Engine Build Advice for 71T

[spyerx]

Hey all - so I have this car, a signal orange 71t, it's a nice 'very mild' hot rod with a stock-ish look and I plan to keep it that way. The car does not have its original engine, a 2.7 from a 77 was swapped back in 1992, and the case is long gone. Have all the receipts too! (wow were prices cheap).

Current engine is pretty fresh, about 5k on the top end, with refreshed rings on the bottom at that time. Engine is just a slight bit weapy, but not leaking/dripping. It starts and runs good. Has Webers on it now.

What I don't like about current setup: I'm not a carb fan (ok love the noise...but that's it), the engine has great torque, but would like it to rev/pull harder in the higher ranges, and feel a bit more "lively".

My goal: a lively, revvy motor, not 'peaky', reliable, can drive it hard, canyons and occasional track/DE/AX, call it around 225HP. I think i would want EFI. I would want all the tweaks that make it robust and reliable. I don't want a car that only runs right on race gas, or is super cold blooded, etc.

I'm curious to the thoughts here. My first reaction is to build the 2.7 to an RS type spec and do a motec/PMO EFI system...

Thoughts? Keep current case/build that? Go source something else?

Would like to not break the bank, but I am willing to spend some $. I'm a driver not a collector/seller. :-)

[jpnovak]

9.5:1 JE pistons
Mod_S cam
Open the intake ports to match new air flow requirements

Keep the webers or add your EFI/ITB of choice.

Plenty powerful enough for a 71T.

[Catorce]

Oh, this one is easy. Buy one of my 3.6 cases and build up a stockish 964 motor. I can get you practically every used part for that motor.

What you'll get is a high torque, easy running modern build that you won't have to screw with and it will out power anything else you could build with a smaller case.

[spyerx]

Originally Posted by Catorce

Oh, this one is easy. Buy one of my 3.6 cases and build up a stockish 964 motor. I can get you practically every used part for that motor.

What you'll get is a high torque, easy running modern build that you won't have to screw with and it will out power anything else you could build with a smaller case.

Hahha. Man I’ve been watching your process on rennlist and love what you’re doing. We need to talk when my 964 is ready for a build. That’s next on the list.

For this, I’m really not sure i want to go that big, and then there is the 901 trans....

[Catorce]

Originally Posted by spyerx

Hahha. Man I’ve been watching your process on rennlist and love what you’re doing. We need to talk when my 964 is ready for a build. That’s next on the list.

For this, I’m really not sure i want to go that big, and then there is the 901 trans....

Well the 901 is a limiting factor for sure. I have a 3.6 and a G50 in my 73, and it's a hoot but it is a properly prepared car with huge brakes and wide rubber.

So build a motor like I have in my 914. It has a 2.7 mag case with a 901. Weber 40, 964 cams, electronic ignition, about 220HP, hauls ass. It's got just about everything you can do to a 2.7

[MST0118]

Will a 964 engine work with the stock 71 tranny (901) or would that have to be changed to a stronger 915?

[spyerx]

Originally Posted by MST0118

Will a 964 engine work with the stock 71 tranny (901) or would that have to be changed to a stronger 915?

Well... depends how you drive but a 901 with 300+ HP probably is t going to be long loved the way i drive these things :-)

The 901 in my car is fresh and has some strengthing parts from the rebuild. Like the center carrier i don’t know what the part is called.

And i love the dog leg and way it shifts. It’s really nice to drive.

Originally Posted by Catorce

Well the 901 is a limiting factor for sure. I have a 3.6 and a G50 in my 73, and it's a hoot but it is a properly prepared car with huge brakes and wide rubber.

So build a motor like I have in my 914. It has a 2.7 mag case with a 901. Weber 40, 964 cams, electronic ignition, about 220HP, hauls ass. It's got just about everything you can do to a 2.7

I’ve weber 40 and a pertronix on it now. It runs and drives great. I’ll probably go efi.

Do you mind detailing what you did to your 2.7?

Thanks.

