Hey Ron! Whaaazup! I pulled it apart and cleaned a couple of weeks ago. I've tried the reverse hose cleaning method before and found you can bend fins if you're not careful. That said, I gave it a "mild" hose cleaning while I was at it. But, I didn't "hose through" the backside of the A/C condenser with the radiator pulled. I "hosed" the front.

This really isn't a new problem. And, it's not worsened over the 5 years since the build. (Geez, has it been that long! )

The occurance of this issue isn't unique to me. I've seen several people posting about curing slow-creep with more fan. Churchkey recently posted/echoed the general position that:
overheating at speed = need for more radiator
overheating at idle = need for more air flow (fan)

I've thought about creating a poll to see if/how many Champion owners have seen this type of issue. Maybe the rows are configured where they DO restrict airflow somewhat? Aftermarket fan companies don't mention "static pressure" for nothing.

To bad I through the OEM radiator away (back then), I would have tried it out of curiosity. Just to see if it allows better air flow (through itself).

I also posted about...and thought about electronic timing. In short, I'm running more timing (at idle) than [whats marketed on the internet] as the stock 89 bin. It doesn't cause knocks AND it makes idle/off-idle transition smoother for a stick. So I left if that way. I'm pretty sure I tried stock level timing (at idle) WAAAY back then. It's been awhile, but I'm fairly sure it slowed radiator creep but didn't "cure" it. That was a long time ago...so I'm not sure. Even it helped, I probably liked the way it sits now better (enough so, that I kept it at this setting). FWIW, I think I'm running close to the same timing as the stock bin. But, the stock bin assumes 20 deg timing AND 600 rpms! Because mine idles at 800 rpms, that row jumps to the 26-29 deg range. In short, where it idles dictates that it's running quite a bit more advance -- due to the timing table. OTOH, if compared to an Alvin PCM4Less superram bin, I'm also the same as that. I would think that superram would idle out the same as mine -- because of having about the same size cam....the SR cam from Lingenfelter.

 

Fans are working as designed. Here's some food-for-thought:

Almost exclusively dual 11" fan setups (like LTx cars have) pull considerably more air than a single 16" -- like L98's have. When they went to higher compression...and ultimately the LTx motors, GM converted to dual fans. Do you think it WASN'T because our bottom-breathers didn't need more help....especially when compression is pushed higher and higher?

 

Do you have a pusher and puller, I dont recall

 

I couldn't speak to why GM changed fan designs. I think its a safe assumption thinking Y body cars need a little help moving air across the radiator. I don't think there is a correlation between fans and compression ratios as it relates to GM. I also don't think cam timing is going to affect engine temps as long as ignition timing is adjusted properly. I can tell you for certain that retarded ignition timing will cause the car to run hotter than normal, but this wouldn't have anything to do with the a/c or cam timing.

 

There is a myriad of things that can throw cam timing off from parts machining to block machining. If a degree wheel and dial indicator were not used you don't have the slightest idea where the cam timing is for certain. That said if you like the performance and have no issues it does matter other than it might run better in a different place. If it is a wide lobe separation like 112 to 114 rather than 107 to 109 the cam timing changes are less dramatic as there is less overlap to play with.

To anyone that thinks distributor location has something to do with cam timing all I can say is no it has nothing to do with anything cam related.

Without dyno figures it is hard to guess what is going on with the engine good or bad but as you said you like it.

To the original question about over heating. Is it high speed low speed or both? Is it only with AC on? Do you have an under drive pulley, if so lose it as it causes more problems than it fixes. How old and what type water pump? When is the last time the cooling system flushed? How old is the fan and does it get full voltage and come up to speed at low speeds, caused by either the motor wearing out or low voltage possibly from the under drive pulley.

If it were me and not everyone is I would shotgun the problem.
Flush system completely until you get clean water when draining and do poke around up inside block drains. I would pull radiator and have it flushed professionally or lacking that mix up some coolant system flush with hot water and soak and slosh repeating until it comes out clean. While that is going on check lower pulley if under drive change back to stock for more water flow and voltage at low speeds. Swap water pump for a Howard Stewart or similar noting correct rotation. Reassemble with distilled water water wetter and water pump lube and drive a few days to a week to knock anything else loose then fully drain and refill with coolant. Any second thoughts about the fans just change them as well.

My way is the most expensive way though for me working on cooling systems is one of the most miserable ones short of exhaust systems. Bottom line is if still over heats you are fresh out of cooling system causes.

I think there is a lot to be said for the dual fans as when I am stuck in traffic in my '91 and start getting nervous I click on the ac for a couple of minutes and they come down fairly quickly the shut off ac so as to not heat up the parts for it too much.

Hope this helps.

 

I looked at that article and I can tell you that the author is not correct and anyone trying to makes claims that Cam and Ignition timing are not dependent upon each other is just lying. Increased cam timing will boost low end performance at the expense of higher RPM performance, just as increased ignition timing will offer a similar effect.

This thread is NOT going off-topic and your overheating issues could, as many have suggested, have other contributing factors however the fact that you engine creeps and only overheats when at a low RPM with a load (AC on) makes me wonder if YOU even understand what that means.

Okay, well now we're getting somewhere... Can you tell me, in what case any person, manufacture, or automotive company would build an engine where as optimal "performance" was not the goal?

There is only one place a cam can/should be installed... In the correct position! That is NOT an opinion, it's a FACT! The correct position would require you to degree the engine. That is just that.

That has nothing to do with cam timing or ignition timing. That is more or less an air velocity/movement improvement that is performed on vehicles with proper cam/ignition timing.

