1985 3.2 to 3.4 rebuild questions

[86RedCarerra]

Hi Everyone,

I have been lurking here for the last month, reading and researching for my rebuild of a 3.2 California smog engine that will run on 91 octane with a single plug ignition. I’ know I’ll have many more questions, but right now I’m trying to get answers for these two:

1) I would like to upgrade to the Mahle 98mm cyl/piston 10:1 kit, and because my cams are worn, I’d like to have them ground to 964 specs. (I cannot find the old Max Moritz Mahle 9.8:1 CR 98 mm kits- perhaps they aren’t made anymore, or they are the same exact kit that is now stating a 10:1 CR?

Because this car must pass smog, and run on 91 octane, I realize that a 10:1 CR, even with the “Max Moritz” piston design, will be too high and I will need to reduce the CR, as i won't be changing to twin plug.

Has anyone accomplished this? Offset con rod bushings/ sinking the valves/removing chamber material from the heads/cylinder barrel shims? What is the proper way to bring the 3.4 kit compression ratio down to 9.5 - 9.7? I really do not want to use JE pistons, either….

2) I am in Northern California. I’m looking for machine shops not too far away who understand these engines and are equipped to sort out my case, rebuild my heads, grind my cams, resurface and harden my rockers, etc… I am wary of machine shops in general, due to past experiences, and with this engine, I do not want to take any chances. Doing a proper rebuild of the heads will require someone who understands all the particulars - equalizing cc’s, equalizing cyl and head heights, etc…

A long first post, I know- most info that I find here is very old- sometimes over ten years olld.

Thanks for any replies.
Dave

[PeteKz]

Dave, welcome to the forum.

First question: How will you use the car? Primarily a street car, or will it spend most of its time on a track?
Second question: What's your budget? Whatever it is, you will likely exceed it, but you should start with a number that you are comfortable with.
Third question: Why did you decide to rebuild the engine? Is it worn out, burning oil, smoking, low on compression? How many miles are on the current engine?

[86RedCarerra]

Originally Posted by PeteKz

Dave, welcome to the forum.

First question: How will you use the car? Primarily a street car, or will it spend most of its time on a track?
Second question: What's your budget? Whatever it is, you will likely exceed it, but you should start with a number that you are comfortable with.
Third question: Why did you decide to rebuild the engine? Is it worn out, burning oil, smoking, low on compression? How many miles are on the current engine?

I bought the car from a friend who has had it for about 15 years and rarely ever drove it. Mileage and mechanical history were pretty much unknown.

The car will be used as a daily driver and I have no plans to track it.

The car’s odometer broke at 215,xxx many years ago, right after the PO bought it. It developed a loud timing chain slap a week after I bought it (turned out to be the right tensioner), and when I dropped the engine I did a leak down test and 3 cylinders were below 80/50.

Engine tear down revealed right chain tensioner is soft, IMS bearings very worn, one cylinder has something tar-like caught in the exhaust valve/seat, cam shafts have wear that most likely will not polish out, right cam will not turn freely in the cam housing with housing removed from engine (unknown if it turned freely prior to tear-down, but based on a visual inspection, it is likely that the cam turned freely when it was torqued down- Note to self: BEFORE pulling the cams, check for cam binding while assembly is still torqued down). Frustrating not to know whether the cam was fine when everything goes together….

So, the right cam housing may be warped, and I must decide whether or not to have it skimmed at the machine shop- if I do have it machined, then it may ruin any chances I have of running it in the car. Cam could be bent, but I’m thinking that probably isn’t the case. V blocks and a dial indicator will tell. Not there yet.


Nothing I am seeing in the engine points to 215,000 plus miles, but there is no indication that anyone has ever been inside the engine. It was leaking everywhere, so it is possible. No broken head studs, cylinders still have hone marks, all rings were free and unbroken, no cyl scoring, timing sprockets look great, but sprocket wear needs to be determined by someone who has seen a lot of these sprockets, has chains with no master link- original? Don’t know.

Budget? It’s going to be a slow, pay-as-you-go project. The car needs transmission work, every wearing component replaced in front and rear suspension- there are decades of deferred maintenance….

The reason I want to go with the 3.4 Mahle kit is because it is way cheaper than 3.2 right now, and anytime I rebuild an engine I want the performance to be enhanced at least slightly over factory.

