I am elbow deep in replacing my old set of twins with a newer low mileage set.
The problem I am having is when I try to install the new set I can't get the turbos to mount on the studs. I can get the back on, or the front, but not both. It is just a fraction off.
I was wondering if it makes sense to remove one or two of the front studs, then mount the turbos, and install the studs after the turbo is semi bolted up?
I left the old studs in the manifold, only one screwed out by itself. They all look to be in good shape (the engine was rebuilt around 15k ago), even the nuts are in good shape (but i am using new). I have all new studs, so that's not an issue. I am just wondering if I can get the stud tight enough.

 

If you can pull the studs and you have new replacement studs, pull them and replace them.

When I pulled my turbos way back, they all seized onto the nuts so thats how they came out naturally.

 

Just try to redrill the holes with the next size drill like 1/32 or 1/16 bigger I'm sure that there is more than enough material on the turbos.

 

Well, I can do that, but I am not sure why. I understand why you shouldn't reuse the nuts, but what is wrong with reusing the studs?
And I still have the original question, can I install one or two of the studs after I have the turbos mounted?

 

fcapo, I don't need to redrill the holes, everything is fine. It's just when I mount the turbos on the manifold, the studs aren't lining up perfect. They are off just enough to keep the turbos from slipping on to them. I could force it, but I think that will tear up the threads.

 

Do not listen to this guy. There is no reason to even think to do this.

Maybe try and pull a few out, most of the time when removing the turbos most of the studs will come out with the nuts anyway, so there is no harm in taking them out. It just makes installing the gaskets between the exhaust manifold and turbos a PITA when there are no studs there to hold the gaskets on.

 

Stokedxiv, that's what I am thinking. If I pulled the front one or two, and then mounted the turbos I think I could get it to line up properly. I was just hesitant to do that, because I didn't know if you could get the new studs in good enough (tight enough) having to mount them "through" the turbo mounting. If that makes sense.
Basically, what I am asking is can you put the new studs in AFTER you have the turbos mounted on the engine?

 

As Stokedxiv mentioned, yes you can. However, it makes it more difficult to keep the gaskets in place doing so. Have you tried just getting the turbo in place and giving it a slight bang to pop it on? If you put the front on, you won't get the rear on, and vice verse. They need to go on at the same time.

 

I have tried forcing a little, but I was scared to put too much force on it.
I will try that, but I think if I just remove one or two studs, I might be able to keep the gasket on, but maybe not.
I am going to work on it this afternoon.

 

The worst that could happen is that I fubar a stud or two, and I have plenty of spares.

 

Hanman.... I recently rebuilt my 13B w/stock twins.... here's the thread link ---> https://www.rx7club.com/3rd-generation-specific-1993-2002-16/stock-13b-rebuild-w-sequential-twins-709438/

Now... to answer your questions...

1. The studs are made of (Probably spelled wrong) "Inconel" Pronounced "Ink-A-Nell". The metal seems to take a temper that is extremely brittle... once they've been exposed to the High-Heat exhaust environment.... the threads especially show the result when the nuts are removed... the thread surfaces experience cracking and metal chip loss as the nuts are removed. The result is a "Notchy-feel" when you reuse them and go to re-install nuts and torque em down. The brittle nature of the metal at this point is further damaged when trying to slip turbos on/off as a unit... So, I'd recommend replacing the studs... there's 7 that take 14mm nuts ( I think... going off memory here) and "1" 12mm nut-sized stud on the rear/bottom exhaust boss of the turbo assembly cast iron housing... see the picture --->
https://www.rx7club.com/attachment.p...1&d=1196624113

Anyway, if you install most of the studs except for that 12mm one on the rear, bottom and the rear-lower corner 14mm stud... your assembly should slip into places. Then you should be able to run a few nuts on and snug everthing into place to hold it... install the final studs by hand and install the nuts... But you're Right... this assembly is a really tight, exact fitment.

if you need to gently muscle the assembly around a little to screw in those remaining studs... use a brass punch... you're less likely to damage the threads in the block..

Anyway, hope that helps... if you have any questions, pm me....

Good luck!

 

Sounds like the turbos were taken apart and weren't aligned properly to the center section (the portion that the DP bolts to)... Or they are not properly matched to the manifold.

In my experience building my twins, I came across a center section that was slightly less in width than the others, which caused an alignment issue. I had to swap it out with one of the many I collected.

I think you're problem is going to lie in the center section or a slight misalignment of the primary and secondary with respect to the center section.

The way to align them is to take the manifold off of the block, clamp it to a table. Then, with the bolts that hold the hot sides to the center section loosened, bolt the turbos to the manifold (without forcing them on the studs, I didn't use the gaskets of this procedure). Then tighten the center section bolts, remove the turbos from the manifold and proceed normally.

If you still have issues or it wouldn't go on even with the bolts loosened, the center section's dimensions may be slightly different. Mine was too narrow, which brought the prim and sec closer together.

 

Alexdimen:

I think Hanman is talking about the entire assembled unit, i.e. as a new OEM Turbo unit would be supplied direct from Mazda... At least, that's how I understand it... of course, I could be wrong... But, I don't think so...

" The problem I am having is when I try to install the new set I can't get the turbos to mount on the studs. I can get the back on, or the front, but not both. It is just a fraction off.
I was wondering if it makes sense to remove one or two of the front studs, then mount the turbos, and install the studs after the turbo is semi bolted up? "


Maybe Hanman could clear this up... for us..

 

I know he's talking about a whole set. The only thing I can think of that can vary the hole pattern, aside from the hole patterns on the turbo flanges themselves, is a different center section. I'm not talking about a CHRA, but a center section with the DP flange on it. I've found variations in the width of these and ran into a similar problem because of it.

I understand he hasn't been mixing parts from different assemblies like I have, but someone else may have fiddled with it in the past or it may be a set with a narrower center section like I ran across.

I came across some other strange stuff too... like holes cast in the turbos for the heat shield bolts (M6X1.0) that were never drilled or tapped. Had to have a machine shop finish them because they were the best hot sides I had found and wanted to use them. The hard *** cast metal destroyed my drill bits.

 

well, I pulled the 12mm stud out, and one more next to it, and the whole assembly slipped right on. I am still in the process, but so far so good.
I truly appreciate the advice.

 

My only regret is I didn't rob a bank and just buy some BNR's and do this one and only one time.
This has been a pretty good sized job.

 

I always replace the turbo studs and nuts. You might get away with reusing them once or twice, but eventually they will strip or break and you will have a huge pain on your hands.

 

I understand, but remember, these studs have only been in for 15k miles.
I hope to replace these turbos with something else (BNR's or single) in the next 25k or so. At that point I will replace all of the studs.

 

I always replace the turbo studs and nuts. You might get away with reusing them once or twice, but eventually they will strip or break and you will have a huge pain on your hands.