Re: Thank you Chris... (archive)

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In Reply to: Thank you Chris... posted by YEROS on December 02, 2001 at 16:06:48:

First, regarding the reliability of blocks. I've heard stories about the 3453cc blocks wearing out faster due to the thinner walls. However, I've seen numerous high mileage examples without a problem, and every tech I've spoken to (that actually knows these cars) says that they last a long time, period. Remember that the M5/M6 uses the same bore/stroke as this and they don't have trouble revving past 7k. I think it's more an issue of quality of materials used at the time of production and maintenance of the engine. Original 3453cc engines are now almost all over 20 years old.

As for higher compression, the only thing you'll have to worry about with that is gas octane. 9.5:1 or 10.0:1 is about as much as you can run with L-jet. 10.5:1 is about as much as you can run with Motronic. More than that and you'll need custom programmable FI.

The decision of which engine to use is dependent on what work you'll want to do to the engine. The reason most people upgrade engines on E3/E9/E12 is to go to FI. It's relatively easy to bolt in an E24 or E28 M30 B34 engine with the correct engine mounts, oil pan, and wire it up. In fact, Pete Schro... (can't remember all of the last name) has done this to his E3, as well as a bunch of guys in the SSR and CSR. Someone on the E12 first fives board also has a good write up on the conversion. You could also convert the electrics to a more modern car like the E28 or E24 like Rob Anderson is doing in his ground-up restoration of a '72 CS. He's put in a M30 B34 low compression engine with headers and a chip which he had available, and E28 electrics into the '72 coupe.

Dropping in stock 3.5 liter engines, my choice would be to go for the M30 M35, which has Motronic 1.3. However the wiring into the E9 will be a nightmare. More people have put in the low compression B34 motor and there is more info on the web for this. It is also easier to do, cheaper, and offers the best bang for the buck because these engines are stone reliable and a dime a dozen. The 3453cc engine is a rare breed in the US, but is even easier to wire in (it's only L-jet, w/o 02 sensor input). It all depends on your mechanical skill, what is available to you, what you're looking for (screamer engine or daily driver, for example), and your budget.

Now, if you plan on doing internal modifications, this is an entirely different story. This requires $$$$. M30 3.5 liters can be built to around 270/280 bhp, naturally aspirated, at best (w/o stroking). It also depends on your base. For example, if you start with the 3453cc engine as a base, and change the cam and put in Motronic FI from the B34, port/polish the head/intake, bigger valves, add headers, and leave the bottom end alone, you'll end up with about 245 +/- 5 bhp. If you take a M30 B35, with Motronic 1.3, build the head with a cam, headers, and up the compression to about 10:1 or 10.5:1 with JE custom pistons for example, you'll end up with about 260 bhp +/-5. If you increase the bore of the B35 motor to make it a 3.6 liter and do the required mods, and add programmable FI, then it'll be up around 270/280 bhp. But this is A LOT of work, time, and money. It's a case of how much money do you have to how fast you want to go.

Since I'm doing the conversion myself in the E9, I'm going to use carburetors (it should be easier conversion). In YOUR OPINION Which 3.5L engine would give me the best bang (POWER / reliability) for the TLC / money.

The best bang for the buck is this. Get a B34 motor out of a E28/E24/E23 that's been maintained well. Stick on headers and a chip (you'll be at around 210-220 bhp then). Then wire it into the coupe electrics using the info from the SSR, CSR, and First Fives group.

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