Good news guys! I have crappy compression!

[CManT1914]

But on all my cylinders. Doesn't it mean if you have bad compression on all cylinders that it's leaking valves or rings? If you have bad compression on just one or two cylinders, then that means bad head gasket right? You don't even want to know what my compression was, it was THAT bad!! I'm gonna start pulling off my intake/valve covers to reset the lash on the rockers.

 

[94MustangGT5.0]

Are you sure you did the compression test correct? It seems odd that every cylinder has bad compression, so I just wondered if maybe your methods were incorrect (not to say you don't know what you are doing, just make sure you did it correct before you go to all of the work of tearing the motor down). Maybe your torque wrench was off when you snugged down the heads and you don't have them tightened properly, just a thought. I hope it's an easier fix than it sounds, because if you truly do have bad compression in every cylinder (or I suppose just one for that matter) it may be time for a 306.

 

[HISSIN50]

Chris, from the sound of it (what you said about your cam's characteristics), dont read too much into the compression numbers (unless they completely suck). When a sloth of a cam is installed, it can be normal for the absolute compression numbers to go down.

The leakdown test you have planned sounds good.

Good luck bud.

 

[CManT1914]

I just really don't know what to do right now. I got one guy who is a certified mechanic (doesn't specialize in mustangs but still) telling me bent valves, and that I should have at least 200psi compression. Then I got another guy who could get certified if he took the test telling me the rockers are just to tight probably. Then I got a mustang guy with the same stuff as me telling me he doesn't see how I could have bent a valve just like that, especially since I haven't been revving it and I've only driven it around the block twice. I mean I do have 110k miles on my car, it's not gonna have the greatest compression anymore right? The mechanic is saying 135 and the car shouldn't even start. Well it did, and it drove, just poorly. Should I readjust the rockers and put it back together and see how it responds, or wait for the leakdown test tomorrow morning?

On a side note, when I went to take my upper intake off, a few bolts weren't tightened all the way, causing me to think I MIGHT have had a vacuum leak afterall. I'm tempted to put everything back together and tighten down those bolts good to see how it acts then. There aren't any torque specs on the upper intake are there? I never found any, so I just tightened them pretty snug (well half, Mike did the other half).

GAH!!! This is frustrating and depressing, I don't even feel like doing anything right now, except maybe push it off a damn cliff. How could I tackle a complete H/C/I swap in a weekend, then be dumb enough to tighten the rockers to much and f*** up my valves?!?!?!?!

 

[igotyofire]

lol im just gonna guess and say the compression is fine, i dont know much, but 200psi seems high IMO would 9:01 really create that much pressure....actually now with ur heads i dunno what the compression is now, i know lil bit higher, keep in mind i dont know anything just stating what i think to be true, hafta call up my buddy later and ask

 

[94-302-vert]

I would tighten the intake back down then see where you are.

Not to knock either of the guys working with you but a friend of mine fought with an overheating problem in his early 90's 4Runner and I was the only one (including his mechanic buddy and a toyota dealership) that suggested a weep hole in the t-stat when he replaced it or to get the correcToyota one.

Solved his problem for $15 after a week of screwing with it...

Let us know where you are after...

 

[final5-0]

I just really don't know what to do right now. I got one guy who is a certified mechanic (doesn't specialize in mustangs but still) telling me bent valves, and that I should have at least 200psi compression. Then I got another guy who could get certified if he took the test telling me the rockers are just to tight probably. Then I got a mustang guy with the same stuff as me telling me he doesn't see how I could have bent a valve just like that, especially since I haven't been revving it and I've only driven it around the block twice. I mean I do have 110k miles on my car, it's not gonna have the greatest compression anymore right? The mechanic is saying 135 and the car shouldn't even start. Well it did, and it drove, just poorly. Should I readjust the rockers and put it back together and see how it responds, or wait for the leakdown test tomorrow morning?

Chris

Like JT talked about, sometimes a cam can cause the numbers to be lower.

Just tell us the results and don't worry about it. Main thing is that they all are close to each other in value. btw......no way are you gonna have 200lbs, lol.

Don't be upset but it is possible that you might have have a few valves too tight.

On a side note, when I went to take my upper intake off, a few bolts weren't tightened all the way, causing me to think I MIGHT have had a vacuum leak afterall. I'm tempted to put everything back together and tighten down those bolts good to see how it acts then. There aren't any torque specs on the upper intake are there? I never found any, so I just tightened them pretty snug (well half, Mike did the other half).

