Header installation

[Vettefan87]

Well to the hesitation problem I was having is not the ECM I threw it in my bros 86 a few days back and we finally test drove it and it friggen ripped the hard out of the hole. So I dont know what I am going to do about that, and I have the backfiring to deal with now. Could they be somewhat linked together?

 

[rrubel]

If your timing is off, you could have big hesistation problems and the popping...

If your fuel pressure is under 48, I'd not worry about it.

[RICHR]

 

[Achilles]

This may be way off base, but I vaguely remember something that I once saw on one of those Sunday afternoon hot rod shows and it stuck in my mind because I once had a problem years back in setting the timing on a Monte Carlo I had. I had put a new motor in my car and that thing never did run right and I was constantly checking the timing because I thought that was the problem....Never got it fixed to run right.

Anyway, to the point. On this hot rod show, they were saying that a common mistake with engine builders is the timing gears being installed incorrectly. Don't hold me to this, but it seemed like they said the common mistake is to install the crank and cam gears with the timing marks at 12 and 6 o'clock respectively. That this can cause 1/2 to 1 deg. off in the valve timing even though the timing light may show correct timing. The proper installation is to install the gears with both timing marks at the 12 o'clock position for accurate timing and there is no way to correct this other than to pull the cam gear and reset it.

I don't know if this is correct or not. Maybe somebody else knows better, that has more engine rebuild knowledge than I. But judging from his poor engine performace, sound exactly like what I went through.

 

[Mad-Mic]

when you listen to a small block chevy with open headers at idle it will sound like it's popping per 4 stroke revolution due to the firing order. crack the throttle and listen. if it's all popping on the throttle and off the throttle then more than likely you crossed the wires.

starting from the bottom in a clockwise rotation 1 past the connection for your tach and ground is...

18436572

always check and recheck till you make sure you got it ALL right. make sure the plug boots and distributor boots are tightly on!

you SHOULD not be having these problems and the ECM should not be hunting like it is.

BTW i cut my flange on the passenger side header because my dipstick was crudded in and it would of bent it all up so i did what i had to do to get it all bolted up

 

[C4Tom]

Hmmm...not likely the header heat would cause it, unless it has burned a wire and cause a misfire.

You need to start it and listen for the backfire. Is it coming from the TB or the exhaust? Is it intermittent or steady? Is it at idle or at a higher RPM? Is it worse under load? What happens when you start it and put it in drive?

 

[Vettefan87]

Yeah my fuel pressure is around 41 or so, it was hard to get a reading due to the idle which I think is from that EGR tube blew off, and I cant crimp that lock ring down.

If I add more timing how will I know if its knocking or not since I cant hear the motor over the headers. the last time I upped the timing it started to knock, and the code for the knock sensor did not come on. I am starting to think about selling this car and getting something else. I am totally tired of this car and being broke, or not working.

I will try to get a sound clip of it when my friend with his camera has time, which I think will be on thursday, maybe some of me driving it too.

 

[Vettefan87]

Well I finally looked underneath when it decided to backfire, and it shoots a foot and a half flame out of the Y pipe. My friend said it sounds like an M-80. I turned the fuel pressure down to about 37 with the vaccum line connected and the car would barely idle, and it still backfired.

 

[Vettefan87]

Hmmm...not likely the header heat would cause it, unless it has burned a wire and cause a misfire.

You need to start it and listen for the backfire. Is it coming from the TB or the exhaust? Is it intermittent or steady? Is it at idle or at a higher RPM? Is it worse under load? What happens when you start it and put it in drive?

it seems to idle weird as I have said. When I put it in Drive it idles down like normal and moves, with the idle still being a little sparatic if I can remember right. What I dont understand is why does my brothers car not do it, but then mine does. Is it because he has full length pipes on and mine go about half way? The backfire once warmed up to about 135 degrees coolant temp it does it about every minute or so. I have not really cranked it up past 1500, one it is still cold, two I dont want it to run that long for it to get warm. three I dont know what will happen, or want to imagine what would.

 

[C4Tom]

Okay, I went back and read all the posts again. For some odd reason I wasn't reading/seeing all the replies and missed some responces. :confused

1) Headers cause the engine to breathe better, requiring more fuel to the engine. So, with no fuel changes it would create a lean condition. A lean condition causes cylinder temperature and exhaust temps to rise, each can and will ignite unspent or incoming gases... causing a backfire. Intake & exhast valve have an overlap were they are open at the same time to help with scavaging gases. This is probably when the backfire is happening.