Perhaps 3.4L conversion is a bad idea, and I shouldn’t have dreams about more power with a California smog car that I’m going to drive regularly?

Anyhow, I am generally astounded by how little internal wear there is in this engine- the cylinder plating must be tougher than chrome, as there are no ridges in the cylinders. Crank looks like it will polish out.

Big caveat: nothing has been measured yet, as I have only begun my cleaning and visual inspection.

[mikedsilva]

swap the left and right cams over and see if the "tight" camtower is still tight..

[86RedCarerra]

Originally Posted by mikedsilva

swap the left and right cams over and see if the "tight" camtower is still tight..

Hi,

I did that, but the left and right cams on this engine have the center journals in different places, so the left cam placed in the right housing will not have the center journal inside the cam housing’s “bearing” hole. And vice- versa with the left cam in the right housing…

[Edit] of course, I could drive the caps out of the cam housings and insert the opposite cam into the back side of each housing for a check, but I’m not there yet….!

Zoom into the pic and you can see this…

[Flat6pac]

All bearings are located properly, either side, either cam.
Bruce

[86RedCarerra]

I am confused....my 3.2L cams have journals 2 & 3 in different locations.... see pic. the only way I can do the check is to remove the rear cap from the left cam housing and install right cam through the rear of the left housing.
.

[PeteKz]

Good info. I STRONGLY recommend that you try to keep this as a "driving project" not a "garage project." The longer it sits, the longer it sits, and you eventually begin to lose motivation and patience to see it through. That's happened to many of us here.

The engine is out and disassembled, and the tranny too, so get those together and reinstall them first. The suspension and other stuff can be done independently. Then keep driving it as you repair and upgrade it.

As you have discovered for yourself, the 3.0/3.2 engines are extremely durable. Chances are good that the case needs no work. Measure the bearing bores. I don't recall if these engines had steel lower row of studs, or Porsche installed steel studs from the factory. It's also possible that a PO had the studs replaced when some broke. Use a magnet to see if the top and bottom rows are equally magnetic. If you still have Dilivar lower studs, replace those with the standard Porsche steel studs. If the upper row of studs is not pitted from corrosion, leave them alone.

Don't throw away the main or conrod bearings yet (don't throw away ANYTHING yet). They probably are still within tolerance and can be reused. Measure them and use Plastigage to check the clearance with the case bolted together. You are a DIYer, not a pro building for a customer on their wallet. A pro will replace the bearings because they want to show the engine was completely rebuilt using all new wearing parts, and they don't want come-backs. As a DIYer, you should reuse things that are not worn, especially if you want to conserve funds. Bearings are one of the parts that should not wear out, if proper oil filtering and pressure have been maintained, because the crank actually floats on an oil wedge in the clearance and does not touch the bearings, except when shut down and settled on the bearings. We have also seen bearings that were out of tolerance, out of the box. The aftermarket quality has been slipping, and even some OE Porsche parts are not the same quality as 30+ years ago. Good used bearings have already proven themselves in service, so you should not hesitate to continue using them.

IMS bearings: These wear off the tin top layer very quickly, and then settle in for the long run. Even though measurements might show they are still good, they are cheap enough to just replace.

Pistons and cylinders: Unless you just want to spend money to get 6% more displacement, you may be able to reuse the original pistons and cylinders. Measure them to see what's worn. As you have noted, the cylinder surface is extremely wear-resistant. The surface coating is a process called Nikasil, which "lasts forever" unless it is damaged. A new set of rings may be all they need. They may not even need rings. Your low compression may be due to worn valves.

Heads: at 215K+ miles, the guides and seats at least need to be restored. Unless you can do the machine work yourself, just send the heads to a well-known Porsche machine shop, NOT a general auto machine shop! Pay attention to the sealing surface between the heads and cylinders too. Touch that up only if necessary.

Re cam housings: you should be able to insert the cams far enough into the opposite housings to see if they bind. Be careful about refacing the housings--if the cam bores are out of alignment, it's most likely because the housing is warped, and when you tighten it down on the heads/cylinders, it flattens out again and doesn't bind. If you do face the housing, then you may end up with a housing with a permanent warp in it, that will not flatten down when torqued to the heads. A machine straight edge will help answer the question. Check the cams with a straight edge too.

