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Question 1968 re rebuild

I am in the process of helping a friend out with his engine 1968 911 T.

Long story short. 4 years ago motor was sent out to " mickey Mouse"outfit in california. After a year wait motor was sent back with many expensive missing parts etc. dealing with rebuilder was frustrating as he was rude insulting etc. 8500$ bill.

I installed motor for friend . It ran well for 1500 miles then suffered internal piston damage? dont know why. Owner parked car for 2 years as he was too upset to deal with it. Then he took motor out and 1/2 dissasembled it . Stopped as he realized he was in over his head.

Brought motor to me ( I have euro shop) but I dont rebuild motors , have done 3 or 4 911 rebuilds 30 years ago.Tried to find someone locally, or somewhat close with experience, no luck, plus owner was unwilling to spend big bucks again.

I had heads gone through at local machine shop, now putting motor back together.

I believe previous motor had high compression pistons J E installed. Dont know why as owner wanted a normal tractable motor. I am in process of procuring normal pistons ( T) But as this motor is somewhat of a Frankenstein, I need to know if it has stock cams and heads. ?? Basically I want to build a stock motor, but have to figure out what I am working with .. any help would be appreciated ( how can I figure out what cams are in motor??.


Last edited by 304065; 01-15-2012 at 09:53 AM..
Old 01-15-2012, 06:45 AM
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I did a search and found info by tom1394 racing spread sheet. very helpful. this should get me started.Next stop cylinder heads. valve size.
Old 01-15-2012, 09:04 AM
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Tepps, I blew a little air into your post to make it easier to read. There are literally thousands of guys here with experience who can help you out.

OK, so you have already determined that a 911T has 39mm intake valves and 35mm exhaust. Port size should be 29mm for the T, maybe 32mm.

Do you have the part numbers for the camshafts?

Can you take some photos of the pistons? We can tell you what you have.

Good luck, I have been finishing a 2,0 liter motor recently and there are dozens here who have gone your route before. Post your questions here in as much detail as possible and the answers will be forthcoming.
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Old 01-15-2012, 09:56 AM
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Enclosed find photos of previous engine with damaged piston, engine case, heads ,cams , and replacement parts.

Why did engine destroy piston like this??.

I will start guessing. Appears to be a high compression piston, but the cams are supposed to be stock? when I measure the lobes though,they are a full mm less than they are supposed to be.

For example they should be 36.25 and35.51 but they measure out a full mm smaller than my specs from an old stoddard catalogue. the lift is less than it should be. they are not worn. Maybe someone did a regrind? but why lose a mm of Lift???

I talked to 2 people at EBS racing about the JE pistons , got 2 different answers, one guy says pistons are high compression and need 2 plug head, high octane gas. Other salesman says they should be fine and it is hard to raise compression in this motor.

Why would Previos MM builder put High c pistons in motor with lower cam lift.???

Also valves measure Intake 42mm exhaust 39mm. ?? But book says it should be 39 and 35.

Basically I want to build stock street motor that will last. Thank you

Last edited by 304065; 02-08-2012 at 04:07 PM..
Old 02-04-2012, 05:56 AM
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looks like only one picture came through. I dont know if you can send multiples or only one at a time. but that is what piston looked like after 1500 miles.
Old 02-04-2012, 06:00 AM
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This is camshaft. engine is 901/03 serial #2080218.weber carbs 40idt. heads 901 104 306 or. Cams 901 105 134 and 133 . OR.

The lobe size and lift is throwing me off as it is about 1 mm less than the specs I have from stoddard catalogue .

I have a shop manual, but it was printed in 65 I think. The dempsey book shows lift, but I think that measurement is height of camshaft total, not height _ diameter, which I believe would give you lift.

The lift I measured was .276 inches probably ex, and .308 inches, intake. I am using inches because that is what is used in the old white stoddard catalogue.

Last edited by 304065; 02-08-2012 at 04:08 PM..
Old 02-04-2012, 11:02 AM
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Tepps, a few notes to help you out.

1) Try to put carriage returns between lines of text-- it makes it easier for forum members to read your questions and help you out. I have added some space to make it easier to read.

2) You can upload about five photos per post.

3) That looks the remains of a high compression 911S or 906 piston. There are some part numbers on the underside, can you post them, or a clear picture of the number? Should begin with 80.

4) Those are 911T cams according to Tom Butler's chart:



5) How did you measure the cam lift? With a digital caliper between the cam base circle and the nose?

I'll let some others offer their opinions as well. If nobody chimes in, sometimes it takes a couple days to respond-- be patient and you well get plenty of information here.
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Old 02-08-2012, 04:14 PM
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Your heads, casting # 901-104-306-0R, are 2.2T heads. See my cylinder cross reference chart below. These are designed for an 84 mm bore size. Are you sure the cylinders are 80 mm?

The cams are also T carb cams. Measure the lobe sizes using a hand held caliper measuring the distance from the base circle to the tip of the nose.

Need to see a better picture of the piston tops to tell you what pistons you have. Your one photo does not look like a T piston.

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Old 02-09-2012, 02:45 AM
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68 re rebuild.

