Tuning a big roller cammed motor - how to do it?

[Brewzer67]

I am in new territory and am looking for help from the brain trust here. I have my engine back together and am now ready to start fine tuning it. This is the biggest cam I have ever run and my first solid roller so I have no idea what to expect normal baseline numbers to look like.

Here is the combination:
526" (4.375 bore and stroke)
.715 custom tight lash Solid roller by bullet ([email protected] intake, [email protected] exhaust, 110 lobe separation, installed@107)
Trick flow 270's with Indy max wedge 4150 manifold (flow [email protected])
850 mighty demon square jetted with 84's and a 2.5 power valve (5.0" to 7.5" vacuum at idle)
Initial timing@24 with 34 total in by 2500 (MSD pro billet)
MSD Digital 6 ignition box
Jacobs ultimate coil
Motorcraft 3934 plugs with clipped electrodes
180 thermostat and runs at 180
93 octane pump gas
7-1/2 psi fuel pressure

I tried 81's for primary jets but then it ran hot going down the road so I know I was a little to lean so I am currently back at 84's.

I am having problems getting it to stay running in gear at idle and can't figure out why. Everything should be close enough to not have this occur but it still does. Idle speed is set at 1050 out of gear and it drops to 850-950 in gear (3800 stall converter for now, 4600 Ultimate converter from Lenny going in next week).
It starts to add advance at ~1250 rpm

It also has a "skip" here and there that seems like I have an ignition miss but I don't know why it would. The vacuum gauge also has an intermittent flutter like there is possibly a valve sticking but I don't think that is even possible as they are new and Larry Smith went over them as well as Mike from B3 so I doubt they both missed an issue with them.

What should my base idle be set at? Am I close on jetting? Too much initial timing? I am getting frustrated so I am all ears. I am trying to tune for 1000rpm out of gear and 850 in, is this what should be shooting for or should I be looking for different target numbers?

 

[Mike Gaines]

I had an 850 Mighty Demon (with INDY Dual Plane Intake) on my 505" when I first built it. 12.2-1CR, 275@50 Comp solid lifter cam with .650 lift. It went a best to 10.91. I replaced the 850 Demon and INDY Dual Plane with a Edelbrock 440 Single Plane with 4150 base and then added a HVH 4150 to 4500 adapter and put on a new 1050 Dominator. Went 10.61 first run and then 10.60's all day....with only a carb and intake change. same weekend, same day.
Made a believer out of me that big mopar 500+ motors WANT A DOMINATOR CARB.
All with 36 degrees total timing all in @ 2400rpm.
I have now ported my INDY SEZ heads (standard Port) and enlarged them to Max Wedge Size and put an INDY Single Plane under my Dominator and picked up another 3/10's...now running 10.30's and 129 and change. More fuel, more air, more MPH and lower ET's. No real trick to it. When I get some good air this fall I know the car will go into the 10.20's at 1301 or 132.
With your cubes and cam your car should go 10 flat with a single plane and dominator if it weighs less than 3800lbs.. ( I trust you have at least 12-1 CR)

 

[dieseldazzle]

I've never been happy with mighty demon carbs myself but I'd go over the valves again, regardless EOIC.

 

[Brewzer67]

I've never been happy with mighty demon carbs myself but I'd go over the valves again, regardless EOIC.

Are you thinking lash is too tight or too loose? When I checked them after initial start they were all very close. Any that needed adjusting were a little tight (.003 maximum I needed to change).

 

[Brewzer67]

I had an 850 Mighty Demon (with INDY Dual Plane Intake) on my 505" when I first built it. 12.2-1CR, 275@50 Comp solid lifter cam with .650 lift. It went a best to 10.91. I replaced the 850 Demon and INDY Dual Plane with a Edelbrock 440 Single Plane with 4150 base and then added a HVH 4150 to 4500 adapter and put on a new 1050 Dominator. Went 10.61 first run and then 10.60's all day....with only a carb and intake change. same weekend, same day.
Made a believer out of me that big mopar 500+ motors WANT A DOMINATOR CARB.
All with 36 degrees total timing all in @ 2400rpm.
I have now ported my INDY SEZ heads (standard Port) and enlarged them to Max Wedge Size and put an INDY Single Plane under my Dominator and picked up another 3/10's...now running 10.30's and 129 and change. More fuel, more air, more MPH and lower ET's. No real trick to it. When I get some good air this fall I know the car will go into the 10.20's at 1301 or 132.
With your cubes and cam your car should go 10 flat with a single plane and dominator if it weighs less than 3800lbs.. ( I trust you have at least 12-1 CR)

I haven't decided what to do for a carb yet so will be sticking with the demon for now. I've spent a bunch this season so that decision has to wait until next year. Last two projects this year are rebuilding trans with all of the billet goodies (next week) and putting in the tilt column. What I want to accomplish is getting the tune as solid as I can with the Demon for now. More than likely I will have Biggs carbs work it over next year and switch to annular boosters. I am shooting for 10.30's and everything else will be a bonus. 9's get pretty expensive. Compression is only 10.85:1 so I could keep it on pump gas. I am cranking at 185 psi so I am right there.

