2.5 or 2.6?

[Scott Clarke]

I'm working towards actually building the motor that has sat around for a year. The facts: 7R case (2.7spec), drag honed, case savers, oil bypass mod., E heads (machined for 90mm cylinders), E cams, rebuilt throtle bodies, rebuilt MFI pump (by PO). 66mm crank has been polished, and the rods have been reconditioned and balanced. Unfortunately, ports must remain at 32mm due to budget restraints.I am considering JE pistons, and noticed that I seem to have a choice between 90mm and 92mm. The cost difference is $150. Since I have only biral cylinders, I need to find a set or pay EBS a core charge.

So, any reason not to go with the 92s?
-Scott

[Tim Walsh]

What size are your cylinders? If they're 90mm go with that if they're 92's go for the 92's.

at 92mm the spigots are getting pretty big. I'm not sure I'd go with them but I don't know if the smaller area between the spigots and your head studs will create a reliability problem down the road.

BTW how many HP do you think this will make? The 2.8rsr(92mm cylinders) had logevity problems but they also made something north of 300 HP

[Scott Clarke]

Tim-
I was assuming that the 92mm cylinders were just bored out 90mm cylinders, and would therefore be of the same outside diameter. Is this incorrect? I don't have any cylinders at the moment, so the question of which to use is fairly open. I have been told that the limiting factor of horsepower with this set up will be port size, and there seems to be little evidence that a naturally aspirated motor with 32mm intake ports has ever made more than 165HP (2.4E). Since compression ratio will be about 9.5:1, I would hope that the 2.5 version might make 170, but this is little more than a guess.
-Scott

[Tim Walsh]

Scott,
I'm no expert but I think that for those sizes (90&92mm) you need to have nikisil cylinders and those cylinders you cannot bore out or hone in the normal fashion. These cylinders aren't the normal biral cylinders (steel cylinders with Aluminum fins) they are all aluminum with a special nickel silicon carbide coating on the inside to prevent wear.

The 90mm nikisil cylinders are fairly easy to obtain since about half of all the 2.7 liter engine out there use then (the others use ausil which is sort of nikisil on the pistons). THe 92mm cylinders will be harder to obtain and will probably be a fair amount more expensive since they are an aftermarket cylinder sold by mahle(OEM manufactuer) and were only use by the factory in the 73 Carerra RSR (2.8 liter).

The biggest problem I see with the 92mm cylinders other than cost is that you have to bore out the spigots even more than what you need for the 90mm cylinders, weakening the case even more. The 2.8liter engines had longevity problems because of this combined with the fact that they made huge amounts of horsepower for the magnesium case. Don't hold me to this but I think with your short stroke application as long as you have a 7R case the 92mm cylinders would be just fine.... well frankly it would rock.

BTW this is one of my dream engines, the 2.5 Short Stroke with MFI.

Tim

[Wayne 962]

We are selling the 92mm cylinders as part of a CIS kit. If you're on a budget, you can use these, and machine the tops of the pistons. I also have the same available in a 2.7 Nikasil kit for $1200 - the ones used in the Engine Book for photos - never run.

-Wayne

[Scott Clarke]

Tim-
I was thinking of using the reconditioned cylinders available from EBS. They are re-surfaced with nikasil. I read a previous post that said that they can even do this with alusil cylinders. The reconditioned cylinders cost $1000. I don't know what kind of core charge is involved, an issue since my biral cylinders are not valid as cores.

Wayne-
92mm CIS? Weird. It might make sense to purchase a CIS set just for the cylinders. Perhaps I could sell the CIS pistons and get JEs. Another idea is purchase an RS set and replace the pistons. Perhaps RS pistons might be marketable on their own? I looked in the catalog and didn't see the 92s listed. How much are they? What is the spigot size?
-Scott

[Tim Walsh]

Ok as long as the cylinders are nikisil you should be fine. Regular iron won't work for sizes that large. I don't know what kind of prices they are at all since my case is too weak for them and a 70.4mm crank.

[Bobboloo]

A little info here.

Scott has a 2.7 7R case. That means that the spigots do not need to be cut for using 90mm or 92mm pistons. Or for that matter the Mahle 2.9 P+C set from Andial.

All use the 97mm spigot. The cylinders for the 92mm or 93mm just have a larger inner bore.

Yes, Alusil can be bored and replated with Nikasil. You can usually find a set of core P+C's for about $200. Just ditch the pistons and have EBS bore and plate for you. (I think they probably just send them out to US Chrome but it's still cheaper than dealing with US Chrome directly)

So your options are.

1) JE 92mm pistons C/R of choice with bore and plated cylinders. about $2200

2) Mahle 2.7RS 90mm P+C set. 8.5:1 C/R.
about $1400.

3) Mahle 2.9 P+C set choice of 9.8:1 or 10.3:1
about $2500 from Andial if still available.

[Tim Walsh]

Thanks bobby, I didn't know that they used the same spigots as the 2.7

[Scott Clarke]

Bobby-
Thanks for the clarification concerning spigot size. Good tpo hear that Andial has some 93mm sets that are reasonably priced. Last time I checked the 93s were about $3400. Also on the list of possibility are 90mm Mahles with 10.5CR (9.5 when used with a short stroke crank). They were $2900 when I last checked.
-Scott

[jgparker]

It seem like the 93mm P/Cs were around $2700 at Andial and Brumos a year ago, but when I checked last week, they were unto $3150, or unavailable. The only reasonably priced 93's I know about right now are the 9.1:1 CIS set at Pelican.

I did see a set of used-up 90mm Alusils at the Zim's swap-meet early this year for $100. Alredy had a set of them though.

[Bobboloo]

I checked with Andial after I posted and yup. The 93mm 9.5:1 set is up to $3150. And the 10.4:1 are $3354. I guess this is one example of the downside of a weakening dollar. Last time I checked (about two years ago) they were $2300. Dooh!!!

Anyway,

Hmm... let's see... the cast pistons cost $1k more than the forged ones.

... the JE's are looken better all the time.