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Blower Motor - Timing - Spark Plugs: Need Clarification Please

26K views 19 replies 7 participants last post by  41willys 
#1 ·
I know this has been asked numerous times, but I just do not seem to get it. So, here it goes again. Sorry...

Again, the engine is a 502 with an 8-71, I am fouling plugs rather quickly. The spark plugs in it now are AC Delco Rapidfire #4's. Carbs are set good. Every where I read, and have been told here, set the initial timing 16 to 18 degrees.

At first, I set the timing to 12, runs great and very strong, but fouled the plugs. Car was not driven much at all, but still the plugs were extremely black.

I changed the plugs out, with the same as above. I went ahead and attempted 16 degrees, but the black smoke and raw fuel was extremely bad. I stopped there.

I have a question about going two steps colder on the spark plugs, I ask and ask, but it does not make sense as to why. How is going with a colder plug going to help this? It would make since going to a hotter plug.

Do you think that a colder plug and keeping the timing at, lets say 12 to 14, would be better? Borti stated he went 1 step hotter, and it would better for the street.

Now, I did call the blower shop - they said two steps colder, went to a race shop where I get my fuel - they said the same, called NGK tech support - they too said colder plugs.

Give me some advice please. It is irritating me...

Thank You,

Jason
 
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#4 ·
F-BIRD'88 said:
if the carbs were really "set good" you would not be haveing a problem with spark plugs.

What carbs, what cam. details matter.

fouled plugs and black smoke indicate a extremely rich AFR and or a severe ignition issue.
Yes, it is very rich. I have determined I need 16 to 18 degrees advance. I backed off the timing some, that is when it got crazy rich. O.k. I will take the advance back up, but my question is, how does a colder plug make things better. In my head, that tells me it would burn less fuel. At least that is what "everyone" is telling me. The only thing I can come up with is, more advance will bring me to a leaner state, and the colder plug keeps things in check (cyl. temps, etc). I am basically just trying to understand it all, before I pull the plugs again.

Gap - I was able to do some research today while "at work" and found that I should keep the gap for a blown engine .030 to .035. I was thinking of opening it up to .050 to .055. From what I understand, that would be incorrect to open the gap up.

I am just trying to figure how this all works out, and of course, in my head it works out backwards.

Thanks F-Bird,

Jason
 
#5 ·
How much total advance do you have??? This is the important thing. I'd guess you should set the timing at around 32-34 total at about 2800 rpm and let the initial fall where is might. If you have low compression I doubt it will kick back even at 14 initial. I like to run a separate ignition switch and get the motor turning before lighting the fire.

Your carbs are very rich. I'd set up the carbs with manifold referenced power valves. Try not to wash the cylinder down too bad or you may scuff a piston or contaminate the oil with gas.

As for plugs my thought is to run about stock possibly one range colder untill you run enough to start showing some real heat on them. If you have room I'd run and extended tip too at least for starters.

With that big motor and light car it's hard to run it long enough and hard enough to create a lot of heat so you are mainly dealing with part throttle.
 
#6 ·
Total is about 32.5 to be exact, yes, one of them fancy little timing lights.

It seemed to do real well with 12 degrees, but noticed that my plugs where extremely black. So, that is what started this thread. I put a new set of plugs in, and was going to adjust the timing. I moved it some, then started loading up - this is where the heavy richness in the original post came from.

What I am really searching for is the whole, "needs to be 16 to 18, plugs two steps colder, etc."

Basically, I ordered some NGK plugs, two heat ranges colder than the AC Delco Rapidfire #4's. I will put them in this weekend, and adjust the time to about 16 degrees and go from there. What should the gap be? Is .035 good?

I am finally going against what my head thinks, and realizing that more advance is leaner, and with colder plugs this helps with cylinder temps and at the same time keeps from detonating - I guess.

Correct me if I am wrong.

Jason
 
#8 ·
See, that makes sense to me as well, but as the experts put it, that is wrong.

Again, the only thing that makes any sense to a colder plug, is for more advancement. I am trying to figure this out before this weekend. I do not want to be chasing my tail back and forth.

Jason
 
#9 ·
Thanks.

First, it ran great with the 12 degrees and #4 plugs. Did not run hot, or have any drivability problems, but keep in mind, it only idled alot vs. driving. It has not been opened up. The plugs were fouled, and I put new ones in. They have only been fired one time, and are o.k. now.

