To try to make a long story short, I acquired a 70T with this engine 2 years ago. I cleaned the engine up, got it running to find I had low compression in cylinder #1. When I pulled it a part, I found that #1 had a blown head gasket. I pulled the three pistons and cylinders on the 1,2,3 side to clean off the carbon. I had the heads checked out and the heads and valves, guides etc were in spec. I accidentley broke an oil ring attempting to take it off and clean the piston. So, I ordered a new set of rings and have successfully put them on cylinders 1,2,and 3 as well as alot of "while your in there" gaskets to reseal the engine. So here's my question. Is it necessary to rering cylinders 4,5,and 6 with the new rings as well? Those cylinders had good compression before I tore down the engine. They were all in the 150-155psi range. I've rebuilt a type IV engine before but never a six. But I have Wyanes book from the bird board and have read it several times. Thanks in advance for your assistance. By the way, this engines going in my 74 teener and will be a nice summer/spring project. java script:emoticon':wavebye:', 'smid_58')

No easy answer.

'Is It Necessary?'
Unless you believe you did something to disturb them, they're no worse than they were originally.

But there are a lot of unanswered questions. F'rinstance, a '69S is a MFI engine. Does it still have the MFI or something else?

Changing from a 2,2T to a 2,0S is an interesting swap, especially if the gearing was not changed...

The real question is: why would you have the cylinders off and _not_ replace the rod bearings ?

The engine was rebuilt 5 years ago. It was pulled from the car and sitting in an autoshop for 3.5 of those years because the transmission had shifting problems and the PO could not afford to have the transmission fixed. It sat in my garage for 1.5 until I got it running last summer. I haven't touched the left side at this point. I had the heads inspected on the right side because I was afraid that the #1 might have had an uneven surface and that's why the gasket blew. The machinist said that the surface checked out o kay and most likely the gasket was faulty.
It was not a true "S". The PO was going to make the car into a track car. The engine originally started as an "E. ". He built the engine with S pistons, heads, and solex cams. It was switched over from MFI to 40IDS carbs. I don't know if you could rering one side and leave the other alone. When I checked the ring gap, it was right in the middle of the tolerance limits for where. So I knew the pistons were within spec. At this point I don't think the engine needs to be rebuilt, but I didn't know if new rings on the right side would cause a major compression difference. Or, would that difference be negligable?

We're getting outside my experience range here, so we're heading into speculation-land. At one end of the spectrum you replace everything any time the engine is apart. At the other end of the spectrum, inhabited by cost-cutters and unscrupulous engine-builders, if a part is not past its published service limit, it's fine, just re-use it...

You've got so few miles on the 'existing' rings that they're probably just seated. You'll have to repeat that ritual to get the side you've done to seat, but that shouldn't affect the side that's done.

I don't think there's any way to predict. You either do both sides now pre-emptively, or you run the risk of having to do it all later. With both sides fresh I'd think you'd be fine after everything seats - but I could be wrong. Most 911's need valves before they need rings anyway...

You've checked both the tops of the cylinders and the head sealing surface for identical depths and parallel, yes?

Face it - it's a crapshoot either way. If it were me looking at this at the start of a long winter, I'd probably say "Do everything." But at the start of the driving season, I'd say 'get it together, go drive it.' If it's not as smooth as you'd like at the end of the season - you know what you're doing _next_ winter...

A 911 engine is NOT a type 1 motor. You can safely get away with the " replace whats broken " attitude with a type 1 motor all day long. You can not on a 6. Anytime you consider buying a 911 engine, do so with the expectation of a complete rebuild. and an assumprion that is is junk unless you KNOW 100% the engines history and/or have build recipts from a reputable shop. Only replacing what is worn right now will only put off the inevitable, and when it does go, you just wasted a lot of money. These are not 1600 c.c. VW motors, nor are they a Chevy 350.

Well, yeah, all that's a statement of the obvious...

And yeah - not rebuilding everything now is a bit of a gamble.

But re-read the original post.

Essentially zero time on rebuild, blown head gasket (which I agree has me worried, because this should be extremely rare in the absense of assembly issues...).

