Cam is in, car is running, now the TUNING begins!

[Kern Dog]

Greg,
Have you sprayed carburetor cleaner around the base of the carburetor and all your vacuum takeoffs on the intake manifold?

Yeah, I used Brakleen. There was no change in idle speed. To make sure the Brakleen was combustible, I sprayed some across the primaries. It sped up immediately!

Budnicks.....F I V E jet sizes? Thats funny!

 

[Meep-Meep]

Sounds like you are running a Holley. Which one? Your timing is very reasonable and you are still pinging because you are way lean based on your O2 readings. Did I mention you have a fuel curve problem? What I meant is your problems seem to be beyond simple jetting and PV changes. Your idle feed restrictors probably need to be opened up and I suspect the emulsion tubes will need to be drastically altered. I suggest contacting Promax or similar company and get a custom tunable metering block based on ALL of your engine data. FYI: The amount, size and position of the holes in the emulsion tubes can tailor the fuel curve very precisely under load and throughout the RPM range. For example, holes up high will lean the top end but have little effect on the low end.

 

[Kern Dog]

I was thinking that there MUST be more to this than just changing some jets.
The carb is a Barry Grant Speed Demon 850. Here is a strange bit of info:

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

The Holley Street Avenger 870 in the link shows to have jetting of #78 and #84 with a 4.5 Power Valve. This surprises me that a carb with a higher CFM rating would have jets so much smaller than my 850.

 

[Supershafts]

You're going to need to change the air bleeds and not just pv's and jets, hold your finger over the idle bleeds lightly first and watch your guage, most likely you need smaller bleeds already then you'll know what else needs tuning, you're moving more air at idle.

you may need more than 850 also, my 500 is using dom based bg and so is my 490, that 850 wouldn't work on my 490

 

[Sweet5ltr]

Sorry, nothing to add that hasn't already been said but this..

Are we are talking a street car, or an all out strip' car!? Why would you run a 1050 Dominator on the street? Throttle response would be down the drain, and you would be getting mid-single digit gas mileage for maybe 10-15 additional HP on the top end in this application? Sure you can make a few more horsepower, but what kind of return are you getting for the cost?

I lucked out and bought a fully modified 750DP w/ a modified proform main body, baseplate, modified metering blocks, etc. For the street, the carb couldn't run better with my single plane. Cranks up instantly, idles steady when cold, plugs are perfect and lightly browned, and has instant throttle response. Made 430RWHP with a 347 solid-cammed SBF on the rollers, we would be lucky to turn those numbers going through our running gear in these Mopars. It also gets 10MPG around town, 14-15MPG on the interstate. I had a factory 750DP on it before for comparisons sake with cast iron heads, 9.75:1 CR, .509MP, and a Performer RPM and it was absolutely terrible! I would compare it to a factory 750/850 Eddy...

In these type of applications, you nearly need to order a custom carburetor or take it on the dyno and get it tuned their. The carb I run has more money that I would ever be willing to dish into a 750 thrown into it, but I purchased it from a close friend that has an street 8 second turbo, glide' foxbody and a brother with a 9 second, Tremec 5-speed, procharged foxbody. Both cars run 750's modified for blow through use. I can assure you though, you don't need a bigger carb for a street car. Many other places to throw your money away into other than that if your looking at improving your ET/MPH..

Little bit of info as well is BG flow rates are wet flow rates, holley's are dry. Not sure if you had known that. Ie: 650 BG is comparable to a 750 Holley.

 

[Kern Dog]

Thanks Sweet,

My carb is an 850. I bought the carb in 2003 for a .030 over 440 with a 284/484 cam. I should have known it may be UNDERsized for a 493.
Now I wish I would have installed this wideband guage with the previous cam and jetting. It would have given me a baseline to start from.
Anyhow, here I am now. I have 2 other square bore carburetors here to test on the car. One is a 750 Holley. I will bolt it on to see how the numbers differ. I have no intention of keeping a 750 on the car, just wanted to see if the A/F numbers differ. Summit Racings online CFM calculator reads that a 493 with a max rpm of 6200 needs 751 CFM for street and 972 for strip. I figured that the 850 was pretty close. I didn't build the car to drag race. It was built for handling and cornering but I have considered making a few 1/4 mile passes to know its potential.

