Last weekend a friend of mine cracked his front iron at the dowel area next to the oil feed for the turbo on his s4 TII block. Needless to say, I was very surprised to see that his front iron cracked and not the rear one, which is the one without any reinforcement. Although he was boosting at 17 psi and only had 1300 miles on it, I expected the rear iron to break at the dowel area.
So, I guess that's pretty much my question: how often do you guys see a front iron crack?

Brian

 

my brothers RE motor crack the front iron as well, i don think its a common thing.

 

Really? How much hp was he putting down? I'm surprised about that because the RE's dowel areas are REALLY thick............unless it got cracked by the oil feed banjo bolt being tightened soo hard that it cracked the iron maybe, and made it weaker? This is the 3rd time I've ever really heard about this in my life. A guy on here with an REW block about 3-4 weeks ago, my friend, and your brother.

 

BDC has cracked at least one, maybe 2-3 I forget. There's a few interesting discussions over on nopistons in the engine building section about cracking irons.

 

I've seen this happen many times.Most times tuning issues.Tuning is off.

I have tuned cars with no pins up to 25 PSI no problem.

 

Which motors were these ? S4, S5 or RE motors ?

Just curious.........

 

After 3 hours of reading mostly on nopistons, it seems to point to misfiring and RFI interference. Alot of guys with Haltech ecu's seem to have had this problem. Here is a link to my other thread:
https://www.rx7club.com/showthread.p...ight=misfiring

 

That's got to be the lamest reason I've heard for cracking end plates as yet!
It does not matter what ecu you're using. If that was the case then from my experience I've seen the most plates crack with the stock T2 ecu then.
Like Rene said above I've seen and tuned many cars that don't have extra dowels that did not crack.
You guys need to stop looking for excuses for taking shortcuts.
The power output 90% the people are at in here, tuning is the main reason for cracking end plates.
If you know that you're using a pre FD, early 13B/20B-RE motor and nothing is done to re-enforce the housings then in the event something goes wrong to cause the plate to crack then don't look for excuses. IT will CRACK! The later FD and 13B/20BRE motors do stand up to more abuse before cracking becomes a problem but also will crack when the abuse is taken pass the design limits of the housings. Even the 1000HP 13B motors with studs and dowels crack plates. Some of those motors also don't even crack the housings around the dowel area. Most of them crack closer to the top and intake port side of the motor and that's mainly from ignition/fueling issues.

 

I was referring to the problem of misfiring at high rpms, not that haltech users crack front irons.

 

(double post)

 

I just went thru this myself.

https://www.rx7club.com/showthread.p...ight=redbaron7

 

Ive even seen a rare plate crack on an All Motor engine,top that off

Thanks crispeed

This is one of my cracks.Life saver,long story.

 

The pics show how poor the casting are on the newer housings. Even the thread area for the oil feed is pitted/porous.
The weak spot on the newer irons. Don't you hate when that happens!
That's not too bad though. I have friends that remove the entire side of the plate to the extent where the water jacket is exposed and even a couple that you can see the rotor!

 

You'd figure the newer they are, the better the manufacturing process........not the other way around

 

That's life.
I hope the aluminum ones are much stronger!

 

Maybe I'm missing something here, but why can't you....................


Use front and rear FD irons and just drill tap the irons to fit the TII intake bolts ?

 

You can, but the runner size and angle are way different. You would also need to adapt the oil oan to fit over the FD rear iron, since the motor mounts go through the pan and into the rear iron.

There are T2 Irons out there with the large dowel casting like FD motors, front and rear. They are quite rare but they pop up in the for sale section every now and then. I have one of the rears.

 

Porting the irons is a must anyhow, so port size and angle can be fixed. Drilling a few holes into the bottom of the iron for the oil pan isn't a big deal either.

Anything else I'm missing here ?

 

If that's the only thing involved, I don't see why more people don't go that route.

Yes, you could just buy a FD motor. But, that would make it too easy.

 

I don't see why more people don't buy the thick casting FC irons and be done with it. There was a set of them that sold for 300 in the parts section last week.

 

My friend who cracked his front iron got a set of front and rear series 5 TII irons in great shape, and although the rear dowel area was definitely the more rare thicker dowel area with the added reinforcement that goes from the landing to the oil pedestal, his supposedly matched front iron was the same thickness as the s4 he had.

 

All 86 and newer irons come from factory now with the large casting. Even the 6-port ones.

 

Interesting.........but in 2 ways. The 1st is that it's great that they do that, but the 2nd one is that you mentioned how the casting is poor on the newer ones.
That's no fun...

 

+1 Correct.

Trying to mix and match the FC and FD irons won't work. As previously mentioned, the angles are way different not to mention runner size as well as mounting points. It just won't work.

B

 

As a general rule, the best ones come out first. After that, the beancounters have their way when they see that the failure rate is better than acceptable, so they can start cheaping out and save some money. Plus, tooling wears out, casting forms degrade, etc.

My favorite example is when Jeep started putting stickers over the stamped "Jeep" on the sides of the CJs. (70's I think?) The tooling was so worn out that the "e"s were coming out as plain circles. These are known as "Joop"s.