2.7 Build Review & Recommendations

[sportsbeetle]

**Edited as I'm converting this into a build thread. Original post below. Will be posting updates as they come up.

PSA - be gentle, this is my first 911 **

Hi folks,

Wanted to get some advice on a 2.7 I'm getting built to go into my 77 backdate hotrod. This is my first 911 build so any and all advice is appreciated. Looking to make sure I'm not making any obvious mistakes.

Goal is a weekend backroad bomber and occasional small track/autox day car. I tend to prefer to wring engines out and keep revs high. Low end torque isn't a priority to me (have a turbo car for that) - visceral driving experience is. Car is being put on a diet - ending somewhere around 2100lbs.

Starting with a 7R case and doing the following:
- Case sent to Ollie's - line bored, case savers, etc
- PMO 40mm carbs
- 90mm Euro 74-77 Carrera P&C 8.5:1 comp (these came with the car)
- DC40 cams
- SSI heat exchangers + 2in/out exhaust
- single plug (keep costs down)


Trans:
- 8:31 R&P
- Guard short gears 2-4 (2.00 2nd, 1.429 3rd and 1.167 4th)
- Guard LSD
- Wevo streetlite kit w/ AP racing clutch
- Wevo gateshift & side plate

I'm anticipating compression to be in the high 8s once all is said and done. Wondering if I should sell the euro Carrera P&C's to go with JE 9.5:1 units but not sure...

Expecting to be around 210hp at the flywheel with the current setup. I hear the JEs get the power up to 240ish hp so maybe it's worth changing the P&C?

[Jonny042]

I highly approve of the choice of close ratio gears. Everything else looks good too.

JE or CP pistons might allow a bigger cam like a DC43-102. Talk to John Dougherty about the engine combo before you do anything he will set you straight.

[sportsbeetle]

Originally Posted by Jonny042

I highly approve of the choice of close ratio gears. Everything else looks good too.

JE or CP pistons might allow a bigger cam like a DC43-102. Talk to John Dougherty about the engine combo before you do anything he will set you straight.

Thanks, appreciate the input.

I'm struggling with the P&C's as budget is already stretched and nothing wrong with the 8.5:1 Carrera units.

Suppose I could always upgrade to JE & a more aggressive cam down the road without cracking the case open again but likely wouldn't happen.

Will definitely give John a call!

[chrismorse]

Hi Sports,

Talk to John Dougherty about having the ports opened up. My guess is you could have 35 mm intakes and if you want a hi end screamer, this would help. You might even have 32s. Make sure your guides are good.
What are you using for ignition?? Having the distributor re-curved might find some free HP.
I know it is a few more bucks, but having the jetting and timing worked up on a dyno could save you a lot of time and effort.
Lastly, I'd reccomend a front fender Carrera cooler to keep temps from getting expensive.
Are the Carrera pistons for CIS??? Will they work with the DC40 ???

I'm going for torque and responsiveness with my 2.7, not necessarily high revs, so im close to what you are building, maybe a DC-35, 92mm pistons, 10.5 CR, bigger ports, SSI, Scart, RSR wheel and Kep 6-7 all alum clutch, guard lsd, 8/35, Wevo shift gate, rennshifter,, PMO ITBs, AL's megasquirt/EDIS package, crank fire, twin plug & heads by CGarr.

[targa72e]

Here is a friends engine that is very similar to what you are building.

911 Engine for sale

The heads were 36I and 35E port size. It was installed for a while in my 914 with short gearbox. It was very fun. I am going to build a similar engine for myself but it will be higher compression with JE pistons.

john

[sportsbeetle]

Thank you for the replies, lots to think about!

Pardon my ignorance on this but is it possible keep the 90mm cylinders that came with the car and just replace pistons for the 9.5:1 JEs?

Looks like they're available for about $1300 from our host - a 30hp gain for that price seems worth it if my existing cylinders could accommodate...

https://www.pelicanparts.com/More_Info/JE261665.htm?pn=JE-261665&bt=Y&fs=0&SVSVSI=911M

[sportsbeetle]

Originally Posted by chrismorse

Hi Sports,

Talk to John Dougherty about having the ports opened up. My guess is you could have 35 mm intakes and if you want a hi end screamer, this would help. You might even have 32s. Make sure your guides are good.
What are you using for ignition?? Having the distributor re-curved might find some free HP.
I know it is a few more bucks, but having the jetting and timing worked up on a dyno could save you a lot of time and effort.
Lastly, I'd reccomend a front fender Carrera cooler to keep temps from getting expensive.
Are the Carrera pistons for CIS??? Will they work with the DC40 ???

