9mm injector head to 7mm injector head
03-10-2018, 05:21 PM
#1
Registered User
Thread Starter
9mm injector head to 7mm injector head
Hello all,
I have a 91 dodge W250 with a 5.9 cummins non-intercooled, that I got from my good friends family after he passed in a car accident. It was a project of his he was working on, he went to replace the head gasket to find that he had a cracked cylinder head (as is common with 9mm injector nozzle early model heads) he found a used head. After taking it to the machine shop to have it Mag Fluxed they found cracks in the "new" head as well. This was all the farther he was able to get with the project.
I have also been looking for a 9mm injector head, I have found a used one and again after Mag Flux we have found cracks. So we have gone through 3 different heads to find cracks in all of them. So now I want to change my plan of attack on this issue and purchase a new aftermarket cylinder head. Though it looks like the aftermarket doesn't offer a new "9mm head" only the "7mm head".
So my question is what is involved in using a "7mm" injector nozzle head from the later year 12v cummins engines on a earlier "9mm" injector head short block? I understand that i will need to purchase the cylinder head (PROMAXX makes a replacement) and 7mm injectors (i'll probably go with a 50hp upgraded bosh injector). But is this swap just as simple as swapping those two items? If anyone has done this i would love to hear about it and what other factors were involved?
Thanks,
Sorry if this subject has already been covered in a different area of the forum, please point me towards it. There is a lot of treads to go through....
I have a 91 dodge W250 with a 5.9 cummins non-intercooled, that I got from my good friends family after he passed in a car accident. It was a project of his he was working on, he went to replace the head gasket to find that he had a cracked cylinder head (as is common with 9mm injector nozzle early model heads) he found a used head. After taking it to the machine shop to have it Mag Fluxed they found cracks in the "new" head as well. This was all the farther he was able to get with the project.
I have also been looking for a 9mm injector head, I have found a used one and again after Mag Flux we have found cracks. So we have gone through 3 different heads to find cracks in all of them. So now I want to change my plan of attack on this issue and purchase a new aftermarket cylinder head. Though it looks like the aftermarket doesn't offer a new "9mm head" only the "7mm head".
So my question is what is involved in using a "7mm" injector nozzle head from the later year 12v cummins engines on a earlier "9mm" injector head short block? I understand that i will need to purchase the cylinder head (PROMAXX makes a replacement) and 7mm injectors (i'll probably go with a 50hp upgraded bosh injector). But is this swap just as simple as swapping those two items? If anyone has done this i would love to hear about it and what other factors were involved?
Thanks,
Sorry if this subject has already been covered in a different area of the forum, please point me towards it. There is a lot of treads to go through....
03-12-2018, 12:15 PM
#3
Registered User
Don't have an answer for your question but wow, I did't know ProMaxx made a head for the Cummins. $585 is pretty cheap for an assembled head.
03-12-2018, 01:34 PM
#4
Registered User
The 1989 to early 1998 12v Cummins in an automotive application utilized the same head and block. Any of the blocks within that year range will accept a cylinder head from the same year range and vice versa. The only difference being the injector bore diameter within the head. While there may be other variations among them, they'll be subtle but from a mechanical standpoint, they will all bolt together the same. Engines from 1991.5 and up have the 7mm injector nozzle.
The only way you'll find a head that accepts the 9mm injector nozzles is somebody selling a used one. The reason you won't find a "new" head with 9mm bores is because Cummins recognized the issue of cracking in the 89-91 heads between and into the injector bore and intake valve seat. Which is why they stepped the nozzle size down to 7mm.
A small crack is not a very big deal and there are numerous engines that have been put back together with the said cracks and are running strong without issue. Typically, if the cracks are small enough, a simple valve job will get rid of them. At least, was the case when I had the head on my 90 redone. Even if the cracks remained and were hairline, it's very unlikely you'll have any issues.
As for the head you've sourced, I'd be weary about it as any "new" cylinder head you buy from anyone will more often than not, be an aftermarket, China-cast piece. Rather, I'd highly recommend trying to make one of the current heads you have work or buying a reman'd head from Cummins or many of the reputable retailers. Pure Diesel Power is a good one to buy from.
The only way you'll find a head that accepts the 9mm injector nozzles is somebody selling a used one. The reason you won't find a "new" head with 9mm bores is because Cummins recognized the issue of cracking in the 89-91 heads between and into the injector bore and intake valve seat. Which is why they stepped the nozzle size down to 7mm.
