cylinders ? Just doesnit seem right as were never opened and were in fact made wrong

Need solution of least additional cost …
Seems rods must go as been mentioned …….or change crank 66mm ? Cost decides
Seems piston skirts will need machined as has been mentioned ? Cost

Sorry for lengthy overview but decisions must be made to more forward with engine build
Appreciate all input, knowledge assistance and advise

Regards
Frank

"Manufactured incorrectly" ? What does that mean? If you're saying they were made with too much clearance, you could send the cylinders to Millennium and have them replated to fit the pistons. Should cost less than a grand.
As for the crank and rod combo: If the pistons are 2.3 ST [short stoke 66mm] by using a long stroke crank (70.4mm) your compression ratio will increase by about .5 points. That could be good or bad depending on your application.
If you want to use the 2.4/2.7 crank, rods are cheap. 911 Vintage Parts probably has 40 sets. $300 should get you a matched set.
Beyond that, 911 engines are never cheap to build. It's hurts going backwards but believe me, you aren't the first engine builder to feel this pain. good luck.

[82 sportsc]

Henry….great info , thanks again for wisdom

Manufactured incorrectly meaning made for cast iron vs aluminum cylinders
A correction to my post …we have 2.4 rods and 2.4 crank …

Can 2.4 rods connect directly to 2.2 type pistons ? Different wrist pin needed ?
If CR needs to be reduced ( think we may have 10.3 ) can we machine heads of pistons or other ?
Also CP pistons has offered to coat pistons to be compatible with Billet cylinders using PC-9 coating ?
Thanks

[Henry Schmidt]

Originally Posted by 82 sportsc

Henry….great info , thanks again for wisdom

Manufactured incorrectly meaning made for cast iron vs aluminum cylinders
A correction to my post …we have 2.4 rods and 2.4 crank …

Can 2.4 rods connect directly to 2.2 type pistons ? Different wrist pin needed ?
If CR needs to be reduced ( think we may have 10.3 ) can we machine heads of pistons or other ?
Also CP pistons has offered to coat pistons to be compatible with Billet cylinders using PC-9 coating ?
Thanks

Offering to add coating tells me your only design issue is piston skirt to cylinder clearance is too large.
Wrist pin sizes are the same, 22mm.
The problem with reducing the piston dome volume may be two fold. First, where to remove the material?
If the pistons have under-crown milling [a lightening process] removing material from the top/crown of the piston although desirable may not be doable. You need a minimum of .180" [.280" for turbo engines]
You can reduce the compression by adding base gaskets [try to keep it to only 2] but if your deck height exceeds .060" you risk detonation because of poor flame propagation. Given what I expect to be "pent top" pistons.

We can machine the domes in-house and we have .20mm to 1.0 mm base gaskets.
CP is very close to us so having them drop ship the pistons to us is easy. They do it all the time.

[82 sportsc]

Henry
Thanks again for assistance
I will call you Monday and see if we can get coordinated with CP
And have you modify and advise as needed

Appreciate all advice
Regards
Frank

[Henry Schmidt]

Originally Posted by 82 sportsc

Henry
Thanks again for assistance
I will call you Monday and see if we can get coordinated with CP
And have you modify and advise as needed

Appreciate all advice
Regards
Frank

Sorry, Supertec is not open on Mondays.....
At my age, it takes three days of rest just to keep up with my guys.