I did a compression test on a 302 mustang, and am looking for others opinions on the results...

1-135
2-140
3-140
4-140
5-135
6-140
7-135
8-140


The fact that they're pretty even is good, but they seem a little lower than I'd like. The engine has 100k miles on it. Is that near rebuild time?

 

Normally yes, but with those results your good for a good long while yet.

-Matt

 

The reason I ask is because I might be purchasing the car, it's a 94 cobra, and it's down on power. Not much power coming from the motor, so I'm trying to find out why.

So those #'s are acceptable and I wouldn't have to do a rebuild in the near future...what's considered the rebuild area?

 

I'd be more nervous if it was down around 100-120, and using oil or smoking a bit. I'd say it's got some life left in it at this point. Go for it, what the heck!

 

Personally, I consider a "rebuild" as having the engine bored, decked, the crank being turned, heads shaved etc...etc.

It could'nt hurt to run a bottle of SeaFoam through your brake booster tosee if you can clean her out and unstick some things. Just might bring up the compression on those two banks.

-Matt

 

I've seen suggestions of that procedure before to others. If I buy the car I will consider it.

It's just down on power and I am nervious it's internal, since a low compression motor will burn lots of oil and not be very powerful, but sound/work fine.

 

I think you said before that this car belongs to a friend or something and is one you're fairly familiar with? So, does it burn lots of oil? If so, then I'd think twice for sure. I assume you don't really want to get into a major rebuild right now, especially since you're still dealing with your truck.

If it's got 100k on the clock and is using oil, then I'd say it hasn't exactly been babied. I'm not exactly going back on my earlier statement, but it does warrant further investigation.

 

My buddy said it doesn't really burn oil, but I won't know the real answer to that unless I figured it out myself. He drives it using a lot of RPM. Not really a high winder, like he doesn't rev it out to max RPM, but he likes to drive it in the 2-3k rpm range, he doesn't drive it below 1500 rpm. So the motor sees more RPM then, atleast I would run it at. He's only had it for 2 years or so, and it's been stored during the winter. I think he's only put about 20k miles on it. But the previous owner....who knows...I'm sure it's been a little beat on...what mustang isn't...ya know lol.

I'm just afraid of having to rebuild it within the next year or two. I don't mind doing it over in the future, but just not so close to the project i'm still workin' on lol.

 

See if you can pin him down a little better on that statement. "Doesn't really burn oil" might mean, to him, "It only uses a quart in 500 miles" or something of that nature. If it's more like a quart in 1500 miles, then I wouldn't really worry about it and I'd look elsewhere for your power loss. The numbers you quoted aren't really bad and I'm not sure exactly what they should be for that engine, but I would expect that, with everything tight it should more on the order of 150-160. And of course there can be variations depending on exactly how the test was performed.

And I know what you're saying. You need a chance to recover a bit before tackling another major project, because if I know you, you wouldn't be able to just do a stock rebuild and let it go at that, would you?

 

To be honest, he probably doesn't even know how much it burns oil. He's not a super techncial guy, he likes fast cars and knows some basic car knowledge but doesn't really get into it.

I could tell you anything about the history of my vehicles off the top of my head but he couldn't...

If I were to rebuild the motor, I'd either do a 306 or 331, pretty mild intentions though. I'd probably put the GT-40Y heads off my 393 onto the mustang engine, and get some big mothas for my 393. I bet a few parts off the 393 will make it onto a 5.0.

Probably stock cobra cam, use my 1.72 roller rockers, stock intake, yada...keep it simple for the next engine project. I would intend the car to be more of a civilized vehicle, with a mild motor. My truck is not anywhere near that status lol.

The truck would be the project vehicle and the mustang the more daily driver....although....something I drive is never really a daily driver lol.

 

See, I knew you couldn't leave it alone! I wouldn't be able to either!

Justin, at this point it's really up to your gut feeling. You'll just have to go with what feels right to you. If you don't trust the car, then walk away from it. Something better will come along. But if you get to thinking about it and decide you're willing to take the chance and accept whatever comes, that's great too. I guess you just have to have the right mindset about it. And sometimes, your gut feeling can be wrong, when given time to settle a bit. Case in point:

On Saturday I bought a Taurus SHO. It's primarily for my mom to drive, to replace her aged '88 Tarus L, a plain, stripped-down car. I liked the Taurus SHO on first sight, but I started to get a strange feeling about the guy selling it. After we decided to buy it we went into his office to do the paperwork and that's when he told me there was no title to the car, and it wasn't even in his name. We had driven 2 hours to look at it, and I was ready to walk away. But my mom really wanted the car, and I have to admit I did too. (Never thought I'd want a V6 FWD sedan before!)

The short of it is, I went against my immediate gut feeling and it turned out okay. DMV gave me no problems on registering it, there was only one other paper needed and it's in the mail, so it's a done deal. Sometimes, it's just meant to be!

So, is there a snake in your future? Are you gonna have to change your username to "Cobra221", or "MustangCobra221"?

 

Heh, I've had this user name on other things (like AIM) for years upon years. 21 was my number for varsity ice hockey in high school.

I'm still not sure what I'm going to do about the car. Here's a picture of it...

 

Just a bit of useless trivia, the cobras came with 1.72 ratio roller rockers from the factory.

 

Yes they did, but I can put new ones on it if need be.

 

I talked to my buddy more today. He told me he thinks he fixed the car by cleaning the MAF sensor.

I mentioned that to him before, saying it should be done, looks like he may of taken my advice and done so on his own. He said no more check engine light (used to come on occasionally) and it has a lot more power. We're taking it to the track on friday, but I think I'm going to buy this car