A small crack is not a very big deal and there are numerous engines that have been put back together with the said cracks and are running strong without issue. Typically, if the cracks are small enough, a simple valve job will get rid of them. At least, was the case when I had the head on my 90 redone. Even if the cracks remained and were hairline, it's very unlikely you'll have any issues.
As for the head you've sourced, I'd be weary about it as any "new" cylinder head you buy from anyone will more often than not, be an aftermarket, China-cast piece. Rather, I'd highly recommend trying to make one of the current heads you have work or buying a reman'd head from Cummins or many of the reputable retailers. Pure Diesel Power is a good one to buy from.
03-12-2018, 01:40 PM
#5
Registered User
Not everything that comes from China is junk. There are many Chinese cast engine parts finish machined and inspected in the USA in high performance and race engines in this country and many do very well. Cylinder heads, connecting rods, crankshafts and intake manifolds are just some of the parts. I'm not saying these heads are good, I really don't know but I'm not that quick to lump all parts made in China as junk.
03-12-2018, 01:44 PM
#6
Registered User
Thread Starter
Thanks for the info.
thanks for the info. Just want to reassure myself that I was going down the right path before I spent the money.
I ask the machine shop if they would recommend using the heads i have. They didn’t recommend it and I’m sure they would rather have the work than turn away the work. They are cracked in a large majority of the valves and injector bridges. I will keep an eye out for a used head but now I can broaden my search.
If anyone has used a PROMAXX head I would sure like to hear there opinion on it?
Once again thanks!
I ask the machine shop if they would recommend using the heads i have. They didn’t recommend it and I’m sure they would rather have the work than turn away the work. They are cracked in a large majority of the valves and injector bridges. I will keep an eye out for a used head but now I can broaden my search.
If anyone has used a PROMAXX head I would sure like to hear there opinion on it?
Once again thanks!
03-12-2018, 02:00 PM
#7
Registered User
Not everything that comes from China is junk. There are many Chinese cast engine parts finish machined and inspected in the USA in high performance and race engines in this country and many do very well. Cylinder heads, connecting rods, crankshafts and intake manifolds are just some of the parts. I'm not saying these heads are good, I really don't know but I'm not that quick to lump all parts made in China as junk.
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03-12-2018, 03:17 PM
#8
If anyone cares to search my post history I did this exact same thing already.
The 9mm stock 1991.0 head off my engine with 85k easy original miles was cracked. I then sourced a new 7mm OEM cummins head straight from china. The price was around 1000 bucks if I recall plus or minus. It was an excellent piece that even had the current style "top hat" valve seals. (an upgrade that usually requires machine work on our era heads)
Non i/c pistons require a different spray angle than the later i/c pistons. I don't recall all the numbers on this, however you can get a set of new Bosch 7mm with correct spray angle for this non I/C style piston as well. This is what I ended up doing. Good luck. Call B&R head and block repair @ (916) 371-0512 if you want the info on new cummins heads from the horses mouth.
The 9mm stock 1991.0 head off my engine with 85k easy original miles was cracked. I then sourced a new 7mm OEM cummins head straight from china. The price was around 1000 bucks if I recall plus or minus. It was an excellent piece that even had the current style "top hat" valve seals. (an upgrade that usually requires machine work on our era heads)
Non i/c pistons require a different spray angle than the later i/c pistons. I don't recall all the numbers on this, however you can get a set of new Bosch 7mm with correct spray angle for this non I/C style piston as well. This is what I ended up doing. Good luck. Call B&R head and block repair @ (916) 371-0512 if you want the info on new cummins heads from the horses mouth.
03-12-2018, 06:36 PM
#9
Registered User
I’m with Angry Johnny on this one.....All Genuine Cummins heads are now made in China at their 50% owned plant....have been for many years. Promaxx & Pure Diesel Power heads come from China too. Chances are from the same plant, so all good. Just saying.
03-22-2018, 12:20 AM
#10
Registered User
hi
i am using a china cyl head on my 98 12v got it from odesa cyl head in florida .
might have a look there price was aunder 400 for a empty head , they had loaded ones also but i do all my own valve jobs and mild porting .
loaded ones were about 100 more .
5000 miles on mine now no problems yet .
i am using a china cyl head on my 98 12v got it from odesa cyl head in florida .
might have a look there price was aunder 400 for a empty head , they had loaded ones also but i do all my own valve jobs and mild porting .
loaded ones were about 100 more .
5000 miles on mine now no problems yet .
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