Most common rebuild mistakes

[vichang4]

I installed 1/2 of the pistons up side down. Before sealing up the engine, I consulted this board and fixed the mistake. 3.4 RUF turbo flat top pistons.

[Rich76_911s]

I think a common mistake for the first time rebuilder , ME. Is that while photographing the engine I did not step back and take photos of the complete set up step by step. It was so exciting to look deeper and deeper into the case that sometimes I got too caught up in checking out what more I could see and learn instead of taking more pictures to reference later. Have not rebuilt yet, but hopefully i do not learn too many mistakes on the way. Good thread I like it.

Rich

[asphaltgambler]

Main reason is usually lack of knowledge and not being detailed enough.

[snowman]

The most common mistake is common to everyone. Lack of experience. There is no, and I mean no way to mitigate this problem. Either you pay for a true professional, experienced mechanic or you take some kind of gamble with your rebuild. Even the most professional, meticulous, engineer, with bokoo knowledge cannot outdoo a seasoned mechanic with bokoo experience.

Whats this mean??? Goes back to you get what you pay for. That simple.

[hcoles]

I hate to say it, being an engineer and all that, but Jack is likely right on. There are just so many ways to mess up. I hope I come out of this with some luck on my side 1000mi on DIY top end 3.2. The only issue I have is a not great idle and some surging otherwise the engine seems to run very good, even compression, no noticable funny noises. Another thing to consider, if you try to sell the car, if you DIY buyers may not give you much credit compared to rebuilt by a person that has done 100's of them with few redos.
-h

[911pcars]

I sort of agree.

On the one hand, an inexperienced rebuilder can "paint by the numbers" and, given accurate instructions, follow steps 1 through 500 and rebuild an engine; that is assemble it and it should run.

However, the experience will provide answers and anticipate issues before and when they occur. Experience will recognize when something is not right; if the machine shop machined something incorrectly, if the incorrect replacement part was supplied or if that just-tightened fastener doesn't feel quite right, among other examples.

Knowledge and experience are great unless you're lazy, have a lapse in concentration and/or don't pay attention to what you're doing and why you're doing it.

Lacking experience, I suggest taking it a little slower and make sure everything looks okay, goes together correctly and operates the way it should. Then, the final steps:

- Hammer to fit
- File to shape
- Paint to match


Sherwood

[sammyg2]

I pulled my 3.0 apart after 102,000 miles due to one broken head stud.
The only damage or wear I found was one broken head stud.
Everything, and i mean everything was within specification, most of it was as new. It is a nikasil engine BTW. I laughed as i replaced the piston rings with new ones that had almost identical gaps as the old ones.
My cost to rebuild (not including tools which I re-sold) was around $1200. It makes it a little cheaper when you have a full repair shop/machine shop, but I could have done it just as cheaply in my garage.

Oh yeah, the original topic?
The only mistakes i made was to time the right side cam before the left, not really a mistake but I went back and re-checked the timing twice just to make sure, and my dizzy was 180 out when I first got ready to start it. That took 5 minutes to correct.
That and thinking that these are magic engines that should be feared. They aren't that complicated or hard to work on, the only thing that made me nervous at all was timing the cams and they weren't hard, just time consuming.
I guess having this board and Wayne's book and doing my homework made the difference. If I had dove into one of these engines 5 years ago with nothing but a hayne's manual the outcome might have been different.

[ChrisBennet]

Originally posted by 911pcars
However, the experience will provide answers and anticipate issues before and when they occur. Experience will recognize when something is not right; if the machine shop machined something incorrectly, if the incorrect replacement part was supplied or if that just-tightened fastener doesn't feel quite right, among other examples.
Sherwood

Sherwood brings up a good point. The less experienced engine builder will often trust critical items to machinists and venders without verifying that the items are OK.

