Cam degreeing: I USED to think it was a waste, but now IT RUNS !!!

[firefighter3931]

Good Job getting the cam installed and broken in. 

I'm sure the fuel system is fine....it sounds like fuel boiling/vapor lock based on the symptoms you've described. You need to insulate the carb from conductive & radiant heat.

http://www.dodgecharger.com/forum/index.php/topic,52284.0.html



Ron

[Kern Dog]

I think Firefighter is right.
Last night in my sleep, I began thinking about heat soak. My 75 Power Wagon runs great in cool weather but bogs and sputters when I drive and idle it in hot weather. Getting up to speed helps a bunch. I guess with the truck, it is a matter of getting airflow.
Yesterdays breaking-in was in 94 degree weather in my garage. I do not have a fan shroud on the car and my helper fan wasn't very big. The fuel was bubbling in the filter just as the pressure was dropping. After cooling down, it ran great again.
Has anyone ever put a rubber hose over their fuel line to insulate it from heat?

[firefighter3931]

I think Firefighter is right.
Last night in my sleep, I began thinking about heat soak. My 75 Power Wagon runs great in cool weather but bogs and sputters when I drive and idle it in hot weather. Getting up to speed helps a bunch. I guess with the truck, it is a matter of getting airflow.
Yesterdays breaking-in was in 94 degree weather in my garage. I do not have a fan shroud on the car and my helper fan wasn't very big. The fuel was bubbling in the filter just as the pressure was dropping. After cooling down, it ran great again.
Has anyone ever put a rubber hose over their fuel line to insulate it from heat?

Todays fuel formulations are designed for high pressure fuel injection systems that often operate at 50psi or more. When that junk fuel is subjected to heat and low pressure (carburator) at 6-8psi....it just starts to boil. When i ran a mechanical pump I used the DEI tubing to insulate my fuel lines and it seemed to work well....never had an issue with vapor lock  

But....I also had the carb well insulated and i'm sure that helped as well 

http://www.summitracing.com/parts/dei-010415/overview/



Ron

[Kern Dog]

I haven't had an issue with vapor lock on this car since 2003.
I think that I must be running excessively lean. I must have screwed something up when I worked on the carburetor. The distributor is the same. The fuel line is routed the same way. Same fuel pump. All that was changed was the cam and the guts of the carburetor. Are all Holley and Demon carb bowl and metering block gaskets the same? Are there any gaskets that have holes where others do not? I ask this because I am amazed that it ran like it did.
Here are the stats:
It ran hot during the Cam break in and boiled the fuel.
The exhaust smelled clean, zero smoke.
The engine detonated at 30 degrees and approx 25 degrees. Not heavy knock, but it was there.
I used new jets but a used power valve. 
Setting the total timing to 30 ( Initial 16) resulted in a great idle and throttle response, but spark knock.
Backing off the timing to 20 total ( About 6 initial) resulted in an erratic idle, lazy low rpm performance, glowing headers but NO spark knock.
Some say to pull the plugs with a hot engine, then read the plugs. Uhhh... 2" headers and all that heat? No thanks.

I have no

[firefighter3931]

What carb are you running on this engine ? It definately sounds like you're running lean and need more timing. With no load you should be able to run with 35* at 2500 rpm and no detonation. 

I think you're on the right track with the carb being too lean 


Ron

[Kern Dog]

Hey Ron,

The carb is the same Barry Grant Speed Demon 850 Vacuum secondary unit I have had for many years.
The engine ran fine under no load. I heard zero detonation during break in or at any other time when the car was sitting still. Even at 30 degrees, it sounded fine and ran great until 1/2 throttle when light detonation was heard. Oddly, I'd lift off the gas, the detonation would stop, I'd get into it and at about 3/4 throttle it did NOT knock then at full throttle it came back.
Read that last sentence again.
Today I set the timing to 19 initial, 33 total. It ran great while sitting still. I checked the vacuum in neutral at 1000 rpms. 10 inches in Park, 4 inches at a 700 rpm IN GEAR idle. I have NOT touched the idle mixture screws. With a PV of 6.5, having an in gear idle
vacuum number that is LOWER than the Power Valve is obviously backward. I plan to get that wideband guage in tomorrow. This will give instant data to every change I make. I read that the goal is to jet the carb to read 14.7 Air/Fuel for cruise and 12.5 to 13.0 at WOT.

