Build an engine from my parts bin...

[JohnJL]

I've got a 71 Targa on the way that will be my "nice day" daily driver (which is like 320 days a year.) By daily driver I mean I take the public transport to the office (its a nice ride and traffic sux) and put about 10K kms (7000 miles) per year and will use it on mostly 1-hour trips about.

I have a bunch of bits around and while the car runs fine now, I know I'll have the bug for more performance soon...

So, if you had the following bits, what would you build?

1 83SC 3.0 engine case and bottom end
1 2.7L engine case and bottom end

Solex cams
SC cams
DR-20 (Dr Camshaft/John Dougherty GE20 cams)

Complete CIS intake and fuel plumbing off 1983 sc
2nd CIS set of intake runners and airbox modified to accept injectors for use with motec/megasquirt/etc
Weber IDA40's

2.7 Cylinders (90mm)
3.0 Cylinders (95mm)

2.7 euro pistons (8.5:1 CR 90mm)
3.0 SC US pistons (9.3:1 95mm)
3.0 SC Japan pistons (9.8:1 95mm)

2.7 crank
3.0 crank

6x2.7 rods
12x3.0 SC rods

6x 74 heads (35mm intake 35mm exhaust ports)
6x 83SC heads (34mm intake 34mm exhaust ports)

SC ROW dizzy
2.7 euro dizzy
SC US dizzy
Complete EDIS wasted-spark crank trigger & coil setup
MSD 6T box and Blaster 2 coil

Spare megasquirt IIv3

Your ideas much appreciated. My first pass is the following:


1 83SC 3.0 engine case and bottom end
DR-20 (Dr Camshaft/John Dougherty GE20 cams)
Weber IDA40's
3.0 Cylinders (95mm)
3.0 SC Japan pistons (9.8:1 95mm)
3.0 crank
3.0 SC rods
6x 83SC heads (34mm intake 34mm exhaust ports)
SC ROW dizzy
MSD 6T box and Blaster 2 coil

Any other suggestions? Can anyone confirm I'll have clearance on the DR20 cams with that combination? What would the characteristics of that kind of engine have? Things I care about:

1. Torque
2. Snappy throttle
3. Reliability
4. Acoustics

Things I don't care about:
1. Passing emissions/inspection
2. Gas mileage
3. Originality

thanks all!

[JohnJL]

Anyone confirm the valves in that configuration will clear the heads with Solex and/or GE 20 cams?

thanks

[YTNUKLR]

Seems like this to me:

1. Torque...3.0 is better
2. Snappy throttle...2.7 is snappier
3. Reliability.....same, as long as you do good prep work (machine 2.7 case correctly, etc.)...3.0 will last longer overall
4. Acoustics...can't argue with any 911 engine music, but my vote would be for the 2.7

Things I don't care about:
1. Passing emissions/inspection...some sort of ITB setup
2. Gas mileage...some sort of ITB setup
3. Originality...some sort of ITB setup

Out of parts you listed, you should go with your Webers over any CIS system for your wishes. EFI is really a much better idea than carbs, but if you're using it with a single throttle body intake, you're not going to be having more fun than with Webers.

You already nailed the best combo out of your parts..but...

I personally would pocket the pistons as deeply as possible (perhaps 4.5mm crown thickness in the valve areas) and then check how much piston/valve clearance you have. This is sort of uncharted territory on CIS pistons, but it will pay dividends to run as radical a cam as possible on CIS pistons...perhaps you might even be able to run a DC40 (Mod-S), which is a hoot in a carbed 2.7 or 3.0. If you were able to run a Mod-S, you would need a different distributor from ROW 911SC, but that's not too difficult an obstacle, especially considering how fun and fast this engine would be for the $$$.

-Scott

[JohnJL]

Thanks Scott.

Can anyone chime in with experience in valve-reliefing CIS pistons? I could do my own rudumentary measurements, but anyone know just how much material is under the crown and how deep they can be reliably cut?

Drcamshaft around?

[YTNUKLR]

SC pistons probably around 5.7mm thick at the top, 4.5mm is a pretty safe thickness to run

[camgrinder]

I would trial fit the 3.0 engine with the Japanese pistons and check the V-P. I would be suprised if you needed more than 1mm cut to clear the DC-20 cams.
Use the weber carbs and put together the parts for the EFI set up later.

[JohnJL]

I've changed my thinking a bit....god, what a slippery slope!

