2.7 combination
 

Hi, I was planing to build a strong 2.7 engine for street use and daily driving. The fuel available here is 87 and 91 octanes. After I read a lot of the forum finding good information for what I need, I would like to know what would be the better choice for my engine: the JE 90mm 9.5:1 or 10.5:1 pistons?

Also for that pistons what of the following camshafts would be the best combination: 911SC or the 964?

I would use PMO's carbs ( I think that they know how to jet the carbs for this combination), headers and dual in dual out mufflers. The engine is going to a complete rebuilt so there is no problem for the other parts. Any recomendations woul be great

9.5:1 is as high as you can safely go without twin plugs. If you intend to use twin plugs then go with 10.3:1. In either case use 91 octane. Also 10.5:1 is a little too high for twin plugs with 91 octane.

Since your going with PMO carbs and JE pistons then you can get a more radical cam. Something like a Solex or Mod S cam would be nice. Considering the motor is for street use then the Solex cam might be the best choice. It won't be to radical for a street motor with a displacement of 2.7L.

I use 8.5 RS pistons and never have a knock problem on 87.

I use E-cams as it's a highway go-cart. If it was more of a street hot rod I would have installed early Solex cams. Solex is a great comprise street cam imo. The E-cam has nice overlap for a sweet sounding engine.

My stock 915 tranny gearing allows it to pull better than a stock 3.2 from 3.2k rpm up.

I just built a motor 2.7 very similar to what your building...

I live in Ca. and 91 is pretty much the highest gas I could get.

I went with JE 9:5 pistons, PMO carbs, Elgin MOD S cams, Recurved my dizzy w/petronix, ported/some polishing on heads, cross drilled cranks/micro pollished, case was time certed / shuffle pinned, etc......

The cars feel good / quick....

http://forums.pelicanparts.com/uploa...1194387865.jpg

jtkkz-

Any idea how much HP/Torque it is making?

For a street car, I agree the E would be a good choice. For a more track oriented car, an S is good. I have an eary S cam in my 2.7 now. I have the euro P&C's, don't recall off the top of my head the compression ratio with them. It was a little higher then the US spec for the 2.7. With your choices, I agree with the rest of the guys and would recommend the 9.5.

I built the motor with a friend who have built many 911 motors... We had it on a engine dyno for a week running the motor but did not get a chance to dyno it.... (too loud, too new etc...) I wanted it dynoed but he decided not to do it.

According to a few people I have talk too who have built similar motors they all have claimed HP around 240-250HP on flywheel....

We did some mods to the PMO carbs.... :)
Jerry Woods did my dizzy recurving to our specs..:)
Heads were match ported to the PMO manifolds...

I also have a '97 993 C2 and it is quicker than the 993 to about 80-90mph then gearing on 993 will take over pretty quickly :)

This motor is off my '74 carrera which also much lighter than the 993...

http://forums.pelicanparts.com/uploa...1194387865.jpg[/QUOTE]

jtkkz, that is a beautiful engine compartment and engine! I see a lot of detail even making sure that the tabs that support the firewall pad are perfectly bent and aligned. Don't mean to get off-thread but wanted to complement your eforts.

I'm running RS pistons/cylinders in my 2.7 with Webers, SSIs, peashooter sport muffler with S cams. My experience is that the S cams are great on the street and very tractable with the 2.7...and of course they are really nice up top too. Its not like the S cams are so radical when combined with the 2.7 that you'll experience inadequate power at lower revs in your street driving. Try 'em and you'll like 'em!

Hi Bob

I almost went with the S cams but after discussing it with Elgin, we decided on the MOD S cams, cause power comes on much sooner than the S cams. MOD S also produced more HP... according to Elgin..

I am sure they are all good...

Also after talking to a few Famous Engine builders, most of them like E cams for street use...
I wanted a bit more, since I do not drive this car daily.. Weekend fun car..:)

I agree, they are all good. I have heard the same things you mention about the Elgin mod S cams and they would be my current choice for a street 2.7...if they had been available when I rebuilt my engine I surely would have used them. I wasn't vey clear, but my comments weren't meant to address the mod S cams.

I wanted to encourage Nitrometano try something other than the SC or 964 cams with the PMOs and headers he mentions...and I did mean to dispell the idea that the S cams are maybe a bit peaky for normal street use.

it's good to know who else likes them but me.. sometimes i feel like an outlier around here with the E... thx

the E suits my needs. I had the car in N Nev last May heading N from Austin, which is in the Mountains, at 5k rpm in 5th for 30 miles. The cam had plenty of pull as the road was one of those where torque 4.5-5.5k is your friend.

It could have been snappier with cleaner plugs and leaner main jets. The EGTs on that run were 25-50deg cooler than same 30mi /4k rpm/5th. I'm runing 135 mains. So i'm not disappointed per see.

changing cams is no big deal.

The sound of cam overlap and carbs. Right there is the dividing line. Either overlap or a FI cam.

Dont go with the 10.5:1 pistons. Mine cc'd out to 11:1. The extra point of compression doesnt return enough performance (2-4%?) to justify the risk.

I've had a very good experience with the Solex cams, I can't speak for any of the others.

My 2.7RS+ has Mod-S cams, and they're brilliant on the track, and are nearly as great on the road.

My somewhat unsubstantiated feeling about the peakier cams is that when run in light cars like most of us are talking about--say, sub 2,300 lbs--there's still more than sufficient power below 5K RPM to keep these cars more than tractable on the street. There's no doubt that the cams in my car don't really open up until fairly high in the power band, and when it does, with short gears, the acceleration borders on violent, but the car more than easily gets out of its own way even at street speeds.

