3.0 Engine Rebuild Sanity Check

[86 911]

I'm rebuilding my 1978 3.0 SC motor. The car will be a street car and will have to pass CA smog. The engine components are currently at Ollie's in Lake Havasu being inspected and rebuilt. Here is what I'm thinking about running:

1. Fuel Injection: Stock CIS due to CA smog. May have the fuel distributor modified during the rebuild for more fuel delivery by K-Jet Specialists. Anyone have experience with this? I wish I could do ITBs but I'm not going to go through the trouble of registering in another state etc.

2. Cylinders: Existing cylinders need to be bored to be reusable (4 thousandths worth of play between the cylinder and piston). Thinking about going the 3.2ss route to increase bore diameter & power. Would be the economical option too as I can re-use my cylinders. Seems like a win-win. Heads will get a valve job & resurfacing. No additional porting.

3. Pistons: Replace existing CIS pistons with either JE 353249 or CP XP5002 set. Both are 98mm 9.5:1. I know JEs & CPs have been hotly debated. The guys at LN Engineering seem to think both are about the same in quality. Thoughts? Does the hemi shape of the JEs and CPs have any adverse effect on the performance of the CIS? Note: sticking to under 10:1 compression as I won't be twin plugging.

4. Cams: Existing ones will be machined by Dougherty to the 964 cam profile.

5. Case Machining: May have it boat tailed & knife edged. May also have cylinders mooned. Still debating this, but heard it will make the throttle a bit more responsive as crank can spin more freely.

Anything I'm missing? The goal is to have a fresh motor with more power than stock while being able to pass emissions. Also looking not to break the bank ($5k-$10k is my budget for this engine rebuild). Since this is a street car, I would prefer more torque over the lower rev range than 4K+ rpm. Have done a ton of searching but want to hear your collective thoughts.

[porschedude996]

Interested in what the responses say.

[targa72e]

1: You have a good starting point if you are staying with Stock CIS. Early/Euro big port heads and runners with higher compression pistons are a good starting point.
2: Generally considered that 3.0 cannot be bored to 98mm as it makes the wall between the cylinder and head gasket (CE ring) to thin. Borring is generally done on 3.2 cylinders that do not use a head gasket.


3. Either of these will work. I have used standard design with single plug without issue. May want to look at Mahle Max Moritz style piston which is shaped for single plug. I think JE offers this style as well.



4: Cams have limited choices with CIS. 964 is one choice and has more lift and duration than stock SC.

5: Probably a waste on 3.0L if you look at the bottom of the cylinder in the case it does not stick out below the bottom of the case material. So mooning cylinders may not have as much benefit. Since the most windage at high RPM and you are looking at midrange power it may be of little benefit.

john

[PeteKz]

Ditto targa72E comments.

How many miles on the engine now? If you have already split the case and sent it to Ollies, you will greatly exceed $5000. Lucky if you can stay under $10,000.

1. Stick with stock CIS to pass emissions. Do NOT have the FD modified. It can deliver more than enough fuel for any build on a 3.0 case. Put the stock CIS back on and get everything optimized BEFORE you even think about any changes. The CIS can work extremely well on a street car (and race cars). If you think you can get through inspection without the thermal reactors, get rid of those. They have little effect on power, but they do increase heat on the engine and extra crap to go wrong.

2. If you want to go to 3.2, you will need new (or gently used) pistons and cylinders. $5K new. Don't try to cheap out on this. The CIS doesn't care what shape the pistons are, but the cam does. Pay close attention to getting the piston/head clearance as close to .030" as possible.

3. Since you have a tight budget, don't waste money on knife-edging, mooning, etc. That won't make any difference below about 6000 RPM, and not much above that. If you want to shave weight off rotating mass, change to a lightweight clutch. But I don't recommend it on a street-driven car. It will lose smoothness at low RPM.

4. Cam: I'm a fan of the Knight Racing M1 cam with CIS systems. $1000 new. I can stomp the gas pedal at 1200 RPM in higher gears and it pulls smoothly to redline (with CIS). I know from my measurements and discussion with William Knight that it uses all the available lift and duration possible with CIS pistons. If you go with pistons with deeper valve reliefs (like the wedge-shapes above), then you can go higher lift. However, more aggressive cams reduce low to mid range torque. Choose your tradeoff.

[icarp]

1 "May have the fuel distributor modified during the rebuild for more fuel delivery by K-Jet Specialists"
This is a waist of money, you will see no improvement .

JE pistons are of a very old design , CP new and up to date .