I was just going back through the info. that has been posted here before, and all of the things that Hampton, Dyers, The Blower Shop, and BDS have to say, and it all points me in the same direction - 16 to 18 degrees initial, 32 to 34 all in by 2500 to 3000. That is all understood, my question was how does a colder plug make a difference. You answered it completely, thank you. See Below
"Hotter plugs" retain more combustion heat and tend to burn off combustion deposits (run cleaner) But tend to cause detonation and preignition at WOT.
I did also purchase a new set of NGK's, two ranges colder than the #4's.

As for your questions:
Cam - Hyd. Roller, lift .527" I .544" E, 224/234 at .050", 110 lobe centers.

The carbs are Mighty Demon Blower Carbs. I do not have the power valve info with me now, again, they have been matched. I do have them boost referenced.

Starts great, no pump, fires right up, idles good, but obviously better warm - with current timing and plugs.

As for ignition pointer, it is correct. Again, the engine has run great before and after blower install.

Total timing is in at 32 degrees, by 2500 RPM.

Thank you very much for your explanation, you have verified what I was "studying up on". Again, the engine ran great before the blower, installed blower, no change in plugs, ran great, of coarse with the timing advancement on initial set up. I am trying to fine tune, and will install the new plugs, and advance the timing from 12 up to 16 - 18.

Much Appreciated,

Jason
 
#10 ·
F-Bird,

I printed this out. I will start plugging away at it this weekend. We will see what she likes. Even at 12 degrees, starts great cold and hot. I will start with 16 degrees, and the new NGK plugs, and move on from there.

Thanks again, I will post the outcome...

Jason
 
#11 ·
re: Blower Motor - Timing - Spark Plugs: Need Clarification Please

If your are to rich you need to lean out the jets and idle mixture... You also need a CD ignition. Timming will only increase or decrease vac.. Causing the power valves to come in hurting the plugs more... You are way to rich check the basics float level, etc..... I have seen carbs with spray tubes on the acc pump fuel sucked right out of it... The fuel pressure on a pull through carb only needs 6 # no more !!!

My holley DP 650' s on a 6-71 468 10" vac at 900 rpm have 71 pri and 78 on sec, 30 cc shot pv is 6.5 . Timming is 18~ at 900 7.2 comp... 12 # boost...


Hope this helps

:welcome:
 
#12 ·
Well, set in the new NGK plugs, two steps colder. Set timing to 16 degrees. Starts cold and hot, easily, idles great, responds great, just like it did before. I am leaving it where it is for now, to set a second baseline from the original plugs and 12 degrees timing. I am feeling happier again. :D

Again, it was not huffing and puffing, but I do also need to realize, I never really drove the car. The two times I did, it mainly idled around the neighborhood with only a touch of the pedal to get to a coast. I opened it up one time about 1/4 to 1/2 throttle and it scared the poooop out of me :sweat: . So this in itself is enough to foul some plugs.

I am thinking of getting it out later today, slow roll it some, take it out to a back road and open it up a little. This will keep it happy, I HOPE!

I have also made a little log book, scratch pad noting the specifics on plugs, timing, etc. from the very start. Hopefully this will help me keep track of where I started, when I have problems, and when I have made changes. This way, never back step.

I will keep the board posted on the outcome...

Thanks Again :thumbup: ,

Jason
 
#13 ·
Rapidfire plugs are not the way to go on something like that, neither are NGK's unless it's got a Honda engine. A good set of straight resistor style plugs is what you are after. If the car is just idled around, that could be most of your problem. Blowers are not meant to just idle around the neighborhood. Find a back road somewhere and give it a good run, clean it out. I have always went hotter when fouling plugs with success, regardless of what the "experts" say.
 
#14 ·
That is why I removed the plugs, I was running the Rapidfires on it before the blower.

Running it is my biggest problem. The car weighs nothing it seems, and honestly, I THINK I made a mistake with the blower. Is there such a thing as too much power for your toys?

All I can really do is give it some little spirts here and there, maybe that will keep her happy.