[Kern Dog]

*******UPDATE*******UPDATE*********UPDATE********

I got the wideband guage installed. I haven't jumped into tuning much yet, just wanted to pop in to post this:

Engine as is without touching anything: 9 1/2 inches idle vacuum at 1000, 4 in gear at 700-800. Idle mixture screws were only 1 1/4 turns out from being seated. IN GEAR the guage reads between 15.0 and off the guage which tops out at 18.0. When I revved it above idle, it pegged past 18.0!
I had a feeling it was lean!
I seated the idle mixture screws, then backed them out a full 2 turns. Idle vacuum went up to a solid 10+ with 5+ in gear. At idle, the guage reads between 14.0 and 15.0. It still pegs when I lean into the throttle.
Here is a thought: The primary side is running lean with the 86 jets. Being that I have 5.0" of vacuum and a 6.5 Power Valve, I think the PV may be covering for the UNDERjetted primaries. When I rev the engine, there is no additional fuel to keep the Air/Fuel ratio in check.
Sound right so far?

[Kern Dog]

I switched the 3.5 PV back in. The idle readings went down to 13.0 to 13.6. Kinda odd for it to richen up when I went to a smaller rated PV. I turned the idle mixture screws in to where they sit at 1 1/4 turns out again and the A/F reading came back to the 14.5-14.9 range.

NOW it goes off the charts lean when I put it into gear or hold the brake and ease on the throttle.

I thought I knew a little about carburetors, but tell me if i have this right:
* The IDLE circuit works when the primary throttle blades are closed. The main jets are NOT in play when in the idle circuit.
* The primary jets begin to function when the engine is put under a load and the primary throttle blades open.

If the above is true, would that mean that my primary jetting is still too lean? I understand that you are supposed to make only one change at a time which is why I only changed the power valve when I had the bowl off.
Looking at the gaskets I used, they actually are fine. They are a rubber like red gasket that came in a Demon rebuild kit I had.            

[Kern Dog]

I changed the primary jets to #88s. The in gear idle numbers hovered around 16.0 but the guage still pegged lean when I eased into the gas, power brake style.

I know that something is off here. Jets this big should not allow an engine to run so dang lean. I have been curious as to what jets others use in their 500 inch engines. This lead me to look at this:

http://www.summitracing.com/parts/hly-0-81870?seid=srese1&gclid=COP_-4CDrLkCFYU5Qgod8VsAzA

This was confusing. The Holley Street Avenger 870 uses  #78 primary and  #84 secondary jets along with a 4.5 Power Valve. This is a carb with a higher CFM rating but with leaner jetting. I'm wondering if my carburetor is AFU.

[firefighter3931]

Hi Greg,

The idle circuit is independant of the main circuit. If the throttle blades are too far open at idle it will expose too much of the transfer slot and the engine will be pulling fuel from both circuits at the same time. 

Often with long duration cam profiles the carb will need some additional air at idle. One thing that helps is drilling small holes in the primary throttle blades to allow additional air into the venturies. A 1/8in hole on each blade is what i use. 

I'm not that familiar with Demon carbs but i've heard that they use a different numbering system for their jets. What works for a Holley might be different for a Demon. 

It's definately going lean as the A/F is showing on the wideband....you need to address that to keep the engine healthy. 

The other thing to consider is the carb itself and the fuel curve calibration. With bigger cam profiles and high flowing cylinder heads you need a more agressive fuel curve. A vac secondary carb is not what i would run on a build like yours. You might be able to get it better but it will never be as good as it could be with a double pumper carb.



