"Sleeper" hotrod - homebuild 2.7CIS to high comp 2.7 MFI
Posted: Sat Jan 11, 2014 6:33 pm
So, I have finally got around to posting something about my winter project. Flikr seem to have done a great job of making it as difficult as possible to post photos these days 
... but I think I have finally re-learnt how to make them work.
Anyway, about the project.... the 911E has been very slowly evolving over the years as time has permitted, with a general plan of creating a "hotrod sleeper" - sleeper because the original bodywork, trim and interior are pretty well preserved and are worth not messing around with. But for me it's really all about the driving, I want to bring out the maximum performance potential with some sensible mods, although all changes are "reversable".
The car currently looks like this - as pictured with Will B's red targa S -
It already has bilsteins, aluminium rear arm conversion, 3.2 front calipers etc, so now it is time for some more power
This green US car is the closest I have so far seen to my vision for my car - mine would be less extreme in terms of running spec, but appearance wise I see a lot to aspire to...
So, back to the winter project: I have been wanting to carry out an engine rebuild for quite a while - my 2.4E motor is matching numbers for my car, but has now coverered about 110,000 miles and, at 40 years old is showing its age. The oil leaks have really got out of control, in particular the crankshaft "0" ring around the bearing carrier at the pulley end is thought to be leaking, and that means splitting the case... The engine has never run particularly smoothly regardless of countless tune-ups of the MFI and ignition, throttle body rebuild, distributor rebuild, MFI pump rebuild etc etc, so the condition of the top end is really in question; leak-down tests show 15-17% leakage on all cylinders, and there is some evidence of valve guide wear - noise, burning oil etc.
This winter I finally have some time to put together a new engine which will deliver extra performance, but also remain practical for everyday use - the car needs to be as useable in London traffic dropping my son off to nursery as it is for early sunday blasts and the occasional track day...
So, I am planning to put together an E-cammed MFI engine on steroids - the E-cams giving the famous midrange torque for general all-round driveability, but increased capacity and compression ratio for extra punch. I am also pondering twin-plug...
As discussed elsewhere by others on this forum, to increase capacity of the 2.4 engine to 2.7L requires machining of the crankcase to accommodate the larger diameter cylinders. This is all very well, but I have decided that I would prefer to keep my matching-numbers crankcase intact. Therefore, a couple of years ago I picked up a '74 2.7L CIS motor from a fellow DDK'er, which has been waiting in storage for the project to begin. The photo below is the engine as I bought it - not a particularly pretty sight
It had already been stripped of anciliaries but came with all the CIS and CDI parts including 3-PIN CDI box and black coil -
I had no information regarding the history or condition of this engine, other than that it turned over by hand and was complete. There was talk of it having spent some time installed in a VW camper, and being a 2.7L US-spec motor with 9-blade fan, the prognosis for it's overall condition is not great....
However, the plan is to strip the CIS motor, recondition and repair wherever necessary and rebuild it as a 2.7 MFI engine. This would include new pistons and appropriate machining work to the heads for use with MFI injectors. E-cams will be used, either from my current engine or re-grinding the CIS cams. I'll also use the complete MFI and other anciliaries from my current engine. I am carrying out the strip-down and rebuild myself, but will be leaving the machining work to the experts
Current thinking on the spec is something like this -
New high-comp pistons
CR~ 10:1 if single-plug
911E cams
911E throttle bodies
shuffle pin case
boat-tail case and cylinders
re-plate 2.7L cylinders
rebuild E MFI pump to fuel increased capacity
lighten flywheel (not too much though)
external oil cooler
It would of course be interesting to hear what others think of this spec. As mentioned above, I'm also not ruling out twin-plug at this stage, although I do want to avoid unnecessary complexity which might compromise reliability or useability.
As of today, the 2.7CIS engine is ready for strip-down - with engine-stand kindly donated by Chris Turner - thanks Chris
As you can see, there's plenty of surface corrosion and general grime from all that time out of use. I will be dismantling it over the next few days, so it will be interesting to see what internal condition it's in...
