I was talking to a local builder this afternoon. He WANTED me to post (repost?) a question to the forum....

I probably brought this up when I built my 383 five years ago, but I think it's possible/probable that my cam is installed resulting in 8-deg mechanical advance.

Because it was several months after purchase before installation, I had forgotten there was 4-deg advance "ground in" to the cam. And, though I can't remember for certain, I think it was installed in the 4-deg notch on the timing kit. So...it MAY have 8-deg total advance.

After this thought occurred to me, I called Bullet -- who made the cam. I asked them if I had screwed up. The guy I talked to was convinced I was fine...and that in many cases, 8-deg is desirable for a street car.

I never saw any problem to prove it was a bad move so I let it go. In fact, the car is so d@mn snappy, I decided that my little "torque monster" had benefited from this "mistake". Mostly, it's driven on the street and doesn't exceed 4-5k rpms. PROBABLY that's a combination of it running out of torque by then AND that it gets up to speed so fast underneath that level. It doesn't take but 2-3 seconds in any gear to "accomplish a goal".

I would also describe the torque as big block territory. And, numbers on the dyno bore that out.

The reason I bring this up is the long-term issue I've had with temps rising with the A/C on in the summertime. The guy I spoke with today was CONVINCED I shouldn't need an aftermarket fan with a large radiator on a 383. In his "career", he's never seen the need for a fan upgrade...on ANYTHING.

Hey...it's hard to argue with a guy "in the profession".

At the end of the conversation, I remembered the 8-deg advanced config when he said "bingo"! I think that's the "problem". At his insistence, I decided to post and see if/who feels that's detrimental (in any other way than power curve)?

Personally, I think a swap to an HSR and better exhaust would wake things up -- if that was my ultimate goal. Having super-advanced mechanical (and electrical) timing just makes it more fun on the way to the grocery store!

 

Usually you don't advance or retard a camshaft 4 degrees unless advancement thru the distributor is not possible. If you degreed the camshaft you would have known if it required 4 degrees advance, but it's very rare to have NA engines advanced or retarded on the camshaft. Most people use the base setting on indexed timing chain kits and this usually provides the best performance, and it would run cooler than being jacked up 4 degrees at the base. Often you see engines retarded at the cam (base) for large nitrous, turbo or supercharger applications that are strictly race cars anyway.

Still, there is nothing wrong with a better radiator! The factory fans aren't all that bad, but I'd defiantly rather have a larger radiator in a performance application. There ain't nothing wrong with a nice all aluminum aftermarket radiator, just like there is nothing wrong with the plastic jugged unit that's probably factory.

 

I already have a larger radiator.

As for your comment on mechanical advancement not being optioned unless the dizzy can't provide what you're looking for, I'd have to disagree with that (at least on the surface). That's because there's a difference between the two.

Mechanical changes in cam "orientation" will determine where maximum compression occurs. Advancing produces low rpm "compression". Retarding moves power upward in the powerband.

I suppose electronic timing MIGHT do a little of the same but I thought it was mostly to hit the ideal spot in the compression stroke to insure clear burn and maximum power -- with regard to the "mechanicals".

 

And what might that be, exactly?

Did the cam card call for +4 degrees at base? Did you degree the cam to see?

You saying 4 degrees advance timing is not 4 degrees of advance timing? That somehow it's more magical if built into the base?

 

Its not answering your question but when was the last time you pulled the fans off and with a high pressure garden hose (from the engine side) blew the fins out real good? make multiple passes, ac too. It works.
Mine gets plugged with less than 8k a yr driving and its not a bottom feeder like a vette

 

Cam timing and ignition timing are two different things. You can have a cam that's installed in a four degree advanced position and ignition timing four degrees retarded if you wanted. The one has basically nothing to do with the other.

 

@ the original poster. I seriously doubt your possibly advanced cam has anything to with your hot running issue. In fact I would put that idea right out of my mind and start basic cooling system diagnostics. Your problem (if there even is one) is probably something like the fan isn't turning on with the ac.

 

If one has nothing to do with the other, then why even use a "base"?

Distributor is run off camshaft, indexed keys are usually on the crankshaft. TDC will change with an indexed crank sprocket set to +4 degrees, which will also change where the #1 position of the distributor is in relation to the cam, or where it "was" prior to the base setting.