You are at the limit of 95mm cyls , go up to 98mm new P's C's Mahle Motorsport .

M1 cam is oh so good

Ian

[Jeff Alton]

What Ian said.

However, no disrespect, or argument starting over cam choice..... I have a ton of Respect for William and his knowledge, and he has been nothing but kind to us. That said, We have only built one 3.0 with CIS and the M1. We have built countless 3.0 with 964 cams. From the seat of the pants only (none have been on a dyno, as these are not the builds we dyno) I really can't say any performance difference one way or the other. But we and our clients get the same "feeling" PeteKZ does when driving the cars.

Not saying one grind better than the other, just saying what our experience has been. Again, William was a true gentleman and always available with his time. Very knowledgeable to say the least.

Hope that makes sense.

Cheers

[86 911]

Thanks all for the input. I tried reaching William Knight last month but never heard back. I’ll try giving him a call tomorrow.

Yes, the case and most of my engine components are at Ollies. I dropped them off on Tuesday. Work will take 3-4 months as they’ve got a lot of engines ahead of mine. True mileage on the engine is unknown but with low oil pressure and 110-120 compression numbers, I assume it’s got well over 100k.

There is one point of conflicting info I’d like to address. Tim at Ollies had mentioned that they can send out my 3.0 cylinders to US Chrome to bore & re-plate to 3.2. I asked Tim about the wall between the head gasket getting too thin as I also read about this on the forums. He was under the impression that I would be fine with the larger bore. Now, I certainly want to do this the right way and not compromise the structure of the cylinder wall. Can you all elaborate more on this issue? Perhaps prior failures were from the over-boring not being done right? Just trying to get some more insight on this.

[911MANN]

I just increased displacement in my 3.0L to 3.2L, along with some other performance improvements. I used the Mahle 98mm "Max Moritz" style piston/cylinder set to maintain single plug and CIS. Purchasing that P/C set new costs somewhere right around $4,000 That setup came highly recommended by some experts, as it reportedly provides a solid, long-life solution, equivalent to an original factory P/C set. That, combined with 964 cams is supposed to be very nice and very smooth.

I'm also using the Melissa M1 cams, and they are impressive. But William said they are not good for emissions. Let us know what you do.

[mikedsilva]

Originally Posted by PeteKz

4. Cam: I'm a fan of the Knight Racing M1 cam with CIS systems. $1000 new.

maybe i should be buying cams from you

[runner4fun]

I'm doing a 3.2SS build now w/ Al Kosmal's X-Factory ITB EFI. It's for my 1973 911 hot rod. We are using the Mahle 98mm P&C set designed for a 3.2SS conversion from a 3.0 SC engine. Webcam S cams. The CIS is somewhat limiting but as you note in your case required due to CA emissions requirements.

[PeteKz]

Originally Posted by mikedsilva

maybe i should be buying cams from you

Heh, heh, I should get a commission! But, really, I have no financial interest, yada, yada. I respect William and his hard-earned knowledge. I'm not a pro builder, just an intense hobbyist/engineer.

[phunt]

The 3.0 and 3.2 cylinders have the same cylinder wall thickness. The 3.0 heads have a ring in the head mounting surface. The inner side of that ring is around 2.75 mm wide. When you take 1.5 off the wall to get a 98mm bore that leaves the ring around 1.25mm wide. Some believe that is not enough and some say that is plenty. That is how they used to do it. When the 3.2 cylinder became more readily available they were used. Then the after market started making cylinders so they got used. On a budget I would use my 3.0 cylinders and I would go 98. Now it seams people would only go 97 because of that ring land on the top of the cylinder. I don’t think the cylinder seals there anyway. And I don’t think cylinder pressure would be high enough to cause an issue. Even on a high compression engine. You are building low compression and trying to not go over board on the spending.
Everyone has their opinion. Like about these cylinders. I do not agree with a lot the “builders” opinions. But that’s just my opinion
It seams like you have an idea in mind. Listen learn then do what is right for you. In California with the smog stuff it is not easy. One last opinion be realistic get it done then drive the **** out of it that’s the fun part

[pmax]

Originally Posted by PeteKz

4. Cam: I'm a fan of the Knight Racing M1 cam with CIS systems. $1000 new. I can stomp the gas pedal at 1200 RPM in higher gears and it pulls smoothly to redline (with CIS). I know from my measurements and discussion with William Knight that it uses all the available lift and duration possible with CIS pistons. If you go with pistons with deeper valve reliefs (like the wedge-shapes above), then you can go higher lift. However, more aggressive cams reduce low to mid range torque. Choose your tradeoff.

