I took my truck to ford to have the IAC, PCV, and EGR replaced along with an oil change. i also asked them to do a compression test to see if my engine could be burning oil to determine whether or not it was burning or leaking oil. they gave me the following results back

Relative Compression
CYL 1, Difference 0%
CYL 3, Difference 0%
CYL 7, Difference 0%
CYL 2, Difference 0%
CYL 6, Difference 1%
CYL 5, Difference 2%
CYL 4, Difference 1%
CYL 8, Difference 9%

they said that Cylinder 8 probably has a bad valve or valve spring and it would cost around $1500 to $3000 to fix. should i get a second opinion or is this plenty evidence. If infact i do need to do head work or rebuild the engine i would like to get performance heads but i know nothing about that, so please help me with this because that is a lot of money to play guess and check with. thank you.

 

Did they borescope it? That would check for a valve sealing problem.

9% isn't that much. What was the highest compression? These engines are known to burn some oil. If your at 125lbs on all the "good" cylinders, then 9% of that is still 113-114lbs... not too bad. When you reach 100lbs, then you start having a problem and looking at an engine rebuild. The valve sealing wouldn't 'cause an oil burning problem...

The aftermarket performance heads are very pricey. Try the price they gave you for the headjob is what you'd pay for one aftermarket head. Your gonna need two, plus two cams, the springs, valves, and other hardware plus an ECU upgrade to account for all the improvements. Do the job right and you're into the price of a Hi-Po 4V 5.4L engine offered from the factory with out any labor involved, yet.

If it is a valve or spring... a complete head job could cost you $1500, it's mainly in labor.

You can find a head for your model truck ('cause a mis-match would definitely be a no-no), have it machined if necessary. Fit the valves, springs, and cam. You might save yourself a couple hundred on the $1500 bid.

I'm not saying throw a band-aid at it... but I'm not convinced you need all that work. These engines are expensive and expensive to work on. They might be working that edge to sucker you into a never ending mechanic's bill.

-Kerry

 

well the only other thing i can get off the sheet they gave me was that the Mean Cranking RPM = 174, i dont know what that is tho. They did tell me that it was not going to cause any immediate problems and wont cause anymore to fix now than it will if i wait to fix it. I was planning on doing head work next since i cant get much more power with bolt ons. money wont be to much of a problem when summer hits so is there a kit i can buy to upgrade the heads or do i have to buy individually? also i was wondering if yall knew any good performance shops out of houston that could help me plan out the most efficient way to upgrade my truck involving internal engine work. (2001 4.6l VIN W)

 

9% isn't much to worry about.

Are you using synthetic oil? It tends to evaporate and you "use" .5-1 qt between changes.

If it were me, I'd take the thing out on the highway and wind it out a few times. Chances are, that 9% difference will go down when you blow the carbon off the valve seats

Oh, and by the way, a valve spring, unless it's VERY weak to the point of not holding the valve closed (very rare and you'd notice the misfire), is NOT the cause of your low compression. It would have to be a valve seat leaking or rings. But again, I wouldn't worry about it too much. The dealer should have shot some oil in that cylinder to see if the compression came up or not. If it didn't, it's valves, if it did, it's rings.

art k.

ps: even if the static compression was 200 lbs, 10% low is 180 lbs. That's just not a whole lot of difference.

 

Not too sure about that rpm... way to high to be cranked by hand and way to low to be the starting rpm. If it was averaged over a minute that may be what they came up with.

I've got some very good leads on parts and suppliers, not any in the Houston area, though. Try the local chapter of FTE for recommendations.

When you swap a head, especially on these mod motors, you want to do it right. It can be a vicious cycle. Then you have the money thing.

You claim you'll have the money, then go aftermarket all the way (heads, cams, springs, valves, and guides) that'll give you the most bang. If you do realize money isn't limitess. Keep your factory heads, have a machine/engine shop go over them. I suggest going with a set of oversized valves (45.5mm intake, 37mm exhaust), titanium springs, and for streetability - 2 hot street cams. Don't forget to have a good valve seat grind and port match done. I've seen prices at just about $1700 for both heads using the old PI heads you have now.

Eventually you'll need to upgrade all else to fit those heads. The computer program will be a must, as the stock program will be overwhelmed by the flow rate of those heads, and the engine will not function properly.


-Kerry