Hi all,
Seeking some help of the M20 Gods on here. Very new to forced induction so excuse my stupidity in advance.
Some background info: Recently blew my M20B25 (bought used from someone) which was stock except ARP studs and an MLS HG. Ended up melting a piston in Cyl 5 and blowing the rings / ring lands in 1 & 6. I think either the timing was too aggressive but not sure exactly how it happened. Instead of rebuilding bottom end, I found a stock ETA bottom end and wanting to try the 'budget stroker' out, I re-used the 885 Head from the 2.5 on this with the ARP studs and ran it with an Elring HG.
With the help of Panici in the passenger seat tuning the MS2PNP, the car seemed to be handling okay. No real problems except some blow-by. Hoping to solve at least some of this with a catch can set up soon.
The real problem came when we were doing a 5th gear pull. Started at around 90km/h and pulled to ~ 200. Got to around 6k rpm and a huge cloud of smoke let out the back and the temp gauge shot right up. Pulled over on the side of the highway and popped the hood to find coolant all over the drivers side of the bay except in the expansion tank. Unfortunately we had no coolant with us but shut everything off and let it cool down for a while. Tried again to start and had no luck whatsoever. It sounded like there was some compression still but for sure a couple of cylinders were missing so didn't try any more. The car didn't see any more than 8.7psi in this run and the timing map showed it at 13deg. I'll throw up some screenshots of the timing, fuel and AFR target maps tonight.
SO,
In my limited knowledge I'm thinking it could be one of three things:
1. Cylinder head wasn't flat enough or is cracked without me knowing - When I pulled the head from the 2.5 block it had very recently been machined and I couldn't see any visual signs of cracks. Checked with a straight edge but no feeler gauges and *looked* ok. (stupid mistake I know)
2. Head gasket wasn't seated properly or incorrectly installed (I prepped both surfaces using a 3M Roloc Bristle disc (Yellow 80 Grit) and made sure both were clean of gasket material before install)
3. The studs weren't torqued enough - I did 3 equal steps to 70 ft/lbs but DIDN'T retorque as I'm learning some people demand doing after a heat cycle.
If anyone can help I'd really appreciate it. Current plan is to pull the head, already ordered an OEM BMW Headgasket, I'll get the head pressure tested and resurfaced to ensure flat and then try again with lower boost?
Seeking some help of the M20 Gods on here. Very new to forced induction so excuse my stupidity in advance.
Some background info: Recently blew my M20B25 (bought used from someone) which was stock except ARP studs and an MLS HG. Ended up melting a piston in Cyl 5 and blowing the rings / ring lands in 1 & 6. I think either the timing was too aggressive but not sure exactly how it happened. Instead of rebuilding bottom end, I found a stock ETA bottom end and wanting to try the 'budget stroker' out, I re-used the 885 Head from the 2.5 on this with the ARP studs and ran it with an Elring HG.
With the help of Panici in the passenger seat tuning the MS2PNP, the car seemed to be handling okay. No real problems except some blow-by. Hoping to solve at least some of this with a catch can set up soon.
The real problem came when we were doing a 5th gear pull. Started at around 90km/h and pulled to ~ 200. Got to around 6k rpm and a huge cloud of smoke let out the back and the temp gauge shot right up. Pulled over on the side of the highway and popped the hood to find coolant all over the drivers side of the bay except in the expansion tank. Unfortunately we had no coolant with us but shut everything off and let it cool down for a while. Tried again to start and had no luck whatsoever. It sounded like there was some compression still but for sure a couple of cylinders were missing so didn't try any more. The car didn't see any more than 8.7psi in this run and the timing map showed it at 13deg. I'll throw up some screenshots of the timing, fuel and AFR target maps tonight.
SO,
In my limited knowledge I'm thinking it could be one of three things:
1. Cylinder head wasn't flat enough or is cracked without me knowing - When I pulled the head from the 2.5 block it had very recently been machined and I couldn't see any visual signs of cracks. Checked with a straight edge but no feeler gauges and *looked* ok. (stupid mistake I know)
2. Head gasket wasn't seated properly or incorrectly installed (I prepped both surfaces using a 3M Roloc Bristle disc (Yellow 80 Grit) and made sure both were clean of gasket material before install)
3. The studs weren't torqued enough - I did 3 equal steps to 70 ft/lbs but DIDN'T retorque as I'm learning some people demand doing after a heat cycle.
If anyone can help I'd really appreciate it. Current plan is to pull the head, already ordered an OEM BMW Headgasket, I'll get the head pressure tested and resurfaced to ensure flat and then try again with lower boost?
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