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Discussion Starter · #1 ·
My car ('70 with a '72 350) was running at a solid 180 degrees (I have a 180 thermostat) since I got it running again after a couple of years. But it was backfiring through the exhaust intermittently. I drove it around a few trips and it stayed at 180 on a day in the high 90s. But I had to fix the backfiring.

So I pulled out the dwell meter and timing light. Dwell was slightly off, so I bumped it up to 30 degrees. My timing was way advanced, so I brought it back to 6 degrees BTDC as my book said. I adjusted the carb for the best idle speed/vacuum combination I could get. I pulled the plugs and cleaned them up.

The good news is that the backfiring has stopped. The bad news is that the temp now climbs to 220 at a stoplight. I have to rev up the motor to bring the temp down.

What did I do to cause this rising temp?

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TC Member #59
'70 Malibu 350/4speed
'90 John Deere SS165
 

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When I was running points, I set the dwell to 32. What did you have the initial timing set at, if you brought it down to 6? Disregard what the book says, and play with the initial timing until the engine "sounds right". Try running the timing up until the engine pings and then back it off a little bit.

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Better Late than Never Fred
Team Chevelle #400
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I'd rather have a bottle in front of me, than a frontal lobotomy.
1970 Chevelle Malibu
 

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Discussion Starter · #3 ·
I can only say that the timing was at the top of the timing tab. I'm not sure what value that is off-hand.

I'll be glad to mess around with the timing if you think that will help. Are you saying that retarded timing can cause the engine to run hot?
 

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Boldly procrastrinating
66 El Camino 57 Chevy pickup 2004 Tahoe
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Exactly. Sounds like your timing was at about 12 or so, why not go ahead and put it back there? There's nothing sacred about the service manual timing setting, they needed it to get through smog, among other things.

In general, if you change something on your car and it makes it worse, go back and un-do what you just did. Too often, guys change something, get a negative result of some kind, and instead of backing out the unsuccessful change they just made, they go off in some other direction trying to cover up the problem they just created. This is a loser.

Here's my take on the points/dwell deal: as the rubbing block wears down the dwell number gets bigger, the gap gets smaller. So, I always set my dwell at 28 (wide gap), by the time the rubbing block wears down so the dwell is 32 or so the points are usually shot anyway, start over. Use point cam lube to lenghthen the life of your points.

Tom
 

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Hello,
I just joined this forum and don't have a chevelle yet, but have been working on vettes for years. I just had the same problem with a 69 350. For years it ran right on the 180 mark. I only drove the car intermittently so I didn't notice a problem until I drove on a 40 mile drive nad the temp hit 210 and stayed there.Here's what I did:
1-Flush out and clean the radiator, blow air through it to get the bugs out.
2- check the actual temp with a digital temp gauge to be sure the dash gauge was correct-it was.
3- check the fan clutch-I don't know if you have one on your car?
4-pull the plugs and check them- they were white after 200 miles, so I had the carb rebuilt and the jets changed.
On the vette the seals around the raditor are very important to kep air moving through the radiator and not around it, again I don't know if this applies to your car or not.
5- I pulled the waterpump off and added the FlowKooler disc that Summitt sells. It's supposed to add 30% more flow.
6- Installed a Mr Gasket balanced 180 T stat.
During all this I pulled the distributor and rebuilt it. I added an advance kit that a guy in CO sells and timed it to 36 degrees @1500rpm using an adjustable timing light. After which I checked the initial timing and it was now 14 degrees. It doesn't ping and runs right on 180. The biggest thing was rejetting the carb it was much too lean.
I hope some of this helps you out. BTW the engine isn't the orginal 300 hp 10.25:1, it's a GM crate replacement with just 8.5:1 which was what your 72 came with-unless it was rebuilt at some time.
Gary
 

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Great sound advice here..I'd would check the clutch fan for sure.On your timing issue,you might not have "true" TDC,the outer ring can slip on the blancer,and when you put a light on it,and adjust it,the timing isn't where you think it is,or what the light "shows" you,so setting it 'til it pings,then backing it off a hair will apply.

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1970 Chevelle SS396/M21/4.10 My 70 SS396
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1970 Chevelle SS454My 70 SS454
1968 Oldsmobile Cutlass convertible
1982 Oldsmobile Cutlass 350 Olds,TH350(daily driver)
Chris Corwel,TC Member 785
 

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Discussion Starter · #7 ·
Thanks guys! I'll tackle the timing first. I don't have any emotional attachment to the factory settings. In fact, I'm up for some experimentation
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If the timing was the only thing I messed with, I would have already put it back. Unfortunately I adjusted the timing, the dwell (slightly) and carb all at the same time, so I didn't know where to start.

I've got a new flex-fan (no clutch) & shroud, new anti-freeze, water pump, thermostat, so I'm reasonably confident that the cooling system is ok. Also, as I said, it ran at 180 just fine prior to me adjusting stuff.

One final question - Is it reasonably safe to say that the timing is the main cause for the rise in temp? Or could adjusting the dwell a few degrees or leaning out the carb contribute as well?

Thanks, Tom


[This message has been edited by TK-70 (edited 08-20-2001).]
 

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Maybe a little too basic for ya...but:
Always adjust the timing AFTER you adjust the dwell. Adjusting the dwell changes your timing.

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Better Late than Never Fred
Team Chevelle #400
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I'd rather have a bottle in front of me, than a frontal lobotomy.
1970 Chevelle Malibu
 

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Discussion Starter · #9 ·
Nah, Fred. Not basic at all. And I'm never too old to learn something new. I guess I've been lucky - I've always adjusted the timing last, out of habit.

Tom
 
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