Ron

[Kern Dog]

The symptoms with this engine are a bit conflicting. The guage reads that it is lean. The pinging even with mild timing tells me it is lean. It has NO stumble when the throttle is snapped open even though the guage JUMPS to the lean.
I'm wondering if there is something wrong inside the carb itself. I tested for vacuum leaks. I sprayed Brakleen around the base of the carb and the intake ports. There was no change in engine speed until I sprayed it across the throat of the carb.

[Kern Dog]

I have 2 Holley carbs I can bolt on to test, a 600 and a 750. The Summit Racing CFM calculator shows for a 493 with a 6200 max rpm, a 751 CFM carb for street and a 972 for race. I might bolt on the 750 to see what A/F numbers I get. I'll report back soon.

[cdr]

when tuning with a wb,when you crack the throttle it will go lean for an instant.the only way to tune it is to drive it.

[Kern Dog]

I tried running the engine with a stock Holley 750 from another car I have.
The vacuum numbers came up at the same 1000-1100 idle rpm, from 10.0 to 11.5. The IN GEAR idle numbers came up from 5.0 to 6.5.
Also, the Air/Fuel ratio is now within tunable range. 
* Idling in Park @ 1100  13.8 to 14.2
* Idling in gear @ 850    14.2 to 14.6
* Pwr brake in gear        13.8 to 14.5

This shows something. The 750 actually richens up under a load. The 850 goes lean every time the throttle is opened under a load.

[firefighter3931]

I tried running the engine with a stock Holley 750 from another car I have.
The vacuum numbers came up at the same 1000-1100 idle rpm, from 10.0 to 11.5. The IN GEAR idle numbers came up from 5.0 to 6.5.
Also, the Air/Fuel ratio is now within tunable range. 
* Idling in Park @ 1100  13.8 to 14.2
* Idling in gear @ 850    14.2 to 14.6
* Pwr brake in gear        13.8 to 14.5

This shows something. The 750 actually richens up under a load. The 850 goes lean every time the throttle is opened under a load.

A few posts back i mentioned the fuel curve calibration differences between carburators being a factor. The 750 definately has a more agressive fuel curve and is a step in the right direction. 


Ron

[Kern Dog]

I just changed the primary jets in the 850 to #90s. I also sprayed carb cleaner through the idle air bleeds. They were CLOGGED! I got the outer 4 to clear to the point where spraying through the top it exited at the idle transfer slots. The inner 4 sprayed though but I think they lead to the metering blocks or somewhere else inside the carb.
With these changes, the A/F numbers changed a bunch.
Idle in park:  13.0 to 13.8
Idle in gear:  12.8 to 13.5
Pwr brake:    12.0 to 12.9
Before with this 850 carb, any movement off idle resulted in a terrible lean A/F reading. Now it is too rich. GREAT news, now I can go back one jet size and fiddle with the idle mixture screws to get it right!

[firefighter3931]

Good work Greg 

The outer holes are the idle bleeds....inner holes are the high speed bleeds. 

It'll be interesting to see how well that carb can be dialed in for your particular combo 


Ron

[Kern Dog]

I've read that it is recommended to set the initial timing at a point where I get the highest manifold vacuum. What if that results in a 25 degree setting? Wouldn't that make it hard to crank over, especially when the engine is warm? With an initial at 25 degrees or so, I'd certainly need to modify the distributor so it is limited to 33-35 total. I guess this is just another part of tuning. Before this engine, I never degreed a cam. Fuel pressure was never an issue in the past. I never used an Air/Fuel guage either.