I'm going for torque and responsiveness with my 2.7, not necessarily high revs, so im close to what you are building, maybe a DC-35, 92mm pistons, 10.5 CR, bigger ports, SSI, Scart, RSR wheel and Kep 6-7 all alum clutch, guard lsd, 8/35, Wevo shift gate, rennshifter,, PMO ITBs, AL's megasquirt/EDIS package, crank fire, twin plug & heads by CGarr.

I do have 35mm intakes and we will be checking the guides.

Planning on talking to Barry at IAE about the distributor recurving. Wish we had a dyno nearby to get timing and jetting sorted but my local Porsche Indy has been at it for 30+ years so have to lean on him for that.

The Carrera pistons are 8.5:1 euro versions so they should work with the DC40 but I'm really considering going the extra mile and getting the 9.5:1 JE pistons (and perhaps reusing my cylinders since the bore is the same?)

[combatic]

Hey sportsbeetle,
I am mid build on my engine as well and we have very similar specs. Your cams are more radical than the E cams I am going to run. Some thoughts below on your build

My Build in Progress:
1976 7R Case. Work in process C&D Engine Performance (align bore, case savers)
Weber 40IDA (jetting formula for E cam / 2.7 / 9:5:1 / CIS heads)
90mm Nickies / JE 9:5:1 Pistons
Oil Fed Tensioners
“E” Webcams
SSI
Rallye 2 out sport muffler (pea shooter)
Single Plug

Ignition
Recurved Dizzy for webers
Pertronix Ignitor
MSD 6AL

Elephant fender mounted cooler

Trans:
Close Ratio Gears
A 3.091 (11:34)
F 1.889 (18:34)
KA 1.4?? (22:31)
Q 1.125 (24:27)
V .9259 (27:25) ←too short switching back to Z or ZA!

I compiled a spreadsheet when spec’ing my build. If you compare your DC40 Mod S cam, 8:5:1, and CIS heads with a 73 RS. The CIS intake/exhaust valves and the port sizes are basically identical so you might not have to do any port work. Just another data point. If you talk to Dougherty it will be interesting to hear what the recommendation is.

PMOs: Check on the jetting package in the PMO’s based on your cams / compression ratio / 2.7 etc. (you may have already done this) Someone has a formula out there for a baseline. If your jet package is close…run it! You will likely have to tune it or fiddle with main jet/idle jets etc to optimize the PMO’s

Additional Cooling recommended. You are up north like me and may not need it. Monitor your temps once you get it built up and running and see how hot she runs. Extra cooling is good insurance though. On our drives and track days down to California I was having incredible spikes in engine temp in the summer heat and had to upgrade.

Have you spec’d your bearings yet? I am going through that right now and the recommendation is OEM Porsche or Clevite. OEM Porsche are big dollars but the quality and more importantly the tolerancing are spot on…according to my web search and threads here on the ‘bird’.

Oil Fed Tensioners: You might consider upgrading to Carrera tensioners for reliability

Camshaft Oil Line Restrictors: add to reduce excess oil building up in the sump and improve flow to the mains/rods.

[combatic]

You should be able go with JE 9:5:1 pistons and your existing cylinders after honing for a good ring seat. Check on your DC40 cams...they have a lot more lift and I know the JE's have pretty deep valve pockets but it would be good to verify all the clearances. Another thing to chat with the brain trust about and/or just talk to John Dougherty.

Dizzy Recurving: Highly recommend JWE Motorsports...turnaround time/$$$/service were top notch and they are West Coast. Jerry Woods himself does the dizzy work so you are in good hands.

[sportsbeetle]

Originally Posted by combatic

You should be able go with JE 9:5:1 pistons and your existing cylinders after honing for a good ring seat. Check on your DC40 cams...they have a lot more lift and I know the JE's have pretty deep valve pockets but it would be good to verify all the clearances. Another thing to chat with the brain trust about and/or just talk to John Dougherty.

Dizzy Recurving: Highly recommend JWE Motorsports...turnaround time/$$$/service were top notch and they are West Coast. Jerry Woods himself does the dizzy work so you are in good hands.

Thanks for the tips on the PMOs!
I do have Carrera tensioners already so that should help.
Regarding camshaft oil line restrictors - is there anywhere I can read more about them?
Will talk to Jerry Woods as well, thanks for that tip!

If I can reuse my cylinders, definitely going 9.5:1 JEs. Wonder if I'll have any fuelling issues on hot days since we only get good 91 here consistently. Suppose I could have a couple bottles of booster handy...

[al lkosmal]

you'll need to verify that your cylinders are Nikasil, if you plan to reuse them with JE pistons.

