ARP Main Studs vs MBSP vs BP05
 

I was wondering if anyone else has had this problem. I bought ARP Main Studs for a Miata, and they're too tall, causing an interference issue with the MBSP. I had to drill holes in the MBSP to clearance the studs and let them protrude through so that the MBSP would sit flat on the block and main bearing caps.

ARP main stud interference
http://i844.photobucket.com/albums/a...d/IMAG0784.jpg

What it causes
http://i844.photobucket.com/albums/a...d/IMAG0787.jpg

drilled holes in MBSP and it sits flat and the bolt holes now line up.
http://i844.photobucket.com/albums/a...dclearance.jpg


Anyone else ever had an issue like this? I'm building a 93 protege BP05. The MBSP has BP01 stamped on it, and the main studs were for a Miata BP. Yes, I did put the studs in the block until they bottomed out.


Very sorry about the bad pics, my camera lens is scratched up pretty bad, I'm trying to fix that too..

Did you clean and chase the bolt holes first?

Yes, many of the Miata vendors have a disclaimer up with the ARP studs, this one taken from MiataRoadster:

The machine shop that built my engine used that method without issue. Although the other accepted method is to add holes in the MBSP as you did.

Ah hah, well it is very good to know I'm not the only one who has ran into this problem. Thank you sir, props given for good info.


@bogussvo, yes I did chase EVERY bolt hole on the block and head, and every bolt I've put back on this engine has been cleaned. There's alot of 10x1.25's ! I think I ran through 4 different 10x1.25 tap and dye bits, probably an overkill but they tend to dull out.

You should be using special thread chase taps and not regular cutting taps. You have to be very careful with regular cutting taps to not cut into the metal and loosen up the thread fit.

--Ferdi

Woops.. maybe by next time ill know the difference. I don't think I cut much metal out of the holes, it was .mainly just old oil/gunk and fresh paint I got in the holes.

I had already assembled my shortblock before finding this interference.

I called up ARP to find out if they could supply bolts 0.120" shorter. They didn't stock anything. I asked if I could trim the bolts by using a grinder and then chase the threads. He thought that this could be done as long as I was careful not to heat up the bolt (which would ruin the heat treat) and warned me not to use a standard tap/die ti chase the threads (as thes threads are rolled and a die would cause sharp edges which would weaken the bolt; instead, he said to use an extra nut to chase the threads. A better pan would be to chuck them in a lathe and turn them to shorten them.

After reading this thread, I decided to just clearance my tray/saddle-brace. What a bad idea... first, it took all morning to get the holes right and the saddle cleaned of metal shavings. second, did I get it all cleaned out? I don't know... I think so. The problem is that the saddle consists of two pieces of sheet metal that are spot welded together. This creates a potential space between the layers that might trap metal shavings. https://cimg8.ibsrv.net/gimg/www.mia...aef8ad349b.jpgclearanced tray
https://cimg0.ibsrv.net/gimg/www.mia...fa340db971.jpg
https://cimg1.ibsrv.net/gimg/www.mia...748514ff92.jpg
https://cimg2.ibsrv.net/gimg/www.mia...ef3165c92d.jpg
I guess the oil filter would catch the shavings before they hit the bearings, ...but what about that nice new billet pump?

Yup. I had the same annoyance. I used lots of water, air and a tried my best to make sure there were no shavings.

I grind the bottom part of the stud and chase it. i dont think you are going to weaken it at the last 3 threads in the block enough to matter. Id be afraid that if you messed with the top part, your nut torque could be affected by any burrs that are left behind.