[Kern Dog]

I tried running the engine with a stock Holley 750 from another car I have.
The vacuum numbers came up at the same 1000-1100 idle rpm, from 10.0 to 11.5. The IN GEAR idle numbers came up from 5.0 to 6.5.
Also, the Air/Fuel ratio is now within tunable range. 
* Idling in Park @ 1100  13.8 to 14.2
* Idling in gear @ 850    14.2 to 14.6
* Pwr brake in gear        13.8 to 14.5

I am going to try this carb again tomorrow. When I had it on the engine on Monday, I didn't get to road test it. The numbers above indicate that the 750 already runs pretty close to the goal A/F numbers. I know that a 750 is way too small for this engine, but if it runs without detonation, I can consider the Demon 850 to be the main problem here.
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[Kern Dog]

I am damn near out of ideas here.
The 750 ran pretty good. It idled smoother than the 850 and the A/F ratios were pretty close to the goal. The engine still detonated at anything over 3/4 throttle. From a stop, from a roll, from 3000 it didn't matter. Spark knock and light black smoke. I am baffled as to how after everything I have tried, it still knocks.
I've tried different jets, Power valves, timing settings, distributors, carburetors. The only time the engine didn't ping is on the first test drive after breaking in the cam when I backed the timing off until the knock went away. The timing at that point was 6 initial and 20 total.
I really do not know what to make of this. It defies logic. The cam swap resulted in a 15 lb drop in cranking compression which should make it knock LESS.
****************************************************************************************************
Grasping at straws here, but here are the only variables between the 509 cam setup and the current one.
Cam-lifters-pushrods-timing set. Different timing cover and oil pan.
Intake was installed with the valley tin only compared to using the paper gaskets last time.
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I may reinstall the 850 with totally stock jetting and see what happens. I really do not expect any improvements.

[RECHRGD]

Bad gas?

[Cooter]

What style intake?
I know no matter how well that carb is tuned, some cylinders will show lean and screw with your sensor..
This is why these work best with port FI...

[Kern Dog]

I'm running an Edelbrock RPM intake. It is a dual plane.
I took the 850 and put the #86 primary jets back in. It actually idled pretty good. Better than it has in awhile and the best it has since the cam swap. The A/F ratios were better than they have been, though a bit on the rich side. I still get knocking at 3/4 throttle and more. It doesn't matter whether I'm at a roll or from a dead stop. Up to 3/4 throttle, it barely pings at all, but once I get to the secondaries @ 3/4 throttle it pings.
I came home and poured in 5 gallons of 100 octane unleaded that I was saving. I considered it a last resort. I still had about 5 gallons of 91 in the tank, so without a degree in petrochemical science, I can only guess the mix results in about 95 to 95.5 octane. I drove the car 4 or 5 miles to use up the 91 octane that was in the fuel line, pump and carb. When I tried to hammer it, it still knocked. I tried it a few  more times in the next 3 or 4 miles and I got the same results.
I am still confused as to how an engine can react this way. When I ran a 40/60 mix of 110 and 91 in the car with the '509 cam, it didn't knock one bit. Even if I had my numbers wrong and the cam timing is off by 4 degrees either side of the 106 number, I still wouldn't expect it to knock.
A guy on another forum wrote about a  496 that had the same problem. His Fel-Pro head gaskets had burned "Fire-Rings" that  were hanging into the combustion chambers. He put in larger bore head gaskets and solved the problem. I wonder how you determine that they are burned. I guess I could pull the heads to check, but I'm getting tired of chasing dead ends!
http://www.summitracing.com/parts/edl-7325

[Kern Dog]

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Update:
After chasing all sorts of possibilities, I decided to do a cranking compression test. It turns out that my numbers now are actually 3 lbs HIGHER per cylinder than they were with the '509 cam.
Yeah, that is what I found out. I did the test like I always do:  All plugs out, engine cold. I had an average of almost 188 before, now the average is 191. I wrote that the engine knocks more now than before, THIS may be the reason. I am totally baffled at HOW this cam can produce MORE psi when it has a later intake closing. It just defies logic.
509 cam                    Lunati cam
#1 188  #2 188       #1 190   #2 190   
#3 185  #4 190       #3 189   #4 190
#5 188  #6 189       #5 192   #6 195
#7 185  #8 190       #7 190   #8 192

I reinstalled the plugs. Tomorrow I'm going to run the tank down a bit then pour in 5 gallons of 110 octane leaded fuel. I'll have to unscrew the O2 sensor to keep from damaging it.

[Cooter]

 I told you in the beginning you will have to lower that compression.