 

[Sweet5ltr]

Some articles on Mopars and Carbs:
http://www.moparmusclemagazine.com/techarticles/engine/mopp_1207_carburetor_dyno_test/viewall.html

http://www.moparmusclemagazine.com/parts/engine/mopp_0111_demon_carburetor_dyno/viewall.html

Not much difference between a 750/850. Maybe 1-2RWHP at most, even in the second test with a solid-roller cammed 440.

 

[Kern Dog]

I decided to try a carburetor from another car. The Holley 750 is a bit dusty but works great on a mild 360. The 750 is untouched inside.
First off, the idle vacuum went up from 10.0 to 11.5. The IN GEAR idle vacuum went from 5.0 to 6.5.
The Air/Fuel readings improved.
At idle in park : 13.8 to 14.2
At idle in gear: 14.2 to 14.6
In gear, pwr brake 13.8 to 14.5
This shows that the 750 actually maintains a "ballpark" ratio when a load is applied. The 850 would go totally lean when put inder a load off idle.
I wonder if the 850 has some crud stuck in the passages?

 

[Budnicks]

Dennis H, Quickfuel's Billet adjustable adj. air bleeds & elmulsion, in their Metering blocks both front & rear would be a great start.. I was suggesting to try the big jet change to see If it actually changed anything on your A/F gauge, it will/could help point out some problems...

too me it was obvious you are way lean & all over the place, if you don't have an ignition, timing or vacuum problem anyway... good luck

 

[Kern Dog]

Good news!

Since I had the 850 off of the engine, I went ahead and inspected it. It has built in, NOT bolted/screwed in air bleeds. I took some carb cleaner and tried squirting into them. The outer 4 were plugged! Each one sprayed back at me a few seconds, then blew through the idle transfer slots near the throttle blades! The inner 4 must lead to the inside of the metering blocks or somewhere else because they allow the carb cleaner to flow through without sprayback.
I decided to change the jets again, this time I went to the #90s. I started the car back up and was amazed to see the numbers have improved.
Idle in Park: 13.0 to 13.8
Idle in gear: 12.8 to 13.5
Pwr brake : 12.0 to 12.9
This was with no additional tuning. For the first time, the 850 doesn't lean out with a load applied. Tomorrow I'll mess with the idle mixture screws. I may need to go backward to #89 jets to lean it out. I have some nice straight roads near home to test on.
While changing jets, I dropped the metering block and chipped the white plastic extension tube. I'll need to replace that when i change the jets.

 

[Meep-Meep]

I was thinking that there MUST be more to this than just changing some jets.
The carb is a Barry Grant Speed Demon 850. Here is a strange bit of info:

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

The Holley Street Avenger 870 in the link shows to have jetting of #78 and #84 with a 4.5 Power Valve. This surprises me that a carb with a higher CFM rating would have jets so much smaller than my 850.

I'm not that surprised. The difference is probably in the metering block and high speed bleeds. I've always said that if you are making huge jet changes to try and make a carb work you need another carb. Sounds like the 750 might do pretty well.

 

[Sweet5ltr]

Good news!

Since I had the 850 off of the engine, I went ahead and inspected it. It has built in, NOT bolted/screwed in air bleeds. I took some carb cleaner and tried squirting into them. The outer 4 were plugged! Each one sprayed back at me a few seconds, then blew through the idle transfer slots near the throttle blades! The inner 4 must lead to the inside of the metering blocks or somewhere else because they allow the carb cleaner to flow through without sprayback.
I decided to change the jets again, this time I went to the #90s. I started the car back up and was amazed to see the numbers have improved.
Idle in Park: 13.0 to 13.8
Idle in gear: 12.8 to 13.5
Pwr brake : 12.0 to 12.9
This was with no additional tuning. For the first time, the 850 doesn't lean out with a load applied. Tomorrow I'll mess with the idle mixture screws. I may need to go backward to #89 jets to lean it out. I have some nice straight roads near home to test on.
While changing jets, I dropped the metering block and chipped the white plastic extension tube. I'll need to replace that when i change the jets.

