coldy13

Am I missing something huge here, because this seems like an easy task that can be done in any decent machine shop. You enlarge the holes the tension bolts run though, then machine tubes from a hard metal to slide in perfectly and allow the tension bolts to run through them. Stock engines have 4 dowel pins that are 1/2 length of the engine each. Is there any reason for this other than ease of assembly? Why not make them run through the entire engine instead? Seems like a better idea to me. I know that it would take quite a few hours to machine the housings and machine the tubes to fit perfectly, but other than that I don't see why dowel pinning is considered so hard. Everytime I see it mentioned on here it's considered very expensive and hard to do. I feel like I'm either completely missing something here, or these people don't really know what they're talking about.

RETed

Oh, I'd like to see you do it pretty easily.
If you find a machine shop that calls this easy and charges under $200, please tell us!

Drilling holes is not the hard part.  Having 3 housings to line up perfectly is the pain in the *** part.



-Ted

coldy13

Yay, finally a reply after almost 30 views

coldy13

Why would that be difficult at all? Just put in the stock dowel pins and it would line up all the housings perfectly. Then clamp them all together and bore them all out. Hell, there's no reason that you couldn't do each one of them seperatly if you really wanted, but it would take much more time. $200 isn't really that much actually, for some reason I always thought is cost much more. But I'll be doing mine for free. Dad is foreman at a machine shop so when they're not busy I can come use some of the machines. Once I do mine engine I might start building engines for other people, but I want to test everything on mine first to make sure it works right.

peejay

You can't "clamp 'em together and bore 'em out". For one thing, you don't want the new dowel holes to be super deep, you want them just deep enough to hold the dowels (Saturn cylinder head dowels seem like just the right size, btw) plus a little room for heat expansion. Just to be safe. For another, look at how long the tension bolts are. You'd have to drill that deeply through the whole stack, and you'd have to get everything *super* precise so you drill the long bigass hole straight.

The main expense IMO would be in setting up fixtures. But once you set up fixtures (one of the things on my To Do list, after I get the mill set up in the Evil Engine Lair) then you could just set the housings up in the fixtures and mill 'em. And then make sure that it all goes together easily (wouldn't want to pre-stress the housings from the dowel holes being even slightly out of alignment), and scrap the housings if it doesn't...

$200 seems way low, even for my rates.

rxrotary2_7

yeah $200 is a tad low.
i just went and uploaded these pics just for you coldy.

rxrotary2_7

RacerXtreme7

iTrader: (2)

rxrotary2_7

WOW, ohh I wish I had access to one............

Looks like you got it dead nutz centered..lol.. good work.

~Mike..............

coldy13

Nice pics, we've got about 4-6 machines that look a lot like that one I'll take pics of some of the machines next time I go into the shop.

PDF

Hey, it's easy to dowel. I add 4 for about $150us. You're on the right track. I use a radial arm drill and clamp half the engine together(centre plate, housing, front plate) with the factory dowels in place. Run a 15.5 long series drill through until 6mm into the front plate(any deeper and you will lose too much thread) then a 16mm H7 machine reamer. Do the same with the other half of the engine using the centre plate again being careful to line the holes up with the reamer then drilling. Go 17mm into the rear plate to make up for the depth not drilled into the front plate.

This method is for factory dowels(I use them because I have heaps) but there is no reason why you can't make full length dowels. Reamer tolerance is exactly the same as Mazda's holes and if done right the engine is no different to assemble than standard. e.g no tapping housings together

rxrotary2_7

not me. my friend Jay. he is AMAZING behind a machine.

Rx7carl

Or you could go with what I think is an even stronger and easier route. http://www.gurumotorsports.com/ They have 12mm (iirc) studs to replace the tension bolts. These fit snugly in the housing holes so in essence you end up with 18 or 19 "dowel pins". No machining necessary.

frode

I am interested in doing this. Please post more

coldy13

****, why the fu<k didn't I think of that! So then all you have to do it enlarge the holes/threads they go into and you'd be done.

now

iTrader: (1)

i still strongly feel that these above studs will not
allow the same expansion as the stock tension bolts
and will cause problems in the long run, floating pins
is the way to go i think.
also if the studs are of a tight enough clearance to do any
good corrosion will cause them to become stuck in the
holes and you will never get the motor apart again.
mazda uses floating dowels for a reason one of which
is the ability to use a puller to remove stuck pins.

matt

DamonB

Hey, someone bored a big *** hole in the side of a perfectly good housing

coldy13

Even if they did manage to become a bit corroded, it won't matter. When you loosen the bolt it will break loose the corrosion and you'll be able to pull it right out.

RETed

There are more than ones way of doing this.
The obvious one is to run brand new 13B dowels through side-rotor-side housings just like the stock ones.
If you don't have quality machining equipment, try boring a 80mm long hole down the rotor housing with proper evacuating support equipment.&nbsp; Metal chips tend to score the bore or in extreme cases cause the boring bit to seize in the bore.&nbsp; I do not call a "sloppy" job like this a good one.



-Ted

osssh

Great thread, looking at giving it a go on the next engine i build. I may even consider the stud kit, looks the goods, Guru make some great products.

some pics of the stud kit:









some info about it:

High strength stud kit eliminates the need for doweling the engine block.
All studs act as dowels which massively increases torsionial strength 70%. Rotor housing deflection reduced - increases apex seal life. Less material machined from housings and plates than with doweling, reducing the possibility of cracking.

High boost engine expansion reduced.

Studs are less prone to stretching under high boost applications. More accurate tensioning of engine.

Less chance of bolt breakage. High quality 12-point nuts rated at 180,000 PSI tensile strength. Studs manufactured from 4140 chrome moly, heat treated, centreless ground and black oxided.

Engine must be accurately drilled reamed & tapped to give 0.1mm clearance.

Standard replacement 13B kits available with no modifications.

20B kits available soon.

looking at $395.50 AUS.


more feedback would be good.

80-CU.IN.T

Studs are the way to go for maximum strength in my opinion. I checked out Guru Racing's booth at 7 Stock. They have QUALITY products. I was very impressed. Beautifully machined and heat treated pieces. All I can say is that the owner has no life. He must spend his entire life in his machine shop. Gots ta have a very understanding wife or girl friend for that. I guess I am jealous.

Kenku

All righty... I've got a question now. I think I get the dowel pinning stuff... but how do you make those studs go into the end plate? Interference fit? 'cause, that just looks... like it would work really well.

now

iTrader: (1)

how is leakage around the threads on the nuts of the stud kit handled? they should have been cap nuts.

matt

Rx7carl

osssh, man I was lookin for pics of that on their site and couldnt find any, thanks for posting them.

80-CU.IN.T, I was also highly impressed with the stuff GURU brought to SS6. And the guys were very friendly, and knoweledgable.

Kenku, from what they told me, you have to accurately drill and re-tap the endplate for the larger new thread size, then they screw in.

now, good point, I didnt bring that up when speaking to them. Drop them an email, Im sure they'll have an answer for you.

Kenku

Hmm, okay. From the pics, it's not that clear to me that they're threaded on both ends.

Rx7carl

Yea your right, they look smooth on one end. Maybe my mind is going again, I dunno.