1973.5 2.4 cis top end rebuild !
 

Hello, My name is Gibran and I have posted here a few times for information about my 1973.5 T Targa which I am attempting to resurrect after about 18 years of hibernation in the Arizona heat. I Bought the car last November and have had several hurdles to over come with this car. Some have been remedied while others will still need tending to.

At the moment, I have pulled the engine and removed the top end in order to diagnose low compression and poor leak down numbers on #4 and #2 which hinted at bad rings. As the tear down progressed, it was clear that this engine was rebuilt just prior to it being parked as the parts and labor listed on the repair receipt dated 1991 detailed.

Upon inspection, the #4 and #2 cylinders have pitting on the bottom of the barrels. I attribute this to moisture getting into the cylinders as these two would be in the intake position perhaps when it was parked. The photos show this:http://forums.pelicanparts.com/uploa...1313710593.jpg
http://forums.pelicanparts.com/uploa...1313710621.jpg
http://forums.pelicanparts.com/uploa...1313710642.jpg
http://forums.pelicanparts.com/uploa...1313710661.jpg

My question is, can these cylinders be repaired and reused? If so, who do I send them to? My attempts to find out more about these pistons and cylinders has come up NLA?
Any advise from the experts out there would be greatly appreciated.
Thanks You,
Gibran

I will be going through this soon also. My '73 cis engine will be taken apart this winter. There is no way to tell for sure by looking at them, you will need to have them measured by a machine shop.
You might want to post a question in the technical forum about who is a reliable shop in your area to go to. The machine shop can take a look at them and see how they measure up.
They are steel cylinders so if they are not worn you should be able to hone them and reuse them. If they are worn too far, they can be bored oversize. You could always get a set of JE pistons and rings to fit if they are worn out of spec. As far as '73 cis pistons and rings, they were a half year only item. I don't think original replacements are available anymore, unless you get lucky finding someone selling a set. There was an add in the classifieds a little over a year ago where a set of nos pistons, cylinders and rings were offered for $1,800.
Hopefully they will all be good and you can reuse them. I will be following this so I can get an idea of what I'm in for.

84V58 are the Mahle 2.4 CIS pistons and are correct for your motor.

The cylinders are the cast iron 84mm cylinders and are also correct.

When these engine sit for a long time without being turned and lubricated, the piston rings corrode with the cylinder bores. If the corrosion pitting in the cylinder bores is not too bad, they can be honed and re-used.

If you need either replacement cylinders or pistons, contact me as I have some good shelf stock on both.

Thanks guys for your input. I live in Tucson, Arizona and have a good machine shop in mind.
I should know something by next weekend.
Stay tuned for more.

Gibran

Could you have them bored out to 85 or 86mm and just order up some JE pistons?

Would stock cis intake and cams work well with JE pistons?

I think with the CIS system, no alterations to the piston size , cams, or crank are possible. which leads me to my next question.
I am still trying to make it to the machine shop as family matters took up most of my time the last few weeks. So I do not have an answer as to whether or not the cylinders can be reused, but.....
Is it possible to use 2.4 mfi cylinders? The cis pistons are fine and the rings are available, as far as I understand the 1973.5 cis piston is the only difference. Would this be possible?

All the cylinders are the same for the 911T from 70 through the 73.5cisT. Cast iron.
Bruce

Thanks Bruce.

Just dropped off the top end at Machine Works.
Looks like just honing the cylinders should solve the issue.
Having the heads checked and new valve guides and seals installed as well.
So far it looks like it should be good to go next week.
Stay tuned.

Hi Gibran
Do you plan on using the CIS ? Before the tear down did you have the motor running ? I have a 1973.5 T and have had nothing but trouble with the CIS since i got it 10 yrs ago . Do you have someone to help with it in Tucson ? I live in Phoenix . Is Machine Works doing the valve guides ? Were the guides worn ? later John

Hi John, Yes I am using the CIS and the car was running prior to tear down - aside from a problem with the fuel distributor which was repaired ( there is a thread on here about it.). the reason for the rebuild was low compression and leakdown #s.
Chris at the volkstop is a good friend and so far we have figured out what to do.
Yes, Machine works has the jig to rebuild the heads. putting new guids and seals in now, while its open.

