"Sleeper" hotrod - homebuild 2.7CIS to high comp 2.7 MFI

[Bootsy]

Interesting stuff Gavin and sounds like an ideal spec

[911hillclimber]

That will be a great driving engine and an economic build.
The torque band will be a mile wide.
I had a 2.4 E engine , mech inj, with 2.4S P&B. 180 bhp, can't recall the torque, but it drove superbly.

Tune the engine to run on Shell V Power and the world will be good.

[hot66]

looks like you got a good core there .. you never know until its opened up

Your going to have a loverly road motor there .. I love the way my 2.4S delivers its power, but also I'm lucky to live in the country where I can always use the revs and ring its neck .... it can be harder work in traffic , towns etc which I do very little of ...... I also miss having that low down slug when overtaking .. my motor usually comes on cam just as I'm level with the other car

[silver911]

Good choices there...
Don't shout too loudly about how great it is tho'... everyone will want one...

It is everything you could ask for...and in the driving that most of us enjoy (!) the E cam is almost perfect.
I feel my engine is 'livelier' low down than an RS engine as the torque curve is biased lower in the rev range and getting to the lower rev limit (ooppppsss) is easier making progress fast. Its certainly more than enough for my driving ability and bravery.

[Mike911scrs]

HI Gavin
your quote
"I understand that the alternatives are either a new gear and shaft assembly for ?£800++, or to hunt down a good used one."

why do you not just replace the Ally drive gear on the inter-gear, parts can be from ;

http://www.rosepassion.com/en/cat/porsc ... 216/P71261

or

http://www.pelicanparts.com/cgi-bin/sma ... %2529%2520

regards mike

[shoestring7]

The E port size is 32mm diameter (as are the US-spec '74 2.7CIS ports on donor engine heads). I seem to remember the S -heads are 36mm? Apparently the 2.4TE is just 28mm. Please shout if this sounds incorrect!

I'm enjoying this thread, more so as I'm involved with rebuilding my 2.4T CIS engine at the moment. On inlet port sizes, the information I have is that the 2.4T-E has a 32mm port, while the 2.4T CIS has a 30mm inlet port.

Oddly, the valves are all the same size across the range (T,E,S, RS) at I46/E40.

>C

[Lightweight_911]

Yes, the 2.4T CIS engine has 30mm inlet & 33mm exhaust ports.

[haasad]

Interesting discussion and input on the torque producing capacity of smaller intakes, my 2.8 twin plug uses a set of 2.7 CIS heads, home bored 35 mm chokes on weber 40's , S cams and 9.5 :1 , I do have a boatailed case and very carefully balanced crank, rods pistons and flywheel. The flywheel is lightened. Its really strong on torque pulling really well from only 1500 rpm in third. I can feel the power above 5500 but haven't really explored it since I'm not a good enough peddaler. Really must get some final power and torque figures now it runs properly, perhaps when the sun comes out.

[gav p]

Yep, I think the spec seems to fit pretty well considering the ingredients already available.

However, Nick has not been short of suggestions as to what else could be done with it... - the main reason for this is that I almost have two complete engines here - the original E one and the new "short" 2.7. The E motor will be dismantled over the next couple of weeks and prepared for storage, but the plan has been to use the cams and MFI from this in the new 2.7 engine. So the cams are the only internal part which would prevent a future rebuild of the original E engine, because they would be built into the 2.7.

So if I bought a second pair of cams this would not be an issue, and at some point in future I could then rebuild my 2.4E matching numbers engine and even sell the 2.7 if I really wanted to. But, there is then a choice to make, as we could choose something other than E-cams. As nick suggests, you could go for:

- S-cams on a single-plug hi-comp 2.7 which would give something ITRO ~230-240BHP.
- Or something like a GE40 cam, which apparently is also a good allrounder but not as mild as the E. Similar power to the S cam. Anyone running GE40s on here?

The key issue with doing this (apart from expense of buying cams) is the E throttle body and MFI trumpet bore: they are smaller than the S/RS, and therefore are not ideally suited to more peaky cams. The throttle bodies can be bored out to S size, but apparently the plastic MFI trumpets are not so straightforward: they can also be bored out, but due to the limited wall thickness available the resulting internal profile would be relatively straight. This apparently leaves less of a conical profile internally, thus reducing the amount of velocity increase they are designed to provide to the airflow.

A set of S trumpets and throttle bodies would be the answer. However, I suspect these are rarer than they used to be and could be pretty expensive these days.

My feeling is to stick to the plan, and in due course keep an eye out for a second set of E cams. But it's nevertheless interesting to ponder what else could be done with the 2.7. If I was not building an "everyday all-rounder" engine, it would be very tempting to go chasing horsepower with the spec choices

[hot66]

I'm running ge40 spec cam ( custom grind from fresh blanks by kent cams) in my car .... We ran the cam on Neil bainbridges cam machine and the reality is it was pretty much identical to the stock s cam

Have a look on my cars thread for full engine spec

[gav p]

HI Gavin
your quote
"I understand that the alternatives are either a new gear and shaft assembly for ?£800++, or to hunt down a good used one."

why do you not just replace the Ally drive gear on the inter-gear, parts can be from ;

http://www.rosepassion.com/en/cat/porsc ... 216/P71261

or

http://www.pelicanparts.com/cgi-bin/sma ... %2529%2520

regards mike

Hey Mike - thanks! I didn't realise these were available separately. Any experience of the quality of these? - have you used either yourself?

Gearbox is shifting very nicely, by the way

[ian cox]

Hi
I ran GE60 on my twin plugged high compression 2.5. Nick looked at all the various cam timing san decided on this. It made 252bhp. increased capacity will 'soften' the cam so perhaps consider a GE60.
Kind regards Ian

[gav p]

increased capacity will 'soften' the cam so perhaps consider a GE60.
Kind regards Ian

Yep, that's my understanding Ian. Increasing the E capacity would soften that cam even further. But for the kind of mixed driving my car gets used for, that may not necessarily be a bad thing...

Yours sounds like it was a fantastic motor, and 100BHP per Litre is a highly satisfying result I'd say.

[ian cox]

Hi Gavin,
Please remember that our early cars a pretty light say 1000kgs so the torque needed to move them is not that great. When I had my 2.7RS it would pull form 1500 in 3rd all the way to 7000 plus perfectly because the their was no weight to push.
The ST was the same it weight 819kg with oil no petrol so if you want that 6500 to 7200 zing then the GE60 cam may do it for you.
I guess it depends where it will spend mots of its life being driven, road, odd track day?
The GE60 may not increase torque over the E cam but it will give it that top end sound that I personally love.
Horses for courses.
kind regards Ian

[yoda]

The engine in my car was rebuilt with a GE60 cam and the top end hit is very addictive. Really gives the "zingyness" that I was looking for.

It is what I think an early 911 with an MFI motor is all about.