That's great, hopefully it all comes together for you in the road test!

 

[Supershafts]

Sorry, nothing to add that hasn't already been said but this..

Are we are talking a street car, or an all out strip' car!? Why would you run a 1050 Dominator on the street? Throttle response would be down the drain, and you would be getting mid-single digit gas mileage for maybe 10-15 additional HP on the top end in this application? Sure you can make a few more horsepower, but what kind of return are you getting for the cost?

.

I have no problem on the street, idle, start up, light tip in is very responsive, the throttle response is better than fi, i don't know how you get worse throttle response because you go to a 1050 base carb?? but again we get right back to the RR many think plays no role.

Performance is the return, i couldn't get the same perf or return from a 850

Thanks Sweet,

My carb is an 850. I bought the carb in 2003 for a .030 over 440 with a 284/484 cam. I should have known it may be UNDERsized for a 493.
Now I wish I would have installed this wideband guage with the previous cam and jetting. It would have given me a baseline to start from.
Anyhow, here I am now. I have 2 other square bore carburetors here to test on the car. One is a 750 Holley. I will bolt it on to see how the numbers differ. I have no intention of keeping a 750 on the car, just wanted to see if the A/F numbers differ. Summit Racings online CFM calculator reads that a 493 with a max rpm of 6200 needs 751 CFM for street and 972 for strip. I figured that the 850 was pretty close. I didn't build the car to drag race. It was built for handling and cornering but I have considered making a few 1/4 mile passes to know its potential.

You're using a very small cam in that motor, thats also holding back all kinds of performance potential from that motor.

The 850 would be to small for your 490 if it had more cam

- - - Updated - - -

Some articles on Mopars and Carbs:
http://www.moparmusclemagazine.com/techarticles/engine/mopp_1207_carburetor_dyno_test/viewall.html

http://www.moparmusclemagazine.com/parts/engine/mopp_0111_demon_carburetor_dyno/viewall.html

Not much difference between a 750/850. Maybe 1-2RWHP at most, even in the second test with a solid-roller cammed 440.

This is the problem, You want to compare Two articles with LAZY RR motors to that of a 490 that is TOTALLY wanting different things, MOVING way more air at different rpms than that 383 or 440 can.

You can not make carb comparisons like that, IT IS NOT going to be the same.

You don't build motors and pick carbs by magazine tests on 2 motors with 1.88 and 1.8 RR and dare compare them to motors with 1.6 and 1.5 RR

This is why i see MANY mopars not running where they should be, the details are being missed.

 

[Kern Dog]

I must have missed something, Supershafts.
You say my cam is too small? The engine is a 493 with a solid flat tappet, 261*.271* @ .050.
The lift is .556/.578. I degreed it to the 106 C/L. Seems like a decent sized cam to me. I am not interested in racing the car for pinks or anything. I'd give up some high rpm power to gain better street manners.

Yesterday after cleaning the air bleeds and swapping in the #90 jets, I thought I was getting close. The numbers at idle in Park were near 14.0. I put the air cleaner on after testing and shut it down.
TODAY I road tested it. It idled richer because of the air cleaner, now about 13.5. When I put it in gear, it richened up into the 12.5 to 13.0 range. Once I drove it, it went PIG rich below 11.0 to 11.6.
Back at home, I changed to #88 jets. I was able to get the idle A/F to 14.3 to 15.0 but when I put it into gear, it went 17.0+. Huh? I'm back to running lean? Uhhhh, not really. On the road it was still reading below 11.0 to around 11.6.
Okay. I found that the 850 responded to jetting and cleaning. NOW I can reverse direction and setp down the jets.
I switched in # 88 jets. Idle was okay, but when I shifted into gear the A/F went lean again, just under the 17.0 limit. When I drove it, the A/F at a stoplight went from 16.0 to over 17.0 but went down to 12.5 to 13.0 at part throttle. I still get detonation though. I'm curious that I still get detonation with a severely rich reading.
Tomorrow I will road test the car with the Holley 750. If the engine runs without detonation, I'll at least know that the 850 has something internally wrong. If it pings with the 750, I'll focus my attention elsewhere.

