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Old 12-08-2006, 11:32 PM
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Timing for my 350?

Hello all. It's been a while since I posted here, but then again it's been a while since I've been able to work on my car. Anyways, here's the deal. Basically the car I have is a 75 Vega. I have a built 350 for it, and ever since I've had it in it has run hot. I've done a bigger radiator and all kinds of stuff so the car shouldn't be an issue, now I'm looking at the engine. Sitting around in mid-70's got the car up to about 200* in about 10 minutes.

Anyways, that's a different topic, and I'll ask that if the next question doesn't solve it. Now my engine is a 355 with Dart ProI's, RPM intake with a Holley 750, Comp Cams 268H, headers, and about 10:1 compression with an MSD Pro-billet non-vacuum advance distributor, MSD 6AL, and Blaster SS. It's in a roughly 2700lb Vega with a TH350. Now this is my first high performance engine so I've never really had a chance to play with timing before, and I think that may contribute to how hot it runs (I hope!). I don't know much about timing, except that I installed the cam in the central location, not retarded or advanced. Now what should I set my initial timing at? I "think" I set it at around 14-16* but I'm not positive. It's been several months since I did it. I'm going to play around with it more tomorrow (Saturday). Also, to make it run cooler, do I retard or advance the timing? Sorry for the basic questions here, but this is my first car I've had to deal with issues like this. Thanks in advance! Josh.
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Old 12-08-2006, 11:40 PM
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running an engine overly advanced will make it run hot, so to cool it down retard it, and 200* for a 350 is fine i would only start to get worried after about 215, all my engines run about 165* though "4 core radiators and 160* thermostat"
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Old 12-08-2006, 11:44 PM
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What I'm worried about is that this is AZ. During the summer it will easily get 50 degrees hotter to the 115* range.

Anyways, I will check the timing tomorrow. What is ideal timing for that? Around the mid-low teens?

More trouble-shooting to do tomorrow.
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Old 12-08-2006, 11:55 PM
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i always warm up my engine to operating temp and reset the idle screw to 2000 rpm and let it sit reved at 2000 and i retard the distributor until it starts popping and make a reference mark at that point and then i advance the distributor until it starts popping and make a mark there and then i put the distributor directly inbetween those two marks....that method has never once failed me others may diasagree with me but thats how i do it.....

try that out if you want.........

and on the temp thing what if you take out your thermostat and pull it apart and remove the flow valve and spring completely from it and then put the shell of the thermostat back under the water neck to restrict a small amount of flow but it will be liek the thermostat is wide open....i have done that a few times...try that if you please as well
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Old 12-09-2006, 07:55 AM
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Your timing needs to be set at 10-12 degrees BTDC.
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Old 12-09-2006, 11:12 AM
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He could get away with a lot more than 10-12.

Here's what I do, and its just another method, not better or worse, just different.

I set the timing at a guess, let's say 12* BTDC in your case. Start the engine, check initial, shut it off. Go another two degrees advanced, start the engine, check timing, shut it off. Keep doing that until you get starter kickback. It might be, say, 20* in your case. Back it off to 18 or 16 and that is your initial. That will provide the most possible lead at idle for best idle quality without kicking back your starter when its hot. It has never contributed to overheating on anything I've tuned. But, once its running you could go past that 20* mark and then you're getting into overheating range. I'll put it this way; I've never seen ignition timing be the cause of idle overheating.

Anyway, once you've found a good initial, recurve the dizzy to provide 36-38 total. Use bushings to limit total mechanical, and springs to figure out where it comes in. Then you can use the vac advance canister (you are using a ported vacuum can on that 10:1 motor, right?) to add more lead at part throttle cruise for max efficiency.

Initial timing is such a useless number. There is no "right" answer, it has to be tuned in your combo. I have mine locked at 36*. Yep, 36* intial and it runs great with no detonation and only kicks back the starter at really high temps, but mine is an 8.7:1 454 with a 218/224 cam, so cranking pressures aren't very high.

Initial timing is simply a number that the factory uses to tell you where to set the dizzy so that it achieves the right curve and total, but an engine will run fine at idle over a huge range of initial settings. Once you recurve you can set it to where YOUR engine needs it to be. Mine will run fine anywere from 10* to about 38* at idle, but idle quality drastically improves as you advance it.

One question... are you running an electric fan? If so, all the crutch fixes in the world will only patch up what that electric fan fails to do.
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Old 12-09-2006, 07:40 PM
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I`d like more information on the engine. Is a belt running the waterpump or is it a electric? is the system vented? Does it have a thermostat? what temp thermostat? was it checked? are the hoses staying open? If your water pump is a mechanical what kind is it? what year vehicle was it suppose to go on or come off of? What kind of fan are you using? are you certain it has no vacuum leaks? are you certain the carb isn`t set too lean? what kind of gasoline are you using?
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Old 12-09-2006, 08:39 PM
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The first question I ask when somebody brings up timing is...Did you use a timing light or "time" it by ear?

