Tuning questions?

[steves66]

I am running into some tuning issues with my 493 stroker. First I noticed the carb bowls not holding fuel like they supposed to. I parked the car about 4 days ago and yesterday before I started it I pulled the sight plugs out and I couldn't see any fuel. When I started the car and pulled the sight plugs again while it was ideling the fuel was right at the bottom of the plugs like it should be. This morning I checked them again and it was low again! This can't be normal??? The fuel has to be leaking off somewhere. The carb is a Holly 850 DP, mechanical secondaries, manual choke. I have noticed after I shut it down and removed the air cleaner I see some light smoke/steam coming out of the top of the carb, not much though.
Issue 2....The engine wants to run hot. It pings a little too when in high gear and throttling it. I put a vacuum gauge to the manifold vacuum and to get the most vacuum out of it with a steady needle it puts the timing up around 20* btdc. When I try to turn the timing down a little I start losing vacuum and the vacuum gauge needle starts bouncing. My cam is not a vacuum monster. The specs are, Comp Cam, gross lift is .570, duration @.050 is 260, 108 centerline, 1.6 HS roller rockers, 10.5:1 CR, TTI 2" headers, Street Dom intake, Mopar Performance Ignition upgrade with orange box. The most vacuum I can get is about 10 in with a steady needle. Any advice on where I should set the timing to keep it from running hot. I don't have 100 miles on this enging yet, so maybe it just needs more miles on it to loosin it up a little. I also have a new alum rad with the dual spal electric fan setup the pulls 2800 cfm and a high flow Mr. Gasket 160* thermostat. Any advice? Sorry for the long winded post.

[dodge freak]

You may have to limit the total amount of timing, you are not running the vacuum advance right? If so unhook it and see if it helps. On that carb. make sure the fuel is not leaking from the fuel bowl screws, each screw needs a gasket, looks like a small washer. One is damage or missing it sounds like.

[steves66]

Thanks dodge freak. I am running the vacuum advance. I may have to adjust it by turning the screw inside the canister until the pinging stops. That is if the vacuum advance is the problem.
On the carb, there are no external leaks anywhere. It is a brand new carb about 4 months old, so I don't know what the problem could be.

[firefighter3931]

Steve, are you sure about the cam specs ? The original plan was the custom 260*@.050 ground on a 112* lsa....it was specced that way to increase idle vacuum and make it more street friendly. 

It should not be pinging with 10.5:1 and tight quench with a cam that big. You're throwing too much timing into the motor and that's what's causing it. The engine is telling you it likes 20* of base timing so give it what it wants. You'll want to limit the total advance to 35-36* at 2800-3000 rpm and get rid of the vacuum advance...plug it off at both ends. The Copper Bandit has the perfect pump gas specs....properly tuned it could run on 90 octane. It won't make any more power beyond 35-36 degrees total so why push the engine into the "ping zone" when there's no advantage.

The overheating issue could very well be timing related. Retarded timing has the fuel burning in the exhaust instead of in the combustion chamber....where it's supposed to.  Late timing makes for a hot running motor.

The disappearing fuel could be a result of extreme heat caused by the timing/overheating issue. If the fuel is boiling it can turn into vapour when you shut the engine down....then the bowls appear empty the next time you fire up the engine. 


* Get the timing curve dialed in and your other problems will go away. Mallory carries a distributor curve kit that works with the new MP distributors...get one and start tuning. 


Ron


Ps. Have a look at a couple of the plugs and see what kind of color you've got on them. If they're tan/light brown then your jetting is good.

[steves66]

You are correct Ron, the cams LSA is 112 and ground on a 108* centerline. When I set the timing @ 20 with the vacuum unplugged I noticed that it will jump up to around 25 or so when I plug the vacuum back in. I have tried both ports on the carb and both are the same as far as affect. If I run the vacuum advance shouldn't I be able to decrease it through the canister by turning the screw clockwise or is it better to not use it?

