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  #46 (permalink)  
Old 02-27-2007, 01:16 PM
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Up-Date to Misfire 350 SBC

(#2 cylinder is the worst, #4 has issues as well) I can clean the plugs and the engine runs better and within 20 miles it starts to run poor, worst when restarted after hot soak. It seem # 2 doesn't fire at idle until the engine runs a while.
I replaced the intake gaskets and it didn't help. I removed the intake again and have some pictures. The plug was clean and run for maybe 20 miles in the city. The intake surface was wiped off where the gasket makes contact as well. Engine misfires at idle not a dead miss but it is a week firing cylinder. I did install the intake without the gaskets, bolt one side on and found the lower end of the intake to be narrower than the top, not by much at all just a hair, I did find the gap between the block to intake to be less than the small gap form head to intake. I made my checks on the back side of the engine because this is a mid engine car. The front (#1 cyl.) was hard to get to but it seemed tighter than the back of the block at (#7). The cut on the intake looks to be about 35 degrees and the cut on the heads looks about the same. I used a gage to level the two parts block and intake before taking my readings. It looks like to me the intake is leaking. The outside ports of the head all have some black looking oil deposits but #2 is the worst.

I haven't checked the valve guides/seals, since the oil is up in the runner would that eliminate valve seals? This car runs so good when the engine runs correctly I just would like to nail this down and move on.




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  #47 (permalink)  
Old 02-27-2007, 03:05 PM
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5 &6 wires cross ?

sometime if the 5 &6 wires are cross they will ground each other out make sure the wires are not crossing each other
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  #48 (permalink)  
Old 02-27-2007, 03:58 PM
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I hate to say it but it looks like oil consumption A bad oil control ring or valve guide or someone is spraying oil down the intake when you are not looking. the look of that plug brings back the same night mare
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  #49 (permalink)  
Old 02-27-2007, 04:17 PM
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Quote:
Originally Posted by McLeay F1
I hate to say it but it looks like oil consumption A bad oil control ring or valve guide or someone is spraying oil down the intake when you are not looking. the look of that plug brings back the same night mare
The engine admits not smoke at all form the exhaust and doesn't use a much oil. I know that doesn't mean much. If I have to replace the rings I can deal with that, its just a lot of work and has a ending which will give me the result I am looking for. With this conversion I have had to do a lot of things a few times to get things right. This would be the second major engine repair, I have a pull type clutch pressure plate and had too much pre-load, with that I toasted my thrust bearings about 2 years ago. I got that under control but chose maybe the incorrect rings??

I can't rule that out and am not real happy about that. The truth is I used molly rings and may not have had the correct preparation on the cylinder walls.
Keep the opinions coming
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  #50 (permalink)  
Old 02-27-2007, 04:35 PM
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thats pits eh after doing tear down after tear down if the pan is easy access and you pull the one head you can pop the one suspect piston. remove the valve spring to inspect the guide if the valve wiggles more than 2thou in the guide bore. well thats another story to tell of hot roding. scratching yer head till you loose some hair
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  #51 (permalink)  
Old 02-27-2007, 06:10 PM
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Quote:
Originally Posted by McLeay F1
thats pits eh after doing tear down after tear down if the pan is easy access and you pull the one head you can pop the one suspect piston. remove the valve spring to inspect the guide if the valve wiggles more than 2thou in the guide bore. well thats another story to tell of hot roding. scratching yer head till you loose some hair
Sounds like you are a fortune teller, that may be in my future I did try to remove the valve springs but they wont budge from the grip of the keepers. I did use air and tap on the valve hat but they are there to stay. The engine has low miles as well as the edelbrock heads so its "less" likely the guides are damaged. You see I said "LESS" likely. I looked close at the intake gasket and I can't see any variation in sealing anywhere. I could see a clear depression around all the ports so maybe I'm not getting off so easy If I want to see the valve guides I will have to pull the head, not so hard in this contraption so I may do that tonight. I have been fighting this issue for a long time and in this car the engine needs to be right-on running just because it's right next to you
********Keep the ideas coming, I need the help as you can see