2) Timing has a lot to do with it too. You will need to alter the timing to adjust for the better breathing. The knock/ping shouldn't be a problem until you are driving the car. You need to have the exhaust connected so the back pressure is there to set the timing. I'm guessing it's too far advanced at the moment because the old exhaust manifold was causing more backpressure and needed more timing. Back off the timing a little bit at a time(retard) and check the throttle responce. When it falls off, that's too far.

I've built a couple of racing engines(both 350 Chevy's) and modified several smallblocks. The motor in my Malibu is a .040" over 350ci that's producing 525 HP on just a carb. I tune it with open headers and I can hear a backfire when I get the timing too far advanced and I'm dealing with 13:1 compression.

You may be having more than one problem causing your backfire and you will probably have to try a few things to track its cause.

a) Verify ALL vacuum hoses are connected and in good condition(no cracks/holes).
b) Reconnect the exhaust system and check for leaks.
c) Verify correct plug wiring.
d) Retard the timing, try a couple of degrees behind factory setting.

Another thing, if the backfire is irratic, it very well could be an electrical issue. So, I would check the spark module as well.

Hope this helps,

 

[Edmond]

Maybe this is just a sign that you have to go get a C6?

 

[Vettefan87]

It is set at base timing 6 degrees before TDC with the vaccum line disconnected. I guess I will have to get a test pipe, and bang on the front Y pipe more and put my brothers old canister mufflers on it so I can hear if it is spark knocking. Well at least I can roast hot dogs now. :L

 

[vetteboy86]

I cant hardly believe he has a lean condition. He had the injectors tested for flow and spray, and they cleaned them and rebuilt them. The ECM should adjust for a lean condition per the O2 sensor. Playing with the fuel pressure is not the greatest thing to do, because remember the ECM thinks it is controlling 24 lb injectors at the stock pressure. THere is a problem here, that needs to be fixed. The ECM should learn new settings within about 2 minutes of running time. Does that sound right? I want him to hang the rest of the exhaust, and see what happens. And another thing about timing, would the ECM not adjust that too?

 

[Vettefan87]

Yeah I am not playing around with the fuel pressure on purpose. I just wanted to see if It would stop backfiring if I lowered the fuel pressure a little, then go from there, but that did not work at all.

 

[Mad-Mic]

it should sound like this.....

http://www.corvettekillstories.com/photogallery/albums/Mad-Mic/Racing/Sweet_Sin.wmv

i don't know what you did but you did something that you should not have. i am willing to bet the house that your wires are crossed bigger than chit. check and recheck. when i did my headers it started on the first crank and had NO problems like you described.

Matter of fact my car is going to be a test mule at my buddies shop doing true duals with an X pipe and an H pipe. my buddy wants to check mine out and help him do headers on a 90 vette. all i have to do is pay for materials

here is another vid from when i first started her up from the headers install. *Note* i dropped the F Bomb at the end of it

http://www.corvettekillstories.com/photogallery/albums/Mad-Mic/Racing/tpisheaders.wmv

 

[WhalePirot]

I cant hardly believe he has a lean condition. He had the injectors tested for flow and spray, and they cleaned them and rebuilt them. The ECM should adjust for a lean condition per the O2 sensor. Playing with the fuel pressure is not the greatest thing to do, because remember the ECM thinks it is controlling 24 lb injectors at the stock pressure. THere is a problem here, that needs to be fixed. The ECM should learn new settings within about 2 minutes of running time. Does that sound right? I want him to hang the rest of the exhaust, and see what happens. And another thing about timing, would the ECM not adjust that too?

It's hard to tell what he has. I have had a lot of questions unanswered, perhaps because he doesn't know. The engine builder may have put in too aggressive of a cam for the ECM to fully adjust; there could be sensor adjustments off; the injector size could be wrong; the timing could be way off; etc. All of that is very hard for us multitudes who really want this car to run right, to diagnose from afar.

The ECM can make SOME adjustments of both fuel injected and spark timing, but both are limited.

Messing with the fuel pressure is wishful thinking but throws a new issue into all of this; one he doesn't need.

I am still not sure if the the 'backfiring' is just gasses exploding in the exhaust or true backfiring through the intake. If the latter is true, I'm with MadMic on the mis-wiring of the plugs, to start. It is very easy to do. Ensure, also, that the wires are in the right holes and the timing is right on.

