Caterino's 1970 engine rebuild

[mcaterino]

Many of you have followed my general restoration thread (Restoring a 1970 911T) and my blog (link in my signature) covering my restoration of a 1970 T targa. At long last it's time to start the engine rebuild (which was initially my chief motivation for taking on a 911 project). As I get started, I wanted to begin a separate thread on this process, to keep myself motivated, and to give me a place to share the many questions I'm sure will be encountered. This will be my first engine rebuild of any kind, but having read Wayne's book, Bruce Anderson's book, the factory manuals, the Bentleys, and countless threads here on the process, I feel reasonably well prepared. My main handicap is that this engine was disassembled when I bought it, and missing many parts, so I didn't have the benefit of seeing it all together and then taking it apart myself.

The engine was a stock 2.2 T when I acquired it, and had been torn down at least to the cylinders before (half my heads are date stamped 1972). I don't think the case had ever been opened. I was somewhat interested in originality, but also decided that if I was going to sink ~10K into an engine, I wanted something I was really satisfied with. So while using the original case, I've upgraded the crank, rods, pistons and cams. More specifics below. My planned use is weekend drives and some autocross.

Here are my raw materials, with all work done to date:

Crankcase (work done by Competition Engineering)

• align bored to STD
• all case studs inserted
• oil bypass mod completed
• piston squirters installed
• intermediate shaft rebuilt, with new sprockets and intermediate gear
• cylinder spigots honed and surfaced
• original oil pump cleaned and deemed 'nice'
• 70.4mm stroke crank chemical flushed and micropolished
• 2.4 rods rebuilt & rebushed

Ps & Cs (by EBS Racing)

• original cast iron cylinders bored to 85mm
• new JE 9.5:1 cr pistons

Heads (by CE)

• complete valve job, with all new valves, guides, old in-spec springs

Cams

• cam towers surfaced; rocker and cam bores honed (by CE)
• new E spec cams (by John Dougherty, aka Camgrinder)
• rockers rebushed & radiused (or replaced)
• polished and/or new rocker shafts

Intake

• Zeniths of unknown jetting (from a '71 'E')

Exhaust

• original heat exchangers and 2 into 1 muffler

Misc

• gasket kit from Wrightwood Racing, with viton where desireable
• all new chains, bearings, rod bolts, flywheel bolts, basically the whole rebuild kit
• rebuilt (by me) 930 chain tensioners with safety collars
• 'turbo' aluminum upper and lower valve covers
• MSD ignition & coil
• original Marelli distributor with new points
• engine oil cooler ultrasonically cleaned and pressure tested

The weakest points in the current plan are the use of Zeniths (acquired from a fellow Pelican) and the original Marelli distributor. My justification is equal parts originality and cheapness. I must admit I like the idea that I could make these 'challenging' components work well, but I'm prepared to swap the distributor especially, at the first sign of trouble. I do need to talk to the PO of the Zeniths to see if I can find out more about the current set-up. They came off an E, so may be reasonably suitable for my application.

My present concerns are:
1) whether the machining of case, heads, and cam towers are going to lead to some clearance issues, especially given the higher compression pistons (but they do have deep valve reliefs). I should probably be prepared with some thicker cylinder base gaskets.
2) similarly if the reduced component heights will result in too much cam offset, and chain tension issues. The chain boxes were not surfaced. We'll just have to wait and see when it all goes together.
3) whether I'll have bottom end clearance issues with the longer stroke crank - no case web work was done. On the other hand, the new pistons appear to have considerably shallower skirts than the original ones. Walt didn't think it would be an issue. Yet many threads here discuss it, mostly I think in the context of original pistons.
4) cooling. At this point the plan only includes the original engine oil cooler. Given the higher compression and displacement, I've definitely considered adding a front cooler. But at the same time, a handful of modifications should help keep temps down (cooling tin cuts, piston squirters, 11 blade fan). So on balance, for starters I'm going to go with what I have and hope for the best. Southern coastal California's really not that hot.

As far as I can tell, most of these can only be judged on assembly. I suppose a more or less complete dry assembly is in order, especially to check the piston clearances.

Here's a few shots of what I'll be working with:
An exploded view.


Right case half on stand.


New 'E' cams with rockers and polished shafts


An 85mm JE 9:5.1 vs. original 'T' piston.