I'm glad you walked right into that one, and I have been waiting for someone to bring up VVT, although our C4's were never built with such technology, VVT will also help disprove anyone that says cam/ignition timing aren't reliant on one another. So here we go,

Cam timing on your existing engine is "Static", which means once you set it that's it. That is where it's going to stay. Ignition timing is dynamic, which means that it can change or be altered... So YES! On a VVT engine, ignition timing does change with variable "cam events"! Just like it does with non VVT engines. What are you guys going to do when they finally release the cam-less engines?

You shouldn't assume, but I know it's hard sometimes when you either don't know, or don't understand. I'm in no way ripping on you, however you should know that proper cam/ignition timing is not an opinion.

I am addressing your original question about overheating. I have tried to explain that improperly setting your cam timing +4 degrees positive is going to alter the position that your distributor sets at in relation to the cam when dropped in pointing @ #1.

Your camshaft is in a different position than what it should be when set to +4 advance, as opposed to zero.... Thus, regardless if you drop the distributor into the block pointing to number #1, it's still a tooth or more off from where its supposed to be, THUS, ignition timing HAS been altered.

I have never said the cam "should" be straight up! I have only said that in a majority of cases when I have worked on cars where people have made the mistake of adding or removing degree's from the cam timing, it usually performs best at base. This is all just generally speaking because I don't even know what engine or mods you have.

You need to degree you camshaft, PERIOD. Then based on that you will find the TRUE base. Anyone who suggest that cam timing is not going to effect ignition timing when improperly set on a 350 OHV engine is just kidding themselves.

 

I'm not reading all that........... but I agree cam timing and ignition two diff things.

Overbore does put more heat into the coolant, thinner walls. So do bigger/stiffer springs, so does incorrect ignition timing, longtube headers puts more heat under the hood because they have more surface area. Highway temp rising can sometimes be not enough air passing thru the fan shroud n some have to install flaps that blow open. What water pump do you have, do you have a hi-flow thermostat, are you using underdrive pulleys? Power = heat and more power = more heat. Auto or manual car what rearend gears? Do you have a tune?

As you can see there is a ton of things that can help or hinder temps.

I once read that the tpi has 8 deg advance from the factory timing set. I planned myself to retard the stock cam a bit to raise the power band a lil for an experiment maybe. What is the power band of your cam? Basically the common belief is 3-4 deg either way moves the power curve 500rpm, but the main thing to worry bout is valve to piston contact with some builds, I had a friend ruin his engine when he changed the cam position in car on a already tight build. It bent the valve n the head of it came off n you can picture the rest.

 

You do realize how incredibly silly people sound when they say that. How can they be two different things!? They are connected and aligned to work TOGETHER! If one is off, then so is everything else "to a degree", no pun intended!

 

Wow ... some folks just don't know when to quit.

 

This is where your off the rails. I am sure the OP knows exactly where his ignition timing is as long as he properly set it (I'm betting he did). This requires nothing more than a timing light and wrench to loosen the distributor clamp. You don't need to degree the cam in order to set spark timing. I'm not sure why you cant see that.

 

Valve timing or spark timing ??? I don't feel like I'm arguing either so relax.

 

Valve, because that's where the advancement was made... HOWEVER, as a result, the ignition timing is also technically "off" now too.... Hence "The timing is off".

 

Great... In the time that I have been arguing with you, the wife has slipped out the door, opened the garage and is down the road in the Vette!

Now lets be honest, do you think the OP should

a) run out the engine and set timing to optimal setting, which cost nothing but time.

b) buy more parts for the cooling system, which cost time and money for parts.

c) Cam timing has nothing to do with ignition timing, so just ram the pistons into the valves because when the spark hit's wont matter at that point.

 

How is the ignition timing off if he properly adjusted it ?? Certainly you realize that the relationship between TDC and the instant the plug fires has nothing to do with the valve timing. You understand that don't you ? Top dead center is still top dead center regardless of weather you advance or retard the cam within the bounds of its adjustability. This is why spark timing is described in degrees before or after TDC.

 

I was very clear in post #7 what I thought he should do. What is it exactly you think he should do ??

 

Because the 350 distributor runs off a gear on the cam. The position of the cam AND this gear are thus changed at that point. You can not argue that fact. If any portion of the timing is off, cam or ignition, then inherently the timing as a "whole" is also off.

TDC does not change, and I have never said it does... However the relationship between TDC and the cam and ignition timing does in fact change when advancements or retardations are made. It's just important to have the valves opening and closing at the opportune moment as it is to have the spark firing. They are separate but both must be timed in sync, and one does have and effect on the other.

 

Ok so lets say the cam is 4 degrees advanced. Are you saying the ignition timing is irrevocably advanced ?

 

In post 8 you said it does, then I said WTH are you talking about in post 9, and so in post 10 you retracted your comment.

 

I think he should find out more about his camshaft.

If he doesn't have card, and even if he did, I'd still run it out. Cam cards are only "advertised" and "actual" measurements are what is important.

It could be that his advanced cam timing is messing with the vacuum.. I'd need to know more about his ignition and fuel system to say exactly what will be effected, but make no mistake, in both cases OP would want optimal timing both on the cam AND the ignition.

To just assume that +4 degrees positive cam timing is proper isn't the way it works. Cam timing that is improperly set will have an effect on timing. +4 degrees is a WHOLE LOT of timing! It might be snappy but I think he will find it's more powerful when it's properly set up. I'd advise against buying ANY PARTS until he has his timing sorted because that is a root problem that could be causing many others as well.

 

So as a professional certified mechanic your advising to degree the camshaft for a "runs hot with the ac turned on" complaint ?? If so, then I guess we are done with this one.