That said, I have an E cam in my 2.2 SWB, and it's a whole lot of fun, especially since that car is also very light. I keep surprising myself with how pleasant the grunt is between 4k and 5k. To split hairs though, I do have to say I miss the peak above 5.5k. The motor falls off badly above 6k. It goes, but it's mostly momentum at that point.

Thanks for the help. There is a lot of useful information here. I found this info on the drcamshaft web site:

2.7 CIS S I 226 220 .405" 110
E 206 200 .350"

E & L I 238 230 .405" 102 3.0-3.3 mm
E 226 222 .393"

SOLEX I 248 242 .455" 97 4.2-4.6 mm
E 236 230 .414"

EARLY "S" I 268 263 .455" 98 5.0-5.4 mm
E 240 235 .399"

SC I 236 228 .450" 113 1.4-1.7 mm
E 224 218 .395"

964 I 246 238 .470" 113 1.26 mm
E 232 226 .430"

I note that the EARLY "S" is the one that have more durarion on intake and exhaust, but the 964 have more lift on both intake and exhaust. For a N/A engine and carbs. What would be best: more duration or more lift??

The 964 cams high lift is for 3.6 liters and 41.5mm ports. It is overkill on a 2.7L 35mm port motor. Having that much lift will not gain you any power over an S cam due to your 35mm port. The S cam will be more powerful because it is already optimized for 36mm ports and the longer duration will move more air.

An added problem of the 964 cam is that much lift will limit your piston selection. Scratch that one off the list.

The S cam will give you the most peak power with your 35mm ports but it's overlap and long duration will sacrifice some of the low end torque that makes for a nice street manners. That's why the Solex is a nice compromise. It's got the lift of an S cam but with less overlap and duration.

The E cam would be nice if you want to decrease port size to 32mm. This would give you a quicker car off the line but it gives up some top end peak power.


Send an email to Dr. Camshaft and ask his suggestions. Tell him the motor is a 2.7L with 35mm ports and it's for street use. I'll bet he recommends his mod- Solex.

today I contact Dr Camshaft he recomends me the following:

A 2.7 with 40mm PMO carbs, with a set of DC40 cams and 9.5-1 compression would have a powerband from 3500 to 7000 rpm. Idle is decent. For sure as streetable as a 2.7 RS.

The oem 2.7 cams will not take a carb friendly profile. New billets are required.
Thanks,
John

I copy this info from his web site about the DC40 cams:

DC 40 I 266 259 .474" 102 4.5 mm
"Mod-S" E 249 242 .440"

He told me to fill the camshaft selecion sheet. I would wait for the last word that he would tell about the camshafts.

For the moment, do you think that the 2.7 engine block can support the boat tailing modification that Wayne says in the Rebuilt book? Also, I think I would do the half mooning modification to the heads. There is another modification that I need to know?

Yes, the 2.7 case will handle those mods fine. I don't know how much difference they'll make on a street motor but why not?

You should also do the Kremer oil by-pass mod if your case doesn't already have the mod. I believe Porsche started doing the by-pass mod in 77' but I can't remember for sure what year they started.

Aside from the mods do all the normal 2.7 updates like casesavers, for the cylinder studs and the intermediate shaft studs and of course verify the line bore.

I forget the oil by pass modification, thanks to remember it.

What is the problem with the intermediate shaft studs?

There is a home method to check the engine block line bore?

For the cylinder head studs, Pelican's carry some brands, what do yo recomend me?

*Steel, Coated Black Brand: Canyon

*993 - fully threaded, DILAVAR Brand: OEM

*Supertec Performance Cylinder Head Stud Kit

*RACEWARE Cylinder Head Stud Kit

*Casper Labs Cylinder Head Stud Kit

*Also I read in the Pelican's description about the Nickies cylinder that exist ARP brand cylinder head studs. That one can be me included in this list.

Also what is better, the Case Saver or the Timesert insert?

The intermediate shaft studs can pull just like the cylinder studs.

The line bore can be checked at home with plastigage. Get the Green plastigage for the correct range.

Place the pieces of plastigage at twelve, three and six o'clock. You can't actually put it at twelve and six because that's where the bearing halves meet but put it just off the parting lines of the bearing halves. These places are where you're most likely to be out of spec because what happens is the main bore spreads oval leaving a gap at the top and bottom (12 and 6 o'clock) along with getting tight in the middle (3 and 9 o'clock). You don't want to be out of spec on either axis.

When you put the plastgage on the bearings give it a slight pinch to make it stick along the edge of the bearing. Be sure to use "new" bearings to get the correct measurement. Also do not turn the crankshaft once you set it in the case. You don't want it to smear the plastigage. Everything must be clean before the test assembly. Once the shaft is laid in the case mate the other case halve with it's new bearings and torque it to spec.

Disclaimer: I've used this method to verify the work done by the machine shop. I don't know if it's advisable to check the bore with your new bearings, find out your out of spec, then send the case off to be bored and then re-use the bearings. I've heard that the bearings distort after they have been torqued but don't know if that is myth or not. They sure seem like a spring to me that returns to it's unloaded position. Considering the case has to go out for machine work maybe you should just have them verify it for you.

One more thing on the case. Have the case spigots decked because you don't want any leaks at the cylinder bases.

For the studs I don't have enough experience to give you advice on the different brands. I know the 993 Dilivar studs were substantially cheaper than most of the aftermarket brands and they have a good track record considering they are over ten years old now. There's some fancy stuff out there but if I can save a buck I'm all for it.

Case Savers and Timeserts are different brands of the same product. Walt of Competition Engineering prefers Casesavers so I bow to his expertise on this. I don't know, however, if Case Savers makes an insert for the intermediate shaft so you may have to use Timesert there.