For example, I caught 2 big mistakes building the last motor:
- The crank came from the machinest after being crack checked and micropolished. Good thing I checked it, it had a trashed rod journal.
- The JE pistons that were supposed to be 9.5:1 but CC'd out to 10.5:1CR. I sent those back. The replacement set was also 10.5:1CR.

-Chris

[hcoles]

Chris brings up a good point. I had rockers/shafts recon./checked for a new cam. As I was putting things together I was checking the clearance between the shafts and rocker sets....two were way out. My gut feeling at this point is that you just about can't trust anyone 100% and the time it takes to check things is worth it. Another thing I found, and this may be minor but not to me, the replacement rockers had new bushings....that's fine but they didn't have the oil pocket on the inside..to me that's not fine. So I put pockets in. Someone will probably write in and say they have done hundreds of these without pocket and no issues, I figure if the factory did it there was likely a reason. This is the type of thing that the novice, like me, can't know one way or the other and is lucky to catch something like this. You could add another 200 pages to the Wayne book and probably not catch everything the expert mechanic knows just by feel and practice. I expect that even all the factory books and manuals have at least some errors...so you can't be even sure of those and following them 100%.
That's my humble 2 cents.
-h

[snowman]

I have found that there are ways to do engines on the cheep, as I am ultimately cheep. By cheep I mean inexpensive as I do use Carillo rods and whatever else is the BEST possible parts for the application. But I do SHOP a lot, wait years if necessary, to get the best price on the best parts.

As to labor I do all the machine shop work myself. You may be able to do the same. Look for a local community college that has an engines course or machine shop course. Sign up for it, over and over if necessary and you get access to a full machine shop, plus learn something to boot, all for peanuts, eg $100 per 6 months. My local college has a fully equiped auto machine shop, all the high perf stuff, like engine balancing equipment, special tools,dyno, alignment racks, scales, you name it they have it.

All this and you can get over confident. The biggest mistake I make is getting to lazy to keep a log of all the rebuild steps. Ever get the whole engine back togather and think, did I do the final torque on the rod bolts???

Still on vacation in Gods country.

[Avery]

I like SNOMANS suggestion. Keep a log. Since rebuilding for DIYers can span months, it's easy to forget what you did and did not do.

[vichang4]

I found the log to be very helpful. Weeks after the rebuild when I would start to worry about something, I could go back to the log and reassure myself that I did it right.

But, the second rebuild I did was much easier and came out much bettter than the first. I used slightly different parts, looking for the right combination, and really nailed it on the second engine.

So someone who has done 50 engines has an extreme advantage over the novice.

[Ken911]

ok so how do i get the dilavar studs out just grab them with vice grips and crank on them?

[ChrisBennet]

Originally posted by Ken911
ok so how do i get the dilavar studs out just grab them with vice grips and crank on them?

It's all detailed in Wayne's engine rebuild book. The studs are held in the case with (red) Loctite which needs to be heated to release it's grip.
-Chris

[ischmitz]

Ken, doublenut them and use lots of heat (propane won't cut it here) at the case while backing them out. You need to melt the loctite in the threads. If one snaps then vice grips are on order

[markwemple]

HAve a lot of patience!! One took me 45 mins. w/ Oxy-acet. No BS!!

[ChrisBennet]

Originally posted by markwemple
HAve a lot of patience!! One took me 45 mins. w/ Oxy-acet. No BS!!

You must not be living right.
I think it takes me a couple of minutes tops using a MAPP torch before the Loctite breaks free. (post '76 motors).
-Chris

[Ken911]

ok cool so i heat the studs or the block?

[ChrisBennet]

Originally posted by Ken911
ok cool so i heat the studs or the block?

Hi Ken,
Did you get Wayne's engine rebuilding book yet?
http://www.101projects.com/911-Rebuild/index.htm
The "party line" is to heat the block inside the cylinder spigot but I've also had good luck heating the stud at the stud to case juncture.
-Chris

[kenikh]

This discussion would be a GREAT sidebar or appendix in the next release of Wayne's book.