78'-79' CIS on stock 81' long block

[911 tweaks]

has any one done this ?? If so, was there any benefit to doing so ??
I do realize that the earlier runners are larger in diameter and the fuel dist is also different, however, I believe on a USA longblock, the pistons are the same.
I also realize that the earlier cis was 'made/tuned' to the larger port heads on the earlier longblock...
SO, is there any benefit, performance wise or other, to do such ??
Thanks, Bob

[Kemo]

I have heard bits here and there that the 78-79 CIS is the same as the "Euro" CIS. With higher compression 3.0 liter engines, I hear its a good combo and highly desirable in PCA racing for the "E" class.

Does the 81 motor have a higher compression than the 78-79?

[T77911S]

i would think you would want to port match the heads. you dont have to enlarge the whole port, just the first part to smooth the transition from the runners to the heads. i have been considering the same for my 3.0

[carrera1975]

One way to go is the 78/79 SC case, heads and CIS and use the 9.3 (80-83)pistons/cyls. Or even better use the 9.8 euro P/C's, combined with the 964 cams and 2 in 2 out muffler with SSI

My engine dyno'd at 215 on the stand with this combo, a far cry from the 175 hp the factory claimed

[911 tweaks]

nice ideas here guys. I will keep them in mind.

However, I am wondering if this combo i.e. stock 81 longblock + early cis ??

If this combo works, is there a performance improvement and if so, what has to be done to get the most out of this combo ??

Thanks, Bob

[T77911S]

i was thinking of this combo with the 964 cam. i like the torque the small port heads provide, but i would thik the port matching is essential.
check with superman, he may this setup, he loves it.

[911 tweaks]

thanks T77911S... but who is "superman" besides myself ?? ;-)

Are you saying that sman ran the combo I ask if possible and he ran 964 cams and the end result was possible & positive ??

Bob

[chrisp]

I have heard bits here and there that the 78-79 CIS is the same as the "Euro" CIS. With higher compression 3.0 liter engines, I hear its a good combo and highly desirable in PCA racing for the "E" class.

Wouldn't this put the car in GT since that's a mix of components across different model years?

[Gunter]

Originally Posted by 911 tweaks

nice ideas here guys. I will keep them in mind.

However, I am wondering if this combo i.e. stock 81 longblock + early cis ??

If this combo works, is there a performance improvement and if so, what has to be done to get the most out of this combo ??

Thanks, Bob

A great advantage with this combo is that the non-Lambda CIS is much simpler, i.e. adjustable Decel.Valve, no FV......

I used a US '78 CIS on top of a US '82 bottom, bored and polished heads to match the runner-size but, without doing more like 964-cams and SSI's, there is very little gain.

I also used 98mm P/C's to make the 3.0 into a SS 3.2, 964-cams, added SSI's and, very important, use either a distributor from a '78-'79 or have your '80-'83 distributor recurved non-vacuum to match CR, octane and air temps.

US '80-'83 SC's have 9.3 CR, the '78-'79 have 8.5 CR.

If you use the earlier non-Lambda on a later '80-'83 engine with 9.3 (or even 9.8 CR), port the heads, regrind the cams to a 964-profile, which is very compatible with CIS. Add SSI's and you have between 20-30 horses more. Very nice.

Lots of people did this and lots more build a SS 3.2 to add about 40 HP.
Would I do it again? Yes.
A US SC can use an additional 40 horses; lots of fun.

[911 tweaks]

thanks Gunter. Good to hear that this is a "++" option to possibly try.

Can you guys answer my basic question: if I was to just bolt these parts together and tune as needed, to be specific by ONLY doing:
81' longblock as stock
78'-79' cis as stock
ssi exhaust thick flange I also could use from stock
964 cams I could use from stock
have to check which dizzys I have (p/n are: 0 237 306 001 and 0 237 304 016. both have vac advances on them)
Budget is spent, thus no $$ to machine heads, ect. Just trying to see if a bolt-up combo as described will work and be worth it or will it be a hodge podge ??

Thanks again guys!
Bob

[Gunter]

Yes, it would bolt on but..............
There would be a step between the larger early runner and the smaller port on the '81 head.
I wouldn't want that.
It can't cost that much to machine the ports?

Anyway, both distributors have vac advance but I understand that the 0 237 306 001 has different weights/springs to give a better curve for non-Lambda CIS.

So, bottom line, yes, you can do the above but I would definitely match the ports to the runners..

With 964-cams, stock springs can be used. Your 964 cam-timing would be 1.4mm overlap.

[Kemo]

Originally Posted by chrisp

Wouldn't this put the car in GT since that's a mix of components across different model years?

Ya got me on this one. Im not a rules expert by any means.