Just so you know what I'm working on here is a Video of the car
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  #52 (permalink)  
Old 02-27-2007, 07:21 PM
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Great looking car. Does that fuel rail have a fuel pressure regulator on it that also has a vac line going to the runner on the cly that keeps fouling. There was one of the engines back then that did. It has been 25 years since I worked on those cars and I have CRS. But if it does the diaphram in the regulator could have a small hole in it letting fuel bypass.
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  #53 (permalink)  
Old 02-27-2007, 08:07 PM
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Quote:
Originally Posted by RPM
Great looking car. Does that fuel rail have a fuel pressure regulator on it that also has a vac line going to the runner on the cly that keeps fouling. There was one of the engines back then that did. It has been 25 years since I worked on those cars and I have CRS. But if it does the diaphram in the regulator could have a small hole in it letting fuel bypass.
That type of thing I did for 20 years as a tune up and driveability specialist for G.M. dealers, I can handle the outside controls well. Its just the inside parts where is am week. The system is EFI and I have trouble shot that part. I think you thinking of a 88 style GM engine in a corvette, they did have a vacuum port there. I saw a guy feed water in that port to clean off the pistons, it may have done that, but also bent a rod when it got too much to drink
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  #54 (permalink)  
Old 02-27-2007, 08:18 PM
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Here are the Pistons



Here are the pistons, #2 & #4 seemed to fire the worst.
What say YOU !
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  #55 (permalink)  
Old 02-27-2007, 11:57 PM
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well I aints no fortune teller. but from what I can see there is definitely oil getting in the combustion chamber from some place and you have to track it down or put the hottest ignition system on her to burn that oil off
I used to tear down and rebuild engines at a popular machine shop and I have seen a lot of things that I did not think would happen but they do.
as far as the valve spring thing goes hit the top of the retaining area with a dead blow and use a good quality valve spring compressor it will come off
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  #56 (permalink)  
Old 02-28-2007, 12:30 AM
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Machine the intake manifold. It's lean at idle on #2 because it is sucking air from the valley at idle via the pcv or brake booster and getting it's oil at higher rpm.
Smoke at, or coming off idle is guide/valve seal etc (high vacuum). Smoke under load is bottom end. If it didn't smoke when you belted it, it's unlikely to be lower end.
Please refer my post of 20th,Jan,07.
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  #57 (permalink)  
Old 02-28-2007, 02:20 PM
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that picture at the top was that intake manifold runner? if it is its very possible it is coming in there as well but it looks like it was sealing? are the cylinder heads strait? and no nicks or damage dose the valve cover have a baffle under the pcv? do you have a really good strait edge for checking all mating surfaces. make sure every thing is perfect before reassembling
are you using a high tack spray-A-gasket red from permatex? I use that for alum mating surfaces and see if you can get a thicker intake gasket. and dont use those rubber end gaskets just strait rtv. I do hope you find the problem that is a very cool car. it would be shameful to have a miss
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  #58 (permalink)  
Old 03-02-2007, 07:31 PM
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Pulled the engine

I removed the engine, heads and finally got the valve springs free. I don't see any trouble with the valve seals or guides. The seals fit tight and I found out the lower end is about to fall apart. I got this engine second hand and never has the block looked at. The bearings are wearing in a load of different ways. I have decided to look for a short block, 350, 327 etc. This car needs a short stroke SBC, but the cost of building a 3" stroke motor may be more than I wish to spend. I may go with a G.M. Crate motor and install my heads and intake. The car only weighs about 2300 lbs so the faster revving engines with low torque would work best. I guess I can get a G.M. unit, put a different (mild) cam in it. Any suggestions??
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  #59 (permalink)  
Old 03-02-2007, 07:38 PM
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do you have any picks of the pistons yet? it would be interesting to see what they look like check ring end gap and bore taper it just to see where you stand with that bottom end. or how bad it was. hey a new crate bottom would be a great start at any rate
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  #60 (permalink)  
Old 03-02-2007, 09:18 PM
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Curious to know but are the heads/intake truly flat? It could be possible that your surfaces are warped slightly allowing it to suck up oil in the combustion chambers and obviously create an internal vacuum leak as well. I'm not sure if this could happen but couldn't the pressure in your crankcase also be affecting your air/fuel mixture by forcing fumes into the combustion chambers possibly causing a firing problem? I was going to ask if you used Fel-Pro intake gaskets but I saw that you didn't. I've heard a few people having problems with Fel-Pro sealing properly for aluminum intakes, although I use it on my car and it's appearing to seal just fine. Have you done a vacuum test yet? Just throwing some suggestions out there.
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