Firstly, might as well call me Bubba when it comes to timing/fine tuning. I've read a lot, but maybe I'm just more of a visual learner...and I don't have anyone to be the teacher near me.

Overview of what I have and what the current symptoms are:

1. ZZ454 crate, MSD HEI distributor, new plugs (NGK iridium), new wires (MSD), Demon 750, 180* tstat, dual elec fan with Dewitt radiator. Probably about 4-500 miles max on all of this.

2. The car starts/drives just OK, but here are the issues:

a. Cold start = I have to hold my foot on the pedal ~1500-2000 RPM for about a minute before it'll idle without dying. Idled approximately 850 RPM.
b. When hitting WOT at slow speed/from a stop I get initially a sluggish response, sometimes with detonation in the exhaust, then it picks up pretty good.
c. Let off the gas from the above example and about 50% of the time get more detonation in the exhaust as I decelerate - maybe 2-3 loud pops.
d. I have NOT checked the new sender/gauge against an IR gun, BUT at idle the temp rises to past 210, around 220-230ish by my estimate on the gauge. As soon as I'm driving, even just 30-40 mph it'll quickly drop to 180 and stay there. Repeat the "temp dance" as I stop and go at lights. Fans turn on no problem (both confirmed working), but seems like they can't get it to decrease unless I'm moving.
e. Pretty decent dieseling on shutdown every time.
f. Last night for the first time on the drive home I could not keep it from dying at a stop unless I held foot on the gas (~1000 RPM).

So, that's where I was as of last night. I thought about the fact it was hastily timed/carb set about 4 years ago prior to me putting it in storage (stored it with about 200 miles on it, awesome). Based on reading a lot (and maybe I have misunderstood), perhaps my timing was too retarded. I have marked all my starting points and began adjusting the distributor slightly, trying to advance timing a bit to see if I could fix these issues.

Here is what I have done and the results - all sitting in my garage, no test drives yet.

1. Have advanced the timing with corresponding increase in idle RPM to 1500. I then backed off the idle screw to decrease to about 1000 RPM, in conjunction with richening the fuel a bit (1-1.25 turn). The car was at 7000 ft in the previous location; I'm now at sea level.

2. This has caused smoother idling and I can now start the car and it'll idle immediately instead of dying.

3. I go to ~3-3500 RPM and don't hear any detonation in the exhaust, nor do I get any when I let off the gas. Give the the engine a quick punch to WOT (max of 5000 RPM) and no issues with detonation, pops, etc. Seems good, but...

3. Temp increases to 230 pretty quickly at idle, but when I simply set foot on pedal to get ~1500 RPM, temp drops very quickly to 180. Not even moving, sitting in my garage. So clearly no airflow helping the cause. When I hold it at 3000 RPM for about a minute temp rises to around 190, but no higher, and that's with zero airflow.

What is going on with the description in #3? I didn't want to drive yet because I feel like something is not right based on my results described in #3. The car should be able to sit at idle and stay around 180, hell even less than 200 I'd be happy. This also by the way in 65-70 deg weather. What am I missing/don't understand? Any advice greatly appreciated as always!

 

I suggest you start with the basics:

1. Set the initial timing to 8 degrees BTDC with vacuum advance disconnected.

2. Set the PARK idle speed to 750 rpm.

3. If your distributor has a re-curve kit in it make sure the mechanical advance does NOT begin until 1000 to 1100 rpm.

 

You never said what your timing was set at. I have found for street use 454 I set the initial lead at 10 deg BTC. This your base timing and you want to be under 900 rpm when you set this.Otherwise your mechanical advance may start cumming in and giving you a false reading.As stated in above post make sure you do not have any vacuum advance connected. This will make the engine idle properly if your carburetor is not giving you problems. Also make sure your firing order is right 18436572. You have to be able to get the engine to idle first before you try tuning anything else. This engine should idle 700-750 rpm. I do not use vacuum advance.I use mechanical advance only. You have a msd distributor you can buy limit button & advance springs kits. I limit the mechanical advance at 26 deg + the 10 deg initial lead gives a total of 36 deg advance. I use the springs in the kit to allow the advance to be all in at 2800-3000. You need a good timing light. The better ones allow you to dial the advance in the timing light. If you do not have this timing light see if your harmonic balancer is degreed if not buy timing tape and put it on the balancer so you can see how much advance you have.

 

I don't have a timing gun (yet), so couldn't tell you what the timing is currently. I think we set the timing at around 10 without vacuum advance, but that's a 5ish yr old memory, so I could be completely wrong. Vacuum advance is currently hooked up. I know the right answer is to get a timing gun and check everything, but like I said previously, it does idle and run right now, just not in an ideal way. So, my thought was it couldn't be too far off.

If anything, can anyone explain why engine temp decreases simply from increased RPM?

 

The hesitation and the popping on decel lead me to believe that you are running lean at idle and off idle.

 

STOP.
Dont do anything more without a timing light. Trying to set timing by ear is like trying to shoot a target rifle without sights.

I did an engine swap last winter. I set the distributor at what I knew was TDC, had a friend crank the engine until it fired. I gave it little more advance until it was running smoothly and called it a day. The next time I started it, the engine was making a horrible top end noise. I re-lashed the valves 4 more times. I was going crazy. I finally limped the car to a local performance shop to PAY someone ELSE to work on my car. (Thats a friggen sin in my book) They called me up that day and told me I had the engine SO FAR ADVANCED thats its a wonder I didnt shatter a wrist pin. I consider myself an 'old timer' and I made a total noob mistake.

Buy a timing light. Use it. Dont make an *** out of yourself like I did.