Hi Gibran ,,
Thanks for the info,, I hope that the motor goes back together quickly ,, Are you going to do the assembly ? Do you know how to do the cam adjustment ? later John

Glad to see it didn't need new cylinders and pistons. Are you installing new rings? The rings for the 73 cis are unique and I am wondering about their availability and cost.
I had the valves done when I first got mine when a chain tensioner failed and it jumped a few teeth, bending the valves. I went with the carrera tensioner update.

Hello,
Just waiting to get the parts back from Machine Works. I Plan on assembling the engine with the help of my friend Chris. Have not timed cams before, so it will be a big learning curve. The great people on this site will surely be needed.
I am looking into rings. The pelican site lists them as well the local dealership. will let you know what they end up costing.
My car already has the tensioner update. Will probably need to go through the brakes before I hit the road.

Gib

Hi,
Ordered rings from Pelican today $232.50 for all 6 cylinders.
Machine works will have the top end ready next week.
Then the fun begins!http://forums.pelicanparts.com/uploa...1316720989.jpg
http://forums.pelicanparts.com/uploa...1316721008.jpg

I have a set of like new '73.5 pistons/cylinders/rings....Can still see the factory hone pattern.....Would let go of them as I went with a 3.2 instead of a rebuild...

Sorry for the long pause.

LakeCleElum, how much for your parts?

Still waiting for mine to come back from the machine shop.

Also, the cams in my car are S spec 143 and 144 if my memory is correct. thought this was not possible to change the T cams with CIS - any Ideas?
The PO stated that he thought the engine was built to S specs at some point by the person he got the car from.

Hello,
According to the 911 cam table I found at Carquip, the 1973.5 911 t w/cis came with 911 105 141 00 on the left and 911 105 142 00 on the right.
My car has the cams that came in a 1974-77 2.7 S and carrera 911 105 143 00 left and 911 105 144 00 right.
The only thing that seems interesting is that the lobe of the T cam is 38mm on intake and 37.48mm exhaust and the S cam is 38.43mm on intake and 37.38mm on exhaust.

maybe it works as is or perhaps it was ground to stock.

Intrigue!

Gibran911,
It sounds like the engine was modded a little bit. Was their a problem getting the piston rings and that is why you need LakeCleElum's parts? I am curious what I will be in for when I start the engine work.

Was thinking $900? PM me please...

Ordered rings from pelican two weeks ago as they were listed on the site.
Just found out from them that Porsche changed the part list #'s and now only sell them seperatly (each ring in a set of 3 per cylinder - individully)- so the price went from $230 to $540 for all 6 cylinders.
DEVES / PAECO Industries says that the can make a complete set (6 cylinders ) for about $160, but I need to send them a piston.

Good news!
Picked up parts from machine works today and all is well.
Was able to locate rings through Total Seal in Phoenix and should receive them Monday.
Keeping my fingers crossed.
Anyone have a 1973.5 CIS system they are wanting to get rid of?
Need it for spare parts - "just in case"
Also interested in a CIS gas tank. - Need it while I repair mine.

I hope the tank comes out well. Just another of those expensive and hard to get 6 month only items. So far it sounds like its coming together nicely. Could you either post the part # for the rings or pm it to me. I could only find rings for the non cis cars on the website.

Do not have the part #.
Just call them and tell them what you need. The were able to locate the ring sizes from a 4CYL set that had the correct ring sizes (the odd 1.75) and split a second set to get the six I need.
They even went so far as to confirm the piston ring depth ad circumference (I had to measure) to be sure.
I should know by tuesday if they are correct and will post what I find out.