Second, what are you using for a fan/shroud? If you use a mechanical fan get the biggest rigid blade fan you can and use a thermal fan clutch. Make sure you have a fan shroud as well. If you have an electric fan you can make them work just fine as long as you use the correct fan for your needs and the thermostat-switch is set properly. Some people don't want anything to do with them, others like them. I happen to be one that likes them.
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Old 12-10-2006, 07:09 AM
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when I was young I had a v8 vega that always over heated, I found it was because even though I put in a bigger rad the front bumper reinforcement blocked about half the air flow. A good fan and shroud are also definately needed. pull the rad and check to see if anything is blocking airflow as the first step.
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Old 12-10-2006, 11:12 AM
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Wow, thanks for all the replies! I guess I won't make a new cooling thread, this thread turned into it!

Allrighty then, I've got a lot to answer! Anyways, it's a mechanical pump, a short Summit high flow cast iron unit. I have a smaller w/p pulley on now to overdrive the pump (I had underdriven on before and it was overheating) with one belt driving the crank,w/p,and alt, and one captured belt between the crank,w/p. I do have an electric fan. Over the last couple weeks I cut the whole core support out to make room for a 26x19 aluminum two core radiator from Speedway. I also mounted a fan/shroud out of a 90's Taurus behind it. It's a dual speed fan, and on the low speed it feels like it moves a LOT more air than my last mechanical/12" electric setup. Low speed is wired to the key, high speed is on a thermostat/manual toggle. I tried to set the fan to come on at 180* the other day, it's a perma-cool controller with a range as low as 160*, but with the probe in the radiator and the rotary switch at 160* the controller never turned the high speed on?!? I'm also going to have to get a laser thermometer I guess, see if the radiator is getting up to temp also. BTW, I have and Autometer Sport Comp run into the head.

I have run three different thermostats, two different standard 180*, a Mr. Gasket high flow 180* but they all did the same thing, and now last night I tried something else someone suggested... cutting the guts out of a regular tstat so basically it's just a restrictor plate. I'm gonna drive it today and see if it does anything.

Hoses are good, the lower is a flex hose that is really stiff, won't ever collapse. The gas is from July, pump 91 with some race fuel mixed in but it overheated back then also.

Back when I first installed the engine, I did time it with a light. I haven't checked it since, and I ran out of time last night. I'm going back to the shop today and I'll check it out first thing. I'm hoping it somehow advanced itself, but I'll see later.


That's all I can answer right now. I was gonna drive it yesterday, but it was too late when I got done finishing other things on there, so I didn't want to blast up the roads in a mean Vega with half exhaust. So I'm gonna head over there in about an hour, then I'll time it and drive it. Hopefully it'll at least keep cool when moving.
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Old 12-10-2006, 12:20 PM
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Quote:
Originally Posted by fastrehotrods
I also mounted a fan/shroud out of a 90's Taurus behind it. It's a dual speed fan, and on the low speed it feels like it moves a LOT more air than my last mechanical/12" electric setup. Low speed is wired to the key, high speed is on a thermostat/manual toggle. I tried to set the fan to come on at 180* the other day, it's a perma-cool controller with a range as low as 160*, but with the probe in the radiator and the rotary switch at 160* the controller never turned the high speed on?!?
Do you have the controls wired so that the low speed and high speed windings aren't energized simultaneuosly? If you want two speeds you will have to energize them one at a time.
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Old 12-10-2006, 12:59 PM
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I know I beat electric fans like a dead horse, but here is my take on your individual setup. It sounds like everything is in order, except the fan. A single 12" is just not going to be enough. Its possible that it could be enough, but you gotta look at the most plausible source and in this case that is CLEARLY the most probable to me. You have a shroud on a good radiator, you've eliminated thermostat problems by trying multiple units, you've tried two different radiators, you've tried a couple different water pump pulleys...

I know I beat on electric fans, but just do a search. There are soooo many threads here with this exact question; "why does my 400-horse small block overheat with a 12" electric fan?" I know factory electric fans work, but they often use twin 14"s with a 250-hp EFI engine and a huge R&D budget.
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Old 12-10-2006, 03:59 PM
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Basic stuff

Let's get some basic stuff out of the way...

1. Ignition time DOES affect the operating temp of the engine. During the early smog days, retarded timing at idle was used by the factories to increase combustion chamber temps and reduce emissions. Hence the "ported" vacuum advance which effectively kills off vacuum advance at idle. The more retarded the timing, generally, the hotter the chambers.

