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4.0 OHV blowby, next steps


Josh P

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5.0 swap is needed
 


RobbieD

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Tough choice. I think I'd be torn between Options #2 and #3, with leaning toward Option #3.

I wonder if the detonation has anything to do with loose intake bolts.
 

4.0blue98

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^^^ I'd be leaning towards opt 3 as well.
 

gaz

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@Shran ,
95 and up OHV pistons are all dished the same. I will be surprised to learn that it has 1st gen heads. I missed it when I tore down my first OHV 4.0l, which had 98+ spec heads 🤦🤦🤦

I'm pretty sure that the heads must be installed and torqued at the same time as the lower intake manifold.
 

Shran

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I wonder if the detonation has anything to do with loose intake bolts.
Was hoping so but after retorquing them (no guarantee they're perfect, but way better than they were) the pinging is no better and no worse. 91 octane fuel helped to some extent.

@Shran ,
I'm pretty sure that the heads must be installed and torqued at the same time as the lower intake manifold.
That's what my head gasket set instructions said and there is a very specific way to torque both and I followed it to a T but in the end after several heat/cool cycles I had very loose bolts. There is a separate torque procedure for the lower intake by itself if just replacing that gasket - I followed that today - it was something like 36in/lb->72in/lb->132in/lb->180in/lbs. Every single bolt was looser than 36in/lb and the previous procedure had me tighten them all to 15ft/lbs.

Neither here nor there at this point though. Here are some further thoughts -

#1 - I am just out some time & a $20 intake gasket kit but won't cure the pinging
#2 - I'm out $140 for another head gasket set & bolts and the blowby may not cure itself.
#3 - This is where I'm leaning, just burns up my $500 spare set of heads
#4 - If the block needed to be bored I guess I might go this route as I would be buying pistons anyway. Additional cost of pistons... but I could use the heads I have on hand.
 

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Was hoping so but after retorquing them (no guarantee they're perfect, but way better than they were) the pinging is no better and no worse. 91 octane fuel helped to some extent.
I was wondering if heavy detonation might have loosened the bolts. Off the top of my head, I don't think that they call for a lot of torque.

Why gaskets so damn expensive these days? My guess- when you do need them, they have you over a barrel and can just get away with robbery.

I'm hoping that the bores are still within diameter spec. Then all it is is honing and rings, and a judgement call on the bearings. Without going back through the thread, it seems that this truck was relatively low miles (for the age anyway). That would put me in a "minimalist" frame of mind, or approach, to putting just what's needed into the motor to get it into a reasonable running condition.
 

gaz

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@Shran ,
My bust, even the 95-97 heads are fastburn combustion chamber...all OHV 4.0l heads from 95 to the end are the fastburns and all OHV 4.0l pistons from 95 to the end are large dish.

If you pull the exhaust manifolds and have the small nearly round 2.9l size exhaust ports, you will know immediately that they are 98+.

Also, reset your PCM. If it is a compression issue and you don't have a full tank of premium in there, you may need to run out the mixture.
 
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Shran

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I contacted the machine shop and they said worst case I am looking at $1800-2300 to go through the shortblock... less if it's in really good shape.

However they are at least 3 months out. Having used them before, that probably means 6 months.

I'm kind of leaning towards Option #5 and #6 that I didn't mention...

#5 is cleaning up my spare 4.0 and dropping it into this truck, at least temporarily. I know it runs but that's about it, I pulled it out of an Explorer I junked but the fuel in that truck was really bad and I didn't leave it running long.

#6 is taking this engine apart myself and inspecting everything, buy a few measuring tools and a hone and see how I can do on my own since I apparently have time

#5 cuz I have it and would be nice to have it cleaned up & verify that it runs so that I can use it for future projects, #6 because why not I guess.

I haven't had time to do much more with this project but may dig into it this evening and start disassembly.

Thoughts?
 

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I would probably go with 5, and then do 6 in spare time.
 

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^^^ What he said. See if you can get the spare engine to work and work on the bad motor as you have time and money.
 

Shran

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I got the money, I just don't want to wait 6 months to drive my damn truck 😂 😂 😂 I hate having dead trucks stuck in my shop long term.

#5 was always an option, I just didn't want to use up my spare engine for this particular project so I didn't mention it. But being able to run it a while & verify its condition would be valuable I suppose.
 

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