Saying the one basically has nothing to do with the other is about as careless as installing a cam without finding out the base anyway.

Again, without a cam card with the specs, or actually running out the engine on a degree wheel, how can anyone seriously make any assentation's about what is what?

So now what?

 

WTH are you talking about .... TDC never changes. The valves opening and closing relative to TDC is what changes when you change cam timing. Ignition timing will be adjusted via the distributor and is unrelated to cam timing.

I suppose you could argue ignition timing is affected by cam timing if you don't know how to adjust ignition timing properly.

 

TDC doesn't ever change, correct. But ignition timing and a properly indexed camshaft go hand in hand.

Does he need the valves to open up 4 degrees before they normally would? Well the cam card or the actual specs would say weather or not 4 degrees of advanced timing was needed. I see people add and subtract degrees all the time, and 90% of the time they all agree that it runs better at a base setting (unless it's primarily a race car).

Most people wouldn't even think about advancing or retarding cam timing, even a single degree; without running it out! And anyone that says proper ignition timing isn't reliant on proper cam timing is just trying to get out running out the engine with a degree wheel.

That's my feelings.

 

Explain this one too ....

 

Are you just making this up as you go ???

 

Ok rookie... It's like this, cam timing changes vacuum. Vacuum advance is controlled by what? MAP sensor? Vacuum advance?

You really are trying to be difficult aren't you? Sure, if performance was not the objective cam timing and ignition timing are two independent things.

Your unwillingness to acknowledge this FACT show you're just being difficult. But since you're a rookie, and probably haven't had to deal with the issue much I'll explain it for you so you don't have to be so lost in the "system" that you think I'm making things up.

Proper cam timing can only be determined by running out the engine. If your cam timing is off, your ignition timing is also going to be off.

The base must be respected. I've seen some shady cut cams and in most cases street cars aren't advancing their cam timing unless they are mud racers or 1/8 mile junkies.

Go ahead, say cam timing has nothing to do with ignition timing. It's laughable because it assumes proper cam timing has been set.

 

LOL I think its pretty clear who the rookie here is ...

 

That's right, and since I am an expert on this issue, I know your not, and now everyone else does too.

 

Talk about making things up as you go along!

What are your credentials? I've got 25+ years and a master.

How about you?

 

If it helps, although I never did a 383 build in a Vette, I did a few in 4th gen F-Bodies. I always had to upgrade the cooling or I ran into heat issues.

Only 1 of them had AC, and it did cause a rise in temps. I retuned the fans to come on lower, and upgraded the radiator. Problem solved.

 

You may have 25 years + in doing body line and trim or steering and suspension but not engine repair or driveability and performance, or you just plain wouldn't say the nonsense your saying. Somhow during your extensive career you have failed to make the distinction between ignition timing and valve timing. Surely you must realize these are two different things, or maybe you dont.

 

Surely you must realize that the intake stroke is different than the exhaust stroke, and one is not possible without the other, or maybe you don't.

Are you even certified in ANY automotive repair category? When I say certified, I mean certified by some automotive body other than the shade tree you got out back?

4 degrees positive cam timing on a cam that is supposed to be set at zero is a big issue.. Like installing a chain or distributor a tooth off!

Rookies.

 

Read the second half of paragraph 5.

http://www.badasscars.com/index.cfm/...rod/prd370.htm

Before that, you'll see the discussion of why someone might alter cam timing. You suggest mud-racing or 1/8th mile junkies. For purposes of this thread, let's just label me the later (if you need a reason) and try not to steer this thing too far off-topic.

If you think there's only one place a cam can/should be installed, you are allowed that opinion. Mostly, I can see that argument when defining your earlier qualification of "performance" as the highest HP. That is a valid argument.

If that was ALWAYS the goal, then long-running intakes never should have been created...and installed on production "performance" cars.

I could also submit the topic of variable cam timing. If cam timing should NEVER be altered this too would never have made it to production. In these cars, do you think electronic timing magically changes with the variable "cam events"?

Lastly, I must assume your response is: Never install a cam except straight up. Your opinion is duly noted. You are allowed that opinion. Of course it doesn't address my original question of whether advancing a cam might contribute to additional heat. But, then again, you have steered away from such "atrocities" your entire life.

Just out of curiosity, I wonder if you know WHY altering cam events raises and lowers where power is generated (with respect to RPM)?