Has anyone just bolted Webers onto a 2.7 CIS engine?

[Rich911E]

Here's the deal, a friend of mine finally prevailed on his better half to let him have the roller chassis I was converting into RS replica. He is coming to visit fairly soon and we are planning a banzai weekend to put the car together (which will have the added benefit of getting me out of the used Porsche parts business, thank God).

To save time, I am going to give him the engine and trans out of my 911.

Unfortunately, this will have a detrimental effect on the driveability of my car! I have a completely rebuilt (zero mile) 1977 2.7 liter longblock assembly and a pair of Webers. I was planning on disassembling the 2.7 and putting in different pistons and cams but I cannot afford to have this work done right now. I was hoping to be able to get my car running (for the moment) by just swapping in the 2.7 with Webers and no internal modifications.

I had heard that the CIS cams have so little overlap that they don't work well with carburetors. Anderson talks about putting Webers on a 3.0 CIS but those cams are a little different and advocates different cams and pistons.

Has anyone just done a straight swap by putting carburetors onto a stock bottom end 2.7 CIS motor? If so, I would really be interested in how it ran and what jets/venturis you used to make it run right.

Thanks in advance for your help.

Rich Murphy

[john walker's workshop]

it will run fine with the webers as long as jetting and venturi size relate to the engine size. there's lots of them around like that.

[Joe Bob]

Rich, it's not that they don't work well with a CIS cam, it's that they don't IMPROVE performance (much). They look nice, clean up the engine bay, sound great, but the MPG goes down the toilet.

Until you get an agressive cam, at least compared to the CIS cam, there will be a negligible increase in performance. Just my experience......

Also as a side note, most states with smog rules will fail the car on the visual inspection even if the tail pipe emissions are within spec.

[Rich911E]

Mike & John:

Thanks for the info. I just want to make sure it will run with this combination. I would have hated to go to the trouble of installing the engine just to have it run so miserably that I would have had to pull it all back out again right away. I plan on changing the cam and pistons, but this will have to wait until finances permit.

Thanks again for your help.

PS -- If anybody can suggest a emulsion tube, main jet, air corrector jet combination they have that works, I'm all ears!

[iustasail]

The car will run great in congested conditions; little overlap on the cams will generate a lot of vacuum at idle resulting in nice low rpm operation with little punch in the top end; it will not come "on cam" at 4000+ rpm like an S engine w/ carbs and high compression does; There will be better throttle response over CIS and the gas mileage will go down to about 15 MPG!

I would try 65 idle jets, 135 mains, f26 emulsion tubes, 170 air correction jets, 32mm ventures

[Rich911E]

Thanks for the specifics on jetting. I was afraid it would not run worth anything with the carbs, but from the feedback I have received it that does not sound like that is the case. Gas mileage is not really an issue -- I spend more time tinkering with it than driving it anyhow. With only an 8.5:1 CR and that cam, I can probably buy regular!

Stock specifications for a 1977 2.7 engine were 175HP at 5800RPM and 195 lb-ft of torque at 4000RPM. If I can maintain these numbers and maybe gain a HP or two with the carbs and headers, it should go pretty well. After all, 175HP is more than a 2.0S motor -- no substitute for cubic inches (centimeters?) I guess.

Thanks again,

Rich

[Early_S_Man]

Rich ... the '74 engines had 175 hp with the 'good' exhaust system, '75 thru '77 were only 165 hp on paper (probably less with thermal reactors) ... but the Webers should help a bit. JE 9.5:1 pistons and '66 Solex, 'E', or 'S' cams would get you well into the 'fun' range of power along with headers or SSIs! Just ask Jack McAlliter how his 'White Beastie' is running?

------------------
Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

[Rich911E]

Early S Man:

Great minds think alike -- your suggestion was just the combination I was planning to use. I was looking to use either the Solex cams (or the Crane cams for something different) with the 9.5:1 wedge dome JE pistons. Unfortunately, I only have two weeks until we do this swap and I don't have $2,000 handy for the pistons, cams, etc. But this will be done over the winter sometime. I am interested to hear from Jack McAlister about his experiences.

Since posting this message I faxed the guys at PMO (PS -- thanks very much for returning my fax!!) and they provided some suggestions as well. They suggested that the combination would work well with the early style exhaust (which I have as well as some headers) and gave me specifics on how to set up the carbs for this conversion. Since they do this all the time I thought I would post their information here for others who are interested but were very close to the earlier reply (thanks again!).

Here are PMOs suggestions for a 40IDAs on a stock 2.7 CIS motor:

Venturi = 32mm
Main Jets = 135
Idle Jets = 55-60
Air Corrector Jets = 180
Emulsion Tube = F26
Spark Plugs = NGK BP5ES
Early style exhaust system.

Thank you all again (including PMO guys) and I hope this may help somebody else out there who is contemplating this kind of set-up.

Rich

[CamB]

Please post the results of this - I am really interested to get a second (rather than third from Bruce A's book) hand view of the effect of Webers on a stock 2.7.