Thanks for your encouragement. I am looking into replacing the swirl pot lid. The tank is fine otherwise. Will take someone with the ability to open the tank and fab a new lid (have the old one in about 9 pieces to replicate). Maybe out of aluminum as the old one was plastic. Looks a lot like tupperware.
Know anyone?
I posted a while back regarding the tank as well as fuel distributor rebuilding.
Till then, I would like to buy a tank for temporary use.

You might be able to use the later cis tank. They have the swirl pot. They will only hold the space saver spare. Maybe buy a leaking later tank to take the swirl pot out for yours. I don't know if aluminium would work. Their might be a reaction between the different metals. You could post a question about the fit on the Technical Forum.
Hope the engine is moving along smoothly.

Received new rings from Total Seal.
Will be taking them to the machine shop to check on how they fit and will post there findings.
The cost was $167 shipped.

How's it coming along? Any luck with the fuel tank.

73.5 cis
 

Gibran,
I have a '73.5 T w/cis also. It runs sweet! Stop by the shop and check it out!
Keith Brooks

I can provide a '73.5 CIS system and CIS tank should you need them

PM me if interested

OK - So I took the rings I received from Total Seal to Machineworks and the situation is this....
the top ring is about 2 thousandths thinner then the one it will be replacing and so, is just out of spec. The Porsche guide the shop has states that there should be no more than 3 thousandth and with the new ring we come up with 3.3 thousands. I am referring to gap between the upper and lower surface of the ring landing with the ring mounted.

The compression ring comes out within spec - good news.
And lastly,the oil ring is also just out of spec. Again, gap just beyond spec.


I spoke with the sales rep at Total Seal and he stated that the have dyno'd engines with 10 thousands of gap with no noticeable effects and said that it would be fine to run what they sent me.

Just looking to hear what the experts think of this.

not an expert by any means, BUT, out of spec = out of spec...!! Yeah it will work, but I would be willing to bet it will work for a significantly shorter life than a correctly spec'd ring...just my 2 cents here...me no use...
Lets see what the experts say...
Good luck...!! Bob

I'm curious if the problem is with the rings or the ring grooves in the pistons. Were the ring grooves measured and within specifications, or is this just a problem with the new ring thickness?

I have a set of 6 NOS 73.5 CIS pistons , The cylinders were used for another project.
If anyone is interested LMK jeff

Gibran911, how are you making out? I hope you are having some luck with the rebuild.

Hi, remodeling the guest bathroom has kept me from my project of choice.

OK - So the rings from total seal did not fit correctly, they were somewhat thinner than the stock ones which came out of the car. the only ones that fit within spec were the middle compression rings (1.75) that are unique to the 73.5 cis car. I have kept these and will be ordering the remaining rings from porsche.
I beleave the rings I ned are the 911 t k and the part numbers for each ring thrue my local Porsche dealer are: top 911 103 348 00, Middle 911 103 358 00, bottom 911 103 355 02 and are $33-$37 each.
Can anyone verify the part numbers?

As an aside, the tech I spoke with said he could only locate 5 of the middle compression rings in the states, somewhere on the east coast in a warehouse.
visions of the ending to Indiana Jones fill my head.

Happy Holidays!

Took a giant leap today and ordered the last 5 sets available of 1.75 middle rings 911 103 358 00, as well as the 5 upper 911 103 348 00 and 5 the lower 911 103 355 02 rings to go with the one OEM set of 911 103 94100 I was able to obtain on E-Bay.
Looks like I will be building in about 4 weeks.

Good Luck. Let us know how it turns out.

Finally received all the rings needed to rebuild the top end.
Will get going on this as time permits.
I am sure to need help from the gang here on pelican!

Gibhttp://forums.pelicanparts.com/uploa...1326142549.jpg

Good to see you found them. The rest of the rebuild should go well now.

Hi,
Anyone know the specs on 2.7s cam upgrade on the 2.4 cis engine?
Also, what are the benefits of this "upgrade" , effect on HP, compression, etc.
When rebuilding with these cams I assume that the specs for cam timing are the 2.7 cam specs, any adjustment?

Thanks,
Gib