Dilemma, wut to do with a tired motor

TrueBlue95GT · Nov 17, 2004

My motor is getting tired and I dont know what to do with it. Should I rebuild it and put some TFS heads on it with a Custom cam, or should I save up some money and get a 347 stroker kit with I dunno what type of heads and a custom cam, or should I save up more and get a 351? Keep in mind that down the road, I will be making a custom turbo kit. I want to be at least deep into the 11's, later. Help me decide what to do now.

Joes95GT · Nov 17, 2004

What kind of mileage is on the motor? What makes it "tired"? Using oil excessively?

I'd save the cash for a cast crank, a nice rod, and a nice set of pistons and put them into the overbored stock block. You could have a nice 425 RWHP daily driven car with the properly chosen parts.

Joe

TrueBlue95GT · Nov 17, 2004

I only have 76,000miles on the car, but I wasn't the first owner. Anyway, its got low compression.

95redSVT · Nov 17, 2004

I bought m cobra and promptly dynoed it at 140 hp to the back wheels. Is she tired? hell yeah. Is she still the last year they put the 5.0 in a mustang, hell yeah. Im rebuilding mine over the winter. If i were you Id keep the motor no matter what so that you still have the stock block/heads that kinda stuff. If you buy a new motor then just store the original and if you keep the car for any long term, slowly rebuild it and sell her in 20 years

Joes95GT · Nov 17, 2004

TrueBlue95GT said:
I only have 76,000miles on the car, but I wasn't the first owner. Anyway, its got low compression.

Did you do a compression check? What did it check out at? If it sounds like I'm trying to disprove you or call you wrong, I'm sorry; I don't mean to.

Anyway, it kinda sounds like you are looking for a reason to build a 347?

Joe

TrueBlue95GT · Nov 17, 2004

Well I did do a compression test, but I didnt do it totally right. I did the test, but forgot to keep the throttle butterfly open. So I got basically 130psi in most of the cylinders and got 142psi in one of them and the other I got 65psi. This makes me think I have a burnt exhaust valve and low compression overall. I dont want to replace the cylinder heads thinking its a burnt exhaust valve and find out that my piston rings are shot because this is my daily driver. So I might as well build a setup and drop it in. It's never run up to "par". I ran a 14.8 with the mods I have on now with a 2.2 sixty foot. Enough said.

Joes95GT · Nov 17, 2004

TrueBlue95GT said:
Well I did do a compression test, but I didnt do it totally right. I did the test, but forgot to keep the throttle butterfly open. So I got basically 130psi in most of the cylinders and got 142psi in one of them and the other I got 65psi. This makes me think I have a burnt exhaust valve and low compression overall. I dont want to replace the cylinder heads thinking its a burnt exhaust valve and find out that my piston rings are shot because this is my daily driver. So I might as well build a setup and drop it in. It's never run up to "par". I ran a 14.8 with the mods I have on now with a 2.2 sixty foot. Enough said.

I wouldn't go by track times in this case. Track times don't necessarily tell you if something is "wrong" with your car.

Those compression test numbers are typical of some old 5.0's with the butterfly OPEN. Well, I shouldn't say typical, but they certainly aren't out of the ordinary. The one cylinder's 65 PSI seems kind of fishy, but I think maybe you didn't test that one the same, causing you to get a "bad" reading?

I honestly don't think anything is wrong. Maybe it just needs a tune-up of some sorts? Have you tried putting it on a dyno and checking the A/F ratios and seeing what kind of power it's spitting out?

Just for your reassurance, I have never seen or heard of a car that blew the rings out of it and didn't have oil consumption problems, and that was still driveable. Again, just because I say that doesn't mean that it does not exist.

Good luck.

Joe

TrueBlue95GT · Nov 17, 2004

i checked the 65psi cylinder three times and got the same result each time which makes me think bad exhaust valve. Could the butterfly not being open lower the compression numbers?

Joes95GT · Nov 18, 2004

TrueBlue95GT said:
Could the butterfly not being open lower the compression numbers?

Eh, well, um, see, I, well, I...I don't know.

There are too many other factors playing into that.

What do you mean when you say bad or burnt exhaust valve? You think it's not coming into contact with the seat anymore?

Joe

TrueBlue95GT · Nov 18, 2004

Ya, i heard that an exhaust valve not seating correctly is the most common reason only one cylinder has low compression. it's not likely that the rings went only on that cylinder. And i'm pretty sure my headgaskets are fine because i have no coolant mixed with the oil and no smoke out the tailpipes.

Joes95GT · Nov 18, 2004

TrueBlue95GT said:
Ya, i heard that an exhaust valve not seating correctly is the most common reason only one cylinder has low compression. it's not likely that the rings went only on that cylinder. And i'm pretty sure my headgaskets are fine because i have no coolant mixed with the oil and no smoke out the tailpipes.

If the exhaust valve isn't seating properly, there must be something on that valve not letting it...

Maybe run some kind of engine cleaner through it? The purpose of that stuff is to clean all the carbon off the pistons. It should clean the valves off too (well, do a half-assed job of it). I'm just throwing ideas around....

The only other way is to lift that head.

Joe

WhiteDevil · Nov 18, 2004

I dont think the butter fly being open or not would be a problem, as long as you did all the cylinders the same then that is fine. Why not just take the heads off and see how they look, and then start from there. Most 5.0L last for quite a long time, so unless it was abused before you owned it with no oil changes and high heat and RPMs it should be alright.

94-302-vert · Nov 18, 2004

I would honestly do the following:

With the engine running mist water into the intake tract, this will form steam in the cyclinders and help to clean the carbon. On a mopar since there is no MAF this works well and is easy. jsut keep revving the egnine a bit to make sure it gets sucked in. I usually run about 8 oz through the engine and my missting it with a spray bottle you will not hydrolock the motor.

Then use a scraper of some sort and a scre driver and really celan around the spark plug hole, then remove the spark plug and re-try the compression test. the compression tester not being fully seated or sealed here will give the same results.

Let us know how it goes.

blksn955.o · Nov 18, 2004

TrueBlue95GT said:
Could the butterfly not being open lower the compression numbers?

Dont you do a comp. check on the comp. stroke? That would mean that the valves are closed anyway (or should be) making it realy pointless to have the t-blade open as the cyl. should be sealed by the valves at that point.

The vavles could be bad, and so could the head gasket as not always does the coolant flow into the oil or vice versa. Also the rings could be bad too.

94Blue302GT · Nov 18, 2004

i think you need to just give up mustang racin altogether and gimmie your car... well, at least a drivers side fender.

Dilemma, wut to do with a tired motor

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