Nah, you're more likely to ruin a starter - from it NOT starting the way you were doing it

 

Thats comforting. At least I know how to install one of those haha!

 

It is around 1000 deg. plus to ignite diesel- air mixture. When the air fuel mixture is ignited it hits the piston at around 1650 Deg.




FYI for anyone interested. The reason that engines with precombustion chambers or turbulance chambers, they are different and our 6.9 and 7.3's have turbulance chambers not precombustion chambers which is the reason for a higher compression ratio is because these engines don't keep all the air for combustion in the cylinder wall area. With the turbulence chambers in the head and not all in the cylinder area the air losses it's temp easier. That is why glowplugs are needed in IDI engines. There are alot of newer DI motors that have them but that is for a cleaner start up. Powerstrokes have them to help them have a cleaner and easier start up but they should start without them.

The difference between a pre-com. and a turbulance chamber is the amount of compression air that inters the chamber. Turbulance chambers have virtually all the air intering them and pre-com chambers don't. Cat used to use pre-com. and they were actually part if the nozzle. Those bring back memories. Then ofcoarse as time has gone on they went to DI engines with nozzles and now the injector has taken over, which has been around for years but that is changing to some degree now.


Hey Dave... Have you fooled with any cam timing and valve lift on your 6.9. I have a 6.9 that came out of an 86 and when I get time I am going to get stupid with this motor. I have access to a dyno and I am going to see what I can get out of one. I have been thinking about fooling with the compression ratio. If I can get it down some and it will still start ok, I could through more boost to it plus the lower ratio would leave more HP to the flywheel. Any body have any thoughts?

 

hey dave, as for getting glow plugs off fleabay, i would just mail order 8 of them from www.autozone.com.

at $9.99 each, it is worth it. then after you change all of them out, you can keep the good ones for spares incase one of your friends needs one, cause it will be years before you will need to mess with them again.

 

just as a precaution ohm the glow plugs before and after the install; one to make sure you have good ones and second to make sure after installing them nothing went wrong (internall breakage)
I'm always concerned about buying online for just that reason; and even if you pay more locally ,i've found the source to be more appreciative of your buisiness and willing to assist-nothig like southern hosptality!

 

That is my biggest worry of buying any thing online....Cheaper's experience just confirmed it.

 

I have used AC 8G's for several years and I haven't had any problems out of them. I had a set get fried before I reworked my system and I got them out with no problem. I have had the set in my truck for 7 -8 years now. Ofcoarse I have a completly manual system now but they start my motor fine.

I have used the IH from a dealer but I don't know who makes them for IH. Anybody know?

 

I was thinking about this too, believe it or not. A while back here someone posted some tantalizing comment about cam timing, but when I started asking questions he got real hedgey about it and wouldn't give a straight answer. IIRC I pretty much figured out that his dad fiddled with the cam timing and he really didn't have enough info to answer the questions himself. I know that advancing/retarding the cam is an old hot-rodder's trick. From what I've read, on any given engine, going one way will boost low-end torque, and going the other way will boost top-end HP. Seems like retarding the cam timing a little gives low-end torque and advancing it a little gives more top-end HP. Might be the other way 'round, but that's what I seemed to remember....

That pretty well describes what Dave did when he rebuilt his 6.9. Milled the pistons 40 thou to lower the CR to around 18:1 so he could run 20+ psi boost. Seems to be working for him

Though he did say he felt he had lowered his CR about as far as he felt like he could without creating hard-starting issues.....

 

No worries guys, I personally kinda hate ebay for reasons like sellers similar to what cheaper experianced. Good news, a set of 8 Beru plugs are on order from NAPA and should be here next week

 

Oh yeah, I also meant to mention that of the DOZENS of eBay transactions I've done, this is only the second time I've been unhappy and the seller wouldn't make it right. FWIW....

 

I don't think you could do much with more lift, from what it looks like to me, the pistons and valves would probably touch if you left the head gasket out with stock pistons.

Did not take time to see if the valve timing could be altered any, I think you are probably talking custom cam to do much in that area.

I did shave 40 thousandths off the crowns of a set of Sealed Power hypereutectic pistons, that dropped the compression to 20.25 to 1. With the night temps here in northern WV I think that is as far as I would consider going, and it may be to far for me if we ever get some weather like we had a couple years ago. Never got above 25 for about 5 weeks and was much colder at night. I do spends a lot of time in some remote locations at work, so no chance to plug in. It has to start after setting all day by it's self on lots of cold days.

Something I have been considering is the precups. 21 pounds of boost puts the normal amount of air into the cylinder plus 150% more air. And since the piston is as close to the head as it is, most of that air has to go through that little hole in the precup twice per power stroke.
At 3300 RPM the cylinder is firing 3.4 times per second.
That means about 132 cubic inches of air has to go through that little hole in the precup 7 times every second or in other terms 919 cu. in. per second.

That little hole in the precup has got to be costing me some power.

I should have put them on the milling machine right after the pistons came off.

I know this is going to bother me till I yank the engine out, pull the heads off and work on them some.

 

Actually advancing or retarding the cam a few degrees is pretty easy. Depending on what size/style of key is used to index the gear to the cam. You can either buy an offset cam key - if the right size is available - or have a machine shop make you one if your engine uses an odd size.

 

it seems to me with the somewhat limited rpm range of these engines the actual cam timing would be better off set (to spec)and left alone. Maybe a little more duration if you had enough turbo...
i would like to know more about the pump timing (power/heat) relationship

 

Advancing the timing lets the fuel/air mixture burn longer.
The longer burn time increases the power.
Longer burn time also increases the heat.

Since power out is a result of the conversion of fuel to heat, any increase to the power will increase the heat generated under full engine load conditions.
Also since you are converting fuel to heat for the power, any increase in power out will also result in more fuel being consumed at peak engine load conditions.

Where any increase in power can benifit you with lower heat generated and lower fuel consumption is when you are running the same speed as before at lower throttle application.

This is true for any internal combustion engine.
Also since the

 

A while back here someone posted some tantalizing comment about cam timing, but when I started asking questions he got real hedgey about it and wouldn't give a straight answer

Cheaper, I take exception to that remark. I did NOT get hedgy about answering your questions. I told you that changing the cam timing ALONG with turbo, exhaust, injector pump and injector changes "can" make a difference. I don't know where you think I was hedging about an answer.

You did not want to entertain the idea that to make any significant power, required spending money. You now have a truck with a turbo and can see the REAL difference. Now imagine that along with a correctly built and matched IP and injectors.

BTW, my "dad" had nothing to do with my truck. I had some ideas and had a very good pump and injector man do the work. I've been driving and working on diesel trucks for over 30 years, my dad doesn't need to do anything for me.

Point is, if you wouldn't spend the money to even start with unlocking the real potential of the engine, why should I bother to keep trying to tell you where to start? The timing remark was offhanded at best. I wouldn't even bother to do it again, the minimal gain was not worth it in the 6.9...as I said, it "can" make a difference.

I don't understand why you got so hostile over the remark anyway and kept hammering at it. What did you need to know? You already know and mentioned the ways to make the change so why keep on it?

I was going to just let it go but this is about the 3rd time you've made mention of that thread. Get over it already.

Other than that.....you have done a good job with your ideas and research. With your new truck you now see there truth to what I told you before.

cheers