4-71 overhaul complete, ready to slide back in.

[TomC]

Great looking job, and I like the paint job!  I'd like to tell a little story-not to scare you, though.  I have a transit with a 8V-71 with the oil filter remote mounted through braided lines.  A few years ago coming back from the Rickreal, Or get together, I was on Calif 299 from Redding to Eureka when the oil filter broke off and lost all oil on the highway.  The oil filter was the canister type you have mounted straight to your engine.  Briefly, I both repositioned and replaced the canister filter with a modern spin on, and have always liked the spin on oil filter better.  Maybe you should consider converting your canister filter over to a spin on?  I figure mine broke (it broke at the casting holding the threads for the bolt) from old age.  My bus is a '77-with yours being even older... Good Luck, TomC

[Gary '79 5C]

Great Job & wonderful paint job, love the choice in colors. I still have my oil stained original..

Dallas, What a way to bust on someone..But It reminded me of caddying, as young youth, for a local surgeon. He knew of my interest in cars and was describing his engine rebuild of a MG. Totally closed up and he pulls it thru by hand, and is greeted with a sudden Clunk !!! He then pulled the head and retrieved his Zippo lighter. I looked at him and with wisdom beyond my years, replied that, If I were a surgeon, I would never repeat that story.

[lostagain]

Tom C, as a matter of  fact, I have a spin-on filter assembly on a spare engine I have. I will rob it and install it on this one at the next oil change. I still had a filter element for the old canister that I didn't want to go to waste.

I forgot to mention last night, I used the high compression 18 and change to 1 pistons. More people advised me to go with high comp. than low.

My biggest asset for this project was the DD Inline 71 Service Manual. I followed it to the letter from start to finish. That is the easy part because everything is very well described and detailed step by step. You have to read instructions and follow them. It also showed me some guys that worked on this engine before me were "hammer mechanics", wether they were "professional" or amateurs like me. For example the stripped bolt holes I had to Helicoil here and there. Some people don't use a torque wrench, and don't have a feel for how tight it should be...
The hard part was choosing what parts to use like pistons, or injectors, or to go for standard timing vs advanced, etc. I picked mechanics brains as much as I could. I got a lot of good advice on this board, thank you. And from mechanics I know, and suppliers, etc. You have to sort through the advice too, because a lot of guys think they know it all...
The more difficult aspects are figuring out how to install new things like the dry air filter, the after cooler, and fabing all the associated piping and finding room for it all in the engine compartment. That draws more on empirical knowledge than anything else. And the results will be felt by the seat of the pants. If something doesn't work right, I can tear it off and redo it differently.

It was a great learning experience. I had never rebuilt an engine before. It is just a hobby, I don't depend on the engine for my living.

I went into it knowing it would be a big job. It took twice as long... I spent a lot of time cleaning up greasy parts. A lot of time fixing little things in the engine compartment, etc, etc. I do it because this bus is special to me. If I got another bus, it would be a lot newer and not require that kind of work.

Anyway I'm  not quite done yet, and I won't know wether it is a good job until it has run for a while...

JC

[Stormcloud]

Looks good... hope to see it in person (and running!) next weekend.

Regards.

Mark

[TomC]

Since I have the same setup, but with the 8V-71 and 9G75 injectors, my engine puts out (on the dyno) 375hp and 1125lb/ft of torque.  Cut this in half for yours, and you should be getting 188hp and 563lb/ft torque-which will be like having a 6-71N for power.  Don't be afraid to twist it up to 2500rpm for more power.  Detroit had a 6-71TI marine engine that from the factory was rated at 485hp at 2500rpm.  The inline 2 strokers are incredibly tuff engines.  Good Luck, TomC

[HB of CJ]

Am I to understand that they made two different compression ratios with the turbo type two piece pistons for the 71 Detroit?  If sooss, I have just learned something new and thank you.

Some help here please.  Running the new-to-me (honestly!) high compression pistons with 75 injectors, will you have any detonation concerns?  I am guessing sooos bear with me please.

Would the main limiting factor be the boost level and pyro temp levels?  Again, with a 4 speed manual, you will not have the luxury of selecting the perfect gear like with a Roadranger 10 speed.

Also I missed the Jake Brake.  Shame on me.  Was going to mention it in my prior post, now glad I didn't embarrass myself further.  I would love to build a Cummins Big Cam 2 mill for my....

....next Crown Supercoach ownership thing, but don't have the facilties right now to do sooss.  Some diesel parts are so cheap right now.  It is so cool you can do your own work.  HB of CJ

[TomC]

Over the past few years, Detroit stopped making the one piece piston in favor of the two piece iron top.  It is made in both the 18.7 to one non turbo and 17 to one for turbo.  I also am using the 18.7 to one pistons, but with a Series 60 turbo that has the exhaust waste gate set at 15psi.  A non waste gate turbo can get into the 20 psi range.  Once warmed up, my engine makes no visible smoke. Good Luck, TomC

[lostagain]

Several Detroit mechanics recommended the 18.7 to 1 high comp. pistons over the 17 to 1 low comp. because the low comp. makes it harder to start, especially at altitude. My supplier (Alberta Engine in Calgary) recommended high comp. (I got FP parts by Federal Mogul).
Even though Da Book (mine is 1978) calls for low comp. pistons, after talking with as many pros and experienced people as possible, you get a feel for the current practices and go with what sounds the most reasonable.

JC

[lostagain]

Question: charge air piping,

The turbo outlet and cooler inlet and outlet are 3.5". The inlet at the blower is 4". Would you use 4" or 3.5" pipe? I can get hump hose adapters eather way.

Instead of using pipe, is there a flexible hose that could take the boost and the temp. that I could use? That sure would be easier for me than welding thin walled pipe.

JC

[TomC]

The best way is to use aluminum pipe (which is hard to weld).  So I used exhaust pipe.  The norm is to use 6" lengths of intercooler hose (it looks like hose with bellows and wire reinforcement usually made of silicone) just to connect the pipe from one length to the next.  It is a pain to make, but once your done, it will last the lifetime of the engine.  Be sure to paint the outside of the pipe with engine paint to keep from rusting.  Use the same size as the intercooler.  On the final run to the blower you could increase the size to match the blower-this extra expansion will further cool the air.  Good Luck, TomC

[JohnEd]

My understanding is that the lower compression allows you to run more boost safely.  The more boost, the more power, right.  Lower compression means lower compression temps for starting and hard starting in cold weather AND at high altitude.  My question is:  without regard to hard starting, what is the difference in HP between the 17 to 1 and the 18.7 to one?  What did he give up?

Thanks,

John

[TomC]

Like my setup, using 75 injectors is a moderate increase from the 65 injectors-so the turbo pressure will not be that high with the high compression pistons.  If you want to go to 90 injectors, then you'll be in the 20-30psi range of turbo boost-most likely too high for the high compression pistons.  Don Fairchild had a 8V-71T with military pistons in it that only had 16 to one, and he was running 120 injectors-making for 600hp.  Smoked on starting, but you should have felt the power!  Good Luck, TomC

[Chopper Scott]

I hate reading about engine builds....... the best part is hearing them take their first breaths. Reading about them just isn't as good!!!

[Len Silva]

I hate reading about engine builds....... the best part is hearing them take their first breaths. Reading about them just isn't as good!!!

Like hearing your baby cry at the moment of birth.

[Van]

Where's the video,Pleeez! ,then all we will be missing is the aroma LOL.