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Discussion Starter #1
Ill give you some info on what i did today

My nova was overheating, had anto exhaust leak, and thethe valve covers were leaking (no backfire at that time)

I had put dexcool in it that turned to slugde... anyways, so i flush the system (found a cap in the top hose blocking it, removed cap) changed thermostat.

Then i swapped out the valve cover

Changed the oil and put in antifreeze

Went to change the exhaust gasket but realized i bought the wrong gasket so ill change it tomorrow

So i start it up and it idles fine, but when ever i give it gas or when i drove it down the street it backfires out of the driver side exhaust and gets worse and worse the higher rpm i go. (Backfire is the same side as exhaust leak)

It wasnt backfiring before today so im not sure if its the already existing exhaust leak.

Anyone know whats going on?
Thnx
 

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Leaking header gasket, or maybe a spark plug trying to fire.
 

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is it popping or backfiring? there's a difference...

if it's backfiring i'd pop the dist cap/rotor and check the mechanical advance assy and make sure it's free... if it's hanging up it can cause the engine to backfire on decelleration...
 

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Popping out of exhaust

Hi,
It's the exhaust leak. Oxygen is mixing with hot rich exhaust and "burning" in the exhaust system. Fix the leak and it should go away.
Rick
 

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Discussion Starter #6
Found the problem, had wires 1 and 2 mixed up on the cap... :slap:

Seems to be running good now, except its kind of chugging as i drive it (chug chug chug chug) until i get around 3000 rpm and there's white smoke coming out of the exhaust. Too lean?
 

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White smoke sounds like a blown headgasket or bad oil seal somewhere. I'd do a compression test.
Yeap and that could be why the antifreeze was so sludgy as he originally stated.
 

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White smoke sounds like a blown headgasket or bad oil seal somewhere. I'd do a compression test.
If you're burning coolant, that's gonna smell like boiling anti-freeze if you get a chance to whiff some into your nostrils. Usually starts coming out pretty thick, if you have a compromised cylinder/head or head gasket, as it warms up.

Video? :D
 

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Pull all the plugs, keep them in order and see which one is bad, then you can start diagnosing that cylinder to find out what the cause is.
 

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Pull all the plugs, keep them in order and see which one is bad, then you can start diagnosing that cylinder to find out what the cause is.
Yeap rusty or wet plug. That cylinder will be the one with the cleanest piston in it also.
 

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Discussion Starter #12
Sry i took so long to respond, ive been super busy working on my car and it coming out awesome. Thanks for all the info, the chug chug chug was just because i didnt put the #2 wire on the distributer on fully and it fell off as i was test driving it (put it back on and the chugging went away). I still have the white smoke though. I fixed the overheating problem (there was a bottle cap blocking the top radiatot hose...) i can now idle, cruise, smash and my car never gets above 185-190 and the antifreeze is now a clean green with no slugde.

I read somewhere that a leaking trans cooler modulator line can cause atf to be sucked into the system and cause white smoke and my line was loose and leaking bad. I tightened it up and stopped the leak but i still have white smoke.

I smelt the exhaust and there's no presents of anitfreeze, they exhaust fumes are really strong though.

Compression check show 180-170 all around.

Can it just be running lean?

Chris
 

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Discussion Starter #14
Sry again guys, ive been getting my info on what color the smoke is from my family was i drive by. They told me its white smoke, i guy i talk to down the street that has a nova as well, confirmed that it is BLUE smoke...

Blue smoke = burning oil?

It only really happens on start up and when i rev the motor or stomp on the gas. I noticed some smoke yesterday when i was at a stop light but it was faint.

Thnx guy,

Chris
 

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Sry again guys, ive been getting my info on what color the smoke is from my family was i drive by. They told me its white smoke, i guy i talk to down the street that has a nova as well, confirmed that it is BLUE smoke...

Blue smoke = burning oil?

It only really happens on start up and when i rev the motor or stomp on the gas. I noticed some smoke yesterday when i was at a stop light but it was faint.

Thnx guy,

Chris
Blue smoke = valve seals at best, but maybe more likely rings. It really sounds like it's getting to be time for a basic rebuild. The good thing is that you can most likely re-use most of your "hard parts." A re-ring kit for a 350 is about as cheap as you can buy for any engine ever made. If you can put it together yourself, then you're looking at way under a thousand bucks including machine work. You can get the rings, bearings, and gaskets for less than $200 with not much shopping effort, but don't order any parts until you get everything checked and measured. Take it apart, label everything, and take the block, heads, and crank to the machine shop to let them clean it all and measure everything for you to determine if the block needs boring and the crank needs turning. Let them do a valve job on the heads, which will include grinding the valves and installing the new seals, along with checking the surfaces for flatness. Have them install new freeze plugs and cam bearings in the block. Don't have them do any boring or turning unless it really needs it!

