| Author |
Message |
Michael & Cydny (Mjcruisin) (64.136.26.228)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 23, 2004 - 10:26 pm: | |
I have a 4104 with a 671 DD. I have to replace the head. I have been told there is a benefit to replacing the two valve head with a 4 valve one. Any advise or experience would be appreciated.
Michael |
Buswarrior (Buswarrior) (64.229.211.195)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 23, 2004 - 10:40 pm: | |
Since you have to spend some ca$h anyway...
absolutely a nice thing to get the four valve head. You will be pleased at the improvement in power when you get it done.
Others will be so kind to post the power gains?
happy coaching!
buswarrior |
Geoff (Geoff) (66.238.120.53)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 23, 2004 - 10:43 pm: | |
Which injectors are you running now?-- HV or N's? |
Michael & Cydny (Mjcruisin) (64.136.26.228)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, February 23, 2004 - 11:22 pm: | |
I just went from HV7 to N7
Michael |
FAST FRED (65.154.177.86)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 6:10 am: | |
After a bunch of phone calls I finally talked to a Geezer gent at Amityville NY DD,where the cache of DD/Grey marine parts is located.
Geoff correctly posted to not use N injectors in a "low compression DD", but never explained WHY.
Seems when the N injectors were simply installed in engines that had the H series , the heat generated by the faster fuel injection would expand the piston crowns and excess piston wear would result.
Some engines actually "stuck" like a new 2 stroke motor bike in break in.
Also made starting harder.
GM solution was simply to raise the ring land , exposing less of the piston crown to the combustion heat.
"Mechanics" called this "high compression" pistons , although the CR was not raised.
SO IF your engine has NEVER been rebuilt ( doubtfull in a 50 year old coach) you MUST use the H series injectors.
Pulling an inspection port and looking with a flash light will end any suspense.
Interestingly my 6-71 Grey Marine was on storage till the mid 1990's and came "out of the can" only 1200 hours ago.
So it was stock 1944 and could not use the N series injectors.
The engine has advanced timing ,(rated 235HP at 2100 BATTLE rating, 1900 for normal use) but dropping from H90's to H 60's works fine and seems to give a cleaner exhaust. All the H series smoke a bit more than were used to with todays engines.
Hope this explains what series injectors you can use and why.
FAST FRED |
Geoff (Geoff) (66.238.120.4)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 8:51 am: | |
Michael
If you are running N70's you must have replaced the pistons with the higher compression "N" type? If so, the 4-valve head will give you better exhaust flow than the two valve head. When you go shopping for a 4-valve head be sure it comes with all the hardware since nothing off the 2-valve head will work. The injectors will also have to be changed to the off-set fuel line body style.
--Geoff |
mel 4104 (208.181.100.8)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 10:59 am: | |
there is more to replacing a 2 vale head to a 4 valve one,and it is not cheap. you will need to change the pistons, new rings and go to the large ported liners which is like a in frame rebuild. the valves on the 4 val. head will hit the top of the old pistons, you need the new large ported liners for nore air novement such as intake and exaust. go to a DD repair shop and as them to explain the change over to you but be sure the have some one that has worked on the 6-71 they can show you the differance in the pistons and the sleeves. it would not be the first time that a shop gave advice and then found that they had to change every thing and the repair bills keep rolling in. i have a 2 val. on mine and i even went to the trouble of finding a good 4 val. and after checking with a old dd mech he just laughed at me and said are you in for a shock as to the cost of puting that thing on, it is now on my brother inlaws bus as he was doing a engine rebuild.let us know how you make out......mel 4104 |
Michael & Cydny (Mjcruisin) (64.136.26.228)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 11:06 am: | |
Actually I blew an injector, drove 10 minutes to a shop and paid $500 to have 2 rebuilt injectors(HV7s) installed. It ran worse than ever and the mechanic told me I had damaged the engine running it to the shop. I had to be a couple of hours down the road ASAP and he told me I probably could make it. I barely did. There a friend of a friend was a retired diesel mechanic, and agreed to look at it and try to get me home (6 hours away). He told me the injectors that the diesel shop installed were bad and I had hurt the engine driving it the 2 hours down there, not the original 10 minutes. He replaced all the injectors with N7's he had laying around the shop and told me it would get me home, but I had serious problems--too much for him to under take. He worked on it enough to let me huff and puff home. So even though it ran with N7's, it ran so badly I don't know if they are right.
