Competition High EGTs vs. High Boost

[BCarmicle]

Which will hurt engine life more, High EGTs(1400-1900) or High Boost

Pressure(60-80psi)? Since I've had the twins on EGTs have been way down. With the single I could hit about 1800 degrees and with the twins I can't get over 1400 degrees. My single was wastegated at 40psi and with the twins I can hit 80psi(that as high as the gauge goes). I only have ARP studs in the head and when I hit 70psi or above I can sometimes hear more of a rattle sound coming from the head. Is there anyway to tell if the head has been partially blown?



Brandon

 

[lmills]

do you mean you are running 80 psi with just the MLS head gasket and no o-rings?

 

[BCarmicle]

Yeah, but have only hit 80psi once. I try to keep it under 65psi most of the time. I was told that with ARP studs the head gasket should be okay. I know I'm at risk of blowing the head but just trying to see how much boost it will handle with my current setup. If it blows then I'll do the 0-ringing.

 

[mattymac]

I thought that studs and the stock MLS HG is good to 80 pretty easy? Piers had his at high 60's with just stock headbolts.

 

[lmills]

the discussion the other week they said Piers felt they were ok to 70-75 psi.

 

[BCarmicle]

the discussion the other week they said Piers felt they were ok to 70-75 psi.

Is that using stock headbolts or ARP studs?

 

[lmills]

They were saying that Piers was safely running 60 psi with stock bolts, but that he felt you could get by with 70-75 with studs. However, I believe this was hearsay. I don't think Piers posted it himself. I believe another member might have posted that. It was in the thread about O-ringing that was going around about 2 weeks ago

 

[Idaho CTD]

High egt typically has a more detrimental short term effect than high boost. High boost will beat out bearings over time and potentially cause headgasket issues. EGT can melt pistons, crack heads, and kill turbos.

 

[mattymac]

Hey Nathan, Did you have a headgasket issue with your truck over the weekend?

 

[Idaho CTD]

I'm not 100% sure I didn't blow some combustion into the coolant but the reservior level never went up. I actually lost a freeze plug in the back of the block. It totally blew out so I lost almost all my coolant in a matter of seconds. Short of pulling the head I dont know if there was any internal damage to the motor. I'm going to try and get a soft plug into the truck and run it a little to see if it is knocking before I drop the transmission to put a new freeze plug in. If the truck knocks then I guess the motor will have to be replaced. Not my idea of fun. I know there was a recall for freeze plugs on some of the 04. 5's but I never received a notice.

 

[BCarmicle]

Nathan,



At what boost level did this happen? Keep us updated on what you find out.



Brandon

 

[Idaho CTD]

Brandon,



I dont know exactly when it happened to tell you the boost numbers. I would bet they were 50psi or so. I just got the soft plug in the truck and I'm going to go get some distilled water for the rad. Then I'll fire it up and listen for the knock. If that is okay and it's not leaking I'll take it for a spin. Then I'll pull the transmission and put a hard plug in it when I get a chance, providing everything is ok. I would recommend everyone change to green antifreeze so you dont mistake it for transmission fluid like I did. The orange stuff they come with is even oily like ATF just not as dark. They say it is long life antifreeze but in my case it might be short life. We'll see.



Nathan

 

[Idaho CTD]

I got the hard plug in yesterday. On the way to Canada the soft plug blew out and we had to be towed. Thanks to Lenny of DDP for that. Also thanks for the use of his lift all day yesterday (the first plug didn't cooperate). I used a little sticky stuff so it wont come out again. The motor did seems to have a little more knocking than it previously had so when I get home I will pull the head and check for damage.

 

[MCummings]

Nathan, I know of another 3rd gen truck that is having alot of problems keeping the freeze plugs in his truck too.



It's the passenger side, rear plug. Keeps popping out under power.



Any idea's ?



Merrick

 

[Idaho CTD]

Merrick,



I used some bearing retaining liquid on mine. It's good for up to 400* and wont break down in water. This afternoon I'll put water in it and take it for a spin. That particular plug I didn't want it to come out again because unless your watching in the mirrors or the water temps you wont know it blew. Yesterday I saw the water pouring out but sunday I didn't. There are 5 of those plugs in the block so to glue one in basically permanent doesn't bother me. I bought a few extra plugs so if another blows I have spares. My personal opinion is it was a factory defect. I miked the hole though and it came out ok but other than a blown headgasket there is no other reason it should have popped (BTW the hole size fron Cummins is 57. 8mm). With a blown headgasket you would think other thing would give before the freeze plug. The rad cap is rated for 16psi and it never blew nor was the reservour level up. BTW there was a recall on some 04. 5's for this particular issue right after I bought my truck and they say it doesn't cover my truck but I'm sceptical.



Nathan

 

[Turbo Thom]

50 lbs of boost day in and day out is all the stock head gasket can take. And even that won't last to long. Call Cummins and ask. You can re-torque the head with bolts and last a little longer but the EGT's will get ya. On the exhaust side the gasket just fries. Drys out, and when the boost hits it the powder the gasket has turned to will not take it. Then out comes the water. Really, I thing the heat of the exhaust does more harm the the boost. But if the head is not flat and the bolts not correct it can't hold. O-ring the head, torque the head bolts and you will be good for a good while.



. . Preston. .

 

[Idaho CTD]

Preston,



The gaskets on the new trucks are totally different then the ones on the 2nd gens. IMO going back to the 2nd gen gasket with o-rings is a step backwards. I have ARP studs in my truck also and it doesn't see 50psi daily. This was a special occasion/event that it saw a workout during (to the tune of 13. 34 @ 101mph, if you get my drift). The plug blew at about the 330' mark from what people tell me. The truck has made probably 30+ passes this year without a hitch until now. There is no evidence of a headgasket problem on the outside of the block either.



The thrashing after the plug install was uneventful. It's just like it's old self again, no leaks or problems. Ho hum it's boring when thing work right .

 

[BCarmicle]

Nathan,



You said that your truck doesn't see 50psi daily, I'm running around 60-65 daily. Is this a bad idea to run this much boost daily? Also, what have you found to be the best boost for the track? I haven't got to do much tuning of late but planning a trip to the track soon and would love to get in the 12's. Any suggestions.



Brandon

 

[Idaho CTD]

Brandon,



My truck only makes 60psi max tuned for the highest hp like it is now (48psi on the dyno). I haven't tuned it for the track to see if it is different then the dyno so I cant answer you there. My personal feeling are that the more you beat on a truck daily the shorter it's life will be. I run with the TST off on a daily basis. With the pressure box on I can still hit 42psi but rarely get there even. The only time I play is if a ricer see's the dial numbers from the track and needs a thrashing. I would say that's about 2x a month. I think the harder you work items such as injectors, pumps, bearings the shorter their life is going to be. If these trucks were like the older ones (which I only run on injectors for 99% of my driving) I wouldn't even run the pressure box. Those big injectors sure were nice except for the smoke. If you want to run in the 12's then drive to Spokane, WA and run there . Play with your wastegate settings and leave the line HARD and you might get close. It might surprise you if you change your EZ settings too or even run without the EZ. I ran faster in Muncie without the pressure box.



Nathan

 

[BCarmicle]

Thanks Nathan. I was planning on running without the pressure box and seeing what happened. I've been leaving the line at 20psi. Do you leave any harder than that?