How to rebuild 3.0 for DE's
 

I have a stock '80 small port 3.0 with weber 40s in a 2080# '73T used primarily for DEs. She does ok under braking and in the twisties, but gets eaten up on the straights. Maybe time for more power. So...

Is adding 964 cams worth the trouble?
How about machining the stock pistons for a more aggressive cam?
Or should I go right to more aggressive cams and 3.2 P/Cs?
Can I keep the Weber 40s with a 3.2SS?
Should I open up the small intake ports?

Thanks!
BK

BK,

JMHO,.....

If you want real power for those DE days, I'd strongly recommend:

1) Install either large port heads or you can have yours CNC'ed to suit.

2) Install some pistons that accomodate a camshaft profile that will give you power between 4K & 7K RPM.

3) Displacement increases to 3.2 really add torque & power. With the right ones, you can safely bump the compression and still retain single ignition.

4) Add some SSI's and a good sport muffler.

We've done some carbureted 3.2's with Mod S cams that made over 265 BHP, even with the restrictive SSI's and that should make you very pleased. :)

Naturally, you will need a decent oil cooler setup to control oil temps at the track because more HP means more BTU's.

Steve is the man, Straight shooter no BS. Thanks for your energy!

Steve
you recommend big heads. Would CIS runners and airbox need to be replaced too, from 2R to 4R ?

Thanks Steve.

So you recommend:
Having intake ports opened up
3.2 P/Cs (have mine bored and JEs?)
More aggressive cam

Time to open the piggy bank!

Can I keep the weber 40s?

Yessir, to take advantage of the increased airflow capacity needed for a large displacement CIS engine.

There are many ways to do this and some are better than others. :) :)

Simply opening the face of the ports does not replicate the flow of the large port heads. This requires some CNC work to do this correctly.

There are several choices for P/C's and some are more durable than others. For maximum compression with single-ignition, I use the Mahle P/C's that have the wedge domes.

Cam choices are many and depend on what you want and how the car is driven.

Your Weber 40's can work, however they are really too small for this configuration. Contact Performance Oriented for Weber options or replace them with PMO 46's.

If you're looking for more power, the stock pistons and the 964 cam (which is a mild step up from the stock SC/Carrera cam) are not going to give you a whole lot more, even with your carbs. But the carbs themselves are already an improvement over the CIS in terms of what HP increase they can provide and improved throttle response.

Carbs also afford the opportunity to run a much more aggressive cam. However the cam selection is dependent on what you're looking for in terms of power curve. Do you want it to have some low end grunt or do you want top end power (at the expensive of reduced low end grunt).

Steve often says that the place to uncork power is in the heads. So you should give good consideration for that modification.

I would also say that don't go thinking larger pistons and cyls are not a must for you. Staying with the 3.0L displacement allows you to reuse the cyls if they're still in good shape and you can make some good HP with the 3.0L displacement. Just need better pistons with more effective domes and higher compression to get that power. So if you're doing the heads, you can safely achieve that power/compression bump with twin plug ignition.

See how it all adds up to be changes to each system of the engine. Intake, heads, cams, pistons, exhaust, ignition. It all has to be a matched system. Just adding one thing or another doesn't get you a whole lot.....

What are the Mahle's you are referring too? These would have the same dome shape as the ones that are stock in the SC to begin with? Doesn't this impact cam choices? This part always confuses me. Seems like there are the "flat" top with the deep pockets which are great for cams/carbs but maybe not single plug, and then the wedge shape (used to be MM???) that are not great for cams, more suitable for CIS, etc.

Todd

Todd,

I wasn't referring to any CIS-dome pistons, I was referencing the old wedge dome, "Max Moritz" piston design that was originally made for Motronic engines. These are around 9.7-9.8:1 and are designed for single-ignition operation.

These work very well with several cam profiles,... :) :)

Agreed - I have at 3.0 with the Max Moritz 3.2 P/C's in my 73.5...364 cams, MSD and early exhaust.....209 RWHP.....It's a hoot in a light longhood with short gears.......

My 3.0L single plug with the Mahle 9.8:1 pistons, more aggressive cams, headers and Weber 46 puts out a mild 215 to the wheels in a fairly decent state of tune. It's been previously dynoed at 235 on race gas. Not necessarily boasting here, just saying that you can get some solid power by staying at 3.0L

HEADS IS THE SECRET HERE GUYS...LISTEN TO WHAT HAS BEEN SAID SEVERAL TIMES...ONCE THE HEADS ARE CHOSEN BASED ON WHAT TYPE OF USE THE CAR WILL BE SUBJECT TO, then ALL OF THE OTHER ARES CAN BE SPEC'D...just my 2 cents...enjoy...sounds like a fun quest...