 

[Supershafts]

I didn't see that cam, i thought i seen some pimply 284 mentioned.

Street manners, this confuses me, what exactly are these street manners everyone seems to have or worry about getting from a particular cam.

You're going to have to get involved with the air bleeds to further tune some issues you're having,

 

[Meep-Meep]

I'll say again it's very possible that the 850 is the wrong carb for this particular engine combo. If it's happy with the 750 - no pinging, good power and overall correct mixture - consider the problem solved.

 

[Sweet5ltr]

I didn't see that cam, i thought i seen some pimply 284 mentioned.

Street manners, this confuses me, what exactly are these street manners everyone seems to have or worry about getting from a particular cam.

You're going to have to get involved with the air bleeds to further tune some issues you're having,

Supershafts,

I never doubted an 850 Holley or 1050 Dominator would make 'additional HP'.. as we all know, more airflow equals more power. Some of us (not insulting) use common sense when we think of "hp per/dollar". I picked up my race tuned and modified 750 for $150 from a friend... I couldn't imagine spending $500-$700+tuning costs for an 850 in order to gain an additional few HP if any at all. For a street car, you would NEVER notice 5-10HP at the crank. Many aren't running 6,000+RPM from stop light to stop light. An arcing plug wire can cost you that much horsepower! In the second article, the 440 made 550HP. That is no typical street combination with a lil' sub .500 lift flat tappet cam... Many of us don't plan on placing really radical cams in our street dedicated cars, as they are just going to wipe out and go flat in a matter of months with the spring pressure they recommend while we idle down main street in heavy traffic. I ran big lift cams in my SBF's, but they were all hyd. roller and their duration was pathetic! Heck, I run slightly below the recommended spring pressure with my .590 in order to further my durability over the minimal power gains; and it has a slow ramp rate to begin with...

 

[Kern Dog]

For me, street manners means the ability to run fine on 91 octane and not overheat. It means having the ability to idle in traffic yet still run clean. No clouds of black smoke on startup or full throttle. No vapor locking in 100 degree weather. I'm willing to deal with the vibration and noise. The smell of some unburned fuel is cool. I don't want to deal with knocking, dieseling or the engine being hard to start when it is cold or hot.

 

[Meep-Meep]

261 / 271 @ .050" with nearly 100 deg of overlap is not exactly the type of cam that epitomizes street manners.

 

[Kern Dog]

Yeah, but this isn't a daily commuter car.
The 750 idled great. It has some lope, but I was able to get it to idle at 600 in gear. I was impressed with how docile the engine sounded and felt. The 850 wanted to flop around and stall below 700 rpms. I drove it and found the Air/Fuel numbers were pretty close to the prescribed goals.
It STILL detonated at 3/4 throttle and above. From a standing start, from a roll, from 3000 rpms it didnt matter. Light black smoke and spark knock. This totally defies any logic I have. I have tried different jets, power valves, carburetors, timing settings, distributors...I've tested it on a warm engine, a cold engine, under 85 degree weather and 94 degree weather. Everything I have tried has resulted in spark knock except retarding the timing.
I am damn near out of ideas. Now it seems like a case of...."When the logical solution does not work, time for the illogical".
I have a few stock 440 distributors I can try. I have different spark boxes/ECUs. I have a 5 gallon can of 100 octane unleaded fuel.
I don't know what else to try.