That is normal. You gotta check all bolts after a couple of heat cycles. Things loosen up a bit and thats just how it is, lol.

GAH!!! This is frustrating and depressing, I don't even feel like doing anything right now, except maybe push it off a damn cliff. How could I tackle a complete H/C/I swap in a weekend, then be dumb enough to tighten the rockers to much and f*** up my valves?!?!?!?!

I doubt if you bent any valves. If your c test showed low values on just some of the holes, then that is the one you wanna focus on, make sense, yes/no, lol.

Quit being too hard on yourself and just calm down. You've learned a lot from this upgrade.

and remember this .................................

We've all seen some folks who don't have the balls to even try what you just got through doing.

Later
Grady

 

[95strokerPSU]

Yeah, you'll get it fixed soon enough and then all the frustration will be worth it. Last summer when I did my whole rebuild, I actually had to leave to go back to school in August for my senior year without having gotten the car to run. So I know what you're going through, just keep a positive mind and keeping asking questions.

Sorry I can't help with any of the tech stuff.

 

[94 Cobra 5.0]

im not exactly the smartest person in the world and definetly dont claim to be but 200 psi sounds way to high. i would think that 125 - 130 would be a better number to see from my experience with stangs. things you might want to start looking into replacing if you havent already would be the timing chain. it just doesnt sound like you bent a valve cause your car probably wouldnt start at all if you did bend a valve. if all your compression numbers are low i would start looking into the cylinder head gaskets being bad rather than a bent valve. i know they make a tool that you can leave your cylinder heads on the car and change the springs. it threads into the spark plug well and you hook a airline to the fitting and it acts as if the cylinder is compressed. might be something to look into if you dont want to pull the cylinder heads off to see if the valves are bent.

 

[bimmertech]

low even compression on all cyl typically means a bad timing belt or chain. low compr on 2 adjacent cyl would be head gasket. low compression on one cyl would be rings/valves/etc.. i would have to say that since i remember you asking how to adjust valves in another thread(i think that was you) you prolly got the valves to tight. you don't go 3/4 turn once you can't twist the pushrod. you go 3/4 turn after you can't move the pushrod up and down anymore.

 

[CManT1914]

Chris

Like JT talked about, sometimes a cam can cause the numbers to be lower.

Just tell us the results and don't worry about it. Main thing is that they all are close to each other in value. btw......no way are you gonna have 200lbs, lol.

Don't be upset but it is possible that you might have have a few valves too tight.

So a cam can cause lower compression huh? That's good to know. I really didn't think I was supposed to have 200psi+ of compression, that just sounded ridiculous. Tomorrow after the leakdown, if I pass, I'm just gonna relash all the rockers, put it back together, make sure I get the damn intake bolts good and tight, check for vacuum leaks and see how she runs.

That is normal. You gotta check all bolts after a couple of heat cycles. Things loosen up a bit and thats just how it is, lol.

I'll redo them tomorrow, maybe they just came loose with the heat.

I doubt if you bent any valves. If your c test showed low values on just some of the holes, then that is the one you wanna focus on, make sense, yes/no, lol.

Quit being too hard on yourself and just calm down. You've learned a lot from this upgrade.

and remember this .................................

We've all seen some folks who don't have the balls to even try what you just got through doing.

Later
Grady

Well I have steady compression across all cylinders. When I did back off the rockers and relashed them, I came up with a steady 145 or so. I figure that should be plenty good enough for a 110k miles motor. Yea I'm getting a lot of guys telling me I did an awesome job especially for my first time. I just gotta work out the bugs they're saying.

im not exactly the smartest person in the world and definetly dont claim to be but 200 psi sounds way to high. i would think that 125 - 130 would be a better number to see from my experience with stangs. things you might want to start looking into replacing if you havent already would be the timing chain. it just doesnt sound like you bent a valve cause your car probably wouldnt start at all if you did bend a valve.

I replaced the timing chain with a FRPP double-roller steel one, so it should be good to go. Well she started all right, just ran like poop.

Thanks for the encouraging words guys. I really don't think I could have bent any valves, as the motor hasn't seen the topside of 3500rpm since she's fired, and only about 1/3 throttle at most. I'll definitely update yall tomorrow morning after I get the results from the leakdown.

Worse case scenario, if I did have to pull the heads, I could put my stockers back on with the Stage 1 cam, and she would run decent right? Like would the cam be too much for the stock heads and make me run slower than before? I gotta look at all possibilites right now. Thanks again!!

