head gasket questions

[lb7lbz]

going to rip my 01 w 275k apart in a couple of weeks for head gaskets. i have access to a shop on the weekends with a lift so i am going to pull the cab off. also pulling the bed to fix the fuel sending unit and run all new brake lines while cab is off. i have a few questions i was hoping someone could answer. 1. how much hp/ torque will stock head bolts hold reliably? 2. according to my predator scan tool i have 1 injector out of spec +5 is there any way to find out which one it is? 3. where the truck has 275k should i replace the injector cups while it is apart and reseal everything? 4. does anyone have an injector cup removal tool they want to sell me or rent me? 5. are there any bearings or anything else i should replace in the motor while i am there?

[More Power]

going to rip my 01 w 275k apart in a couple of weeks for head gaskets. i have access to a shop on the weekends with a lift so i am going to pull the cab off. also pulling the bed to fix the fuel sending unit and run all new brake lines while cab is off. i have a few questions i was hoping someone could answer. 1. how much hp/ torque will stock head bolts hold reliably? 2. according to my predator scan tool i have 1 injector out of spec +5 is there any way to find out which one it is? 3. where the truck has 275k should i replace the injector cups while it is apart and reseal everything? 4. does anyone have an injector cup removal tool they want to sell me or rent me? 5. are there any bearings or anything else i should replace in the motor while i am there?

I'd consider ARP studs for serious power, but the factory head bolts should be good for 500, with a little safety margin. Kennedy would know more...

#3 is the second injector from the front on the passenger side.

The stainless-steel cups shouldn't need to be replaced, but I'd re-seal them while the heads are off.

Injector removal tools are pretty cheap on eBay, but the the injector cup (sleeve) removal tool is a little pricey. For perhaps less than the cost of the tools, a dealer might do the injectors/cups for you if you take the heads to them (well packaged to prevent damage to the aluminum).

Water pump replacement....

Jim

[lb7lbz]

thanks for the info jim however i think you misunderstood one of my questions i wasnt saying it was the #3 injector i dont know which # it is. all i know is its the last one my predator lists. thanks again kevin

[DmaxMaverick]

The LB7 Predator injector #'s are: 23456781 (follows traditional GM cylinder numbering). Cylinder #1 is the right/front, #8 is left/rear (as if sitting in the driver seat, looking forward). If your high value is the last in the list, it is cylinder #1, nearest the primary alternator.

DO NOT rely on injector balance rates or PWM to identify a failed injector. One injector showing an unusually high fuel push/pull seldom indicates that injector as the problem. Idle balancing is achieved by the injectors compensating for an unbalance of combustion events. A single very high value usually indicates a significant compensation for another event error, commonly adjacent to it in the firing order (depending on the push/pull, the amount, engine temp, load, fuel rail pressure/stability and fuel temp). You cannot identify specific failed injectors by observing only the BR and PWM. More specific testing requires a Tech II.

However, some examples can be more telling. Post your entire PWM and BR values, as well as ECT (it should be above 170°), ambient temp, engine load, fuel temp (should be above 72°, but not more than 96°), battery and ign voltage, and RPM (all according to the PCM, with your Predator). It helps if you take 3 readings, idling in Park with ALL accessories off (including HVAC, device charge adapters, dome/ctsy lamps, brake lamps, head lamps); idling in Drive with all accessories off (set parking brake); and idling in Drive with the A/C on coldest, high speed (continuous, not cycling). All of these values with a fresh air and fuel filter. Some of us may be able to help decipher the picture.

[Kennedy]

DO NOT rely on injector balance rates or PWM to identify a failed injector. One injector showing an unusually high fuel push/pull seldom indicates that injector as the problem. Idle balancing is achieved by the injectors compensating for an unbalance of combustion events. A single very high value usually indicates a significant compensation for another event error, commonly adjacent to it in the firing order (depending on the push/pull, the amount, engine temp, load, fuel rail pressure/stability and fuel temp). You cannot identify specific failed injectors by observing only the BR and PWM. More specific testing requires a Tech II.

However, some examples can be more telling. Post your entire PWM and BR values, as well as ECT (it should be above 170°), ambient temp, engine load, fuel temp (should be above 72°, but not more than 96°), battery and ign voltage, and RPM (all according to the PCM, with your Predator). It helps if you take 3 readings, idling in Park with ALL accessories off (including HVAC, device charge adapters, dome/ctsy lamps, brake lamps, head lamps); idling in Drive with all accessories off (set parking brake); and idling in Drive with the A/C on coldest, high speed (continuous, not cycling). All of these values with a fresh air and fuel filter. Some of us may be able to help decipher the picture.

Taking this one step further don't trust the Predator's balance rates. Use a Tech 2 to get any meaningful data. I've always seen the Predator show odd high numbers. I don't know if it is the sampling rate or what it is, but it did not jive with the Tech 2. Reverse engineering only gets you so far. They hadn't got the Boost or baro working last I knew either.

x2 on the water pump and associated hoses with that many miles.

[lb7lbz]

thanks for the info guys not sure what pwm stands for but here are my balance rates idling in park. +1.4 +1 -.4 +2.5 -.2 -1.9 -.7 +5. truck runs just fine, and commanded fuel pressure and actual are always close. these injectors have 175k on them and seem to be fine except that one reading +5. i will get the rest of the info to you soon. yes j/k you are right neither boost or baro work on the predator.

[lb7lbz]

other readings are as follows ect 175 degrees fuel temp 78 degrees 36% frp iat 89 degrees ambiant temp 75 degrees 6.7 maf 14.2 map 22% engine load 14.2v ign 14.2v battery 650 rpm

[chessy56]

Others can correct me if in error, but I believe the BR (balance rates) are from + to - 4.0 in park, + to - 6.0 in gear. PWM is your pulse width that is commanded by your ECM- tells the injector how long to stay open. A Tech II will give your those.

I had my head gaskets replaced about @ 340K and 60K later, one began leaking- exhaust was pressurizing my coolant system and blowing coolant out of the overflow reservoir. OEM head bolts may've been a contributor to this failure. As recommended by Kennedy, I bought a set of studs and had the dealership install them with a new set of gaskets. So far, no problems.

When I replaced my injectors last time, I used one of the feed pipes to rock the injector and pull it out. Replacing the feed tubes may not be a bad idea as any corrosion from within the big nut on the injector pipe will get into your injectors and ruin them.

I got my parts from GMPartsDirect.com. Their prices are just as good if not better (in some cases) than what I can get as a GM employee from the dealership! You'll get rebuilt Bosch injectors- none of them are "brand new".