2.7L Rebuild thread, Sad findings Options

[Cfletch]

Wanted to share an update and also use this thread as way in holding myself accountable and give you guys updates regarding a 2.7L rebuild.

Backstory:
In 2014 or so I had purchased a 2.7L that had been rebuilt and was removed from a running car. The engine then sat for roughly 10 years or so and after coming back from college and a few years of lack of interest in the conversion project I finally got some interest back in the car and wanted to finish what I had started. I ended up getting the engine in as well as my other conversion parts and the car ran and I was so excited thinking that I would be able to more or less have a running project I would be able to drive on the weekends and also tinker on to fix things that bothered me that I found while driving it. I never thought to give it a good ol compression test because when it was purchased, it was sold with good leak down numbers and I had trusted them since it came from a well known shop. Whoops! After waiting about 7 months or so for an appointment at a local indy Porsche shop, I had them do a proper alignment and just check over the car to be sure its safe. One thing they did was a compression test which led to a leak down test. Cylinder #4 has 25 compression and about 80% leak down which was a big bummer to hear. The other Cylinders apparently were more 'okay'. The numbers were as follows for compression: 125,140,145,25,140,130. They mentioned the air was escaping into the crank implying that the rings on #4 were shot or something else that I won't know until I get into it.

Plan of action:
I cannot afford a shop to do a rebuild, and welcome the task of learning to rebuild the engine. I'm still concerned about cost and it might turn into a slightly longer rebuild than I would like because of the cost. My plan is to ditch the CIS pistons and go with the Mahle 90mm 8.5:1 Euro RS P/C set and probably go with some Solex style cams or E. The engine has Carbs already. Main goal here on the piston change is to allow for a more aggressive cam than the CIS cams that are currently in it.

Based on my reading from the engine rebuild book. 1974 could either have cylinders that could be honed, or not and there is not a recommendation to just replace the rings on the other cylinders as it runs the chance of just eating the walls alive shortly after install.

Another point of concern is I don't really want to split the case, but think I should. Assuming I have case savers, which I am not certain I do, that might end up being the reason why I end up splitting it.

If anyone has any video recommendations that go through the whole process of disassembly and reassembly of an engine in depth, please feel free to send me the links!

I only care to post this here at 914 World as the community is more tight knit than at the Bird!

[mepstein]

If you split it, you will need to send out the case to get line bored. They always need it on a mag case. Then have the machine shop do the case savers. Grab your wallet because there’s no way to rebuild an engine for penny’s.

Are you sure it’s not just a slightly stuck valve from a bit of carbon. That happens all the time. Especially if the engine has been sitting.

[Cfletch]

If you split it, you will need to send out the case to get line bored. They always need it on a mag case. Then have the machine shop do the case savers. Grab your wallet because there’s no way to rebuild an engine for penny’s.

Are you sure it’s not just a slightly stuck valve from a bit of carbon. That happens all the time. Especially if the engine has been sitting.

Based on what the shop said, where the air was leaking into the case, seems more like rings- they also mentioned bore was scored a bit so I'm inclined to believe them.

[Ninja]

(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif)

Flush oil

Drive it like you stole it.

Lather, rinse, repeat.

Do the comp test both stupid hot and cold.

Same way with the leak down.

That's looks like it might come back...

Might be worth checking valve adjustment also. A tight valve can reduce compression big time.

[mepstein]

I sold a 2.7 to a member here. Sold it as a core since the numbers weren’t great. He put it in his car and said it ran great. I was happy for him. I’m agreeing with Ninja. Adjust valves. Install it. Drive it and if it really needs a rebuild, figure it out then.

[ctc911ctc]

(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif)

Flush oil

Drive it like you stole it.

Lather, rinse, repeat.

Do the comp test both stupid hot and cold.

Same way with the leak down.

That's looks like it might come back...

Might be worth checking valve adjustment also. A tight valve can reduce compression big time.

(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif)


Vice Grip Garage “Eye-talian tune up”; Derek Style

[ctc911ctc]

(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif)

[Ninja]

I've used both Marvel Mystery oil and Seafoam to clean sludged ring packs before.

You replace 1 qt of oil with the Marvel and drive 50 miles then oil change again.

It is light chemotherapy.

When it no-longer matters I'll try the same thing with Seafoam.

It is BAD TO THE BONE chemotherapy.

That only stays in for 10 miles, oil change then 50 miles, and yet another oil change.

I've had the Marvel "fix" stuff many times.

I save my neighbor 5K once on a VW Vanagan with noisy lifters.

He was taking it to the dealership for an engine rebuild and the Marvel cleaned his lifters right up.

[Cfletch]

Just to clarify in case it was missed and this also serves as a question. The leak down test indicated that it was leaking into the crank case, not through the valves. Would adjusting the valves do anything in this instance? Maybe if it was just a compression test I could see that, but with a leak down indicating the other direction? Also the engine is still installed in the car and could drive it now.

I never thought the engine was down on its luck in terms of a dead cylinder- felt peppy enough, though my comparison was a really beat/sick 1.7 4 cylinder.

[sixnotfour]

Get a bore scope and check the bad cylinder...If they are the KS cylinders and something got it the cylinder it will be scarred easily..

[Ninja]

Just to clarify in case it was missed and this also serves as a question. The leak down test indicated that it was leaking into the crank case, not through the valves. Would adjusting the valves do anything in this instance? Maybe if it was just a compression test I could see that, but with a leak down indicating the other direction? Also the engine is still installed in the car and could drive it now.

I never thought the engine was down on its luck in terms of a dead cylinder- felt peppy enough, though my comparison was a really beat/sick 1.7 4 cylinder.

You are correct!
I went back and read more carefully.
Borescope should be the next thing. Look at # 4 first.
only 25psi on a single cylinder is bad news.

It's worth while to verify valve clearance on both exhaust and intake. If one of them was at zero lash it could cause this. Any clearance at all and this is not an issue.
If the rockers are actually tight when on the base circle of the cam this MAY be your problem.
This WOULD make the leak down test flow through either exhaust or intake.

I will often "pop" valves during a leak down. You hit the rocker arms/tops of valve stems with a small plastic hammer lightly. Pops them open for a split second. When you have a LD test going it makes a bonk noise and helps clear crude from between the valve and the seat. This only applies when the valves are accessible.

What I "homed in" on was a ten-year hibernation. This almost always KILLS leak down numbers.
My previous post (chemotherapy) was to help remove the crud that ends up in a used motors piston rings after sitting for a decade.

I would not run that again until I looked at it with a scope and verified I didn't have a tight valve.

And, if I had a trashed bore, I'd PM Mepstein next...

[sixnotfour]

74 had 911 and 911S ... if its a 911 Non S it will have small intake ports..

waynes engine book.
614 = 911 engine type 911/92 valves 46/40, ports 32/32, hp =150
634 = 911S + us Carrera engine type 911/93 valves 46/40, ports 35/35, hp = 175

[Robarabian]

Also, beware of disassembling a mag case and leaving it sit. The warp very quickly. If you disassemble it, I would put the case halves back together very quickly and torque it to spec.. minimize the warpage.

I you can also search out Kurt on "Aircooled Consulting" on YouTube... he walks through these rebuilds weekly.. Mikes restorations did a 911 motor step by step a year or so ago.... Very meticulous.

[rudedude]

Lots of good info in the engine rebuild section on the bird site, I would check it out if you haven't already.