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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 1978Bonanza on April 22, 2008, 04:57:57 pm
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Ok, I am getting exhaust done soon. Like on saturday, but in the mean time I took my exhaust off down to the manifold. I had a real nasty leak and it sounded like my engine was knocking. Well can it damage my engine to run it open manifolds? I would like to run it till friday or saturday but if my engine is in danger I won't. Thanks
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Do you have headers or stock manifolds. Don't know if it is true, but I have been told that you have to be careful running open manifolds because it can suck cold air back into the head and bend an exhaust valve. I don't think that it is true, but I have never tried it. One of these guys will know. At least try to get some of the exhaust plumbed out, I wouldn't want my exhaust baking the bottom of my cab.
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well, i think this is the part where i should chime in. i'm kinda embarassed to admit it (you have to understand my current financial situation-should be changing soon...) but i've been running "open" pipe for right at a year. the previous owner backed into something underneath (i guess) and the mufflers on it were crushed to the point they were causing a horrible restriction and i had NO power...i could have been outran by the same truck powered by an Iron Duke.
so i cut the mufflers off thinking i would have the Flowmaster exhaust i'd dreamed of under it in a month or less...then that became a couple months...then a couple more...see where i'm going with this? the truck hasn't been driven daily the WHOLE time, but a large part of it it has. i'm still running the original 79k mile 305. the only "ill effect" i've noticed (besides the fact that she's obnoxious) is that if you run the crap out of her (i do that from time to time, she was all carboned up when i got 'er and it took me running the pee out of 'er and running a lot of seafoam to open 'er up) when i turn the key off you'll hear a pop. other than that, truck still runs fine...
all i have is stock manifolds and about a foot and a half of pipe...pipe ends right under cab.
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I ran open headers on my 85 Ramcharger when I had it. I think I ran it for about six months and that was through the winter. No problems with the engine whatsoever. Later sold it.
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The concern with it from what i was told, was just the manifolds themselves, headers and a little piping run under the cab is ok because it is further for the air to go, but with just manifolds, the opening is inches from the exhaust port, plus is right in the engine compartment.
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Well It is just stock manifolds. Nothing at all but them not even an inch of pipe. I hope it will be ok as I want to drive it to school and work until payday which is friday. Could I drive it to school in the morning without ruining my engine? It's about 10 minutes away.
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Well the theory behind it is it is easier to burn an exhaust valve or crack it with an open manifold. Whether or not you will I guess we'll find out! :o lol
I wouldn't sweat it unless you're in an extreme climate or pounding on it.
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Well its about low of 48 high of 65 degrees. And i wont be hard on it. I hope i wont do any damage :-\
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1) My personal theory behind the whole "you'll crack a valve if you run no manifolds/manifolds only in cold weather thing" is that:
a) SBC engines don't turn backwards when you shut them off, therefore the cylinders should not be "sucking in" cold air thru the exhaust ports.
aa) hot air generally goes towards cold air and not the other way around, i think?. (not exactly 100% sure, but it's my theory)
aaa) right after you shut the engine off the hot air in the manifold would go to the valve first, if in fact air supposedly gets sucked towards the exhaust valve when you shut the engine off.
aaaa) the area around the exhaust manifold/headers are VERY HOT just after you shut the engine off. Heat is radiating from this area. It would take ALOT of cold air(or cold water) blown on to the valve to maybe cause some damage. Imagine sticking your finger(s) into the exhaust manifold right after you shut it off; i don't think it's cool enough to damage a valve.
OK, maybe just maybe in very cold weather just maybe. But i'm still skeptical.
2)To those running open manifolds/headers for a street/daily driven vehicle:
No matter how well the cab is sealed, some exhaust, in my opinion, will probably eventually find it's way into the cab. And this is never a good thing. So be careful. I'm not saying don't do it/never do it/stop doing it. I'm just saying be careful; You may want to invest in a Carbon monoxide detector. This is why i like my pipes to run to the back of the car.
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Any engine can turn backwards especially when you shut it off. Ever heard an engine dieseling? The temperatures exhaust valves see can easily exceed 1700°F so when you compare that to ambient air temps that IS cold. Cold to an engine isn't cold as to how you perceive it much like how cold is to a Polar Bear vs a human being.
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I was told to plug the headers/manifolds after running them open. I used to do it with my 350(I just used an old shirt). It's a hassle, but atleast you won't have to worry about cold air coming back in or rapid cooling of the exhuast valves.
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when my exhaust is done like i want it, my pipes will run at 45* angles right in front of the rear tires...as for now, i decided today that i'm tired of attracting Johnny Law's attention so i'm gonna go and buy a cheapo set of glass packs and throw those on for now. i really didn't want to because i wanted to hold out for my Flowmaster system i wanted (i want something to make it sound wicked...even if it's not Flowmaster, i just really like the Super 40's) but i need to get something on there...
so, anyone know of anything other than glass packs that's pretty cheap that sounds nice?
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Ok. I am going to get some nice hedman headers. What type of port comes off the heads? I found it is a 1983 gm goodwrench crate 350 4 bbl. I need to know port type before ordering. Thanks!
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I'm not sure on the port type, I just ordered what fit my application(on the summit website). Maybe PM CaptKaos, he may carry the ones you need.
As far as what muffler is cheap and sounds good...what's cheap to you?. You should try checking ebay or the for sale section in some forums. I found my two Flowmaster 10series mufflers on a firebird site for $70shipped.
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I only have Thorley Headers or Jardine right now, I just got the price sheet Friday though.
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what kind of motor do you have there 1978?
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350 4 barrel. Why?
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I'll admit I'm a big block guy, but I was under the impression that only the BBC had oval or rectangle ports and that all SBC ports were the same. I easily could be corrected however. Drag race guys run open headers all the time w/ no problems I've heard of, although they are usually long tubes. I've run my mid-length headers open and had it WFO w/ no problems either. my guess would be that you should be fine.