[dodge freak]

It does not need it, your gas milage might go down 1-2 miles but that pinging is no good. I have half the cam you have and have no vacuum advance. Your engine will be happy without it. I do know msd makes a timing control you can adjust inside the car so if you are on the freeway for a long drive you can bump the timing up a little for gas milage and back it back down when you step on it. Never got it but might one day if gas hits $5.00+ Lets all hope it does not happen.

[firefighter3931]

You are correct Ron, the cams LSA is 112 and ground on a 108* centerline. When I set the timing @ 20 with the vacuum unplugged I noticed that it will jump up to around 25 or so when I plug the vacuum back in. I have tried both ports on the carb and both are the same as far as affect. If I run the vacuum advance shouldn't I be able to decrease it through the canister by turning the screw clockwise or is it better to not use it?

Steve, i've allways disabled the vac advance on any BB mopar. It makes dialing in the ignition curve so much easier. Pulling in extra timing can cause detonation issues when you stomp on it at cruising speed. Detonation is a killer and you want to avoid it at all costs. 

I would also suggest you use a carb insulating gasket to keep conductive & radiant heat from the manifold to the carb at bay. This will keep the fuel in the bowls cooler and less prone to boiling over. 


http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL%2D9265&N=4294845976+115&autoview=sku


Ron

[steves66]

Thanks fellas! Heading out to the garage now to start tuning w/o the advance and see what happens. I know that she likes at least 20* of initial though because anything less the vacuum gauge needle is all over the place and @ 20* it smooths right out. As far as me having only 10 in of vacuum is that normal with my cam? I was told that with that big of a cam 10in is about normal.

[dodge freak]

10 inch's is great with that cam, it should be ok. You are going to have to limit the advance to 15 or so degrees, or you could lock out the advance all together and just set it at 35 degrees with no vacuum advance. You may have to get a switch to kill the spark to start it up. Once it is cranking good then flip the switch to fire the spark plugs. MSD has all that work out with start retard and high rpm spark retard. You have a great motor, now get a great ignition to fire it.

[firefighter3931]

Thanks fellas! Heading out to the garage now to start tuning w/o the advance and see what happens. I know that she likes at least 20* of initial though because anything less the vacuum gauge needle is all over the place and @ 20* it smooths right out. As far as me having only 10 in of vacuum is that normal with my cam? I was told that with that big of a cam 10in is about normal.

Steve, 10in seems slightly low. Have a look to see if everything is nice and snug. Check the carb base to make sure the bolts are still tight. Recheck any vacuum ports and plugs that might be leaking. If you're running a pcv, check that hose as well. That's not a bad reading but it could end up being a little higher with further tuning. Are you gettin 10in at 20* of base timing ?

As for timing ; with a build like this you have to throw factory specs out the window. Let the engine tell you what it wants   If it likes 20* initial then dial it in and limit the mechanical advance so it's 35-36* total. This will make it idle better and keep the engine safe from detonation. It will also make more power at 35-36* than it would with more timing pulled in.  

Keep at it....you're getting close bud  


Ron

[Ghoste]

Just as an aside question, why do you recommend plugging the vacuum advance at both ends?  If it's plugged off at the carb shouldn't that be enough?

[firefighter3931]

Just as an aside question, why do you recommend plugging the vacuum advance at both ends?  If it's plugged off at the carb shouldn't that be enough?

True enough Ghoste.  I just like the "look" of the vac canister closed off with a black plug....just looks better, inmo.....more of a finshed product. 


Ron

[Ghoste]

Okay, I just wanted to make sure.

[dodge freak]

It look even better with no vacuum advance canister at all. Go to the auto store and have them look up that motor in a lean burn year, and get the pick up coil, it will have no place for the canister  just one plate with a pick up on it. The vacuum advance for those cars was on the computer on the air cleaner. You have to go to the junk yards and find a lean burn car and get the small block off plate that goes on the side of the dist.  Its worth it cause then you can turn the dist. all you like and it looks great.