[Catorce]

Originally Posted by spyerx

Well... depends how you drive but a 901 with 300+ HP probably is t going to be long loved the way i drive these things :-)

The 901 in my car is fresh and has some strengthing parts from the rebuild. Like the center carrier i don’t know what the part is called.

And i love the dog leg and way it shifts. It’s really nice to drive.



I’ve weber 40 and a pertronix on it now. It runs and drives great. I’ll probably go efi.

Do you mind detailing what you did to your 2.7?

Thanks.

Been a while, but Weber 40s, 964 cams, AASCO valve springs, all new valves, electromotive ignition, headers, JE pistons, I forget what CR, but a little hotter than stock. Single plug.

Oh, and it needed 7500 worth of machine work because the case was warped like a pringles chip which was the impetus to make my own cases.

[Matt Monson]

You’ve got to pick your poison. You won’t get the smaller displacement Porsche engines to rev without making them peaky. Anything over 7k on a 3l or less loses something on the bottom end.

So you need to decide torque in the midrange with displacement like Catorce advocates, or more compression, twin plug and a cam on something smaller. I’m putting a twin plug rsr spec 2.8 in my car. I like to rev.

[Trackrash]

Originally Posted by spyerx

My goal: a lively, revvy motor, not 'peaky', reliable, can drive it hard, canyons and occasional track/DE/AX, call it around 225HP. I think i would want EFI. I would want all the tweaks that make it robust and reliable. I don't want a car that only runs right on race gas, or is super cold blooded, etc.

I'm curious to the thoughts here. My first reaction is to build the 2.7 to an RS type spec and do a motec/PMO EFI system...

Thoughts? Keep current case/build that? Go source something else?

Would like to not break the bank, but I am willing to spend some $. I'm a driver not a collector/seller. :-)

As Matt says the way to get 220hp out of a 2,7 is by spinning the motor up. You won't have much power below 4k rpm.

My dream motor would be a 2,9L, dual plugs, mod S cams, and 46mm Webers , or if I win the loto, high throttlebody injectors converted to EFI. With that I would have the best of both worlds.

BTW, the '71 trans should take that kind of power, as long as you don't try doing burn outs.

[spyerx]

Awesome thoughts guys. Seems everyone is centering on a similar pattern.

2.7/2.8
proper headwork to breathe
cams to match, and tilt it towards a revvy motor
dual plug
higher compression to allow 91 CA crap gas
all the little tricks for oiling etc
proper studs, casework, machining to make it reliable
I'm probably settling on an ITB type EFI Motec, possibly coil on plug
I just like EFI, I know, not period.

I don't do burnouts, but I don't drive the car soft. I do shift proper as I don't like spending too much $ with GT Gears :-) I really enjoy driving the 901, it does shift nice. I do need a diff tho Matt!

[Matt Monson]

Once you build an engine you won’t have any choice but one wheel burnouts unless you get a diff.

[al lkosmal]

Originally Posted by jpnovak

9.5:1 JE pistons
Mod_S cam
Open the intake ports to match new air flow requirements

Keep the webers or add your EFI/ITB of choice.

Plenty powerful enough for a 71T.

+1...this is a good basic recipe for a great canyon carver engine...................

regards,
al

[lvporschepilot]

Craig (Pelican screen name: Cgarr) can do your heads how you want them. He does fantastic work, is fast, very reasonable, extreme pro.

[spyerx]

Originally Posted by Matt Monson

Once you build an engine you won’t have any choice but one wheel burnouts unless you get a diff.

I’m already getting some break away/spin in tight canyons now with the 2.7 that is in it on 2nd gear exits.

So yeah, a GT Diff is in the plan as part of this. :-) I’m not used to non-performing open diffs in my 911s!

[evilfij]

Why not convert what you have to EFI?

[spyerx]

Originally Posted by evilfij

Why not convert what you have to EFI?

Mainly because I'm a 'do it once' type person and if i'm going to go that step i'll build the rest of the motor, and likely, the transmission at the same time.

