massive reconfiguration time again.

-
j par said:
Let me say this first and it keeps swirling in my head that after the first year of just basically drag racing only I took the heads off and put 202 valves instead of the 188''s. At that time there was a little bit of detonation on the tops of the Pistons but just very very start of something. I showed the Machine Shop my plugs with the porcelain sticking out about a quarter of an inch LOL and he said well this is way too hot. And recommended the ones that I'm using now. Back when I had an average cranking pressure of 190.
I sure appreciate you taking the time because I'm getting a little bit lost with all these things for some reason. It's always ran at about 35 36 degrees of advance with my old cam. It was used a lot for drag racing but a lot of putting as well. I always seemed to be burning rich and have black plugs.
Now I've changed the cam and my compression is higher so I backed the timing off to 34 right out of the gate. I've been putting smaller and smaller Jets and larger metering rods to lean the carbs to stop having such a rich condition. but here I am reading the plugs and seeing some speckling on the porcelain thinking I'm back to getting detonation. But still seeming to run very rich as you can see from the plug that I just pulled out the other day. All these plug reading things I'm trying as well LOL.. I'm constantly watching my AF gauge. It runs down my driver side header. It was burning about 14.2 on the freeway which I thought was a little high for cruise at 28 to 3000 RPMs. About 68 miles an hour. I have no vacuum advance canister. I would think what timing curve was probably about 3/4 open at the time. On post #1028 I'm showing my timing curve.
View attachment 1715363564
This is a side-by-side comparison of the number 2 spark plug. I believe they're the same heat range that's why I bought the NGK. The one on the right is the one that I've been running for a while and it's in Autolite ar3934. The one on the left has a hundred miles on it mostly freeway and it's the NGK 4554.
That was what really the first time I've ever took it on the freeway and had it like that for 45 minutes at a time. It's mostly driving around town and short verse of yeehaw... I thought it was the timing because I dropped it down 2 about 32 degrees total. a good Lord I was reading somewhere just recently were too low of timing was the cause of too much heat in the combustion chamber. It was running 170 cool-as-a-cucumber the whole time outside the combustion chamber...

View attachment 1715363563
Click to expand...
I think this makes sense to me now...……. I read, and re-read what you wrote in this post. Pretty sure I got it, maybe know what's going on....
 
Last edited:
318willrun said:
yes, white blisters. can be caused by too lean, wrong gap, incorrect timing, or wrong/loose plugs.
Click to expand...
The plugs definitely were not loose. I know the spark plug gap is .040 and I think the MSD wants me to go bigger but I don't think so. Timing is down to 32 all in and that's what I believe the problem is. I'd like to turn back up a couple degrees and go for a drive and see what happens. Besides the plugs that's the only thing I changed and my driving habit I guess of holding it at three grand for more than a half hour. AF 14.2 @ 2800rpm....
 
j par said:
What is it? I've lost my marbles? LOL...
Click to expand...
Ok, I hate typing essays. Let me lay a small footing......
  • Large cams - meaning more duration/lift will bleed off cylinder pressure. You went smaller cam, so that will raise your cylinder pressure.
  • A big question is "how much advancement was ground into the cam??" And when they reground, what about the advancement???? Advanced valve timing adds cylinder pressure.
  • So, between the two statements above, you gained cylinder pressure. This is effecting how the plugs burn. So you are now trying to compensate by Jetting your carbs, which will most likely lead you to "too rich, then too lean" conditions.
 
Also I was just thinking of putting some weaker of metering Rod Springs and because it kind of had an opposite effect when I put stronger ones in like they recommend for a bigger cam...
 
318willrun said:
Ok, I hate typing essays. Let me lay a small footing......
  • Large cams - meaning more duration/lift will bleed off cylinder pressure. You went smaller cam, so that will raise your cylinder pressure.
  • A big question is "how much advancement was ground into the cam??" And when they reground, what about the advancement???? Advanced valve timing adds cylinder pressure.
  • So, between the two statements above, you gained cylinder pressure. This is effecting how the plugs burn. So you are now trying to compensate by Jetting your carbs, which will most likely lead you to "too rich, then too lean" conditions.
Click to expand...
Okay so now what? LOL...
 
j par said:
Okay so now what? LOL...
Click to expand...
Ok, first let me say the picture I thought was your plug blistered was somebody else's post. LOL.
I would not lean it out. I would NOT lean it out. I would pull it back up to 34* timing, fatten up the carbs, and run a hotter plug, like a RN12YC. This is the direction I'd start my ship in...……..
 
j par said:
Okay so now what? LOL...
Click to expand...
Another thing, the A/F gages...….. I hate to say it, but they may not be your best friend. Where is it located, what side it is located? This would change the reading and therefore change the tune of the car. But would it be "right" for the car???
 