What about this guy's cams ?

https://elgincams.com/wp-content/uploads/2019/06/Understanding_Camshafts_Dema_Elgin.pdf

[PeteKz]

Elgin is well-respected too. Based on the specs and description, I suspect his "Improv Stk" is pretty close to William's M1.

[86 911]

Just an update. I spoke to William Knight a couple of times over the last few days. The guy knows his stuff. Talking to him about the 3.2ss P&Cs, M1 cam, and 993 oil pump upgrade. It will be more than I planned to spend, but I figure these are good upgrades that will last another 50 years. By that time, the next rebuild tab will be on the kids Still deciding on a direction but I'll update as I progress..

Curious at this point to see if anyone is running this setup in CA with CIS and is able to tune it to pass smog?

[mepstein]

Our feeling is, with the cost of rebuilding these engines, we never want to build something iffy, like boring out 3.0 cylinders. If you’re on a budget, then you only want to build the engine once, build it rock solid and amortize the cost over 150k miles. It’s best to start with a proven recipe and not just pick cool sounding parts from different builds. It’s all been done before but some engines are done better than others.

[SalParadise]

Originally Posted by mepstein

Our feeling is, with the cost of rebuilding these engines, we never want to build something iffy, like boring out 3.0 cylinders. If you’re on a budget, then you only want to build the engine once, build it rock solid and amortize the cost over 150k miles. It’s best to start with a proven recipe and not just pick cool sounding parts from different builds. It’s all been done before but some engines are done better than others.

Words of wisdom right here. I'd just buy a set of new 3.0 cylinders and be done with it. I know the cost is high - but it's much higher in time and waste and not having the car on the road. My build hit a road block when I thought I should not go with a new set of P/Cs. Now that I have, I am convinced the engine will go much, much longer.

[phunt]

Amortize…that’s funny right there. Spend more than you can now…. Because if you keep it long enough it is down right cheap. LMAO I guess spending outside your means is the American way
When you build these engines do give a 150k mile warranty? You can’t say an engine with 3.0l cylinders bored to 98 won’t go 150k miles any more then you can say the 3.2 cylinder will. If you are build a 3.2ss and making 100hp per liter then ok maybe. But he isn’t. He needs to pass smog. At 300+hp he probably won’t. And I bet it wouldn’t make it 150k miles
To the OP I don’t mean any disrespect. I don’t know you or what you are capable of.
If you don’t trust your machine shop about boring your cylinder to 98. Then go 97. You need to buy pistons so 98-97 same. You don’t need to buy cylinders. The difference between 97mm bore and 98 is 64cc’s. 10.33 per cylinder. How much hp is that going to get you when you need to stay conservative for smog. How much will that 64cc’s cost? Money better spent on all the nickel and dime things that will come up. If you are wanting more torque or your cam to come on at a lower rpm I wouldn’t grind it to a spec that has more duration. I think the 3.0 SC’s and the 3.2 Carrera’s all have the same cam. They just install them at different timing. Retarding a cam raises the rpm band and of course advancing lowers it. It is like 200 or 300 rpm per degree.
My idea would be to use your cylinders new pistons that take advantage of the single plug set up. Keep your cams and degree them in for better low end performance. Get a new high flow CAT.
When all said and done you will be happy driving the thing
I would not to anything that someone says to do when they say it is the only way.
Iffy… that’s funny

[PeteKz]

Yeah, you can go broke saving money on these engines!

If you can get the set of Mahle p/c's for about $4000, you won't save a lot of money by boring your old cylinders, after including machining, shipping back and forth, new pistons, new rings, new head gasket rings, etc. Just buy the new 98mm Mahle set. If you're working with William now, ask his advice, follow it, and buy your parts from him. Don't reinvent this wheel again.

[86 911]

Thanks for the words of wisdom! I will take William's (Knight Racing) advice and do the 3.2ss setup. It's a nice upgrade for a little more than boring out existing cylinders. Plus, I won't have to worry about cylinder wall issues. Will go with the 993 oil pump... might as well give my engine better oil circulation while I'm in there. Crank and rods will stay stock since I'm not racing it. Will go with the M1 cam as it seems like one of the best out there.

My big worry isn't the cost of this project. It's the emissions due to smog which I need to pass every 2 years. I assume I will have to lean it out quite a bit before going to smog check, but I'll have to cross that bridge when I get there.