I went and bought a used 4 valve head and the parts from Luke to replace it. I went and had the head tested and it failed as did the next two replacements. About this time, I'm getting pretty tired of hauling heads and paying $70 a pop to have them tested and the guys pulled one that had just been running and had just a few hours on it since it was tested. It looked great, but it was a 2 valve head. Now they are pulling another unknown one, that looked pretty gunky to me and I am looking at the tried and true 2 valve head and wondering if it wouldn't be better to just go with it. I think I would rather have a 4 valve, but I am not sure at this point.
Michael |
Geoff (Geoff) (66.238.120.4)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 11:19 am: | |
Michael
It would have helped if you would have given us the full story to begin with. You need to find a Detroit Diesel mechanic that knows what he is doing to perform an analysis of your engine. You have too many people telling you different things-- the question is: did you damage the piston(s) besides the head? You may need new piston kits as well as a head according to what I am reading, and if so, you might as well go for the "N" pistons and 4 valve head. |
Phil Dumpster (24.16.189.48)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 11:52 am: | |
And if you value your time, don't try to source replacement engine parts out of a junkyard.
There are some cases where it might be better just to cough up some extra coin and get a proper DD Reliabuilt head which has what you want. |
Don Fairchild (209.234.134.61)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 1:34 pm: | |
These are all good sugestions but after spending all that money you still have an old low block engine, so Why not find a good new style 6L71T, Up grade your cooling system,(see new radiator) and run down the road. You should be able to find one at your local DDC dealer, if not try Adelmans in Ohio at 1-800 643-2001 or any good military surplus dealer. Good Luck. Don |
Michael & Cydny (Mjcruisin) (63.234.124.210)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 4:51 pm: | |
Thanks for the input. I guess I'll go back and get that 2 valve head that was in great shape, that they accidentally gave me. The guy feels bad about so many bad heads and said he'd switch the N7's for H7's.
Michael |
BrianMCI96A3 (206.107.222.206)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 5:52 pm: | |
Key phrase for me:
"He told me the injectors that the diesel shop installed were bad and I had hurt the engine"
What got hurt...just the head(s)?
If yes, then I'd go with what cam off the engine
If no, then when I rebuilt the engine I'd build it to accept the 4 valve.
Brian |
BrianMCI96A3 (206.107.222.206)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 5:54 pm: | |
Uhhh, in other words, I agree 100% with Geoff
Brian |
Michael & Cydny (Mjcruisin) (64.136.26.228)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 7:02 pm: | |
I haven't taken the head off yet. I was waiting to get the new one and do it all at once. I will see what's wrong tomorrow.
Michael |
John Rigby (24.174.233.93)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, February 24, 2004 - 9:17 pm: | |
Mike
The difference between a two valve and a four
two, less parts, lager parts/valves, more distance between the valves( less chance for a crack )a little less power.
for, more parts smaller parts/smallvalves ( more chance to overheat and crack )more power.
My 671 has N70,s advanced timing high commpression pistons. Lots of power no smoke.
One step at a time
Get the head off. FIRST Go out and spray the water manifold and exughst manifold bolts with penitrent. the hardest part is the manifold, got in though the bedroom ( some of the nuts you can get from the front over the engine. its slow and tedeus.
I pulled mine last time in a camp ground( with help from fellow bus nuts) I put two 2x6 on the engine and had them come out to a 55 gallon drum. So I could lift the head up slide it forwad drop it on the 2x6s and then slid it down to the drum.
Have you checked you water ?? any oil in it??
Call me tomrrow if I can help you John 409-658-7003 day |