E engine for 71E coupe??

[BK911]

I am slowly restoring a 71E and trying to figure out what engine to put in her. Most use will be daily driver with a LOT of mountains roads on evenings and weekends. The only thing I am sure about is E cams and MFI. Some initial ideas are:

Stock 2.2E
Boring!!

2.4E with 2.2E pistons
I had a very similar engine in an early targa and it was awesome!

2.4E with 2.2S pistons
Higher compression = better?

2.4E with 85mm cylinders and ? cr JE pistons
No replacement for displacement!

I also have a set of 36mm stacks and TBs which I would LOVE to use if possible. I love the E because of its usuable torque. Will the larger intakes ruin the low end too much?

How about:

2.7E with 36mm intakes?

The car is going in for paint in a couple of weeks and I would really like to get started on the engine. I am open to all suggestions.

Thanks,
BK

[jluetjen]

Hi BK; it's great to hear from you again. Starting at the bottom...

1) a 2.7E with 36 mm ports and MFI. Another poster on this BBS built an engine like this for autocrossing and it was stronger than a 2.4E from 2100 RPM up to about 5700 RPM. After that it ran out of steam quickly. Compared to the S cam, the E cam has lower lift, which made for higher gas flows at lower revs. But once the engine speed picked up, the lift limited the absolute gas flow, resulting in the torque dropping like a stone after that. Compared to the same engine with S cams (ie. a 2.7RS), the 2.7RS won't start to be generating that kind of torque until at least 4000 RPM.

2) As far as a 2.4E with 2.2E or 2.2S pistons -- I think that you need to look at the static CR of each case to make sure that you'll be able to get gas for it. Unfortunately I can't find the spreadsheet that I did, but if I remember it correctly the key points look like this...

- The T, E and S engines end up having comparable static CR's. This is because even though the S has the highest CR pistons, the high-lift/long duration cam closes the intake valve later than the E cam. If you calculate the CR from when the intake valve closes, you'll find that in each case the CR is about the same. Now if the factory engine runs on 91 octane, and you switch to the next higher CR piston without changing the cam -- I'd expect that you'll need to jump a grade is gas. If you go two steps (such as E cam with 2.2S pistons) you may find it hard to keep all of the ponies inside the cylinder given the CR. You could back off on the ignition timing some, but that will increase your engine temperatures. You could move the cam timing later, but that may cause other issues with clearances. The best solution to this would be to twin-plug -- but that takes more $.

- All of the previous points are true, but our engines are dynamic - not static and will often operate at different RPM levels. Because of the intake and exhaust harmonics there will be an engine speed where the intake charge will get compacted into the cylinder resulting in the cylinder pressures increasing. This will happen at the peak torque engine speed. Now imagine what will happen to your 2.4E with 2.2S pistons in it running on street fuel when this happens. Short of having a fully mapped ignition, it would most likely be difficult to adjust the ignition timing to avoid detonation that that point, while not being over-retarded elsewhere in the RPM range. I would think that going one step will be fine if you switch to 93 (or better yet 94 or 95 octane if you can find it), but going further than that will require very specific tuning.

Ultimately it depends on where you want to put the peak torque. E cams will make the engine pull from 2100 to 5200. S cams will make it pull strongest from about 3700 to 6100. One option might be to use something like the MOD-E cam which has more lift and duration than the factory E cams, but not as much as the factory S cams. That should put the torque curve right in between those two options.

That's my $0.02 for now.

[BK911]

Wow. Thanks John!

I am kinda liking option 1). She will be mostly street so 5000 rpm is fine. Stronger than a 2.4E? Nice, count me in!

[Henry Schmidt]

Lately we have been building 2.45 liter engines using the AA Performance 86 mm biral cylinders with JE pistons @ 9.5:1 compression ratio. These little engines run great an are very cost effective.
One note: the AA cylinders Rockwell a touch soft so we send them out for Cryo treatment. So far we are seeing greats service from these cylinders.

[Plavan]

Originally Posted by Henry Schmidt

Lately we have been building 2.45 liter engines using the AA Performance 86 mm biral cylinders with JE pistons @ 9.5:1 compression ratio. These little engines run great an are very cost effective.
One note: the AA cylinders Rockwell a touch soft so we send them out for Cryo treatment. So far we are seeing greats service from these cylinders.

Henry,
What does the Cryo treatment cost for all six?

[BURN-BROS]

I just finished up a 2.5 Mod Solex that the customer is very happy with.

2.7case
90mm Euro RS P/C
66mm crank
35mm ports
PMO 40 with 32mm venturies(can run 34mm)

very good usable power from 2000rpm to 6500

Another alternative would be the same engine with a 2.7 crank and 34 venturies.
A 2.7 Mod Solex would give you very satisfying well rounded engine.

[Henry Schmidt]

Originally Posted by Plavan

Henry,
What does the Cryo treatment cost for all six?

Of course it varies by vendor and quantity but $150-$180 is usual.

[Henry Schmidt]

Originally Posted by BURN-BROS

I just finished up a 2.5 Mod Solex that the customer is very happy with.

2.7case
90mm Euro RS P/C
66mm crank
35mm ports
PMO 40 with 32mm venturies(can run 34mm)

very good usable power from 2000rpm to 6500

Another alternative would be the same engine with a 2.7 crank and 34 venturies.
A 2.7 Mod Solex would give you very satisfying well rounded engine.

66mm crank and Euro 90's means 8:1 compression. Come on Aaron, I thought you were the High compression guy? Short stroke 2.5 is popular but let's start exploring some new thinking.

[BURN-BROS]

Sorry, they are high compression RS (9.5/1) pistons not regular RS....which put it at 9/1...so there.