Oil bypass modification
 

I saw several mentions to the bypass mod in chapter 3 and 4 but I couldn't find any specifics on what size hole to drill. Anybody know?

BTW, the new book is awesome! Definitely a must have.

BK

Yikes, you need to send your case out to a machine shop anyways - unless you have a Bridgeport mill in your garage, you shouldn't attempt this yourself.

I purposely left this information out of the book, because this is *not* a procedure that you want to perform on your own. One slip-up and your entire case is ruined.

-Wayne

Wayne,
I do not agree with this. I would publish the info, and include a note that it is not recommended for the typical home rebuilder. I do have a bridgeport mill and many others do as well.

Jack, well you and I disagree on a lot of things. Probably .01% of the people reading my book will have their own Bridgeport.

I stand by my original statement - you should not use a hand drill to make this modification.

-Wayne

Yea, I don't have a milll at home but I do have access to a machine shop.

Thanks for the info!!

BK

Wayne,
I have to agree with Jack on this one, most of your target audience (with your engine book) are hard core diy's. Don't under estimate our talents, skills and especially our TOOLS! I grew up in a small town (Tool City) where if you didn't have a bridgeport in your garage you were wierd! Machining isn't rocket science, its like most anything- education, hands-on training and lots of experience.
Biff

I am going to drill out the oil bypass on my 2.7. I have 2 different specs for the size of the hole to drill, 12mm or .375". These are different enough to be significant. Any one know which is right? A measurement off any original porsche case which came from the factory with the mod would provide the answer.
Also, how does one check the oil squirters to see if they are clear or pluged up?SmileWavy

The oil squirter part is in 'the book', and recently on this section of the BB in detail.

Yikes, I do not recommend that people do their own oil-bypass mods themselves. It's only a few bucks to get the machine shop to do it, and they do it all day long. The changes of messing up your case are great.

Contrary to what was previously posted, I would estimate that less than 2-3% of the readers of the Engine Book have a milling machine in their garage. It's also very difficult to properly do the right-angle drilling and tapping of the plug hole in the case without the right specialty tools. Definitely not something I'd recommend...

-Wayne

Wayne,

As you know, the best way to hire a machine shop to do custom work properly is either with a good set of written instructions or even better, blueprints.

Please consider including modification information in the next edition of your book. It will help both the machine shop and the owner give/get the best service, making everyone happy.

Otherwise the pat answer is "send your case, heads, etc to California". Shipping costs might equal the machining costs for those of us that live in areas where parking the car for the winter is an accepted practice.

And the case isn't necessarily ruined. If you bozo the job, a little welding and alls right with the world. (or the machine shop you should have hired in the first place has even more billable work!)

Thanks for providing a great forum.

Fin

drill size
 

Hello all.

I have done this several times amd , based on the Factry practice, use a 12mm drill to finish.

Frankly, I do not think it is critical....

But as indicated, great care is needed.. I pilot with 8mm.

And I do admit to doing it freehand, but am NOT recommending this.. I do a lot of machine work...and do not want to set up a special just for this..

I would be very grateful if anyone would divulge the Correct set up for the squirters.. i have done it again by copying the Factry, but do not have the numbers...

Kind regards
David

I don't have this info handy - I suppose I could ask Walt or another machine shop...

-Wayne

This is for those people who do things themselves simply for the knowledge and pleasure of it (or those who are very cheap). Those who would rather have someone else do machine work need not read any further.

Any case which needs a oil by pass mod (7R or earlier I believe) is very cheap unless it already has updates, so find one without any updates just in case something goes wrong.

Doing the oil bypass mod is easy. There is plenty of extra metal all around where the hole goes, unless you miss by more than 6 mm (on a 12mm hole) there will be no problems. The 12mm hole goes about 28deg off vertical. The only way to hurt the case is for the sealing lip for the oil pump passage to be damaged.

Just grab any variable speed hand drill with a small end mill to start the hole. Calculate where the start of the hole must be. Drill in slightly with the end mill. Then drill all the way with a standard drill. Check to make sure the hole is where it belongs, if it isn't adjust with an endmill (I did not have to make any adjustments). Go up 1 drill size at a time until 12mm or there abouts is achieved.
Total time for drilling , 10 min.

Then the side hole must be tapped for the plug. The hole is already the right size for the tap, no drilling is needed. A slight modification to a standard tap and 10mm wrench is needed. Then carefully start tap, use plenty of oil and remave tap to clean shavings a few times in the tapping process.
10 min to modify tap and wrench.
10 min to tap hole.

Total cost $5 tap, $1.5 plug.
Total time 30 min

PS: Anyone who want to use my modified tap and wrench, just email me.

What size of tap please?
Bob

1/4 " pipe plug and tap.

Yay! A great explaination and not rocket science, A few questions
Where do you get the plugs from? What material are they made from?
and do you glue them? When you modify a tap do you start with and inter or taper and just shorten it?

Neven (in NZ a long way from a californian machine shop)

The plug is brass with a square head, not sure if that is what others use but it should aviod corrosion. The plug and tap can be bought at any plumbing supply store or hardware store, although I am not sure about NZ. The size is 1/4 NPT, that is a pipe thread spec so the actual diameter is about 1/2 inch. I think the best threadlocker is Loctite RED 271, the 272 (high temp) will degrade with oil contact.
The tap had to be shortened to fit in the case, and the open end wrench head bent to allow rotation of the tap in the limited space of the case.

Wayne,

I think this info should be made available, so that it can be verified as accurate. Its then up to the individual to go to a qualified machine shop, which there are many, or to chance doing it himself, against recommendations, at least its their choice at that point.

In fact all modifications should be spelled out, in detail. Then people could state that they tried it but ended up paying to weld the case back up or whatever. If a cnc is REALLY required, then it will be so stated and people can plan accordingly. People can be REALLY clever and get around some of the most difficult tasks with the most creative solutions. Vetting these on a forum, with the appropriate disclaimers, is beneficial to all.

My machine shop performed this mod with hand tools on a bench in about 10 minutes while I watched. It's not rocket science.

(Caveat: the guy's been doing 'em for 20 years...)