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Discussion Starter · #1 ·
It's been a while since I've posted. Nice to be back. A while ago I swapped a doner 3.4L of unknown milage and it's been great so far but the motor is getting tired. The compression is about 150 in 4 cylinders and about 114 in 2. So, it's about time to do something with it. The tranny etc. seem fine.
I have 3 options:
1. Buy a crate with a tow package for about $1500. Since I've already done all the swap stuff I'd only have to drill the starter mount.
2. Replace the heads (leaky intake valves seem to be causing the low compression), cam and lifters for about $700
3. Get rid of the Trooper . . . it has about 400,000 miles on it.

I'd like to save as much $ as possible, but I'm worried that if I just replace the heads and cam without rebuilding the lower end I may be just buying myself a little bit of time before the rod and crank bearings go out. Right now the lower end seems fine - there's no noise and the oil pressure is about 27psi at warm idle and 65psi at warm 3500rpm, but I'm worried that the increased pressure from the new heads and cam could put too much stress on the old parts.

So, what kind of luck have you had putting new heads on an older block? Should I just bite the bullet and buy the crate engine?

Any sage advise is greatly appreciated. Jim
 

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not exactly sage advice, but i say rebuild the whole long block!

cheers, john
 

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1st do a dry/wet compression test. Check compression then squirt some motor oil in the cylinders and turn it over a couple of times without starting then check it again. If the number come up significantly then rings are worn and it's time to rebuild the long block. If they don't then pull the heads and have a good 3 angle valve job done on the heads at a good machine shop. Have them check the valve guides for wear and replace if needed and replace the valve stem oil seals and check the heads for flatness. Put it back together and run her till she drops. Your numbers on 4 cylinders is not bad. I really don't buy into the deal about stressing the bottom end with fixing the top end unless the bottom end is already in sad shape. 150 pounds is decent and if oil pressure is good I wouldn't sweat it at all. I wouldn't worry about the cam either.
 

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Discussion Starter · #4 ·
I've almost settled on buying heads (or having a shop rebuild them depending on the price). I am going to get a 252 cam with roller rockers.

I will do the wet/dry compression test, but I did a leak down test which indicated bad intake valves in two cylinders.

I'm a little worried that it may be a blown head gasket (I'm losing coolant too and I can't find a leak) and I have been told that in bad cases the escaping gases can "cut" a grove in the top deck of the block between the two cylinders. If that's the case I would have to have the block mechined flat which would add a lot to the time and expense. Anyone know how likely this is?

If I have to rebuild the whole engine I'll buy a crate engine. The cost is about the same and I'd get a warrantee.
 

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jimmyjammer said:
I've almost settled on buying heads (or having a shop rebuild them depending on the price). I am going to get a 252 cam with roller rockers.

I will do the wet/dry compression test, but I did a leak down test which indicated bad intake valves in two cylinders.

I'm a little worried that it may be a blown head gasket (I'm losing coolant too and I can't find a leak) and I have been told that in bad cases the escaping gases can "cut" a grove in the top deck of the block between the two cylinders. If that's the case I would have to have the block mechined flat which would add a lot to the time and expense. Anyone know how likely this is?

If I have to rebuild the whole engine I'll buy a crate engine. The cost is about the same and I'd get a warrantee.
Are those two low cylinders right by each other? Losing coolant and low compression are classic signs of a head gasket. Your valves may be fine and you may need to just replace the head gasket.
 

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Hi,

Not to hi-jack, but do you have a telephone number for your crate engine source. I have a tired 2.8 V6, and would like to know the contact information.

Thanks,

Mark
 

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Discussion Starter · #7 ·
I don't have a number for the crate, I've just googled for it or looked at other threads here. There are a few places.

I suspect that it might be a blown gasket. But if I take the heads off I will either have them rebuilt or buy replacement heads. In any event I am planning to replace the cam.

Jim
 
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