2. Thermostats do NOT control the final temperature at which an engine runs, only that temperature at which the block no longer retains heated water...if your engine is going to run at 200*, it's going to run at 200* regardless of the temp at which the thermostat opens.

3. Small block chevy engines have always responded to a total MECHANICAL advance in timing to a range of 34* to 38*. Most have responded to 10 to 12* initial and 26 to 24 mechanical. These are INDEPENDENT of vacuum advance, which is an idle through transition (higher vacuum to lower vacuum) situations PLUS high vacuum partial throttle cruising and generally total an additional 15*.

If your timing on a SBC is within these ranges, and you're running hot, double check the jetting on your carburetor. If you're lean there, you'll definitely run hot.

Paul
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Old 12-10-2006, 10:33 PM
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First off let me say that the 12" fan was part of my LAST setup. This setup is running the Taurus fan which is much larger than the 12". The Taurus unit has a shroud which covers the entire width of my radiator, and all but 4" of the height.


Anyways, here is how today went. I got her warmed up first. I did this by disconnecting the fan since I don't have a working thermostat anymore, I installed the gutted one last night. Took a little longer, but it warmed up allright. I checked the timing. Dead on 12*, just like I set it in June.


So I pull it out in front and let it sit for a while longer. About after 10 minutes total of running, it got to about 170*, much better than the other day. So I take it in baby steps. Drive it up the street, to the corner and back. First time I do it it gets to about 190*. Okay, cool. I decided I'd do it again. Same thing. Then I decided I'd take it up the to Mobil and get some gas. That's about 3/4 mile driving through a neigborhood, then at least a mile on the main streets. Got throught most of the neighborhood then my front brakes started to get pressurized, so now I have to keep my foot in the pedal to make it move. I say %$#@ it and drive to the Mobil anyways. After all that and about 2500-3000 rpm to the gas station, it got to about 200* max. MUCH better than before! And that's with only the low speed on the fan! Never once used the high speed. On the way back, same thing. 3/4 mile with the front brakes partially applied and got to only 200*!!!

So I think that really helped my engine! I'll know more later this week. Wednesday I'll relocate the front brake line from the engine compartment to under the car. It was fine with the 4-banger, but I guess the V8 fills the engine compartment just a little more, and creates a little more heat! Oh well, that's what this time is for, finding all the little crap. I may also advance the timing a little bit if it'll make it run cooler yet. Also, will advancing it help with the dieseling I had when I shut it off warm?

onovakind67- Thanks for that advice. I realized that the other day when I had the high speed on, and turned my key on (which turns the low speed on) and I heard the rpms drop! I'll have to figure out some kind of switch or relay.

Thanks again for all the help thus far everyone!
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Old 12-11-2006, 07:37 AM
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Quote:
Originally Posted by vabeach56wagon
Let's get some basic stuff out of the way...

1. Ignition time DOES affect the operating temp of the engine. During the early smog days, retarded timing at idle was used by the factories to increase combustion chamber temps and reduce emissions. Hence the "ported" vacuum advance which effectively kills off vacuum advance at idle. The more retarded the timing, generally, the hotter the chambers.

2. Thermostats do NOT control the final temperature at which an engine runs, only that temperature at which the block no longer retains heated water...if your engine is going to run at 200*, it's going to run at 200* regardless of the temp at which the thermostat opens.

3. Small block chevy engines have always responded to a total MECHANICAL advance in timing to a range of 34* to 38*. Most have responded to 10 to 12* initial and 26 to 24 mechanical. These are INDEPENDENT of vacuum advance, which is an idle through transition (higher vacuum to lower vacuum) situations PLUS high vacuum partial throttle cruising and generally total an additional 15*.

If your timing on a SBC is within these ranges, and you're running hot, double check the jetting on your carburetor. If you're lean there, you'll definitely run hot.

Paul

This is the only "Spot On" correct post to your original question. EXCELLENT!!!

I will emphasize that a retarded ignition will cause the engine to overheat. It will also show up by causing the exhaust pipes just below the headers to "glow" cherry red at idle. An extremely lean air/fuel will also give the same symptoms. I'd check the timing first.

NOTE:

When checking / setting the timing ALWAYS disconnect and plug off the vacuum advance hose. Re-connect AFTER setting the timing.

As to your brakes dragging after a short drive; this could be because of the front brake lines being in close proximity to your exhaust or could be one or more other things. i.e. incorrect master cylinder pushrod (too long). Brake pedal not fully retracting after initial use (causing brakes to be partially applied all the time). If disc brakes, pads not parallel to rotor causing them to "drag" and thus overheat. Other possible causes. Check your system and adjust as needed.
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