318willrun said:
Ok, first let me say the picture I thought was your plug blistered was somebody else's post. LOL.
I would not lean it out. I would NOT lean it out. I would pull it back up to 34* timing, fatten up the carbs, and run a hotter plug, like a RN12YC. This is the direction I'd start my ship in...……..
Click to expand...
Of course not to argue your point and I'm grateful for it but just to make the picture clear I did just back it down the two degrees and change brand of spark plugs. The Heat range and GAP are the same as I've used for some time. And also those plugs have been in since I've had the new cam since the end of last summer.

318willrun said:
Another thing, the A/F gages...….. I hate to say it, but they may not be your best friend. Where is it located, what side it is located? This would change the reading and therefore change the tune of the car. But would it be "right" for the car???
Click to expand...
I know it gets hard to read everything I jabber on about but again it's on the left side just passed the collector and everything done by the instructions and looking like it's working correctly.
Here's another thing to throw in the twist- at 2800 RPMs it had a bit of a stumble jumping on the throttle at first. To me it seems like the accelerator pump. As well as the AF gauge going up and then plummeting down and then leveling back out..
Good Lord that needed correction...
 
j par said:
Of course not to argue your point and I'm grateful for it but just to make the picture clear I did just back it down the two degrees and change brand of spark plugs. The Heat range and GAP are the same as I've used for some time. And also those plugs have been in since I've had the new cam since the end of last summer.


I know it gets hard to read everything I jabber on about but again it's on the left side just passed the collector and everything done by the instructions and looking like it's working correctly.
Here's another thing to throw in the twist- at 2800 RPMs it had a bit of a spider jumping on the throttle at first. To me it seems like the accelerator pump. As well as the AF gauge going up and then plummeting down and then leveling back out..
Click to expand...
So assuming your A/F gage is correct, Optimum on a dyno (or in your garage) would be about 13.0, because it should fatten up under load to about a 12.7. This would be where you'd want it on the street in my opinion. And I'd run 12.7 with a little hotter plug, like I mentioned in the above post.
 
you could retard the valve timing 4*, bleed off some of the cylinder pressure, and add more top end power
 
318willrun said:
So assuming your A/F gage is correct, Optimum on a dyno (or in your garage) would be about 13.0, because it should fatten up under load to about a 12.7. This would be where you'd want it on the street in my opinion. And I'd run 12.7 with a little hotter plug, like I mentioned in the above post.
Click to expand...
And that's kind of where I used to be at wise and had really rich plugs and thought I smelled fuel in the oil and stuff like that? I was kind of under the impression a perfect burn would be 14.7 at idle, 12.5 at wot, and about 13.8 at Cruze? I agree, maybe I'll try some smaller rods..
 
j par said:
And that's kind of where I used to be at wise and had really rich plugs and thought I smelled fuel in the oil and stuff like that? I was kind of under the impression a perfect burn would be 14.7 at idle, 12.5 at wot, and about 13.8 at Cruze? I agree, maybe I'll try some smaller rods..
Click to expand...
But were you there with the cold plugs like you have now?? huge difference.
 
Make sure you don't have any exhaust leaks at the header and collector area on the o2 sensor side.


When you pulled the heads. was there carbon on the intake valve stem.
A leaking valve guide and short runs would show the oil on the plug but not so much on long runs as it would burn off.
 
318willrun said:
Ok, first let me say the picture I thought was your plug blistered was somebody else's post. LOL.
I would not lean it out. I would NOT lean it out. I would pull it back up to 34* timing, fatten up the carbs, and run a hotter plug, like a RN12YC. This is the direction I'd start my ship in...……..
Click to expand...
If your taking about my Post 1046, it is j par spark plug i copied it from post 1043 and added some art work.
 
Cudafever said:
Make sure you don't have any exhaust leaks at the header and collector area on the o2 sensor side.


When you pulled the heads. was there carbon on the intake valve stem.
A leaking valve guide and short runs would show the oil on the plug but not so much on long runs as it would burn off.
Click to expand...
That's been a few years since the heads were off. At that time the heads had about 9-10 months since a total rebuild. 596 heads. I took the heads off and ported for a few days (under shop instructions). They did a couple hours of touch up and put in 2.02's. Oil leaking in all 8?
I haven't heard any leaks...
 
318willrun said:
Another thing, the A/F gages...….. I hate to say it, but they may not be your best friend. Where is it located, what side it is located? This would change the reading and therefore change the tune of the car. But would it be "right" for the car???
Click to expand...
I'm thinking if it was running at 14.2 Cruz that maybe 13.5 at cruz and bring the timing back to 34 and hopefully the stap will turn more gray.,.
 
You must log in or register to reply here.
-

Back
Top