The gunk that'll hold it all together and hopefully keep it from leaking.


At present I'm acquiring the last few bits of hardware, and am busily cleaning everything new and old to an 'eat-off-it' standard. This weekend I will begin assembling.

So wish me luck, and feel free to offer constructive feedback. I suppose if I've made some major blunder in my planning you can tell me that too. But I think things are more or less in order.

Thanks,
Mike

[ratpiper71T]

Well I'm definitely jealous of your progress. I've been following your posts for a while and your blog. You've done a fantastic job up until now. My '71T awaits me to give it some of the same love. I haven't made all of the decisions about where I'm going with the motor but I'm getting there as I continue to collect parts. Up until now I had planned to keep the zeniths but I recently acquired a set of really nice webers. So I think maybe I'll rebuild them- zeniths for fun and sell them or keep them as sort of a garage art- I hear Kundensport has an indie porsche motor in their lobby... I'll have a pair of zeniths... Heh, heh.. I would recommend talking or sending a pm to user pcar119. He makes custom venturies for the zeniths. He is about to run some more and they are $150 a set. With your increased displacement, if you intend on keeping the zeniths, you need this. If you do a search on zenith jets, you'll see someone posted a link here recently for a seller of them on eBay. From what I understand the emulsion tubes should be fine. Regardless, no one is making these for zeniths anyway.
Here is a recent thread where some of these subjects where touched on:

zenith vs weber

Hope this helps and keep the updates coming!

[regency]

mcaterino: About one year ago, I finished my 73 T's engine following almost exactly everything you're doing now. My engine is MFI so I had Matt Blast rebuild my throttle bodies to E spec & Gus @ Pacific Injection do the MFI pump. Now have about 5,000 miles run and it rund great.

Steve

73 911T MFI Coupe, Aubergine

[mcaterino]

Thanks for the comments guys. I have been reading a little more about the Zeniths, and will continue. But most of my effort has gone into getting the last few things taken care of before closing up the case. I spent a good bit of today cleaning things further, and then started checking clearances. I did some plastigage checks on the main and rod journals. Everything is in spec (although one main bearing was borderline - see below).



After checking clearance I also did one trial assembly without plastigage to confirm for myself that everything was going to turn once torqued down. No problems there. It was really good practice mating the case halves together a couple times, giving me a chance to think about the sequence when it's time to do it for real. After that I felt ready to put the crank and rods together. Everything there went fine. I did the initial assembly on the bench (to 15ft-lbs) and then laid the crank in the mounted case half for the 90 degree final torque.



Then I went on to check one of my initial concerns, the piston skirt clearance. After looking at the pistons side-by-side (joined by the wrist pin), it was pretty clear there wasn't much cause for concern. But I went ahead and mounted a cylinder and attached one piston to a rod in the case. Several mm of clearance. No problem at all. (Oh, if you haven't seen my piston carnage previously, the cause of this car's earlier death is evident.)




So with that, I went through my pre-case sealing checklist, and am ready for tomorrow (although I still need to stock the fridge for the post-sealing celebration).



Mike

[BURN-BROS]

Hi Mike,

Nice progress! Can you verify what stroke your pistons are made for?

[mcaterino]

Aaron,

Don't scare a guy like that when he's closing up his case! I went in and checked my spec sheet from JE. EBS ordered these for me, and did specify the 70.4 stroke (you did catch that I'm using crank and rods from a 2.4?) So all's good, I think.

Always good to double/triple check.

Thanks,
Mike

[BURN-BROS]

LOL, sorry! Didn't mean to startle you. It is a very common mistake and I wanted to catch it while it was early. JE puts deep pockets in the pistons so it can be an optical illusion.

Have fun with your build Mike.
Cheers!

[mcaterino]

I guess now I'm not sure what clearance you're referring to Aaron. I was only checking the skirt-to-case clearance (and showed the dome photo for no good reason other than that I'm excited to see even more parts together, if only temporarily.) I haven't begun to seriously worry about dome and valve clearance yet. That's next!