[911 tweaks]

Thanks Gunter & guys... I will investigate further... especially the difference in intake runner i/d and the head intake port i/d to see how much machining is needed as the engine is assembled & I don't want to tear it down for this as I KNOW THE SLIPPERY SLOPE IS STANDING RIGHT NEXT TO ME ON THIS ONE !!! ;-)
Bob

[Gunter]

It's straight forward:

Intake Runners:
’78-’79 = 47.5 mm OD – 39 mm ID
’80-’83 = 41 mm OD – 34 mm ID

The difference is 5mm; definitely a step.

The thread started like you were planning to do certain mods; now you say it's assembled.
What exactly is your set-up now?
Are the 964-cams in there?
Cam-timing is??
Which distributor?
Curve checked?
Timing?
What plugs are you using?

What history on the long block?
Compression??
Leak-down numbers??
Valve job done recently?

I have to stress: With too many unknowns, the end-result may be very disappointing.
If the block has high Miles and never had a top-end rebuild meaning: re-ring and valve-job, you may not be happy with it.
Did the CIS come from a running engine?
The Bosch number on the fuel distributor is important; it'll tell if it is original or rebuild.

[911 tweaks]

well... here is the full info... sorry if my question was vague... hard to self reflect and believe what you are informing readers of your post realy know what the h^ll one is asking... AND I DO APPRECIATE YOUR SPECIFIC QUESTIONS AS I HAVE A LOT OF PARTS HERE AND I KEEP GOING AROUND IN CIRCLES WITH WHAT TO DO... WHAT ELSE IS NEW TO ME... anyway, here are the answers to your questions:
1.set up now: 81' assembled longblock I bought from DC Auto that "supposidly" per Rob had recon p/c's and was traded in for a 3.6 by someone wanting more power than a stk 3.0L. I only bought the longblock as everything else was already sold off of the motor, thus I have lost of different years of many parts.
2. 964 cams are not in the engine. They are on the shelf if they would help here.
3. stock sc cams timed as I presume stock setting... I need to check lift spec.
4. neither dizzy in engine. I have 1 each a 78-79 and a 80-83 dizzy that need a going through to make sure they work properly and which ever one works with the final configuration determined here will be used.
5. can I check the dizzy curve or do I have to send it out ?? I would prefer to do what ever checking needed myself if possible as budget long ago spent.
6. cam timing needs to be checked also to see how the previous person~shop set the cams up when they did the p/c's reconditioning.
7. sparkplugs using... I was going to use stk plugs unless advised differently here.
8. history on the longblock... all I can say is that per Rob @ DC, it had done to is what ever it needed while the p/c's were reconditioned. A look inside the cylinders and they are pretty clean so the engine was not run much after this work was done. I have not done a compression or leak down test either. I have done a very through external cleaning of the longblock.
9. compression...needs to be done
10. leak down tesat... needs to be done
11. valve job done... I don't know other than to repeat what I have already stated. Is there a visual way to check if valve job done other than trying to wiggle them, which they don't wiggle in their guides and exhaust valves are fairly clean looking from a visual inspection.

Let me ask you this Gunter, what is the "proper" procedure or list in order of a way to completly check out an unknown engine if it landed on your doorstop and didn't have any obvious problems i.e. hole in side of case or leaking oil all over the place or something falling off. I have no visual indicators of problems existing and need to check out everything AND I have accumilated many, many, I mean many parts that could turn this into a different animal, which I always contemplate, however, now that the budget has vaporized, I need to work with what I have and get this project assembled and on the road.

Any and all suggestions on where to go from here, especially on doing a physical of the longblock, would be greatly appreciated. Basically, I feel that I am soo deep in the forrest I can't even see any trees...

Thanks guys,
Bob

[Gunter]

Without documentation, it's pretty hard to know what was done.
Verbal assurance cannot replace written details from a reputable shop, IMHO.
What does "reconditioning" P/C's mean?
They're either within spec or they aren't.
If they are within spec, re-ring and a light hone maybe.
To me, the important thing would be: Are they Nikasil or Alusil?
If they're Alusil, how were they reconditioned?

No need to check the SC'cams if you want to use 964 anyway.
One 964 cam has an extra step at the end for the power steering.
For an SC-engine, people usually cut/machine that off.

Valve job is mostly about replacing the guides, 3-step grind.............
Hard to determine clearance with spring tension on the stems.

Sounds like you pretty well have to build the engine and hope for the best.

Distributor DIY:

Distributor service (Clean and lube) real easy without removing the pinion gear!

[911 tweaks]

thx Gunter... I was away all yesterday... that is what I keep coming back to... just put it together and go from there...my only hesitation is it has been soo long getting to this point that I want to minimize the things to re-do ~ do over as all of this project has taken soo much time to get even to this point... waaaaa waaaaa waaaa
I'll stop winning and get back to it.
I think I am just goint to grab what ever part is closest to me and get the flippin' thing put together and cross my fingers...
Cross your fingers everyone as I am going to !!
Bob