2.7 CIS Engine - Worth it to go to webers?

JeremyD · JeremyD's Garage

So I have a rebuilt engine in my car. No receipts - but some detail that includes a new 7R case, new bearings, etc. From everything that I can tell - ~3000 miles on the rebuild.

My long term plan is a 3.6 - which may be a year or so away. My short term question is a 2.7 - is it worth it to throw on a pair of webers?

When I did the PPI - the compression numbers came out very good. It has a set of early (1974) heat exchangers (which the SSI's are modeled on) and a Bursch muffler.

The engine is strong as it is with the CIS - but I've had a few people that I respect tell me that I should look for a set of Webers...

Opinions??

T77911S · 10-13-2010, 10:24 AM

if a 3.6 is definately in the future, and the CIS is fine, then no. save your money, it may mean the 3.6 sooner. i dont know what is holding up the 3.6, but you may drive the 2.7 long enough to figure out its status, then sell it if it is a good strong motor, you will get more for it now than later.

Walter_Middie · Walter_Middie's Garage

You don't say how you are going to use the car. CIS offers good drivability, easy starting hot or cold, and decent gas mileage. Going to carbs gets you quicker engine response, but at the cost of gas mileage and may be harder to start when cold. If it's just a weekend toy, that may be OK.

My opinion? Don't bother spending the money and time to setup carbs if you are just going to change to a 3.6 anyway. However, the 2.7 might sell for more if it has carbs. I doubt you'll get your money back though.

2.70Racer · 10-13-2010, 10:57 AM

Jeremy,
I would save my money for the 3.6 conversion.
Weber's Are fun, but they'll need cams and pistons to bring the 2.7 alive.
$2500 later the 2.7 will really run. See my signature.
Use the $2500 towards the $10,000 you'll spend on the 3.6 upgrade.
I like your car from the pictures.

JeremyD · JeremyD's Garage

I use the car for an odd day at the office - weekends and DE

I have trouble leaving things alone.

At the start of this adventure (the 1974 acquisition) - I made myself the commitment to leave the engine alone - then I've had two people tell me - you should look for a set of webers, it will really wake that engine up...

I just need to focus on the 3.6, I imagine that focus will be sharper after my first DE and not having enough ponies coming into those long fast straights at Sebring...

imaircooled · 10-13-2010, 01:41 PM

So, I've done a little research here and I also have a 74 2.7 CIS and I want to add webers. Can I buy webers from any year and engine size? For example, could I buy webers from a 73 2.4 (if they had webers) or a 68 2.0 and just bolt them on? Minus any tuning like jet changes...things like that.

If I would add webers could I keep my CIS cams for now but know that it wouldn't create anymore horsepower as apposed to using another set of cams. Am I right? What other cams would be best for the 2.7/Weber combo? I wouldn't be using the car for the track or DE's. Just would like to have a hotter motor.

I apologize in advance Jeremy for borrowing your thread for my questions.

Thank you,

Tom '74 911 · 10-13-2010, 05:47 PM

Quote:

Originally Posted by JeremyD

I have trouble leaving things alone.

I imagine that focus will be sharper after my first DE and not having enough ponies coming into those long fast straights at Sebring...

I've been following along in your other thread and you've done a great job w/your car so far. I have a '74 as well w/a 2.7L CIS engine. I can relate to having "trouble leaving things alone" too. I have wanted to add carbs or EFI to my engine forever, but every bit of reading, email correspondence and phone conversations I've had w/people in the know has calmed me down and kept me w/CIS. Unless you're doing a full rebuild w/cams and pistons, the only thing carbs seem to add is a few more headaches and increased fuel consumption. A well running CIS system really is pretty good. Boring? Yes! But reliable and well running. I went on a long drive today where I started at 6000', went to 8500', down to 3500' and then back to 8500'. . . . My CIS was smooth and flawless. I'm not sure carbs would've been the same.