I donno why the OP decided to pull one set of cylinders - for a head issue, I'd have just pulled the bank of heads... But for whatever reason, he's faced with re-ringing one bank.

I'd just do it all all over again - probably. Certainly there's a chance that's what'll have to happen anyway. But with good leakdown numbers on one side and a summer driving season ahead, I'd be really tempted to finish up the side that's been tinkered with, get the rings seated, watch the compression and leakdown, and if they stay stable and the engine is smooth, figure I've dodged a bullet and then just wait for an excuse in the coming years to take it down again.

911 engines are a lot more durable and forgiving than a lot of people give them credit for.

You certainly can't go wrong with the approach that you must replace everything every time anything is done. It's good insurance. It's also expensive. So is an engine failure. Pick one. We know the right answer for a customer car. For a personal play car, we may be willing to assume a bit more risk...

.........My recommendation is to dissassemble the engine, at least down to the crankcase...AND AT A MINIMUM.......clean up the cylinders "glaze brake" them and remove the top carbon lip, at the top of the cylinders.(probably why you broke a ring)....Replace ALL the piston rings....verify cam timing upon assembly, and valve to piston clearances. Have ALL the heads checked for the usual problems., Do a valve job..and install a NEW set of valve springs....There is just no justifiable reason not to freshen up this engine properly. You have no idea of the quality /or IF any of the previous engine work was done/or done properly...take the time do do it right....any thing less than a through top end rebuild is a waste of your time effort,and money....If you do not have the finances to do it correctly NOW...then wait till you do....in the meantime there is a lot of cleanup work you can do to save your self some costs...My advise is to do it correctly one time....you will then have an engine you can trust, and the satisfaction of knowing it,s built right....The bottom end of these engines are bullit proof, and bearings can last forever IF the oiling system is working properly..........you asked , this is my answer, and recommendation......murray mcafee.

I think I knew the right answer all along. I already bought the parts to do both sides. I just need to find a reputable machine shop around Cincinnati that can the head work for a top end rebuild. Besides the car is running great with the original 1.8. It just lacks the power of a six. Thanks for all of the responses. I appreciate it. Hopefully I can get the conversion completed before Porsche 2 Oxford in July.

Status Update 5-2-2010:

I found a machine shop within 10 minutes of my house (which is fortunate because I live in Ford and Chevy country) that had experience with 911 heads. In fact, he's got around 20 rebuilt CIS heads in his shop. So, a month later and the valves and seats had a fresh grind, the springs have been replaced, and everything was cleaned up. He didn't replace the guides because they had almost no wear. The number 1 head was not completely flat. It was off about a couple of thousands of an inch. This most likely lead to the gasket blowing. He resurfaced all of the heads and now were back in business. All the cylinders and pistons have been cleaned and I was able to do a little assembly work today. Here's a few pictures.

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Cool - I'm glad you found that. I was highly skeptical of the 'it's just a bad gasket' story...

Now that's a hemi engine! Those heads look like cereal bowls. This is my dream engine for a teener. I don't know why, but I think it's the coolest 2.0 motor out there.

Is it still MFI? or does it have carbs?

If he machined down 1 head you must shim the cylinder base to maintain an even deck height.

True, good point. Might be a good idea to make sure the cylinders are the same numbered height group as well.

Yep, I had to go from a .25mm base sealing ring to a .50mm to compensate.

I have rebuilt 40IDS carbs to go with it. I lucked into this engine. I paid $4,000 for the whole car (70T) and sold the chassis for $2,600. The only thing I need to finish the conversion is a muffler. I would love an M&K but they're a little too pricey.

I've got an M&K, I'll trade it for the motor.

No seriously, what a great deal. What a cool engine. You'll have to keep us posted on the progress. Can't wait to see it done.

Are you going to have to beef up the drivetrain? I bet you're around 180-190 hp.

I hope to but that's next years project. Once the motor's complete, I'm going to pull the 1.8 and clean and paint the engine compartment. And, I still have a rusty suspension console to cut out and replace. I would like to convert to a 5-Lug. I like the stye of the Fuchs. I also would like to update the front braking and suspension to an earlier 911.