Well we had a remarkably uneventful afternoon sealing up the case. Katie lent a hand, helping to keep the rods and chains aligned when putting the two halves together, and then helping get the perimeter nuts on and snugged, while I o-ringed and tightened down the through bolts. My homemade rod and chain supports didn't do such a great job (too light a steel), and it would have been a huge PITA without the help. The upper chain did end up falling off the sprocket, and it was a little tricky getting it back on after the fact, but possible. The other thing is that the flywheel seal squeezed out a little bit (installing it dry), and is going to need to be pushed in a little further I think. Since others have said they install this after the fact I hope this isn't too difficult. But it didn't move easily by hand or even with a little light hammering. It's not in an easy spot to get to on the stand.

We used 1194 on the perimeter, 574 on the bearing webs, and 1211 on the inner perimeter of the #8 bearing. It was a hot day in Santa Barbara, and it began to set up very quickly. But we got everything done in probably 20 minutes, and had a nice, light squeezeout all the way around. I think it went well. On to the cylinders...





Mike

[RolyRolo]

Try a Cylender compression test, you can do that with out taking the motor out or apart, just need to remove the plugs.

[BURN-BROS]

Originally Posted by mcaterino

I guess now I'm not sure what clearance you're referring to Aaron. I was only checking the skirt-to-case clearance (and showed the dome photo for no good reason other than that I'm excited to see even more parts together, if only temporarily.) I haven't begun to seriously worry about dome and valve clearance yet. That's next!

The dome volume for the 66mm stroke piston is greater than one for 70.4.

Both pistons will fit without clearance problems. The 66mm piston will yield 10-1 comp when used with 70.4 stroke. As long as JE provided the correct pistons(which you stated they did) all is well. No worries!

[mcaterino]

On to the pistons and cylinders. This morning I cleaned and checked the clearance of my rings. I got JE's proseal ring set to go with my pistons. The compression rings checked out fine, but the oil ring was strange, and too large. I honestly had never given much thought to rings, and was surprised to see that the oil ring was not what I'd seen before. It's a three-piece, with two very thing top and bottom rings held apart by what's been referred to as a corrugated spring in between. It appears that the ring gap in the retainer rings is irrelevant, that the spring is the real workhorse here. At least I hope so, because the retainer ring gap is quite large, >1mm. The spring, however, is too large, and overlaps at the ends by about 1 mm, so it is going to need trimming and filing. See pic:



I can find specs for the correct clearance here, but it seems like accurately cutting this to that will be tricky. Anyone have any proven methods for the home engine builder to do this? It might almost be cut with fingernail clippers. Just nick with a razor blade and bend it? I'm open to suggestions.

Thanks,
Mike

[cgarr]

Thats spring gives the oil rings their tension, I don't think you want to cut it.

[BURN-BROS]

Hi Michael,

Assemble the expander and rings on the piston as they were designed and then report back. You cannot measure gap of the expander as needs to be in it's compressed state. If the rings do not sit right then I would start worrying about it.

I agree that the ring gap is a bit large but I am not sure if you can do anything about it. Perhaps you can call JE and verify?

[mcaterino]

I appreciate the comments gents. I have been reading more, and although I haven't found anything very specific about how this oil ring spring should fit - the JE literature is pretty vague - but it more or less sound like everything is intended to fit my bore as is. I put a set of rings in the pistons in the living room tonight, and everything looks all right. I will try a full install tomorrow without modification, and see how well it all compresses.

Mike

[mcaterino]

I took a few 'personal days' this week off work, which means of course 'car days'. I am determined to get this car done before Xmas. My first official act today was figuring out the ring situation. I called JE this morning, and was more or less treated like the novice that I am. They said that the oil ring situation I described was exactly what is expected. So I wiped everything down, laid it all out, and was ready to go.



Installing the ringed pistons into the cylinders turned out to be a major ordeal. Wayne's description of 'gently pushing the piston into the cylinder' had given me unrealistic expectations. The biggest problem was the thinness of the rails of the 3-piece oil rings. They sprung out immediately from the compressor before getting beyond the tapered bottom of the cylinder, and didn't want to budge beyond that. The somewhat fancy ring compressor I used (a screw with two bands around a collar) was too bulky, and these pistons were at the lower end of their size range, so there was quite a bit of overlap in the outer sheaths. This thickness kept me from getting it far enough down into the cylinder. So I improvised. I used a short piece of 26 gauge (in fact the same piece that performed mediocrely as a rod support), and a pair of vice grips, and had much better luck. These could be pushed further down into the cylinder, around most of their circumference, and allowed the thin rings to be pushed far enough in.