In terms of having a low HP 2.7 for DE. . . I've been DEing mine for a number of years and became an instructor this year. A low HP car is THE BEST way to learn how to drive on the track. You will learn so much more, become a better driver and have just as much fun w/your 2.7L. When you're ready for a 3.6L (financially and otherwise) you will have a greater understanding of momentum, being smooth, driving a good line, driving at the limit etc.... and you will fly! IMHO of course.

Tom

JeremyD · JeremyD's Garage

Thanks Tom - and yes I agree - I worked my way up to the instructor ranks with my old 1987 Cabriolet (with a 287 HP 3.4). The tough part about Sebring is that it's a high horsepower track.

When I said first DE - I meant in this car... But yes, appreciate where you are coming from

Tom '74 911 · 10-13-2010, 06:52 PM

Quote:

Originally Posted by JeremyD

Thanks Tom - and yes I agree - I worked my way up to the instructor ranks with my old 1987 Cabriolet (with a 287 HP 3.4). The tough part about Sebring is that it's a high horsepower track.

When I said first DE - I meant in this car... But yes, appreciate where you are coming from

Ahhhhh - I almost qualified my response to include some sort of disclaimer like, "if you've got a ton of track time already then never mind"! You'll still learn a lot w/the 2.7L (while wishing you had a 3.6L already)! Looks great. . . carry on. . . : ) : )

T77911S · 10-14-2010, 06:53 AM

it is very easy to tell somone else to spend money. talk has very deep pockets.
just drive it and enjoy it like it is.

JeremyD · JeremyD's Garage

Quote:

Originally Posted by imaircooled

So, I've done a little research here and I also have a 74 2.7 CIS and I want to add webers. Can I buy webers from any year and engine size? For example, could I buy webers from a 73 2.4 (if they had webers) or a 68 2.0 and just bolt them on? Minus any tuning like jet changes...things like that.

If I would add webers could I keep my CIS cams for now but know that it wouldn't create anymore horsepower as apposed to using another set of cams. Am I right? What other cams would be best for the 2.7/Weber combo? I wouldn't be using the car for the track or DE's. Just would like to have a hotter motor.

I apologize in advance Jeremy for borrowing your thread for my questions.

Thank you,

I'll try and answer a few of your questions as I have been researching this.

Quote:

Originally Posted by imaircooled

Can I buy webers from any year and engine size? For example, could I buy webers from a 73 2.4 (if they had webers) or a 68 2.0 and just bolt them on? Minus any tuning like jet changes...things like that.

Yes, pretty much - You want the IDA40 size anything larger is too large - PMO and a few other places have jets and venturi's to change to the size you need for a 2.7 (and can direct you to the right combination)

Quote:

Originally Posted by imaircooled

If I would add webers could I keep my CIS cams for now but know that it wouldn't create anymore horsepower as apposed to using another set of cams.

From what I can gather - the HP increase from webers - is only around 10-15hp - best case. Where you notice the result is in throttle response and SOUND <--- which is always good for another 10hp on the BuTTDyno...

To really benefit you need to change to a hotter cam with more overlap - but guess what - the CIS pistons don't have much clearance - so can't go too aggressive with the cams unless you replace the pistons.

If you are going to do that - then may as well twin plug and go with a higher compression.

If I were you - I'd look for a set with the air cleaners and linkage already set up. make sure the shafts don't have too much play.

dad911 · 07:19 AM

I have a 2.7 cis with webers. Works, runs great, but I never compared to CIS as the carbs were on my 2.2 when I did the swap, so a carb swap was easiest.

However, I've done a 3.6 conversion and wouldn't go down that road again either. For the track I've gutted a 964, get the same light/raw feel with better suspension and brakes.

If I ever do the engine again in the '71 I would probably look for a 3 liter.

imaircooled · 10-14-2010, 09:05 AM

Thanks Jeremy. Guess I need to start hunting the classifieds.

jwakil · jwakil's Garage

I had a similar decision to make earlier about my CIS, but decided if I was going to do anything, it would be to go to an EFI vs a carburetor. Why would you go backwards in technology? It also looked like the EFI would cost the same or less than a carburetor.