Update 5-9-2010

I made some good progess these past two days. I was able to get the right side put together and torqued down as well as the cams in and the timing set. Cam timing definately has a learning curve. I understood the basics of it but didn't fully comprehend it until I sat down to time it. I followed the directions from Waynes book as well as a few good posts from Pelican. The problem that I incurred was following the directions and tensioning the chains with a vise grip. I timed it to a perfect overlap of 4.3mm (the recommendation in the book) and when I tried to install the tensioners, the chain slacked and my setting was off. I had to install the tensioners and start the timing process all over. The directions should have read "Install the chain tensioners first and then move onto timing the cams". That would have been easier and less time consuming. It's very difficult to try to keep tension on the chain and install the tensioner. Well, enough of my rant. It's nothing an extra hour didn't sort out and the longblock is almost complete. All I have to do now is put the rest of the rockers on and adjust the valves. The rest should go quickly compared to the time I've already put into it. Here's some pictures of my progress.

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Sweet!

I'd bet closer to 150-155hp flywheel
nice though...

Not to rain on the parade, but with S pistons and Solex cams, you have a high compression E. Looking at 130-140 HP, tops, especially with carbs. Good luck with the fuel ............ I had a 2.4S based Solex cammed motor in my bus for 10+ years. Fun motor. In the 37 years I've been working on 911 engines (and for a 3 or 4 years, we did a minimum of one a week), I've NEVER timed them with the tensioners installed. In fact, I don't see how you could. If it were OK to do so, the manual would be written differently.

The Cap'n

So, what do you use to clamp down on the idler arm? I used a vice grips and it was in the way when I went to intall the tensioner. Then without losing tension, I switched to a channel lock thinking it had a slimmer profile but I still could not get the tensioner installed without it slacking. That's when I lost grip and the chain slacked. I was able to intall both tensioners and start the process over. It was a little more difficult because the left side did not have as much room to remove the nut. I was able to position the pin in the correct setting and torque down the nut. From what I understand, cam timing is about repeatable results. I was able to get the same results through 12 rotations of the engine. Just curious, thanks.

The timing is a fine adjustment (like a vernier) on the position of the cam relative to the position of the crank (via the intermediate shaft). Coarse adjustment is set by the links in the chain.

You set the initial timing, put in the pin to hold it there, and YOU ARE DONE on that side. There's no 'maintaining tension' to it - the tensioner acts on the 'slack' side of the chain that does not affect timing. Unless you somehow manage to slip a whole tooth on the chain, your timing does not change.

You tension one side, establish the cam position, pin it, do the other side, pin it, install tensioners and re-verify.

Curious why you went with solex cams? With the IDS carbs and S pistons I would think you could seriously benefit switching to the S cams. Low end would suffer but you'd get another 50 hp on the top easy. Does it have a CW crank? Couldn't really tell from the post. I've seen T,E and S mentioned.

I'm a little concerned for you.....

1. Did you put a straightedge across the top of the case to make sure that it was flat with no warpage?

2. Did you check the length of the cylinders? One shorter than the others?

If the case has warpage or the bad cylinder was jumping up and down and wore the top of the cylinder (making it shorter) it won't matter if the heads are flat it will happen again.

I find it odd that a couple of thousands head warpage would cause a head gasket blow out in 500 miles. I have pulled motors down that were warped way worse than that with no issue. In fact my 3.6 was warped .010 on one head with no leakage. I would look a little deeper, something else may be wrong.....

That makes a lot of sense. I thought you had to maintain tension throughout the whole process. I ended up installing the tensioners and setting the timing with them in. I was able to set to the correct spec, but it was more difficult torquing down the left side cam nut. Thanks.

I did not check the case. The cylinders were checked the same time the heads were in the shop on the recommendation of the machinist.