I have purchased stock 80 mm pistons and cylinders. I am ditching the previous setup as it has blown up twice.Those pistons were 81 mm from ebs , or JE.I thought maybe the valve size indicated it was a euro head, which would match up with 901/03. ?? Anyway I am using stock 80 mm pistons and need to match up heads and cams that will work. Thanks for your help

Last edited by tepps; 02-09-2012 at 04:27 AM..
Old 02-09-2012, 04:25 AM
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68 re rebuild

the cylinder heads are 901 104 306.or. The intake is 42mm, exhaust 38mm.They are stamped k1819d ,also have large casting numbers 7-67 so I think they were made in 1967, so maybe they are not 2.2 heads,as they probably didnt have 2.2s in 67???.
Old 02-09-2012, 03:44 PM
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Those are 2.0T heads and pistons.
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Old 02-09-2012, 04:01 PM
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68 re rebuild

next Question are the camshafts.have a foundry marking of 14.6-67 so maybe they were made in 1967..also marked AE part #901 105 133 OR. 3 journal, size 46.95 .
the lobe sizes are what confuses me , they are: fromThreads, keyway, ( or cylinder#1 2,3.. back cam diameter.28.65 lobe34.73. then 27.76 lobe 35.16.. next pair
28.75 lobe35.31 27.95 lobe 35.10
next pair 27.95 lobe 34.55 27.75 35.06.
If I am reading the Dempsey book correctly my part #s are correct(for a 69 t ,close enough?), but intake should be 36.25. Exhaust should be35.51.
my specs are at best 35.31 35.1. so the two lobes should be.75 mm apart .
mine are all similar, yet they are all about .75 to 1mm shy????. Is this normal. They have no wear marks.
Old 02-09-2012, 04:29 PM
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Here is a pic to demonstrate how to measure the lobe size. I rotate a hand held caliper across the lobe nose and use the maximum reading. The pic show a T cam measuring the intake and exhaust lobes. Do not rely too much on the readings in the pic as it is difficult to hold the cam, the caliper and the camera at the same time. However, the measurements are close to the specs in the above table.



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Old 02-10-2012, 07:43 AM
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Thanks Tom, so my 134 cam reads 34.84 34.89 35.16 34.66 35.03 34.56
then my 133 cam specs at 34.70 35.o3 34.85 35.12 34.62 35.03. all very minor deviations from each other. New should be 36.3 35.1 yours35.76 35.01 mine 35.06 34.72(averages. Do you think this was reground, or just somebody at the factory trying to get close??? Should I get concerned over these tolerances?? my duration is probably good, but maximum lift is .75mm shy( about 30 thousandths , or a sparkplug gap( old plugs).
Basically would you put these cams back in??? they are smooth with no discernable issues. Thanks again. Tom Tepas
Old 02-10-2012, 04:13 PM
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Your readings are pretty close. If the cam does not show any signs of wear, I would reuse it for a stock rebuild.
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Old 02-11-2012, 03:41 AM
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cams

thank you for your ongoing assistance. I would presume that these cams were probably totally inappropriate for the high compression pistons that were inexplicably installed by MM ??Hence inadequate carburetion, detonation, and subsequent piston destruction?It does not show signs of being lean though, as all of the pistons are black. I dont have the plugs to look at .The previous pistons were 81 mm JE . They look like they had serious blow by even though they were new.
Old 02-11-2012, 04:52 AM
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WOW...

Those pistons are incorrect for a single plug 2.0T motor running on pump gas. Compression is likely higher than 10:1. The damage you are seeing is probably the result of detonation.

Stick with your plan to rebuild the motor to stock specs using the T cams, pistons and heads. If you want more power, there are more appropriate options that those high CR pistons.
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Old 02-11-2012, 05:54 AM
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68 re rebuild

Customer never wanted, or asked MM for more power.His only request was that engine would have more torque, or be easier to get off the line as he felt he had to over rev the car at stop signs, red lights etc.I believe the first time he brought it in with internal noise was when we decided on engine rebuild.
I do not have dedicated area to rebuild engines( open 3 bay shop) nor the necessary time to devote to Quality rebuild. Unfortunate choice was MM in Calif. Who knows what or why they built this Motor Mess.It only lasted 1/2 the summer.1500 miles maybe.
I will return engine back to stock specifications and hopefully it will last a lot longer..
Your help has been invaluable. I cannot thank you enough. Allow myself and car owner to at least buy you and wife, friend , whatever, dinner.PM me with address or I will use paypal. Tepps
Old 02-11-2012, 07:20 AM
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Those look more aggressive than my 10.5:1 JE race pistons!
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Old 02-11-2012, 08:05 AM
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68 re rebuild

I called ebs numerous times to discuss these pistons. Depending on who I talked to I received different answers. One sales guy said that it was really hard to raise thecompression on a 2.0, the next guy said they were high compression and needed twin plug head, cams, and high octane gas.
When the car owner bought a replacement piston to try and salvage the remaining 5 , EBS looked up the build sheet and sent a "similar" piston. Not exactly the same.
Im sure that not many builders would feel comfortable with 5 identical pistons, and one that is almost the same. After 3 calls,each time they said they would call me back. I was trying to get correct parts, but not one return phone call. I realize this is my problem, not theirs. When I do business with a customer though if I tell him I will call them back, I do. fortunately there is a forum like this to help. Thanks to the moderator and Tom1394 racing.

Old 02-11-2012, 12:41 PM
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