I was speaking with a friend, one of my techs at work, he has a few all out drag cars. One of which is blown. He stated, for the most part, the fact that the car does not get driven and does not get opened up, this will be something that I may really have to live with. "Blower motors will foul plugs quicker when not driven for the 'intended and purpose' for what they really are". Not exact, but dang close to what he said... Now, this comes from a guy with nasty Outlaw 10.5 cars and such (that may still be a southern thing still, not sure).

...................

Rapidfire plugs are not the way to go on something like that, neither are NGK's unless it's got a Honda engine.
Not to get too far off of subject, but why do you think NGK's are not a good choice? I understand you may think they are for Hondas, but it does not seem to be the thought of many racers, hot rodders, etc. I am just asking, have they had problems with the plugs? It just seemed a clear choice due to so many recommendations from others, NGK and Champion's were the recommended plugs. Let me know.

Jason
 
#15 ·
i have been where you are for 6 months..... i was going through a set of plugs a week.. we did hot we did cold.... we even went as far as putting the motor on a dyno... it ran great... we did everything and it kept fouling out the plugs..finally i took it to someone who is a expert on caebs and blowers.. that was 9 months ago... i have not fouled a plug since then.. i have nevr been down on the car and all i do is baby it when i drive.. It was dynoed at 912 hourse and it runs great... the whole problem i had was with the carbs... jets and power valves...1 pump and turn the key and it fires right up and runs... we did everything called holley / blower company / can company we did everything they said and it did not work.. it was all in the carbs... we even had the carbs off at one time and installed them on a mule motor on the dyno. one did 526 hourse and the other one 522 horse, so we thought everything was ok with them.. NO they were not set up for the blower motor...

good luck
john
 
#16 ·
Update

Well, I decided to stick with the plugs that were in it, they are new and not fouled (factory heat range). I set the time to 18 degrees initial. It runs great, just a little fat at idle, but I understand it needs to be. Starts immediately on cold and hot starts. Idles good, no surge, and immediate throttle response.

Very wicked...

Thanks for your help, information, and guidance.

Jason
 
#17 ·
in my experience blower carbs are usually set pretty fat. When I bought my holley hp600 double pumpers I had to modify the idle circuit on the carbs to get me leaner at idle (involved tapping & drilling the metering blocks) which is something that requires a good bit of knowledge to do right, but that could be part of the problem with fouling plugs....after I did that I had no more problems with fouling. How far out are your idle mixture screws on the carbs?

You need to see what your vacuum is and what power valve you have in your carbs, that will also have a big effect on fouling plugs if not setup properly.

your engine will like being locked out the best at full timing, but that may give you some problems with hard starting when hot...the 18* should be fine. I prefer running a vacuum advance(wish I had one, but i dont) it really helps with the car running better in high manifold vacuum conditions.

oh and FBIRD you CAN reuse spark plugs after they've been fouled. I have been sandblasting fouled ones and they work perfect after being cleaned.
 
#18 ·
I took it out to play last night. Had two other people there with blower cars. One of which is a big bad big block Camaro. Both of these guys said I would be even happier if I locked out the advance and set it at 30 degrees.

They also said that I am fine where I am at, but would be much happier if I locked it out. What do you think?

AND, reading back through F-Bird's posts, that would make since. From what you are telling me, if the it likes 26, 30, 32, or what ever it may be, I might as well lock it down at that point. I am going to play with it here today, see what happens.

Jason
 
#19 ·
41willys said:
I took it out to play last night. Had two other people there with blower cars. One of which is a big bad big block Camaro. Both of these guys said I would be even happier if I locked out the advance and set it at 30 degrees.

They also said that I am fine where I am at, but would be much happier if I locked it out. What do you think?

AND, reading back through F-Bird's posts, that would make since. From what you are telling me, if the it likes 26, 30, 32, or what ever it may be, I might as well lock it down at that point. I am going to play with it here today, see what happens.

Jason
is the blower under or over driven? The thing you have to watch out for with having your timing locked out is that you are much more likely to detonate. I still think you have some issues you need to work out with your carbs
 
#20 ·
No, there are no issues to work out. I will be leaving it at 18 degrees, until I see issues. I will be putting in the colder plugs as soon as the two that were damaged come in.

I am underdriven, 6 to 8 lbs of boost. I would go lock out at 30 degrees if I was over driving the blower, but I am not. I did some more research this morning, and realize that I need to stay where I am at, and if I start seeing problems, I will pick at the carbs.

Jason
 
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