My Conversion Project, Question on Engine Break-In Options

[Ericv1]

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')

[ArtechnikA]

Is it necessary to rering cylinders 4,5,and 6 with the new rings as well?

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 ?

[Ericv1]

Is it necessary to rering cylinders 4,5,and 6 with the new rings as well?

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?

[ArtechnikA]

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...

[scotty b]

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.

[ArtechnikA]

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...

[ME733]

.........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.

[Ericv1]

.........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.

[Ericv1]

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.

[ArtechnikA]

...The number 1 head was not completely flat.

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

[Rav914]

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?

[sww914]

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

[Rav914]

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

[Ericv1]

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

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

[Ericv1]

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?

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.

[Rav914]

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.

[Ericv1]

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.

[Ericv1]

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.

[rick 918-S]

Sweet! (IMG:style_emoticons/default/drooley.gif)

[brant]

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