After spending too much of the day on that, I moved on to checking piston dome clearance. To make a long story short, I now wonder if I have too much clearance, rather than too little. I glued on a small roll of foil (makeshift solder), torqued the heads down, and ran the cylinder through TDC, and found no interference to about 2mm. This was with .25 mm base gaskets. Even if I were to run with no base gaskets, this would seem pretty high. Now I have no idea yet about actual dome volume. But it's looking like I'm going to have to measure it. Many have said that the stated CR of JE pistons can be pretty far off. I would like to end up close to 9.5:1. Although I guess .25 mm of deck height won't affect that much either way.

I think I'm going to go ahead with a dry assembly without any cylinder base gaskets, and go on to look at valve clearance. Then I'll have to rig up some volumetric apparatus. Fun, fun...

Mike

[tom1394racing]

Mike

With your build, I think you must plan on measuring compression, deck height and piston to valve clearance. There are plenty of good posts here to help guide you through the processes.

[mcaterino]

Hey all, I'm in need of some real help on this compression ratio question. I spent quite a bit of time today measuring and calculating volumes, but even more scratching my head in confusion.

So I made some simplifying assumptions to calculate the compression ratio. It seems like everyone overcomplicates this. All we're interested in is the ratio of the cylinder volume at BDC to that at TDC. If you know your bore and stroke, the only volume that must be measured is the compressed volume, right? So I measured my actual stroke on cylinder #1, and got about 69.9mm, either by measuring multiple points around the perimeter and averaging, or by measuring total crown movement. Bore is 85mm. So my cylinder displacement works out to a reasonable 393 cc (2.36 L total).

Then at TDC, with the cylinder on the case and the head torqued down, I measured the amount of liquid (tried with both oil and alcohol with similar results) that filled the combustion chamber through the spark plug hole, making sure there was no trapped air, etc., and got about 36.5cc. So the compression ratio under this set-up would calculate out to (393+36.5)/36.5=11.77!

Now this is with the stock cylinder base shim of .25mm. And with this I have exactly zero deck height. The outer edge of the piston is exactly even with the top of the cylinder. I've read somewhere here that JE's advertised CR is based on a 1mm deck height (for me requiring 1.25mm shimming), but even running the numbers there (adding a 1mm thick slice to the compressed volume) would still only bring me down to about 10.4. To get close to 9.5:1 I would need 2mm of shims to give a 1.75mm deck height. This seems like excessive shimming, and a borderline excessive deck height.

I'd very much welcome some more experienced engine planners feedback to see if this sounds right. I suppose that it's possible that my case and/or heads have had more work done on them in the past than I realize, and my heights are just way out of whack. Anyone run 2mm of shims successfully??

Thanks,
Mike

[cgarr]

I come up with about 11.9 Adding 1mm to the base would drop it to 10.4 2mm you would be down to 9.3 That is adding to what you have in there now. Sure you got all the air out? Were the heads cut? never mind, they would have to be cut a huge amount to make it the problem.

[tom1394racing]

Mike

I think your CR calculation is in error.

The numerator for the CR calculation is not simply the swept volume or 1/6 of the displacement.

You need to measure the volumes at both TDC and BTC and make sure you have both located accurately. You can then take the ratio.

[mcaterino]

Well Tom, you were right, but not right enough. Total volume (including combustion chamber) at BDC is 426. My previous swept volume + TDC volume was 429. This only brings CR down to 11.67. So I'm back to my question. How much shimming is too much (or how much deck height)? Or maybe, although I'm not real eager to get more machine work done now, do I have my domes machined down? If I were to shim up to a 1.25mm deck height (1.5mm in shims), with the new numbers, I'd be at 9.93:1. Maybe this is acceptable (obviously I'm talking about a single plug application with the best fuel I can get.) Or shim to a 1.5 mm deck (1.75 in shims) to get 9.65:1. That would probably be safe.

So in a nutshell the proposal would be:
85mm x ~70mm stroke
1.5mm deck height (1.75mm cylinder base shims)
CR = 9.65:1
single plug
totally stock 2.2 (68cc) heads
E cams

Sound workable? I am very grateful for the feedback to date. This would be much more trying without you all to bounce ideas off.

Thanks,
Mike