Long block or just heads?

[CAHUNTERMAN]

Long block or just heads? - New question

Hi, I need some advice.
The 4.0 OHV engine in my 99 X just blew a head gasket or a head. No water in the oil and it didn't use a drop of oil between changes so the bottom end is probably in pretty good shape. My question is, with 150K on this engine is it worth just doing heads on it or should I be looking for a rebuilt long block? I'll be doing all the work myself either way I'm just wondering which way to go.

Thanks for the opinions.

 

[James909]

The OHV engines are super reliable. They easily go past 250K miles when taken care of properly. I'm sure that there is plenty of life left in that bottom end. So if it were me I would just replace the heads.

 

[Willard]

Yea the bottom ends are hardly ever what fails anyways, it will be fine. Throw some new heads on and call it good. It will likely outlast most other parts of the truck, anyways.

 

[Maniak]

Unless you have abused the motor by not doing oil changes, running it low on oil, over heating it often etc... I'd say just do the heads..

The OHV motor lasts a long time..

At 355k miles we rebuilt our OHV. I did it becuase the heads were cracked again AND one cylinder had only 130psi during the compression test (all others were at 160). We drove for 100k miles with the one low compression cylinder and decided to rebuilt since it needed heads anyway.

~Mark

 

[CAHUNTERMAN]

Thanks guys,
I was leaning towards new heads since the engine has been very well maintained (oil changed every 3k) and as long as I have owned it it’s never been overheated at all. Any recommendations on new heads?

 

[James909]

I bought a new set of GT40P heads to use on my boat from Clearwater cylinder head. I did a lot of researching before I bought from them and I found a lot of good things said about them. I was very pleased with my experience buying from them. They do a very good job on their rebuilt heads and their prices are very reasonable.

 

[CAHUNTERMAN]

Thanks James,
That is one of the two companies I was looking at buying the heads from. The other one is Ideal Cylinder Head. They are only two hours from me so shipping would be a lot less but unless I hear some good reviews about their heads I'll probably go with Clearwater.

 

[CAHUNTERMAN]

New question

Well, I pulled the heads off today and found no obvious failures on the heads or the head gaskets. I did however find some strange vertical grooves in the two cylinders I suspect were taking on coolant (cylinders 3 & 4). The grooves are deep enough that I can feel them pretty good with my fingernail. Could these be cracks in the block that are allowing coolant into the cylinder? I’ve never seen anything like it before.

 

[Cobraguy]

Those don't look like cracks from here, but diagnosis via picture is not a good thing. These look like debris scratches (possibly ring damage) and are quite normal on high mileage engines. Well, not normal, but you see them often. These normally cause loss of compression and oil consumption/blow by. But by all means, if you can't tell yourself, find someone who can. Just because those marks don't look like a crack doesn't mean there isn't one just out of sight of the camera lens. And check the entire bore...top to bottom.

Have your heads checked. If there's a crack...I'll bet that's where it is. Look very closely between the valves. Have your heads magged by a machine shop. It's not that expensive.

 

[Maniak]

Those don't look like cracks to me.. As already mentioned, they look like either ring damage or debris scratches.

I notice you can still see the cross hatch on that cylinder (I could see mine on most cylinders even at 355k miles)..

I would take the heads to a good head shop and have them checked. If possible get them fluxed and if they seem good have them tanked and pressure tested. I had one head that passed during a magnaflux test but failed the pressure test (crack was hard to find).. Assuming the head passes everything have them rebuilt at the same place.. that should save you a little money compared to just buying new/rebuilt heads since you really "need" to make sure it is the heads that are causing the current issue.

Once you know its the heads I wouldn't worry too much about the block.

I haven't seen a 4.0 with a cracked block yet (only a few that have had catastrophic failure due to abuse or hp mods)

~Mark

 

[CAHUNTERMAN]

Thanks for the replies,
I just dropped the heads off to get them checked, should hear back this afternoon. If they find problems with the heads I think I'll just throw some new ones on and see what happens. The more I look at the cylinder bores the more I agree they are just scratches. Probably from the time I made the mistake of installing Bosch plugs only to have them disintegrate in the cylinders a week later. Since it wasn't using any oil I'm going to assume the rings are ok and the scratches aren't causing any problems.