 

Get a timing light on it 1st before you make any changes. If the timing is retarded it will get hot at idle and cool off once RPM's climb.

I had mine just do that because I didn't tighten the nut enough and it moved on me. Idle would jump to 210 fast then come right back down with some RPM.

 

Sounds like an air leak to me !

 

Thanks for the insight guys! I'll get a timing gun and hopefully work on it again next weekend.

 

The temp issue sounds like its rpm related,

If you have a volt meter check the voltage at the fans with the car idling and see if you have 12 or more volts.

Do you have under-drive pulleys installed?

Do you have the bypass hose on the water pump connected?

Neal

 

By increasing the timing and reducing the idle setting you have the transition circuit closer to the correct setting. The only true way to know for sure is to pull the carb and take a look from the bottom.

Some of the issues you have explained can be caused by incorrect setup of the carb.

The adjustments you have made should help,

Neal

 

Update - I got a timing light and vacuum gauge (thanks ddawson and scott for making me do the right thing and not the "right now" thing). Here's what I have now...

With vacuum adv disconnected/plugged:

Init = 16*
Total = 36* at 3000 RPM
Idle vacuum = 17-18"
3000 RPM vacuum = 23-24"
Primary Idle Screws 1.5 turns out from full lean (did not touch secondary)
Smooth idle at 850 RPM

There is no popping or pinging at idle/RPM increase/RPM decrease that I can hear. I have not driven yet; this is just from the garage. Engine starts up easily and zero dieseling. So, overall everything seems much smoother - looking forward to a drive!

HOWEVER, temp problem still exists at idle. Fans turn on about 200* on the gauge ('71), which makes sense because I'm pretty sure it's a 195* on/shut off at 180* switch. However, gauge rises to the line bewteen 210* and 250*, which I assume is approx 230*. If I increase RPM to 1500-3000 the temp goes down quickly (5-10" at those RPMs) to 180*.

I thought about the lean condition mentioned, but even when backing idle screws out another turn (2.5 total) it didn't make any temp difference, but vacuum dropped, so I do think 1.5-1.75 is right for my setup. What things am I missing/should I check? Hopefully I'll get a drive in tomorrow to get a better feel for the overall operation, but even if it drives great, I'm still concerned about the inability of the engine to stay approx 180* when at idle RPM.

Thanks guys!

EDIT to add answers to questions: I have a serpentine system, water hose to heater core currently bypassed (valve closed), and voltage checks good at fans. They turn on as expected and turn off when expected - I see no functional issues with the fans - perhaps a contributing factor, but with the direct link to RPM change, there's something else going on that's the main problem...I just don't know what.

 

Hmmm... if the temp goes down quickly just by revving it, it sounds like an air pocket to me.

Get an IR gun and check the temp at the upper rad hose as well as the upper radiator inlet. If it's less than the temp gauge, I'd really suspect an air pocket.

 

Yeah, an IR gun was my next step. Where is the air pocket you're talking about? What is the corrective action? Thanks.

 

I would trash the dual electric fans and go back to the stock OEM shroud and 7-blade clutch fan. I have never known of any duel electric fan setup that worked worth a damned.

 

If the problem was radiator airflow the temp wouldn't go down when he revs it. And my electric fans work perfectly. On a 454 BBC. With AC. In Dallas.

 

The air pocket would by in the heads/intake so the temp sender would not see much water and read high.

Never had the problem so don't know what to do about it. Mine has always "burped itself" after driving a few miles. Whenever I had the cooling system open the first drive the temp gauge goes up above the thermostat, maybe 200 or so, and then falls right back to 180F. When I get back home I have to add some coolant to make up for the air that came out.

 

Zwede - Are you talking about air in the coolant system? I just read on another site (not vette related at all) about guys having the same problem and the cause was air in the coolant system (hot air does not trip thermostat like hot fluid does). So, my plan now is to flush the entire coolant system and replace with new water/coolant. Don't know if that's THE answer, but I should do this anyways, it's about that time. Hopefully it's the fix.

EDIT: Zwede, just saw your reply. Once I flush/replace fluid, what's the best way to ensure all the air is out? Any tricks other than drive and hope it escapes?

 

That's the way I've always done it. There's a bit of tension as I watch the temp gauge climb, and climb... and then it burps and falls back down.

 

You said you had a crate engine? If so you might have a reveres turn water pump for serpentine belt. Your description of raising the rpm brings the engine temp down is a sign of this problem. Are you using the original belt system? What year is tour car? Also when you run the car with the hood up you restrict 1/2 the air flow through the radiator. If you need to change water pump get a high flow pump from Jegs or Summit.What radiator do you have? I have a 70 454 LS5 Griffin AL Radiator/High flow pump/192 thermostat/Clutch 7 blade fan. I live in AZ and the car will hold 200 in stop and go traffic 108 deg outside temp.The way the cooling system has to work properly is coolant needs to stay in block long enough to absorb heat/Coolant has to stay in radiator long enough dissipate heat.When the thermostat opens the exchange happens. This is why the factory uses thermostat that is in the 190's.Low thermostat will remain open all the time and the there is a constant flow of coolant.When this happens there is not enough time for the exchange to happen. Think of it this way.If you did not run a thermostat the engine would run hot because there is no time to make a full exchange. I use the high flow water pumps so when the exchange happens it's quick.A trick we used in the dealership when changing thermostat we would drill a 1/16 hole in the thermostat so when we filled the system we would not get an air pocket under the thermostat.I have been doing that for 40 years and I can almost get a 100% fill with out running engine.

Chuck