You can take this opportunity to install a better cam, with new lifters, along with a new timing chain. You need to put in a new oil pump too, since it's apart.

Then, just screw it all back together (to specified order and torque values, of course), fill up the fluids, and enjoy your new-found, non-smoky power! (Well, there will still be plenty of smoke, but now it'll be coming from the tires instead of the tailpipes!)
 

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Discussion Starter #16
Vinco you read my mind, i just bought my car about 3 weeks ago and all ive been thinking is rebuild. Its defenitely come a long way from when it came home on a trailer (took it on the freeway for the first time the other day!!)

But this guy i bought it off of "rebuilt" the engine and it seems he just slapped together and did a horrible job. Everytime i fix something the car finds another weak spot to attack and now it seems both front and rear main seals are done.

There's a guy down the street that builds his own hotrods that says he'll sell me a running 350 sbc for $200. So i think ill buy that and start rebuilding that, that way ill still be able to drive my car (its my only vehicle).

Chris
 

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Give us some info on both engines, in terms of casting numbers, etc. Once we see what you've got, maybe we can make some additional suggestions on building it. When I bought my first car, I gave my neighbor $200 for a running 350, and I actually drove the car with that very engine for 2 years before I rebuilt it. In other words, you might very well be able to get by for a good while just by swapping in the $200 motor.
 

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Did it start smoking all of a sudden or have you noticed it before? The Vac. modulator is a possible culprit like you said previously. Maybe change that first. I had one go bad before..... smoked pretty good.
 

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Discussion Starter #19
Vinco, i just recently decoded my 350, im not sure if this info is 100% correct but:

Partial vin: 10W343237
Suffix: V0407CNN
Casting: 3970010

Those numbers gave me this info about the 350:

1970 Chevy Nova
350 L-48
300 HP
380 TQ
10.25:1 CR
4 bolt main
Turbo350

Made April 7th 1970 at the Willow Run plant in Michigan, production number 343237.

I havent had a chance to go take a look at the engine, so i dont know the #'s on it.

Nova_me1970, i think it started when i took it in to get tuned, the mechanic set the timing around 36 and then tuned the carb. I really need to buy a wideband a/f ratio gauge, but that like over $300 i think, and i cant seem to justify that buy when there's a running 350my down the street for $200...

I checked the spark plugs:

All 4 plugs on the left bank are a purty tan color, very clean.

The right bank plug aren't so purty... lol plugs #1 and #7 (the 2 outter plugs) are black and basically burnt to s***. Plugs #3 and #5 are a dark brown, but are pretty clean. So i think i know my problem...

The guy i bought it off of put too long of bolts on the outter holes of the header, so i had a horrible exhaust leak on the outter ports. I had to buy even longer bolt just to get them to actually catch on to the little threads that were left, put a new gasket on, new plugs, and prayed that would stop the exhaust leak...

Its not as bad as it was before (flames were shooting from the outer exhaust ports) but apparently it's still leaking. I'm going to make some calls to different machine shops and price a helicoil install and if its not to expensive, i do that.

As for the $200 350, i'm going to buy it as soon as i see the guy again, and rebuild it like vinco said. Having a fresh 350 with no worries sounds like a dream come true!

Thnx guys

Chris
 

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Discussion Starter #20 (Edited)
Help please!!

So besides the exhaust leak my car was running PERFECT. I was so happy and had no worries that it would make the 2 hr drive to san bruno for my army drill on the 8th.

Yesterday i went and got the helicoils put in and now MY ENGINE IS HAVING A MELTDOWN!!

First as i was driving home, i lost spark completely, pulled a wire and was getting super weak spark. Took the ign coil cover off and the holes in the cap for the bolts that hold the coil and its grounds were stripped, giving me weak ground. Walked to autozone, bought new cap, rotor, and coil. Installed, it started and i was able to get it home but everytime i had to stop at a light i had to put it in park and keep it revved up because it wanted to die at idle.

I noticed gas leaking from my electric choke linkage and backfire coming from the carb and at one point gas was pooring in my carb when i turned off the car. I put new plugs in, the old ones were all black on the right bank (helicoil side) and my car smokes like crazy. I tried to tune the carb with a vac gauge and vac would not drop or rise when i tried to tune it, so right now the mixture screws are at 1.5 turns counterclock wise and the smoking has stopped but its hard to start. Timing is 36.

At this point the smoking has stopped, its hard to start, and now i hear a ticking, like a lifter is sticking. What happened?!?! It was running so perfect before the helicoils and now its a complete mess!

Please help!

Chris
 
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