3.6L with PMO

[ajd48]

Hi all,

I'm appreciative of the helpful info on the forum about various configurations for earlier motors running PMO carbs. I was wondering if I could get some input on an economical (don't laugh) approach to take for converting a 993 3.6l (currently sourcing the engine so could be 964 or 993) to carbs. I'd like to avoid the debate about carbs vs. EFI since there has been much written on this topic already. The engine will be primarily for street use in a warm climate. The specific questions I have are:

1. What is the expected HP pick up of stock EFI VRAM 3.6l with upgraded headers/high flow exhaust vs. the same set-up but with carbs instead of EFI? The former is around 300 hp as I understand it. What is the later's HP?

2. What other work is minimal work required to the engine to bolt on the PMO carbs to a 3.6l?

3. What other work is recommended to the engine to bolt on PMO carbs to maximize HP? I'm looking for the biggest bang for the buck. I suspect its cams and pistons. Is it a sound approach to have the cam reground rather than getting a new cam in this application? Which piston heads are recommended?

Any references to a previous detailed engine build along this line would be much appreciated.

Thx all!

[m42racer]

Originally Posted by ajd48

Hi all,

I'm appreciative of the helpful info on the forum about various configurations for earlier motors running PMO carbs. I was wondering if I could get some input on an economical (don't laugh) approach to take for converting a 993 3.6l (currently sourcing the engine so could be 964 or 993) to carbs. I'd like to avoid the debate about carbs vs. EFI since there has been much written on this topic already. The engine will be primarily for street use in a warm climate. The specific questions I have are:

Mine is why???

1. What is the expected HP pick up of stock EFI VRAM 3.6l with upgraded headers/high flow exhaust vs. the same set-up but with carbs instead of EFI? The former is around 300 hp as I understand it. What is the later's HP?

Less than stock and around 280HP. Plus you will have less response and all ofn the normal head aches of carbs.

You must have a reason that can be understood??? Can only think this is going in a Non EFI car.

2. What other work is minimal work required to the engine to bolt on the PMO carbs to a 3.6l?

Depending on chassis, Fuel system, pumps, plumbing, cams, maybe compression ratio issues on the street and Distributor change.

3. What other work is recommended to the engine to bolt on PMO carbs to maximize HP? I'm looking for the biggest bang for the buck. I suspect its cams and pistons. Is it a sound approach to have the cam reground rather than getting a new cam in this application? Which piston heads are recommended?

A huge can of worms that should be steered clear of.

Any references to a previous detailed engine build along this line would be much appreciated.

Don't know of anyone who would do this for a street engine. Seriously, why not keep it stock or fit an aftermarket EFI system. You at least have all of the sensors etc., it is an easy do. Scared of tuning? Its a one time thing when done correctly, but you will be messing with the cards forever. And make less power and less throttle response.

Thx all!

Interesting question. see above for the short answers.

You have to be nuts!!!!

[MBruns]

Several years ago we took stock 964 engines with rods,JE pistons at 11.5 to 1, cams comparable to GE80's, valve springs, PMO 50mm, distributors/MSD,open exhaust and made 340hp at the crank, these were used for track days/test days to keep the hours down on the race engines.
Mike Bruns

[ajd48]

MBurns - thx. That's helpful. My impression is 11.5:1 is fairly stressed. How was the longevity of the engine?

A similar engine build was discussed in Anderson's Handbook 3rd ed on pg 182



Perhaps someone can shed some additional light on this. m42racer - I'll put you down as a luke warm on the idea...

[Trackrash]

This car has a 964 motor with only a chip and exhaust and makes over 300 HP. Converting race car back to street hot rod

The reality is the 3,6s have such a good engine management system, I can't see throwing it away.

[MBruns]

I agree the motronic is a great system, we ran these engines in historic/vintage race cars with race fuel, carbs and distributors with MSD, we would put 60-70 hrs. on those and 50 hrs on the full race engines. One of the biggest failures we dealt with was 964 head failures that cracked top to bottom around 30 hours when the power is north of 400. On the street/DE leave the motronic and find a proven combination for what you want to do.
Mike Bruns

[m42racer]

Luke warm works for me!!!

You stated it was mainly for street use and most examples here have been race engines. Street driving you will spend your life under 5000 RPM mostly , so high HP will be a number rarely seen.

I agree that going over to Carbs is nutty unless it makes it easier to fit into the chassis. But expect all that goes along with running carbs.

[LeftCoastErik]

Stock 70k mile 964 3.6. Megasquirt and 46mm ITBs with headers and a Dansk Sport Muff. 273hp/252tq at the tire. Translates to somewhere around 320 at the flywheel. And, more importantly, the throttle response is insane. Everywhere. And it sounds pretty amazing too..

[Tippy]

Originally Posted by LeftCoastErik

And, more importantly, the throttle response is insane. Everywhere.

Embedded YouTube video of said throttle response, or it didn't happen!

[LeftCoastErik]

https://youtu.be/QyGEMuyVgLM


https://youtu.be/GCEhBvYdwe4

[ajd48]

Thx everyone. I hear you on the EFI is better point.

LeftCoastErik - I hadn't considered ITBs but that may be a good solution for me. Sound and throttle feel is important to me. A few questions -

1. By stock engine I'm assuming bone stock - no changes to cams, pistons etc., right?

2. Any additional detail you can share about the engine build would be helpful. Which brand ITBs, anything else other othe exhaust and software?

thx again!

[LeftCoastErik]

totally stock, good running motor that I ran in stock trim for a year. I am running 46mm PMOs and Al Kosmal (x-faktory.com) sells a pretty comprehensive kit with Megasquirt or AEM if you want to spend more. I like the mega squirt because it has a blended ITB Algorithm that seems to work really well in these cars. There are a couple of challenges on the ignition side, but I was able to get mine (and two other cars) running great using the factory Dizzy and crank sensor.

[Tippy]

Erik, not doing the ignition side of EFI is half of the gains. 3D ignition mapping makes for a much livelier motor part throttle and cruise.

[LeftCoastErik]

You misunderstood. I have full EFI timing control with the stock 3.6 dizzy

[ajd48]

9m shows a 3.6l with "...stock 9m billet heads & 9m ITBs, all run headers (of various design), all run on Motec." that generates 350 hp on the dyno. See https://rennlist.com/forums/993-forum/749250-ultimate-street-engine-4.html (green dyno line).

Hoping someone can chime in on details of this build....(ninemeister???)

[blockhed]

What is a stock 9m billet head, is it stock or 9m?

[Matt Monson]

Originally Posted by blockhed

What is a stock 9m billet head, is it stock or 9m?

9meister makes all new heads out of billet like CMW does.
History of CMW Billet Heads

[Tippy]

Originally Posted by LeftCoastErik

You misunderstood. I have full EFI timing control with the stock 3.6 dizzy

Ah, my bad. Misunderstood indeed.

[ajd48]

how are the billet heads impacting HP? HP should be a function of displacement, compression, etc.

[safe]

You can get decent power from the stock intake with minor mods, cams, headers, no airflow meter, bigger injectors. It really dies after 6200 so I think the exhaust strangles it a bit, its quiet.



This engine has lots of power, my 3.2 with ITBs has around 260 fwhp at 6800. That engine is louder, angrier and more fun.