I just want to get this thing back together so I can get on to the fun stuff like installing my lift so these will fit

 

[Cobraguy]

The more I look at the cylinder bores the more I agree they are just scratches. Probably from the time I made the mistake of installing Bosch plugs only to have them disintegrate in the cylinders a week later.

Yep....that would do it for sure!

 

[CAHUNTERMAN]

Just got the news... "the heads would make a good boat anchor" according to the machinist. One had several cracks and the other one had at least one. Time to order up a new pair and get this project moving. Thanks again for all the good information and help.

 

[Maniak]

Just got the news... "the heads would make a good boat anchor" according to the machinist. One had several cracks and the other one had at least one. Time to order up a new pair and get this project moving. Thanks again for all the good information and help.

Neither is repairable? Out of 4 cracked heads (in 355k miles) 3 out of the 4 were repairable.. One was pinned and the other two were welded.. the one with the crack on the "shoulder" wasn't repairable.

~Mark

 

[CAHUNTERMAN]

Yes they are repairable but he told me I would be better off buying new ones than paying them to repair mine. Either he was being honest with me or he just doesn't want the job. Should I be getting another opinion on them? I can get two new heads shipped to my door for $480.00 through a buddy of mine that has a shop.

 

[Maniak]

Yes they are repairable but he told me I would be better off buying new ones than paying them to repair mine. Either he was being honest with me or he just doesn't want the job. Should I be getting another opinion on them? I can get two new heads shipped to my door for $480.00 through a buddy of mine that has a shop.

$480 for a pair of heads with valves etc is a very good price.. Bare heads are usually $250ish each..

I paid $300 for my heads to be rebuilt and repaired so $480 is good.. Also, if they are an updated cast or 93TM castings you should be better off.

~Mark

 

[CAHUNTERMAN]

$480 for a pair of heads with valves etc is a very good price.. Bare heads are usually $250ish each..

I paid $300 for my heads to be rebuilt and repaired so $480 is good.. Also, if they are an updated cast or 93TM castings you should be better off.

~Mark

The new heads are supposed to be an updated casting that is thicker in the problem areas. They come with all new valves and springs installed too. I got the impression that it would cost about as much to have my old heads repaired so I'm just going to get the new ones.

What is the difference between the 93TM and the 98TM castings?

 

[Maniak]

90tm and 93tm heads have a large chamber for the valves.. the 95tm and I "think" 98tm heads have a small chamber which will up the compression..

Starting in 1995 the pistons went to a bigger dish and the heads had a small relief...

there is a thread around here (a couple I think) about someone installing 95TM heads on a 1st Gen X to get more compression.

~Mark

 

[CAHUNTERMAN]

90tm and 93tm heads have a large chamber for the valves.. the 95tm and I "think" 98tm heads have a small chamber which will up the compression..

Starting in 1995 the pistons went to a bigger dish and the heads had a small relief...

there is a thread around here (a couple I think) about someone installing 95TM heads on a 1st Gen X to get more compression.

~Mark

Thanks Mark,

I definitely want the 95TM or the 98TM type heads then since I have a 1999 with the lower compression pistons I sure don't want larger chamber heads or I'll end up lowering the overall compression.

I just called my buddy that ordered the heads for me and he said they will be a 98TM equivalent. Hopefully they will be here today or Monday and I can get back to working on it.

 

[Maniak]

Thanks Mark,

I definitely want the 95TM or the 98TM type heads then since I have a 1999 with the lower compression pistons I sure don't want larger chamber heads or I'll end up lowering the overall compression.

I just called my buddy that ordered the heads for me and he said they will be a 98TM equivalent. Hopefully they will be here today or Monday and I can get back to working on it.

I'm glad you caught that.. for some reason I thought you were a 1st gen x.. I'm glad you didn't just get a 93tm.. that would have been bad.. and I would have felt really bad..

~Mark