[Ghoste]

Ah but it makes such a handy lever when turning the distributor to set the timing.

[Just 6T9 CHGR]

Just as an aside question, why do you recommend plugging the vacuum advance at both ends?  If it's plugged off at the carb shouldn't that be enough?

True enough Ghoste.  I just like the "look" of the vac canister closed off with a black plug....just looks better, inmo.....more of a finshed product. 


Ron

I preferr the look of having the thing hooked up at the dizzy but not at the carb myself

[Ghoste]

That's what I have but the way Ron mentioned that, I was worried there was something bad about leaving the vacuum cannister open to the air that I had never heard of.

[firefighter3931]

Just as an aside question, why do you recommend plugging the vacuum advance at both ends?  If it's plugged off at the carb shouldn't that be enough?

True enough Ghoste.  I just like the "look" of the vac canister closed off with a black plug....just looks better, inmo.....more of a finshed product. 


Ron

I preferr the look of having the thing hooked up at the dizzy but not at the carb myself

Further to that idea....if you just wanted to keep it totally factory looking, just run the vac hose to the carb and put a plug (bolt/screw or whatever) inside the hose to block the vacuum at source.

Ron

[Just 6T9 CHGR]

Now Ron, thats really anal! ..........I like it!!   

[firefighter3931]

Now Ron, thats really anal! ..........I like it!!   

I figured you would Chris  You'll make a "resto" guy out of me yet !   


Ron

[steves66]

Well after hours of tuning I got this beast running like a scalded cat out of a bag and as far as the overheating issue, well it never really exsisted. Come to find out I have a sender or gauge problem!!!! I had an old Auto Meter gauge laying around and I put it on and the engine never got over 180*. I still wasn't convinced, so I brought a laser temp gun home from work and shot the water pump housing where the sender is located and it read 178*. At least I don't have a overheating issue. I had all of my gauges rebuit by JC's, so I am leading to believe that it might be that cheap sender I bought from Advance.
I am still noticing a little steam coming out from the top of the carb when I shut her down. I can't see any fuel leaking anywhere from the top. Is this normal?

[firefighter3931]

Steve,

Good work ; so what did you end up with for base & total timing to get the beast happy ? Have you got an insulating base gasket like the one i linked to above ? I'm suspecting fuel is boiling in the bowls causing the steam you're talking about.

The factory guages are known for their inaccuracy.   I allways back the stock cluster up with aftermarket guages (oil/water)....better safe than sorry.


Ron

[steves66]

Ron the base ended up at 18* and total is 36*. She idels good at 900 rpms and starts with just the touch of the starter, cold and hot! She will pin you to your seat and won't quit until you let off. Massive torque!
I have that exact same gasket under my carb now. Maybe I need one of those shields that mounts between the intake and carb that actually supposed to block the heat from rising directly on the carb?
After all of this, the Copper Bandit will definitly have some aftermarket gauges installed soon! The oil will be no problem, but the water might. On my water pump housing both ports are already taken up, one for the stock sender and the other one I have the electric fans sender in it. I can't think of another place to put a temp sender right off the top of my head???

[firefighter3931]

Ron the base ended up at 18* and total is 36*. She idels good at 900 rpms and starts with just the touch of the starter, cold and hot!

Cool  That's about where i figured the timing would end up. I'd say the tune is optimized if it starts that easily hot or cold.    At what rpm is the 36* coming in at ? Any problems with preignition....i'm assuming the ping issue is rectified...

The carb base gasket should be helping with the percolating fuel. Maybe try using a different gas station. Something else might work out better....might take a little experimentation to see what runs best. I've read that some guys have good luck with Amoco for pump gas 

As for the sender, you could allways install a "T" fitting and run both senders off the same hole in the housing. 

Ron

[mikepmcs]