[targa72e]

A couple of things to think about if reusing your existing cylinders. You may be able to use your existing cylinders if a few things check out. They need to be Nikasil to use as is, you can not run JE's in Alusil cylinders. Either type of cylinder can be sent off and coated with Nikasil. If your cylinders are Nikasil you will need to measure and make sure they are in spec for roundness and taper. If all of measurements above check out you may still need to have your JE pistons made to order to get the correct Piston to cylinder clearance. If your cylinders are going to be re-plated you can get off the shelf pistons and send a piston with the cylinders to have the cylinders honed to the correct clearance and finish.

John

[combatic]

Regarding Oil Line Restrictors

There is a lot out there if you search. I didn't even know about it until started digging into my build. I think Wayne mentions it in his engine rebuild book as well.

Your car should have a modern pump to put up enough pressure. I am debating opening up the 2.5mm orifice a bit on the restricted fitting (stock was 6mm) because I run 20w50 VR1 oil and my reasoning is that you want to have excellent flow/volume at cold start to protect all the mains/rod bearings.

[sportsbeetle]

Thanks Al, combatic & targa72e - lots of good info!

Has anyone purchased from aapistons? $2k for a set of pistons & cylinders seems like a great price. I could probably move my 8.5:1 Mahle p&c set for about $1k (I'm guessing) and not break the bank too much.

https://aapistons.com/collections/porsche-piston-cylinder-kits/products/porsche-911s-2-7l-90mm-je-p-c-kit-c-r-9-5-1-cast-iron-liner-need-to-be-edited

"This is a new set of 90mm Porsche 911 2.7L Low compression JE pistons & cylinders. The Compression ratio is 9.5:1 with the 70.4mm crank. JE Forgings are made from 2618 Aluminum, They have a 0 offset with extra material under the top for the valve pockets. The Cast Iron Liners come with out the head gasket grove."

[combatic]

Cast Iron is not as durable ( I think I saw a quote from Charles Navarro, LN Engineering saying they last 50K miles between rebuilds and they do not dissipate heat as well a AL. If you drive your car hard then temperature management will be important (critical?) If you are building up this hot 2.7 to commute to cars and coffee then steel cylinders are probably just the ticket if on a budget.

I did note this about the cast iron cylinders "The Cast Iron Liners come with out the head gasket grove." I think they meant 'groove'. I think the mid year 2.7 heads use the head piston seal with the combination spring wrapped steel seal that fits in a groove so you would have to machine the cast cylinders to match the heads but I could be wrong. I am going to wander out into the shop and check my heads now to verify. Dang my cylinders are at the machinists....so I can't verify that.

[sportsbeetle]

Originally Posted by combatic

Cast Iron is not as durable ( I think I saw a quote from Charles Navarro, LN Engineering saying they last 50K miles between rebuilds and they do not dissipate heat as well a AL. If you drive your car hard then temperature management will be important (critical?) If you are building up this hot 2.7 to commute to cars and coffee then steel cylinders are probably just the ticket if on a budget.

I did note this about the cast iron cylinders "The Cast Iron Liners come with out the head gasket grove." I think they meant 'groove'. I think the mid year 2.7 heads use the head piston seal with the combination spring wrapped steel seal that fits in a groove so you would have to machine the cast cylinders to match the heads but I could be wrong. I am going to wander out into the shop and check my heads now to verify. Dang my cylinders are at the machinists....so I can't verify that.

Ahhh this makes complete sense. I fully intend to drive my car hard and don't want to have to worry about heat.

Looks like the two options are
1) keep the OEM Mahle p&c or
2) splurge for the full JE pistons & Nikasil cylinder set

After reading comparison threads here between JE & Mahle, leaning towards just sticking with what I got, especially with the gas we have here in Canada. Thanks all for the advice!

[sportsbeetle]

Just wanted to update this thread in case anyone in a similar situation reads in the future.
Spoke with John D. who as folks in this thread mentioned set me straight!

Went with a DC43X-102 profile which has a better exhaust profile for 47mm cam housings and is a bump up from the DC40. Also getting his valve spring kit.
Decided to keep my Mahles as the ~3-5% bump in power isn't worth the cost to me.

Will post back here once build is complete and hopefully with a video as well.

[sportsbeetle]

New wheels going on once RS flares go on.
15x7 et23 front and 15x9 ~et0 rear forged 3 piece Augment Fuchs replicas on Toyo R888Rs
205/50r15 front, 235/50r15 rear

[sportsbeetle]

Got the car dry ice cleaned today, pretty great stuff. 45 years of dirt and grease removed!

[75 911s]

Looks good! I had my Carrera cylinders bored and plated by US Chrome. One came back pitted in several places. Luckily a friend had just bought new cylinders so I had a free core that matched. all in I think it was around $1500 to use existing cylinders and over 6 months of time. Not to scare you into spending more money but I think I'd go with the P&C JE set if I were you. That's what I'm planning for my 2.7 build. Definitely avoid the cheap iron cylinders.