I've been busy this past month. I pulled apart the left side on the advice of PRS914-6 to make sure the case was level and flat. I put a straight edge on it and it was fine. At least I know that it's right and it only cost me $30 in seals. I got the engine together and worked on cleaning up the engine compartment. The hell hole was in great shape. It appears it's been replaced before along with the engine shelf. The only way I knew was that they did not grind down the welds. Smythe auto parts mixes spray paint and it's local. They were able to mix my color code and I painted it up. I put a couple coats of clear on it to make it look pretty. My next step will be to drill the holes for the oil tank and mount it. Then, I'll put the engine in and replace the fuel pump. I bought a CB rotary that should work well with the carbs. Here's some pictures of my progess to this point.


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I got some more work done this weekend. I was able to install the oil tank. It was a tight fit. I was able to tilt it at an angle and gentley nudge it in. I had to cut out the support bracket for the blower from the heating system because I could not install the oil filter with it there. I was also able to clean up some surface rust on the bottom of the engine shelf and get it painted. I had to put a dehumidifier in the garage to keep the humidity under 50%. Those of you who live on the west coast don't have that problem but it'll rust a car fairly quickly. Here's a picture of the oil tank. Next I'll work on cleaning and replacing the main transmission drive seal. It is 36 years old and leaking and a cheap "while your in there" project.

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I am a serious fan of the Solex cams. There is more hp to be had with the S cams but with a drivability loss.....they are too peaky, IMO.

In my 2.7 I get excellent torque from 3500 to 5000 rpms.....over 200 ft/lbs and "tuning issues" with the carbs are minimal. The hp drops off about 6300 from a peak of around 230.......still well over 200 at 6800. The S cams get peak torque at 5000 rpms.....no thanks. With the exception of the P/Cs (10.5:1 Mahles) this is a "no trick shit" build using all Porsche parts.

I agree. Ultimately, I want a nice driveable street car with more torque and horsepower than I get from the present motor. Plus, I've always wanted to build a six conversion. If I can get 140hp with 160 ft/lbs of torque, I'll be a happy camper. When I drive my car now, it rarely operates above 5,000 rpms. Most of my driving is between 3,000 and 4,500.

After torquing down the heads & cam tower, the cams should turn freely (finger pressure) in their bores. Any of the many surfaces being a different height will cause a bind at some point in the rotation. This is the last of many checks for parallel.

That said, whenever a mag case comes down, it's wise to have the case spigots decked & squared. Those cases are noodles but if the above was done you should be good to go.

So I was working on the engine harness today and had a few questions. I thought it would be easy to switch the pins in the plug to the configuration in DR 914's book but was mistaken. I have all of the plugs labeled but there are a couple of wires that I need ID'd. The first is a black wire with a purple stripe that that runs from the plug to the dizzy and then goes to the CDS unit. In appendix II of How to convert your 914-4 to a 914-6, I think this is the wire to the control unit. Is this correct?
The second wire is blue with a yellow stripe that goes to terminal 15 on the coil. Is this the wire for the tach?
And finally, I have four wires for the Alternator (B+, DF, D-, and D+/61). The book does not describe where these wires fit on the plug. Any help would be appreciated from the wiring Gurus. The wiring harness is from a 70T and it's a 69 2.0. Thanks.

Black wire purple tracer is tach.
'the control unit' ? wazzat ?
Terminal 15 is 'coil' positive - that'd be from the CDI ignition box.
Make sure you have a CDI "coil" (not really a coil with CDI...).

Thanks Rich. " The Control Unit" in this case is the CDI box. That's how Dr. 914 describes it in his conversion book. The system I have is an exact transplant from a 70T I had running last summer. So, it should work if I wire it correctly. So , terminal 15 is the CDI signal. Where do I connect the four alternator wires? It doesn't really describe where those pins go in his book. Thanks, Eric

Let's clarify the CDI thing because the terminology is important (Bosch CDI boxes are expensive...) Be careful about use of the word 'signal' ...

the Bosch 3-wire CDI box has 3 connections (duh...). Ground is easy and not one of the 3 connections... It takes switched +12 from the ignition switch for power. It takes the points-closing "signal" from the distributor - and that may in fact be the black/purple. Then the high-voltage (~300V) output pulse returns to the "coil." I'm pretty sure that's your green/yellow.

