Hey guys Imm been having some trouble
with my 91 engine. Had it rebuilt with 3mm Hurley seals
It seems to crack the endplate or backplate where the
DOWEL pins stop through the oil line. It's been very
painfull now Its the 3rd time it's happening. I had all my
plates laped down and the dowel pins as well. My
engine had a full rebuild. For some reason when
pushing over 15 - 18PSI I get the endplate
or backplate cracked exactly where the dowel pins end on the oil line. My oil pressure is 4.5 - 5.0 BAR.



Any suggestion comments. It will be MUCH of HELP!!!

My tension bolts are tightened to 39 NM. I can't think of
anything else at the moment.

Thanks!!

 

we had the same problem when we started to push over 400.

 

how much power are you pushing? stock turbo? I think that is a common problem with HIGH HP, like 400+. you are probably running too lean or with too much timming. the cracking is probably being assisted by slight detonation.

 

I'mm using a Garett turbo front A/R 0.72 turbine
76mm /112mm exhaust A/R 1.22 and pushing 15-19Psi
But I can't hear detonation. using a halteck E6K.
Probably round a bout 400 - 480HP. The engine is street
ported

 

Hey guys the oil line on the End plate and back plate
where the dowel pins are has nothing to do with the
combustion chamber does it????

 

here's a reply from brain cain (know FC guy, has 420 rwhp)

"Like any other engine, it goes through something called torsional vibration. Infact, it's worse w/ rotary engines.
I think it's what compromises the weak points in the engine setup. The engine is trying to twist apart per the cycles of combustion force created
Engine knock makes the problem a million times worse and is what actually does it in my opinion. That's why people pin the engines: to keep the housings from shifting
the oil filter stand area where the tubular dowel pin is as well as the oil feed to the turbocharger where the dowel pin is. The iron there isn't very thick and is the first to crack and then shatter."


the 3rd gen rew motor is much stronger in those areas.

 

ok that sounds like a good rule... What do u mean
by " Thats why people pin there engine" ?? What do
you suggest. Lower the timing less than 12degrees or
lower the pressure????

P.S.. that's Excactly what is happening to my engine.
Imm getting that cracks exactly at those point that
you mentioned... ?? Suggestions???

 

I've never delt with the problem myself (my car is still slow ). but how have you tuned the haltech? using wide band o2? on a dyno? what is your A/F ratio at WOT?

I have no idea what the timming should be, others will chip in with more info, I've never tuned a computer.

 

i don't think your having a timing problem. it simply is the end plates are known to be weak around that hp. nothing new thats just the way it is. i can post a pic to show you the difference between the two. the rew or jc side housings have about a 1/4" more surrounding metal in that area. thats the reason we strictly use rew or in my case cosmo steels.

 

ping-a-ping-a-pingy

how many guys do you know that have cracked end plates with stock 2mm seals? there are a few but not a helluva lot, you see when you ping/detonate the combustion chamber pressures are around 4 times what they usually are. so the apex seals normally gives in, but with stronger apex seals the next weakest link goes. what happens is the rotor housing distorts slightly and the combustion side of the housing 'walks' outwards (there are some pics somewhere showing 'walk' marks on a housing) the area around the top dowel gets the most load on it and therefore cracks. According to Chris (Crispeed) you dont need extra dowels until you get to around 650rwhp. According to Peter (RICE RACING) you dont need them at all, he has a 13B making 830HP with no extra dowels and its not cracking plates.

It is the result of detonation or pre ignition at anything under 650rwhp. anything above that, you can choose who you want to believe.

check your A/F ratios, your intake air temps, your ignition timing etc etc etc cause one or more of them is making it pre ignite or ping.

there is a number of guys out there making 500+HP outta S4 13BT blocks, they just go to prove that its not the end plate which is the problem, its the tuning.

 

who is making 500+ out of a 13bt block on a street car?

 

Pinning the engine is the thing to do. The next cracked thing will be your rear housing right by the oil tower.

 

Um, One question.. What heat range spark plug are you running? We cracked the rear plate on my freinds engine, and believe it was because either we where running to hot of a plug. Or 0 split timming.. You might want to try running like 5 degrees split on your next engine. and 10.5 plugs.



-Zach

 

This is good info that a lot of people would overlook.

Brad

 

nothing of that cause the rear iron crack. The cause is the twist of the engine when you accelerates and too much boost is created. The only 2 things that you can do to solve that is replace the tension bolts with the longs case studs. The other solution is what we call here in PR the "dowel pin solution". That consist in adding 4 extra dowel pins to the engine. This modifications supports over 800hp.

 

Why are we even debating this.

The dowel pin area usually cracks due to too much power or detonation, there are so many debates on what exactly always causes it, and on different ways to prevent it.