 

[OLDCHEV]

What vacuum line would you disconnect on an 87 at the distributer? I thought you had to unplug an electrical line to disable the computer advance on this model year????

To set the baseline advance.

 

[C4Tom]

Well...I agree that he needs the exhaust mounted before he goes any farther. I don't claim to be any wizard at engine repair, but I have tuned my own and my friends engines for the last 25+ years, built my own drag car and raced it for the last 5 years(not my first).

I will admit that the computer cars tend to throw me sometimes.

I'm not there and haven't seen or heard the car run. Just as everyone here trying to help, I'm throwing ideas his way that could, and I did say COULD fix the problem.

It's like telling someone how to fix their computer over the phone:
Family member with 'puter problem, "Yea, its telling me I can't do that"
ME, "Well...then don't do that!"
Family member, "It has a box that says if I do that again, it will erase the hard drive"
ME, "Like I said, DON'T DO THAT!!!"

 

[Vettefan87]

Ok guys, to kind of try to clear this up. The only mod done to the motor is that it is bored out 30 over. There is not a different cam or anything it is all stock. The injectors were just totally gone through and cleaned and what not, they are the stock ones to my knowledge. The backfiring is not coming out by the TB, did you guys see the post where I said it is shooting flames out the exhaust? Sorry to kind of get mad, but this car has not run right since I got it back from the shop, the car runs right but it hesitates and stumbles just has had lazy throttle response for about a year now. Sorry that I said vaccum line I meant the EST wire. I will check the wires and check the spark on every plug. My brother has one of those things you put in between the plug wire and the spark plug and it shows if it is sparking. Could one of the wires be heating up to bad around the headers, because it only does it once the coolant gets to about 140ish and does it about once a minute if I let it idle. If I had some RPM's to it, it does it more frequently. Tomorrow my buddy with the VR4 is bringing over a video camera and all you guys can see the flames.

I know I shouldnt play with the fuel pressure but I figured I might get lucky.

 

[WhalePirot]

Now, we're getting someplace!

Good post. I missed the flames and will not claim to ba any kind of ECM or engine guru. I've 'played' as Tom has, with computer cars and others, foreign and not.

Flames? Cool.....NOT, in performance circles! :L Obviously, you are getting way too much raw fuel in the exhaust. The mention of backfiring lead us down the wrong path. Too lean exhaust can also pop there, but flames are a different matter.

I had an arcing problem with #7 that worsened with time and with engine warm-up. The headers put a great ground source very close to the spark plug boot and deteriorated the silicon/rubber, whatever. Straight plugs heads that I have caused this. Changing boots was a short term fix. Only ceramic boots solved it for me. You can look at and listen for arcing at the boots (actually all visible areas of the wires) while the engine runs in a darkened area.

The spark energy can be lost elsewhere, like along thin carbon traces inside the distributor cap (firing the wrong plug), or down the outside of its cap, if those boots are faulty.

I really doubt that a misfire would pass so much raw gas as to have the flaming, though. I think you're getting either controlled or uncontrolled fuel into the engine; probably quite a lot of it.

I totally understand your frustration. Try to hang in there. We've all been there, and sometimes we need a time-out. Ken's said it; rrich has said it; I've said it; others probably have too (sorry). It gets better and our frowns are now upside down; the cars run great.

Family member with 'puter problem, "Yea, its telling me I can't do that"
ME, "Well...then don't do that!"
Family member, "It has a box that says if I do that again, it will erase the hard drive"
ME, "Like I said, DON'T DO THAT!!!"

That, there's funny!

 

[Vettefan87]

Yeah I hear ya, but the light it seems for me is getting dimmer at the end of the tunnel each day. I am almost ready to just start calling shops, and seeing what they say if I don't make any progress by the weekend.

I am going to look at the timing, get a vid of the car from bone cold start up, and you guys will see how it runs. Then my grandfather is going to come down and we will check the plug wires see if any are messed up, then check the spark with that little gadget my brother has. Then I want to look at the MAF, and Corvette Fever recomended holding it plug side up, and misting it with spray brake cleaner. And play with the timing and take it a little advanced, and a little retarded I guess, and go from there.

Should I set the fuel pressure at a base amount per say 40? Then just go from there? Thanks for hanging in with me guys.