For now, I'm just driving the piss out of the car, and it's fine. But, another reason I want EFI. I live at sea level. Car runs/starts/drives fine. Drove it yesterday after sitting for 3 weeks (was on vacation) I take it up angeles crest hwy, which goes up over 6000 ft. Car starts to get spitty... and a dead spot in transition from idles to mains. Maybe that is fixable? But then it drives ass-y at sea level... CARBS!

I talked to a few builders and have an idea of the $ it would be to do it the way I would want it. BTW, doing EFI vs. MFI... MFI is probably more $.

[Neil Harvey]

Your original post stating your desire,

"My goal: a lively, revvy motor, not 'peaky', reliable, can drive it hard, canyons and occasional track/DE/AX, call it around 225HP," is exactly the engine many want.

This revvy engine will require an efficient use of the limited air mass, lightweight componentry, and a serious look at friction reduction.

The engine configuration has to change from what is typically offered along with how you manage the air supply. Its a basic shift in thinking here. With limited air supply, to get the engine to rev quicker, you have no choice but to lighten up the masses involved.

To make use of the engines ability to rev quicker, you have to manage the air you have to work with more efficiently. This doesn't necessarily mean you have to port for more air, (more is always better), but use what you have better. Accelerate the valves off the seat quicker, less mass to lift off the seat, less force to work against in doing so, but having control of the backside as well.

Making use of the turn around at TDC to help with this limited air exchange and increasing the change of direction at BDC to help increase the efficiency of the piston as it does nothing to help performance at the bottom turnaround.

We are involved in a 2.9L project at present where we have changed the basic configuration completely, spent a lot of effort on lightweight components, and a new cam design that is part of our new "inventory". Our goal is about engine acceleration, getting into the useable torque not so much outright HP. It will be nice to have both and we do have a HP goal in mind.

After spending many years involved with the water engines, its fun to be involved in these earlier engines and there is so much new development that can be done to help their performance.

There is life still left in these older engines. I believe that the early mag cases have probably done all of their shape changing and have seasoned into some sort of reliable engine case. As the lively revvy engine is part of the sum of all parts required to get that performance, car weight play huge part here too. A mag case certainly helps in weight reduction.

[evilfij]

Originally Posted by spyerx

Mainly because I'm a 'do it once' type person and if i'm going to go that step i'll build the rest of the motor, and likely, the transmission at the same time.

For now, I'm just driving the piss out of the car, and it's fine. But, another reason I want EFI. I live at sea level. Car runs/starts/drives fine. Drove it yesterday after sitting for 3 weeks (was on vacation) I take it up angeles crest hwy, which goes up over 6000 ft. Car starts to get spitty... and a dead spot in transition from idles to mains. Maybe that is fixable? But then it drives ass-y at sea level... CARBS!

I talked to a few builders and have an idea of the $ it would be to do it the way I would want it. BTW, doing EFI vs. MFI... MFI is probably more $.

I get it. If it were me, if you really want to build something, I would have another engine built and then sell the 2.7 that’s in it. Even better, get a complete set up engine and trans built, and then swap that in and sell the 901/2.7. My point was more like “you have a good non-numbers marching engine now with a fresh rebuild, why not adapt that simply with EFI v. a full build.”

Anyway, I vote for a 3.4 turbo build or 3.6/3.8 build either with a G50. Do it once as you say. And the cost to do a rebuild on a nice engine v. an engine that actually needs it when you are replacing basically enverything but the case is not huge. Plus swapping a drivetrain is much quicker than waiting while your drivetrain is rebuilt.

[mepstein]

“There is life still left in these older engines. I believe that the early mag cases have probably done all of their shape changing and have seasoned into some sort of reliable engine case. As the lively revvy engine is part of the sum of all parts required to get that performance, car weight play huge part here too. A mag case certainly helps in weight reduction.”

Neil - I was under the impression that mag is such a reactive metal that it just keeps getting more and more brittle until it crumbles. I don’t think time is it’s friend.