Well my “Should I buy it” thread has gone on for several pages and I did buy it. Ha ha. But now I’m trying to decide on what to do. So now comes the official “What would you do?” thread. Long story short, I’ve got an 01 quad cab with the 4.7 with a bad valve seat. You can see the long story here:

When I bought it a mechanic had just used a bore scope to diagnose it with a dropped valve seat in cyl #2. He reported the following compression numbers:


135 12
150 150
120 150
0 120

I was really worried about the 12 lbs in cyl #7 but he never mentioned it in his notes and didn’t seem concerned with it so I was guessing that it was a typo and he meant 120 or 125. I only had his notes, I never got to talk to him.

I rented a compression gauge from Autozone and got the following results:

112 98
110 92
100 103
0 105

I know these numbers are lower than the mechanic reported. I’m guessing that the gauge that I rented and the fact that I ran the test cold had everything to do what that. I did the test cold because I’m nervous to run it with a bad valve seat and risk major damage.

I only had a chance to squirt oil in a few of the cylinders before the sun went down and I lost light. #7 went from 98 dry to 110 wet, #5 went from 92 to 105 and #4 stayed at exactly 100 both wet and dry. I didn’t test the rest.

I didn’t do a leakdown test either, but I did leave the compression gauge on each cylinder for about 30 seconds and none of them dropped at all over that time.

I can start her up and try a hot test if necessary. And I can do an official leakdown test as well, but all cylinders (except the one with a bad valve seat) held pressure fine with the compression gauge left on.

With that being said, what would you do?


Option 1) Drop $2300 on a re-manufactured long block and not have to worry about a 160000 mile motor any more. This is for a Marshall from Rock Auto.

Option 2) $1200 for 2 new heads and seals and replace timing set

Option 3) Just put a new head on the side with the dropped valve seat and call it a day. About $420.

Option 4) Just put a new head on it for now and work towards a low miles Hemi swap when this motor does wear out. I think that I have the tools and skills to do the hemi swap, but I’m not sure that I have the time to deal with all the headaches that would involve right now.

I don’t think I’ll consider a junkyard motor. They go for $1700 and up around here, and that’s for high mileage ones. I would spend the cash on a reman first I think…

 

The poll and your question have everything to do with how much money and time you have. I didn't take the time to read your other thread, but you certainly sound like you're capable of doing any work yourself.

Time but no money, you replace the heads and get on the highway.

Money and no time = buy the reman. or work your way into a Hemi.

Decisions Decisions

 

I agree Robbadodge is correct only you can answer that question

 

Well I guess what I'm getting at is if these compression numbers make it look like puting any money into the bottom end is worth it since it is a 160,000 mile motor. I was hoping that I would find something during this compression test that would be more conclusive. If all of the numbers were within a few pounds of each other (and higher than they are) then I would probably have decided right there to just do some head work. And If there was a huge variance on a few cylinders then I would have decided to just replace the motor. But I'm honestly not sure how to interpres these results.

I started this test only knowing that I had a motor with 160K on it that was running until it dropped a valve seat.

 

A compression test is not a good way to determine the condition of the rings or valves and that's about all it is going test. A leakdown test is much better way.

Regardless, you'll get a good idea as to the condition once you pull the heads off. If the bores look good and you don't find a lot of sludge when you pull the rocker covers the bottom end is probably in fairly good shape.

Only your wallet can answer your poll question. 160k or not, how much do you want to invest, time and money wise? How long do you expect to keep it?

 

I could invest the money in a new motor if I want. But only enough for a lower end reman. I'm looking at the Marshall on Rock Auto. I can't afford a Jasper or anything like that right now.

I'd ideally like to get another 100,000 miles out of it and keep it for a long time.

The more I think about it I'm leaning towards just getting this motor up and running and then working towards a built 5.7 Hemi swap over the next couple years. If I could swap in a Hemi without having to cut into the dash harness I would just do that right now, but it looks like it's gonna be harder than just fabing up some motor mounts and changing out the ECU and engine harness.

 

Do you have a machine shop in your area? You may be able to repair + rebuild your heads for under $400 for both-when you pull your heads you can see the condition of your cylinder walls-we normally hone em out using marvel mystery oil and just spinning the engine by hand-you can also pull your oil pan and clean it out make sure your screen is clean and inspect the lower end while your there-a Good Light (we use a spot light) will really help you inspect the insides-A regularly serviced engine block (lower end) will last a long time you can go through another set of rebuilt heads before you need to buy a rebuilt block-

 

Newbie,

Just put the heads on it unless you see something BAD when you pull them.

 

I vote none.

Take the heads off, buy new ones, then you get a core for the OE.

Have the OE block surfaced, AS THE BLOCK will have warped and the new heads wont seat properly on the gaskets. BET ME.

Saves you more than 1400.

OR YOU CAN
have the heads rebuilt. Then youd be good there too.

Simply, New heads=block resurface
rebuilt heads (NON RESHAVED)=stock block, then you can add in timing. But
TIMING IS NOT NEEDED

 

Really? Pulling the motor out and having the block resurfaced seems like a lot of unnecessary work for a simple head swap. Why do you say the block would warp from a dropped valve seat?