And 15mpg - hah! I get only 16-17 from a 2 litre with Webers... But I have been driving around town.

Thanks

Cameron

------------------
Cameron Baudinet
1975 911S (in bits)
1969 911T

[This message has been edited by CamB (edited 10-10-2001).]

[Rich911E]

Cameron:

I will post the results in follow-up. Once I get it running right, I will post the combination of jets, etc. that seems to work best and (hopefully) some performance figures. I have a G-Tech Pro and maybe I will do some 0-60 runs and 1/4 mile ETs and post them.

Hey that might be a fun topic for this board. Have anyone with a G-Tech do some test runs with their car and post the results here. I am sure that would generate some lively discussion!

Rich

[jtdig64]

Rich,

Iam having alot of problems tuning my webers..I live in the mid west and have the same jets as you suggested except the Idle..I had a .60mm in the car and it was running way too rich...installed .55 in the car and it idles and runs well...just have alot of popping in the muffler...can't seem to get it straight...

[Rich911E]

Well, it has been almost two years since I started this project and I still get occasional inquiries of how it is going so I thought I would update the group. Well, other than the weirdnesses of the stretched timing chains that took forever to resolve and fix, I can report that the combination works very well. I have been driving it around quite a bit and feel that most of the teething problems have been resolved to provide a meaningful report.

To recap: 1969 chassis, 1977 CIS 2.7S longblock, Weber 40 IDAs, stock distributor, 901 5 speed gearbox (stock E ratios) with 215mm clutch, headers and Bischoff muffler.

RE: CARBURETION/INTAKE: I did buy the kit from PMO for the manifolds and I am using the jetting suggestions above except that I have not gotten around to buying the 32mm venturis (I still have 30's which probably hurt the top end a bit). The system works great and the car idles smootly. There is no popping or spitting out the carbs or exhaust at all and it idles like it's a computer fuel injected car. I am using the 1969 stock air cleaner assembly from the MFI and I think it makes equal power to the watershields and is a lot less noisy.

RE: IGNITION-- I just set the stock distributor at the TDC/Z1 with the vacuum advance/retard connected per the Porsche stock recommendations. That works quite well and I have had no problem with detonation. The car idles nicely.

RE: COOLING -- I am just using the engine mounted oil cooler and no other cooling. I went to lengths to make sure the engine fan shroud is sealed to the top of the engine and to maximize the airflow with an 11 blade fan and a slightly larger 2.7 crank pulley with the 2.0 liter fan pulley. The car runs at about 190 degrees on the highway and even pressing it a bit it does not go over 200. I have not done a track day with it, but for daily driving around it seems fine. Long periods of idling will raise the temp over 210 degrees but never more than that. I would probably add the oil cooler for the track days but for general use, it doesn't seem essential. I am running 15W/50 Valvoline conventional (non-synthetic) racing oil. I am using the stock 2.0 liter oil tank.

RE: PERFORMANCE -- The power is very broad across the RPM range and the area under the curve makes the car very responsive off the corners. It is not very sharp and racy like a S-cammed motor, but it does put a lot of midrange power. It is a great rally car engine or an occasional track day car. It won't pull big RPM down the straightaways but for a curvy track, I'd bet it would be pretty valuable especially if your gearing is not able to be modified to suit. The MPG issue is not too bad -- I would put it in the 17-18MPG range. KeithO64 is coming to visit in a couple of weeks so we can generate some G-Tech Pro data for you.

RE: DRIVELINE -- One thing I can say is not to use too small of a tire with this combination. I had short tires (205/50/15) that I had just made first gear completely useless and it was very buzzy on the highway. I switched to 205/60/15's and life is much better now and it is actually faster not having to shift so frequently. The torque of the 2.7 really helps out with this. The 215 mm clutch seems to be handling the power quite well and I have not noted any slipping despite full power shifting. The 901 gearbox is fine with this engine and again is holding up fine. CV joints and half-shafts are stock 2.0 liter items.

CONCLUSION: All in all, this is a great swap because it does not upset the weight distribution of the car any differently than a 2.0T motor but produces almost 70% more power than the T and 30% more than the E. The 2.7 weighs the same as the 2.0 motor but provides much more flexible power and torque and better driveability and the area under the curve is much larger. The MPG is not much different, it idles fine and the driveline is up to the task. The overheating worries do not seem to be a problem with a little attention to the fan and fan shroud sealing system. It doesn't give you a track car combination but it does produce a really good all around car that can still blast down winding roads pretty well.

Rich

[keitho64]

Rich - Excellent summary. I guess I can post a follow up after driving yours over the weekend. Now, if I could only get my car out there and put them side by side...

[bigchillcar]

Guys,
I've posted several threads lately on the question of more aggresive cams and the 9.3:1 JE pistons mentioned above used on a 2.7 with CIS. Steve Weiner at Rennsport told me that the fuel and air delivery would be insufficient in my car to support this increase in compression.