 

[moparcrazy]

For starters, install a AFR Bung and gauge (Air Fuel Ratio) you will see your carb is Toooo small, I'm running a 1000 cfm Pro-systems on a 440ci motor and it runs Great !! Also better gas, running 110 on a 10.5 motor, noticeable deference from 93, plus 10% Ethanol here in California makes it run hotter

 

[dieseldazzle]

Are you thinking lash is too tight or too loose? When I checked them after initial start they were all very close. Any that needed adjusting were a little tight (.003 maximum I needed to change).

Too tight

 

[not so famous bob]

For starters, install a AFR Bung and gauge (Air Fuel Ratio) you will see your carb is Toooo small, I'm running a 1000 cfm Pro-systems on a 440ci motor and it runs Great !! Also better gas, running 110 on a 10.5 motor, noticeable deference from 93, plus 10% Ethanol here in California makes it run hotter

^
Agree with this post. But I think ur running a little too much initial timing. I tried 22, and back ed down to 20, then went back to 21. Seems to be kinda sensitive. Your carb is definitely too small. I run a 1200 cfm throttle body on my 505. U can get it to run right, but it will never reach full potential w/ that small of carb. U don`t need to worry about low end torque, run a single plane, What gearing in rear?

 

[dvw]

How tight is the converter? Mine will idle at 1000 in gear. Cam is [email protected]/.800" running 2 stock 750 Edelbrocks .
Doug

 

[Brewzer67]

^
Agree with this post. But I think ur running a little too much initial timing. I tried 22, and back ed down to 20, then went back to 21. Seems to be kinda sensitive. Your carb is definitely too small. I run a 1200 cfm throttle body on my 505. U can get it to run right, but it will never reach full potential w/ that small of carb. U don`t need to worry about low end torque, run a single plane, What gearing in rear?

I'll try to back the timing back a little and see if that helps. I have always set my initial by advancing the timing until the motor stops speeding up and then back off two degrees. That is why I make sure it doesn't throw any mechanical advance until well above idle so as to not get any distributor-added advance. I'll take it back to 20 and experiment from there. I know the carb is too small for the combo but I am just looking to live with it until next year if possible. Bill Gates hasn't willed me a bunch of cash yet so the budget still dictates how much I can do in a season.
I am running an Indy max wedge single plane that has been ported and port matched. Rear gears are 4.30's.

 

[Brewzer67]

How tight is the converter? Mine will idle at 1000 in gear. Cam is [email protected]/.800" running 2 stock 750 Edelbrocks .
Doug

3800 10" Trans King

 

[Brewzer67]

Too tight

Thanks. I will double check to make sure this hasn't settled in to the tight side.

 

[Brewzer67]

For starters, install a AFR Bung and gauge (Air Fuel Ratio) you will see your carb is Toooo small, I'm running a 1000 cfm Pro-systems on a 440ci motor and it runs Great !! Also better gas, running 110 on a 10.5 motor, noticeable deference from 93, plus 10% Ethanol here in California makes it run hotter

I designed it to run on the 93 and that is what I want to tune it for. I'll add a little better gas when I flog it at the track, but for daily use and tune, 93 it is. I know the carb is too small for maximum potential, but it should be fine daily driving. I am just looking to get the best tune in it I can right now without spending a bunch more money. I am over $6k for the year with the heads, port work, roller cam, electric fans, column, etc. Cheap to free is the fix I am looking for now.

 

[68 HEMI GTS]

did you put any holes in the throttle plates? that cam will probably need them.

 

[Brewzer67]

did you put any holes in the throttle plates? that cam will probably need them.

Demon carbs have an adjustable bleed under the air cleaner stuff to accomplish the same thing without having to permanently change the carb. It doesn't seem to have as much effect as it did with my old cam but I suspect it is because I am still too far off on the original tune.

 

[HEMI-ITIS]

Verify the ignition is NOT missing! Does your carb have screw in air bleeds?

 

[68 HEMI GTS]

Demon carbs have an adjustable bleed under the air cleaner stuff to accomplish the same thing without having to permanently change the carb. It doesn't seem to have as much effect as it did with my old cam but I suspect it is because I am still too far off on the original tune.

Just out of curiosity have you verified that the throttle plates are not to far open anyway?

 

[Brewzer67]

Verify the ignition is NOT missing! Does your carb have screw in air bleeds?

Ignition seems ok. All plugs look similar and no burnt plug wire ends. Plugs look pretty rich and will be changed now that I bumped the PowerValve back to a 2.5 from a 6.5. Each plug is "clean" at the electrode (carbon has clearly been fired off by spark). I do have adjustable bleeds.

 

[Brewzer67]

Just out of curiosity have you verified that the throttle plates are not to far open anyway?

I have. Transfer slot is a square on both primary and secondary side, no bigger.

 

[68 HEMI GTS]

I wouldn't get too excited then until you get your new converter in. By the way, the pv shouldnt effect the idle unless it's blown. I run a similar duration 260/266 and run a 6.5 with the six pack. 5.5" @ idle.