 

[bimmertech]

I really don't think I could have bent any valves, as the motor hasn't seen the topside of 3500rpm since she's fired, and only about 1/3 throttle at most.

i hate to be the bearer of bad news but it doesn't matter how many rpm's you turn to bend valves. unless you have valvetronic the valve lift is the same regardless of rpm and the piston moves all the same. i don't think you bent valves, but it's real easy to tell once you pull the valve covers, so don't get crazy and pull those heads back off yet.

 

[final5-0]

145 lbs across all the holes is fine.

Even more so with 110K on the clock!

Nothing wrong at all with that value.

Just get all the little stuff like loose bolts, v leaks, etc all taken care of and your good to go.

After several hundred miles, if you notice a little bit more valve train noise .........
you may want to make a final valve adjustment.

Later
Grady

 

[HISSIN50]

Chris, if you got those compression numbers after having driven it with the new combo, valves should be fine IMHO.

With variations in compression-testing procedures, 130-180 PSI is good to go, IMHO. Like wise ol' Grady said, consistancy between all the cylinders is what matters, so long as the numbers look good, which they do.

Like everyone said, hang in there. Think about how you will be cruising and sitting at lights with that mean cadence (lope) scaring small animals for miles.

 

[CManT1914]

145 lbs across all the holes is fine.

Even more so with 110K on the clock!

Nothing wrong at all with that value.

Just get all the little stuff like loose bolts, v leaks, etc all taken care of and your good to go.

After several hundred miles, if you notice a little bit more valve train noise .........
you may want to make a final valve adjustment.

Later
Grady

That's reassuring. I don't know if anybody remembers, but last fall when I first did my intake swap, I mentioned how I couldn't get a front bolt on it threaded. Well I was inspecting the lower intake today, and one of the lower threads are larger than the rest. Looks like the guy that had it before me must have cross-threaded and stripped the threads and recut them. I gotta find the right size bolt for that.

Chris, if you got those compression numbers after having driven it with the new combo, valves should be fine IMHO.

With variations in compression-testing procedures, 130-180 PSI is good to go, IMHO. Like wise ol' Grady said, consistancy between all the cylinders is what matters, so long as the numbers look good, which they do.

Like everyone said, hang in there. Think about how you will be cruising and sitting at lights with that mean cadence (lope) scaring small animals for miles.

Well I got a consistent 135 before, and after I readjusted the lash on the rockers, I got it up to 145-150 or so. Yea I can't wait until I can actually enjoy the fruits of my labor. It's gonna be real funny come time I run into a ricer the first few times.

 

[final5-0]

Well I got a consistent 135 before, and after I readjusted the lash on the rockers, I got it up to 145-150 or so. Yea I can't wait until I can actually enjoy the fruits of my labor. It's gonna be real funny come time I run into a ricer the first few times.

You see Chris, that right there shows that you most likely had things a bit tight.

It really is easy to go beyond zero lash and not even know it.

It takes a very delicate feel to find that just right spot where zero is and if you have someone to show you ...... it helps a lot.

Stuff like this is kinda hard to explain over the internet, at least for me it is.

Later
Grady

 

[CManT1914]

You see Chris, that right there shows that you most likely had things a bit tight.

It really is easy to go beyond zero lash and not even know it.

It takes a very delicate feel to find that just right spot where zero is and if you have someone to show you ...... it helps a lot.

Stuff like this is kinda hard to explain over the internet, at least for me it is.

Later
Grady

If I were to set the lash with a feeler gauge (much more accurate than my fingers, lol), what kind of tolerances would I be looking for?

 

[igotyofire]

yea i knew 200 was too high, yea a bigger cam will bleed off compression if im not mistaken its becuz the exhuast vavle or intake valve may open a lil earlier then b4 thereby allowing some to escape the compression...i think thats correct, but i dont think its dramatic, thats why with alot of race cams they recommend u have a certain compression or higher so u dont loose too much power.... once again if im not mistaken

 

[Venom351R]

Id start small, adjust your rockers and go from there. If that does not help at all then you can start to think of bigger issues. At this point adjusting the RR's would be the easy thing to start out with.

 

[CManT1914]

Id start small, adjust your rockers and go from there. If that does not help at all then you can start to think of bigger issues. At this point adjusting the RR's would be the easy thing to start out with.

I'm gonna do that this morning. Do they need to be set with a feeler gauge? The mechanic told me yesterday that's the best way to do it.