For real, I think it just comes down to no definitive numerical outline. Obviously both sides are trying to sell you something. The only 3rd parties that have test data are probably on race teams /mazda teams. (still looking for any examples from mazda race cars). It seems the turblown higher clamp crowd believes clamp is all you need instead of torsional support directly from enlarged studs. The machined crowd aims to get the higher clamp and torsional support to prevent stock dowel damage. Again this is where the gap in readily available data is. I don't see oversizing as a negative and I can do it myself, but I do see where having to have replacement housings re-machined is a problem..... but say you need a new iron, likely you need matching porting from the previous builder anyways. Unless you run stock ports, but to my REW understanding stock ports are rarely used above 400hp when you would normally start looking at studding anyways.

I did see that Adam does suggest that for 400hp~750hp you should do 3-5 machined studs which he sells including machining for around $300. For 700+ He has the full machined 1/2in studding for around 1250 (650 for cnc portion) +shipping

Turblown higher yield (higher clamp) studs go for 600+shipping

 

Agree. I am doing Adams $1250 all in. I again think that maybe overkill, but if I can have more clamp force(if needed) and take out any torsion, I might as well.

It is a good suggestion to use the organic/sprung clutch and clutch flow value. Both are on the list of parts to buy.

 

I was told by an old school builder that this was the reason to do it. But maybe with modern fuel management it's less and less of an issue.

 

Full length dowel pins (hollow / solid or solid / solid with external oil line) plus TB's studs is a good in-between solution.
The engine I bought has stock dowels at the stock location with 2 extra solid full length dowels and TB's studs.

There's also an old school trick recommended to reduce rear plate dowel cracking by leaving out the transmission bolt that goes back there. Don't know if true or myth.

 

What we talk about on late comments that was OEM studs might be weakest in some point but since They fit and be one piece with engine they can absorve power torque and temperature from the dowels. The Turbown studs might be stronger but they might not be able to absorve the same amount of torque and temperature since they are not straight fit and they have room around them while they are in place. Do you have any review on them vs the OEM ones? Lets say somewhere in some power levels and some boost pressures and specific temperatures that you experience any possible issues with the OEM that you fix those issues with Turblown studs?Thank you

 

normal combustion is like ~150-350psi the more hp the higher it is and its pretty gentle
detonation is like 3000psi and there is a shock wave, its going to break stuff.

i did one time find an SAE paper about it, but i didn't save it. for something fundamental you need to go way back
iron pistons too

 

there is also this, when Mazda wanted to use the engine as a chassis member for Lemans, they used a plate on top and a plate on the bottom.


and in some form or other the JDM tuners have had a bottom plate available, Super Now! has a 10mm thick one


and if you still want to machine stuff, i've seen people use 8mm bolts instead of 6mm bolts

 

"Do you have any review on them vs the OEM ones?"

i was very interested in that question.

to the point i sent them and 3 aftermarket studs to a certified testing lab. an expanded treatment of this is on my website but here's the result:

YIELD

OE thru bolts 147,500 psi

Chips Motorsports 199,900

Turblown 185,200

Elite Rotary Shop 78,400

it is my observation that if you overtorque the thrubolts you may get them into a yield state.

 

What are these results tell us?First of all They tell us that we have to forger about elite rotary shop. After that they tell us that between oem studs, turblown studs and chips motorsports studs, since the numbers are too close in case of a detonation event the result is that none of the them will survive and the damage will come accordingly low damage, medium damage and severe damage no matter the strength of them since the detonation event will be much more than all of them and what they can hold. So whats the point to overtorque them into a yield state? And i believe and insist on the oem that since they fit to the engine woth a, way that make the whole engine as one piece they can absorve more vertical and horizontal power levels 8n case of an event in a better way than the others even if the oem are 50000 psi less powerfull

 

general bolt vs stud info applies as well.

The bolts may give wrong torque readings because of the twisting of the bolt itself and the friction effect on the threads, they can also damage front plate threads as they are toqued into them. Studs are not torqued to the front plate just hand tightened or very low torque, the stud is not torqued when tightening the nut so the torque readings are more consistent and reliable and damage to the front thread is reduced unless overtorqued.

As far as choices and their performance, Mazda's bolts have been known to come loose over time while properly installed studs are better in this regard.
Chips have been known to snap at the thread to straight interface, maybe the threads are machined instead of rolled.
You saw Howard's results for each so that leaves Turblown as the better choice, maybe?
There are many engines using Turblown's at high HP levels. Best solution and absolutely required? No. Better than nothing? Possibly. I feel good with my choice of 2 extra full length dowels and TB studs on my semipp.