Want opinions on 2.7 Pistons/Cylinders

[jgparker]

Ok, it's decision time for buying replacement P/C for my current 2.7 rebuild project, and I really want to hear everyone's opinions on choices. I'm looking for the best bang for the buck, and these are the options that I know of:

2.7 90mm 8.5:1 Euro RS Mahle, Pelican $1495
2.7 90mm 9.5:1 re-Nikasil, JE Pistons $1890
2.8 92mm 9.5:1 re-Nikasil, JE Pistons $2045
2.9 93mm 9.8:1 Mahle PS93-003 $3150

I will be using early S-cams, Webbers, and single ignition, RS distributor, SSI and AJ dual exhaust. Car will be street legal but used mostly for DE. There is no smog test in Florida, and 94 octane is common.

[Scott Clarke]

Best bang for the buck would be euro RS mahles. If you are on a budget, the money might be better spent elsewhere. If cost is no object, go for the 93s! I hear the JEs are fine, and plan on using them myself for my short-stroke (66mm) 2.6 (10.5:1@70.4mm stroke, 92mm), but since you have a long-stroke crank, the compression ratio issue is not such a big deal. I understand that the difference between 8.5 and 9.5 is not huge, and mostly affects bottom end. Did the prices you were quoted for the JEs include reconditioning your cylinders, or was it an outright price (no core charge)? Were these (JE) prices from EBS?
-Scott

[jgparker]

Scott,

The 92mm cylinders are from EBS and are reprocessed units. The price assumes you return the cores (my old Alusil jugs). They bore them to 92 mm and Nikasil them. Apparently, Mahle's pattent on the Nikasil process has expired.

Thanks,

[Wayne 962]

Here's what I would do. Either the 2.7s with the JEs or the Mahle 2.7s and bump the compression. How? Offset bore the rod bushing (shown in the Engine Rebuild book, page 48.), or perhaps run without a copper base gasket, or a thinner one. You can also machine the cylinder spigot bores as well to raise the compression. Check piston/valve clearances very carefully though...

-Wayne

[emcon5]

Any of the smoking deals left?

WOW - Smokin' Deal on Mahle Nikasil Big Bore Cylinder Kits (2.5/2.9/3.5)

This one gets my vote:
2.7 liter to 2.9 liter 93mm Mahle Nikasil Piston/Cylinder Set, for CIS Injection, 9.2:1 Compression Ratio $2495 SALE (reg $3655)
Click Here: http://www.pelicanparts.com/cgi-bin/dbsql/db.cgi?db=partsearch&mh=20&view_records=yes&uid=default&description=PS93-001

Tom

[jgparker]

I thought the same thing. The smokin' deal was for a 93mm CIS set, and multiple sources told me they do not have the valve pockets to support an aggressive cam. It's a great deal for someone sticking with CIS. Wish I could get the PS93-003 set for that price. They are designed for mechnical injection and S-cams.

[CARRERIC]

Hi JP

I'm in Miami and about to rebuild my 2.7L. Have you found someone good in Florida to do the work on your case i.e., studs case savers, etc. ?

Eric

[jgparker]

Hi Carreric,

No, I haven't found anyone good in FL for case work. I've been using Ollies in CA, and have been very satisfied with their work. I know a number of Space Coast region PCA people who use them too. I hear Competion Engineering (also in CA) is great too, maybe the best there is. Shipping round-trip is about $200 for case, heads, rods, misc from FL to CA. It should be about half that for just the case.

[jgparker]

Thanks for the advice Wayne. How much can I reasonably reduce deck height with RS P/C before I run into valve clearance problems or other alignment issues? Between the machining of the case mating surfaces, and decking the cylinder spigots, I'm already down 0.35mm from stock. Combining that with no base gasket should get me 0.6mm. Is that too much?

[Wayne 962]

Originally posted by jgparker
Thanks for the advice Wayne. How much can I reasonably reduce deck height with RS P/C before I run into valve clearance problems or other alignment issues? Between the machining of the case mating surfaces, and decking the cylinder spigots, I'm already down 0.35mm from stock. Combining that with no base gasket should get me 0.6mm. Is that too much?

It depends upon a lot of factors, and you won't know until you do a test assembly of your engine. The good thing is you can adjust the size of your base gasket to dial in the compression ratio you want.

It will just take a lot of assembly, disassembly and figuring out to get it just right - be sure to have patience, and don't expect to put the engine together in a weekend...

-Wayne

[911pcars]

JP,
Whatever you remove from the crankcase/cylinder/cylinder head "stack" you should also remove a like amount from the chain box-to-crankcase mounting surface; this to keep the camshaft centered in the opening (the cams are closer to the crank center line). B. Anderson recommends a max. of about .40 mm before encountering other issues. You will find the chains will have add'l slack, maybe enough to bring the chain tensioners close to the end of their travel and the chain uncomfortably close to the chain box housing. If so, see Ted Robinson at German Precision for a set of oversize chain sprockets to re-establish the proper idler arm geometry.

Best wishes on your project,
Sherwood Lee
http://members.rennlist.org/911pcars

[hbrand]

I would not increase ompression with the low octane gas !!

better floor it and go through higher rpm's
harold

[jgparker]

Hbrand,

Are you saying 9.5:1 is too high for 94 octane and single ignition? I've heard this is the safe limit. Early 911S engins were 9.8:1 and ran fine on pump gas. Both my other engines are 9.0-9:8:1 and seem to be OK.

BTW, I saw a '70 coupe for sale cheap in your neighorhood this week.(New Smyrna Beach). It looked a little tired for my needs though.

[hbrand]

Yes< this car is bad,
my experience is that you do not want the engine to knock if you floor it.
stay on the save side.
harold

[PorschePilot]

I am rebuilding my 2.7 and going with the Euro RS p and c's, E cams and webbers. This is pretty much the Bruce Anderson ultimate 2.7.

[mark 74 carrera]

What did you end up settling on? I am planning a re-build and am looking for advice. Right now, I was planning to do your first option.

I already have webers and was planning on using "S" cams.

[jgparker]

Mark,

Wow, that thread was a long time ago. I went with the 2.8 9.5:1 option. The cylinders were my old Alusil jugs bored to 92 mm and reporcessed to Nikasil. The cylinder work and the J&E Pistons were from EBS.

That Carrera case of yours should be a great starting point for an engine (if that is what you have).

Good luck,

JP

[cstreit]

I really don't think that 9.5:1 is too much for 94 octane... In fact, I know plenty of people who run 9.8:1 on 93 octane.

Steve Weiner may chime in on this one, he tends to take a conservative approach to compression and octane...

Unless there is something different about the head/piston shape that makes it more prone to detonation, I'm thinking he'll give you a thumbs up. (But feel free to shoot me down for purposes of science and education Steve. )

[Steve@Rennsport]

Hi:

9.5:1 and 94 octane fuel with single ignition will be just fine as long as you keep total ignition timing in the 32-33 deg range.

Remember,.......the threshold of detonation is NOT static; it changes with outside air temperature, cylinder head temps, oil temps, and load. One must factor these environmentals to maintain a margin in these engines without knock-sensing since the consequences of playing things close are very expensive. Never, ever rely on your ears to be the "knock-sensors"!

Lastly, bore size, piston dome shape, and deck height play a big role in each engine's sensitivity to detonation. Big bore motors (95mm and larger) are exponentially touchier about this.