Although I agree with your reasoning that, if you have to buy new p/c's, you might as well go up in size, you DO live in the People's Republik, and you will have to put up with whatever regulations they impose now and in the future (and they hate internal combustion). From what you have said about your driving and budget, I would stay with the original p/c's if they measure good, use new rings if needed, and put the bottom end back together. If the p/c's need to be replaced, I would have to think about whether to use the 3.4 Moritz-style pistons. If you stay with a cam grind that is close to the Carrera/SC grind, or 964 grind, it should still pass emissions. You will need to run 92 octane.

[PeteKz]

Another thing: Oil pump. How was your oil pressure before teardown? Open up the oil pump and look for wear. Common for them to need replacing at high mileage.

[86RedCarerra]

Thanks for the replies everyone.

Pete- thanks for all the tips.

Cylinder studs-They are different top and bottom. The bottom are darker and not very magnetic, compared to the upper studs. I don’t have any corrosion anywhere on this engine- the studs look great. Are the less magnetic studs the Dilivar? I will replace the Dilivar studs.

Oil pressure- I only got to drive the car once, before I decided to drop the engine/trans due to timing chain noise. The Oil pressure light never came on at idle, and the press gauge never indicated less than ~1.2 bar at idle, when warm. Cruising, it was about ~1.5 bar above the Porsche min spec (I forget what that is at the moment, but I did check this on that one drive). Oil restrictors are not installed on the engine, either…. So perhaps the pump isn’t in bad shape. I plan to split the pump to have a really good look at it.

The case halves were not leaking anywhere along the flange seam…I had planned to have the case joining surfaces machined and then align-bored, but now you have me thinking this might not be necessary.

The aluminum IMS gear shows little wear and no damage whatsoever, but that doesn’t mean it’s not worn out. I had planned to replace that as well.

I am wary of replacing the timing chains without replacing all 6 sprockets, just based upon the presumed mileage on this engine. I have not found much information at all regarding how to inspect these sprockets. I know how chain sprockets wear, and when to replace my motorcycle sprockets, but this is different- all of the sprockets look nearly new and run in an enclosed oil bath. None of the typical sprocket wear or damage that I have seen pictures of. It would be nice to know if there is a method of measuring them for wear, but I don’t think a spec is given anywhere. If I had a new sprocket, it might be easier to compare against that.

The piston skirts appear to have normal wear, but I don’t have dimensions yet. I plan to take the pistons, cylinders, crank, cams and IMS shaft to a friend’s house where I can measure bores, journals and piston skirts. I have access to a flat machinist table, v-blocks and plenty of micrometers, but they are all in inches.

Has anyone posted an engine overhaul/blueprinting form for the 911 on the forum? I’m still searching for one- otherwise I’ll have to make a form.

Thanks again,

Dave

Cam housing bores are smooth, no scoring, just like the cam journals.

[PeteKz]

About the sprockets and chains: I have not found a spec for the length a chain either. Nor have I measured my chains to build up a database of chain lengths. I wish someone had. I also ride bikes, and follow the rule of replacing the sprockets when replacing a chain. But in these engines, the chains and sprockets seem to last "forever." So I have not replaced the chains or sprockets on my small number of rebuilds, but I haven't opened an engine with nearly as many miles as yours. The idler sprockets on the tensioners do not get pulled by the chain, so they probably never wear out in normal use.

Note to Henry, if you're watching this thread: What's your experience measuring chain wear? Have you seen wear on sprockets?

As for an engine building sheet, there is one in Bruce Anderson's book on 911 performance.

[silverlock]

re: compression ratio - there’s no magical line where 9.8:1 is fine and 10:1 is dangerous in a single plug application. Further, you’re only looking at static compression: it’s dynamic compression ratio (DCR) that has the most impact on detonation.

You can lower DCR by running a more aggressive cam: the 964 grind is mild vs. a 993SS grind from Dougherty or WebCam. With a 964-grind cam on a 3.2, your DCR is closer to 8.37:1 - with a 993SS grind, closer to 8.14:1.

You can also manage ignition timing here. Lots of variables to play with.

[mikedsilva]

Originally Posted by silverlock

re: compression ratio - there’s no magical line where 9.8:1 is fine and 10:1 is dangerous in a single plug application. Further, you’re only looking at static compression: it’s dynamic compression ratio (DCR) that has the most impact on detonation.

You can lower DCR by running a more aggressive cam: the 964 grind is VERY mild, and a 993SS grind from Dougherty or WebCam. With a 964-grind cam on a 3.2, your DCR is closer to 8.37:1 - with a 993SS grind, closer to 8.14:1.