That's all for now, will post updates as I have them.
Cheers,
... but I think I have finally re-learnt how to make them work.Anyway, about the project.... the 911E has been very slowly evolving over the years as time has permitted, with a general plan of creating a "hotrod sleeper" - sleeper because the original bodywork, trim and interior are pretty well preserved and are worth not messing around with. But for me it's really all about the driving, I want to bring out the maximum performance potential with some sensible mods, although all changes are "reversable".
The car currently looks like this - as pictured with Will B's red targa S -
It already has bilsteins, aluminium rear arm conversion, 3.2 front calipers etc, so now it is time for some more power
This green US car is the closest I have so far seen to my vision for my car - mine would be less extreme in terms of running spec, but appearance wise I see a lot to aspire to...
So, back to the winter project: I have been wanting to carry out an engine rebuild for quite a while - my 2.4E motor is matching numbers for my car, but has now coverered about 110,000 miles and, at 40 years old is showing its age. The oil leaks have really got out of control, in particular the crankshaft "0" ring around the bearing carrier at the pulley end is thought to be leaking, and that means splitting the case... The engine has never run particularly smoothly regardless of countless tune-ups of the MFI and ignition, throttle body rebuild, distributor rebuild, MFI pump rebuild etc etc, so the condition of the top end is really in question; leak-down tests show 15-17% leakage on all cylinders, and there is some evidence of valve guide wear - noise, burning oil etc.
This winter I finally have some time to put together a new engine which will deliver extra performance, but also remain practical for everyday use - the car needs to be as useable in London traffic dropping my son off to nursery as it is for early sunday blasts and the occasional track day...
So, I am planning to put together an E-cammed MFI engine on steroids - the E-cams giving the famous midrange torque for general all-round driveability, but increased capacity and compression ratio for extra punch. I am also pondering twin-plug...
As discussed elsewhere by others on this forum, to increase capacity of the 2.4 engine to 2.7L requires machining of the crankcase to accommodate the larger diameter cylinders. This is all very well, but I have decided that I would prefer to keep my matching-numbers crankcase intact. Therefore, a couple of years ago I picked up a '74 2.7L CIS motor from a fellow DDK'er, which has been waiting in storage for the project to begin. The photo below is the engine as I bought it - not a particularly pretty sight
It had already been stripped of anciliaries but came with all the CIS and CDI parts including 3-PIN CDI box and black coil - I had no information regarding the history or condition of this engine, other than that it turned over by hand and was complete. There was talk of it having spent some time installed in a VW camper, and being a 2.7L US-spec motor with 9-blade fan, the prognosis for it's overall condition is not great....
However, the plan is to strip the CIS motor, recondition and repair wherever necessary and rebuild it as a 2.7 MFI engine. This would include new pistons and appropriate machining work to the heads for use with MFI injectors. E-cams will be used, either from my current engine or re-grinding the CIS cams. I'll also use the complete MFI and other anciliaries from my current engine. I am carrying out the strip-down and rebuild myself, but will be leaving the machining work to the experts
Current thinking on the spec is something like this -
New high-comp pistons
CR~ 10:1 if single-plug
911E cams
911E throttle bodies
shuffle pin case
boat-tail case and cylinders
re-plate 2.7L cylinders
rebuild E MFI pump to fuel increased capacity
lighten flywheel (not too much though)
external oil cooler
It would of course be interesting to hear what others think of this spec. As mentioned above, I'm also not ruling out twin-plug at this stage, although I do want to avoid unnecessary complexity which might compromise reliability or useability.
As of today, the 2.7CIS engine is ready for strip-down - with engine-stand kindly donated by Chris Turner - thanks Chris
As you can see, there's plenty of surface corrosion and general grime from all that time out of use. I will be dismantling it over the next few days, so it will be interesting to see what internal condition it's in...
That's all for now, will post updates as I have them.
Cheers,