A little more background...I have the straight, not 'S' model from '74, so I currently have 8:1 compression pistons and no 'S' cams. Additionally, I believe my intake manifold to be slightly smaller than a '74 'S', but have not yet substantiated this.

Warren, you got me excited about the possibilities of this upgrade a week ago, but I can't find anyone who's done it or agree it will work. I keep getting secon hand accounts from various 'wrenches' that it doesn't work well - but maybe that's because it's CIS. Anyone care to weigh in on this? Are radical cams/higher compression simply out for a 2.7 with CIS?!
Ryan

[Rich911E]

Ryan:

The problem with the CIS fuel injection system (as I understand it) is that the metering plate is very susceptible to any pulsations in the intake tract. If you use a high overlap cam (CIS stock cams do not have hardly any overlap) you end up with pulsations in the intake that cause the air-flow metering plate to fluctuate and not meter fuel appropriately. I would imagine that this is largely a idle and low RPM issue as there would be less of this "backflow" at higher RPM.

So, the pistons wouldn't affect the CIS use, only the camshafts. If you want to use the higher lift camshafts, you would proably have to convert to the Webers to gain the maximum benefit and not get weird low speed problems. Since you live in Arkansas and not the Peoples Republic of California, you won't have to deal with the SMOG nazis.

You might also want to look around for differences in the S and non-S heads. I think there was a substantial difference in the port size (Oh God, were not getting back into this again) which would give you more power. I think the 2.7 S heads had larger ports with the same size valves (46 mm intake/40 mm exhaust) as the other 2.7 liter engines. According to my sources the standard 911 from 1974-1977 had 32 mm intake and exhaust ports while the S had 35 mm intake and exhaust ports. That is a substantial difference.

If you're ever in SoCal, you're welcome to come and drive my car. Keith is going to be here on the weekend and he can give a comparison to his performance with his 2.2 S spec motor with webers and perhaps some G-Tech Pro numbers to back up my seat of the pants evaluation.

Good luck. If I can help, just e-mail me.

Rich

[bigchillcar]

Rich,
Thanks for your reply...I can only wish I were 'in the neighborhood'...Arkansas ain't exactly the end of my rainbow if you get my drift!

For the '74-'77 year cars, at some point I know only the 'S' version was available. In other words, the 32 mm heads and 8:1 may have only been an option in '74, but anyway...

I've heard it suggested that an SC model fuel distributor and WUR would probably be needed with the higher compression. How do you think that variable would factor in the equation? Still need the larger intake ports? Care to guess what I'd expect to pay to upgrade to 'S' ports? I haven't investigated.

I like the driveabiity of the CIS and I have a good understanding of how it works, can troubleshoot and repair it fairly rapidly, so my first choice is to keep it. In all honesty, the engine (90K) is running so well right now that I'd be foolish to touch it for the time being until I need to. It's already fast...has the desireable exhaust, 7:31 r&p...can't really complain, just thought the sound of adding tens (40-50) hp by just making a couple parts swaps sounded too hard to resist...broader power band, no doubt less 'peaky' at 4k anymore, but pulling strong to redline. Hmmmm...why does it always have to be carbs?!!
Ryan

[dd74]

Ryan: I've rarely seen a 2.7 make close to or over 200 horsepower without either MFI or carbs. Off and on on this board, someone will crop up with a turbo 2.7, but that's a whole 'nother ball of wax.

Economically, your best bet is an engine swap. It might be worth considering. Rebuilding my 2.7 with nice bells and whistles like MFI or carbs, pistons and cams would have been twice as much as the swap I eventually went with.

Rebuilt 2.7s are supposedly very nice, but 3.0s get the longetivity prize of most Porsche engines. 3.2s are a close second if the valve guides are in good shape.

With 3.0s, you have more modification options like turbos and superchargers. 3.2s have the same options, plus their DMEs can be chipped and along with a good exhaust, make between 230 and 240 horsepower.

All I'm saying is unless you're dead set on your 2.7, you should consider all options, which includes an engine swap.

[bigchillcar]

DD74,
Well, I've never been known for being a little stubborn...!

The more I consider this, the more I'm beginning to think I should stick with what I've got in this car and that means not modding it as I've considered. I think yours and everyones advice is probably valid. I've heard it said that there are fewer and fewer examples of fairly pristine mid-year cars anymore, and I've got one now. It runs like a champ. Why should I take a chance?

If I want a real kick in the pants I should just buy a project that I won't feel this way about and go for the aggressive mods in it. Within the next year, my car is going to finally look like it did when it left the showroom back in '74...a real 'time machine'!

Of course, we'll wait and see what happens at re-build time and I have all the parts out laying on the table to consider...
Ryan

[dd74]

Ryan: I'd like to see a photo of your car if you can post one.

[Halm]

Rich, Sounds like a fun car / motor combo! I could not tell if you changed out the CIS pistons and cams? If so, what did you go with? And did you use PMO carb's or just their manifolds?