You can also manage ignition timing here. Lots of variables to play with.

well said.

[Henry Schmidt]

If there is a "magical" line for compression it's to error on the side of caution.
Given the propensity for spirited driving, inconsistency of octane at the pump and the madness of the green Mafia, we are likely to see octane restrictions in the future. The easiest way to get old cars off the road is to reduce the octane in street gas.

Compression requirements are a function of camshaft performance. Compression alone offers very little performance.

[PeteKz]

^^^Listen to Henry. He has more experience building engines than the rest of us put together. Err on the side of caution with CR, and realize that CR alone changes performance very little.

Re cam selection: Remember that you are building a street car, so don't look for high horsepower, but look for a broad torque curve in the midrange. That will make a much more enjoyable street car. You also have to contend with emissions tests.

[85RedCarrera]

Late reply- I got locked out of the forum due to forgetting my password and then the forgotten password links that were sent via email repeatedly didn’t work… for days. So I created a new username with the correct year of my car. Now “85RedCarrera”. Password has been written down in three places.

Back to the thread-

I do realize that there are many variables- combustion chamber size & shape, bore diameter, piston shape, camshaft timing/lift/duration, rpm, the fuel you are using, flame propagation, single/dual plug, gearing, plus more things I probably don’t know much about, plus etc…. I will not pretend to be any kind of expert on this, I only know that I would like more torque without risking detonation on 91 octane. I figured an increase in displacement while keeping the static compression close to the factory value would keep me in the safety margin ballpark… with the 91 octane and smog inspection limitations, I am dealing with severe restrictions regarding variables I can modify to increase performance. Would I like to dual-plug? You bet! But California says “no”. Would I like an SSI exhaust and no cat? Yes. California says no. I might upgrade the DME chip if I can still pass smog with a modified chip.

My build will have a 98mm bore, and lower than 10:1 static CR achieved by reshaping the combustion chamber to work with my pistons while keeping the CR “lower”, and a very mild 964 cam. Stock DME will be retained, no enlarged throttle plate, no increase in intake runner diameter. Stock exhaust with catalytic converter. My cams need to be ground, so I might as well go with the 964 cams. How the 964 cam, my piston shape and my chamber size/shape will work together to achieve slightly better performance over stock while keeping risk of detonation near zero, is up to the shop that is going to do my machine work. What will my dynamic compression be? The shop will have to determine that, because I do not have the expertise.

I’m sure there are better ways to build a 911 engine, but this is a limited build, as I have so much more that needs to be done with the car, so I am trying to keep engine mod$ at a minimum. My hope is to have performance similar to a Euro 3.2, but on 91 octane- I am hoping this can be achieved without too much fuss, by increasing displacement 0.2L. I am a mechanic, and I have built engines for myself, but I am not an engine builder.

Some things I have a working knowledge of, and some things I scratch at the surface and try to understand better.

I really appreciate all of the advice given here.

Thanks, Dave

[85RedCarrera]

I brought my cams over to Dougherty, and it was determined they could not be polished and would require a grind, so I am going with the 964 grind + rockers re-bushed and re-surfaced. Some of my rocker shafts will require replacement. Some rocker adjusters will also need replacing, as the threads were buggered up due to over-tightening of the lock nuts- I had to cut them off before threading them through the rocker to remove them, to avoid ruining the rocker threads.

I am still waiting on donor sheet metal from yard car at Restoration Design for my rear longitudinal repair project, so there is no rush with the engine at the moment.

After closer inspection, the IMS chain sprockets have a bit of a sharp edge at the face of the sprocket along the teeth/valleys. I have ordered new chains to look at the fit with the sprockets that I have.


I have read a lot of older threads where people were concerned about the quality of the replacement sprockets, but haven't seen any recent discussions on this- is there still an issue with the new replacement sprockets?

I have also ordered the Supertec stud kit from Henry. It has been spendy week for the project, but it will give me some piece of mind.

[85RedCarrera]

I am shopping for timing chain tensioners and noticed that I can get a carrera tensioner conversion kit that includes OEM tensioners for less than I can buy them individually...... and the kit includes the oil hard lines and line-hoses (and chain covers).

Does anyone know whether the hard lines and line-hoses that are included in these conversion kits will fit as a replacements for the factory parts on a 3.2? If so, this not a bad deal...

Thanks,
Dave