Should I remove heads on a used DOHC 4.6?

[Ashlander]

Just got a 98k mile motor from an 03 Mach 1. Turns over good, and didn't see any metal or coolant in the oil (they didn't drain it before shipping). Was told it ran good and got good compression, but never got around to getting the test numbers. It's pretty dirty, but haven't seen any signs of leakage. I was planning on removing the timing cover, valve covers, and oil pan at the very least to look at the timing components and inspect the bottom end before putting it in the car.

I'm on the fence of whether or not I should take off the heads to check the cylinders. I've heard people say they wouldn't even think about cracking the heads on these motors unless there were signs of a major failure. Wondering what other people's thoughts on this was. Obviously if money wasn't an issue I'd just play it safe, but just removing the heads will run at least another couple hundred just in gaskets and bolts, which could go towards headers or a tuner.

 

[NastyNate420]

I wouldn't crack the heads. id do a leakdown test though . If that came back bad then Id crack it open

 

[98 N/A 4V]

If the motor is on a stand at a minimum I'd check the main bearings. Remove 1 cap at a time and check the wear. But the flip side I can't remember of those bolts are TTY. At that point you rotate the crank (put the cap back on first) then you can kinda look up into the bore to see if there is any scoring. Either that or get a bore scope to look at the cylinder walls.

-Mark

 

[Mrpancho95]

Main bolts will be TTY

 

[Ashlander]

Yeah, I think the mains are TTY.

If the motor is on a stand at a minimum I'd check the main bearings. Remove 1 cap at a time and check the wear. But the flip side I can't remember of those bolts are TTY. At that point you rotate the crank (put the cap back on first) then you can kinda look up into the bore to see if there is any scoring. Either that or get a bore scope to look at the cylinder walls.

-Mark

I was wondering if that would work, but wasn't sure how much of the cylinders would be exposed behind the pistons. I originally planned on just removing the pistons from the bottom to check. I could do that on the old 302s, but it looks like these don't have enough clearance for that.

Thanks for the tips though, helps alot. I was a little wary about not checking under the heads, but sounds like it's not needed unless I find other issues.

 

[99COBRA2881]

A compression and leak down test will show anything wrong inside the cylinder. They will show more than a visual "hmmm yup looks good" will show. Do both it you are worried. If the motor hasn't been run for a while take a long tube and put about a teaspoon of oil in each cylinder and rotate the motor before doing the tests.