(The black/purple then goes forward to run the tach.)

As for the alternator - this is why I consider the alternator harness part of the car, not part of the engine ;-) ...

I believe colors and pin assignments are shown on the 911 wiring diagram (in color) and the Art Zapf 914.6 big color wiring diagram - both of which I have but can't get to this morning. Let me look for/through those tonight and this weekend.

If someone else has the information right at hand - go ahead and post it here...

Especially since I do not have a relay board I can reference...

Thanks for the information. I can at least get the rear plug setup correctly. I'm interested to see how the alternator will be wired in. Obviously the the voltage regulator on the relay board has to play a part. I have the 911 haynes manual and it's pretty usless in this detail. I'll try to search for the Art Zapt 914.6 diagram when I get home.

The battery + wire goes to the battery +. See pic for the wires that go to the regulator. The D+, D-, and DF go to the regulator. I did away with my relay board and simply pluged in the wires from the alt. to the regulator direct....Regulator is #4.

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I just found that diagram under "914-6 Wiring" from a couple of years ago. It makes so much sense now. I can wire the alternator pins directly to the alternator wiring harness on the relay board and be done with it. My final question is: Can I wire the blue wire from the alternator (the one that works the light on the dash) to the corresponding receptacle on the main wiring harness? Thanks for your help.

Connect the blue alt. guage light wire to the D+ wire at the regulator and it should work.....mine does.....

It took some time but I finally figured out the wiring harness. There was a particular blue wire with a yellow stripe that was giving me some trouble because I couldn't figure out what it was. It ended up being nothing that I needed in the conversion. It originally went to the rear fuse box on the 70T. So, I should be good.
I spent some time replacing the input shaft seal on the transmission and some of the bushings for the shift linkage. I was able to replace the seals on the speedo drive gear and stop the leaks as well as replace the throw out bearing and bushings for the fork. The clutch disc measured at 10mm (almost brand new) and the pressure plate was in excellent condition.
Today, I connected the transmission and the engine and torqued it down. It turns out that I overtightened the small nut on terminal 15 of the coil and pulled the post out. This sucks because I just bought the coil last summer and it maybe had 8 hours of use on it. The next step is to get my dad over here and help me put this beast in the car. Here's some recent pictures.

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Congrats !!!! That just looks sweet !!!

Jack / Jaxdream

Awesome work! Keep it up!

Bummer about the "coil". Remember it's not really a coil, but an ignition transformer for the CDI system, and is not interchangeable with something like your standard Bosch blue coil.

Torque those small fasteners with two fingers only, not your fist.

Sometimes I have to learn the hard way. I've been so careful during the top end rebuild to torque everything tho specs. If this is the worst of it, I'll be a happy camper.

I got tired of looking at the engine today and decided to put it in. It took four hours (by myself) amongst the humidity and heat index of 102 but it's in. When I look from the top of the engine compartment, it appears the engine could come up about 3/4 of an inch. But, all the fasteners are snug and secure and the mount is line up correctly. I've added a picture of the motor mount. I used a quick six bar with the original pods. I'm wondering if I installed the mounts upside down. If I flip them that 3/4 of an inch would be taken up. So, my questions is are the mounts installed correctly? In the Haynes manual, it looks like they hang down as I've installed them. The engine doesn't look like it's sitting too low. It would just be more of a flush fit if that 3/4 of an inch were not there. Thoughts please. Thanks.

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Today I was able to install the oil return line. I bought a short pipe from Patrick and some braided line. Somehow, I thought it would take longer but it actually went pretty smooth. I had to bend the tube about an inch so it would not hit the motor mount. I also got the clutch hooked back up and the speedo angle drive. In the next couple of days, I would like to get the CV joints attached, throttle hooked up with the bell crank, and get the headers on. That should take care of all of the work underneath the car and I can put my focus in the engine compartment.

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Looks great.......I remember when my motor went up into the car.....put the axles on BEFORE the headers/heat exchangers.....

Did you shave the ribs on the Turbo rocker cover?