I now have the luxury of time and more parts/cash so am thinking of building a more fun toy employing super-atmospheric pressure.

So how about this:

1 83SC 3.0 engine case and bottom end
Some kind of cam
Supercharger or turbos @ .7 BAR
3.0 Cylinders (95mm)
3.0 SC US pistons (9.3:1 95mm)
3.0 crank
3.0 SC rods
6x 83SC heads (34mm intake 34mm exhaust ports)
Twinplug Megasquirt or Adaptronic ECU
Big honkin intercooler

Any thoughts on compatability, turbo/supercharger or cam choice? I know the earlier 930s had compression ratios around 7-8:1 but the newer cars had much higher ratios and with higher compression/sophisticated fuel and spark control I would hope the 9.3:1 OEM pistons would be OK..?

john

[Grady Clay]

OK, I’ll be the provocateur.

Save the 3.0 for another project; build the 2.7 with the lightest weight components as possible (CF/FRP tin, etc.) Solex cams, 40IDA.

Buy the (expensive) 92 mm RSR P&Cs and twin plug the 2.7 heads.

You will need very high octane fuel and a reinforced passenger headrest (so you don’t injure anyone with the neck snapping performance).

One very nice feature with the ’71 is its light weight. You can make it even lighter without hurting it.

Best,
Grady

[JohnJL]

Thanks Grady. Couldnt I do the same with the 3L twin-plugged using high cr JE pistons and end up with more HP and less $? That's what I already have in the race car, I can easily switch between the Weber 40IDA carbs and 84 aluminum intake holding the injectors driven by either my Megasquirt or my Adaptronic ECU. I was supposed to be at the dyno today (but it blew its power supply.)

I am feeling adventurous for some forced induction. Mayby WydRyd will be heard from. I know he's had some fun with these.

john

[shbop]

signing-up

[JohnJL]

OK, the plans are firmed up now, as a result I'm actually going to build up two engines and sell off the complete 2.7 now in the Targa.

My question is specifically about cams, hopefully John D will chime in here.

The first engine is going to be a naturally-aspirated 3.0 using the assembled engine I have been using in my track car. That has a standard 3.0 crank, some mild boatailing, 11:1 CR JE pistons in nickies with RoW 3.0 1983 heads. That currently has a DR20 cam in it. I have fairly well developed the EFI system on this now and will be transferring it over to the new supercharged project engine. This engine will now run the Webers I have or a new set of PMOs. Twin-plugging will be kept using either a distributor/haltech setup I have or firing off a spare Megasquirt.

My first question is this...if I am looking for a broad torque band and keeping within a 6500rpm redline, what is my best cam choice if I want to keep the pistons as-is? Is the GE20 my best bet? I want to know if I should leave those cams in or whether something else is better suited (and perhaps if the GE20's should go in the second engine...)

The second engine is a supercharged project, I have already assembled almost everything now including 3.0 case, new 3.2 barrels, coated 98MM 8:1 JE Pistons, twin-plugged RoW SC heads, hydraulic tensioner update bits, Carrera intake and 55lb injectors running off the EFI system I have already dialed in. I have a spare set of SC cams (Ray Fowler runs SC cams in his supercharged engine with good results) and the previously-mentioned DR20 cams. Redline will be 6500 and this is a race-only engine. Also had the cylinders tapped to accept 993 knock sensors and bridge which will be monitored by the EFI.

John D and all other advice appreciated.

John

[camgrinder]

The GE20 and DC20 cams are not the same profile.

The N/A engine with PMO carbs should have a more aggresive cam, like a DC24 on a 108 Lobe center. The high compression limits the cam choice, if you go too short on duration, the fuel octane requirement goes up. Short duration is needed for the 6500 rpm shift points.

Put the DC20 cams in the supercharged engine. Do you have a dyno graph on Ray Fowler's engine? Is it the same supercharger? Where does the power
come in with the SC cams?

Fill out my cam info form,
http://www.drcamshafts.com/caminfo.htm
and I might be able to give you some more options.

[JohnJL]

Thanks John, I've filled in your form. Sorry about the DR20/GE20 mixup...it was 3:30 AM here and I was overtired...

Here are two dyno runs from Ray's website. His is a 3 liter, mine will be 3.2 but otherwise we are running the same crank, rods, intake, throttle body, heads and a similar supercharger and intercooler.

[joetiii]

How did the NA engine turn out with the DC24 cams?