Timing Curve on 360 in an RV

-
7

78DodgeRV

Member
Joined
Jun 14, 2020
Messages
13
Reaction score
20
Location
Atlanta, GA
So, I’m completely aware of the name of this forum, but...RV forums are a terrible place for engine advice and after a ton of research it’s clear you guys here know more about 360’s than damn near anyone else online. I figured, what the hell, I’ll give it a shot.

I’ve got a 1978 Dodge RV (B300 platform) with a 360 and a 727 transmission in it. Did a fuel injection conversion (Edelbrock EFI), engine is stock, and have been toiling around trying to tune the new setup. My biggest stumper so far has been dialing in the timing curve.

Right now I’m running 15 degrees initial, 21 degrees total, all in at 2200 rpms. Would like to run more total timing than this, but if I go higher I get some pre-firing and back-firing while under load.

With this current setup, idle in park is around 1050-1100, dropping to 850 in gear.

This is the best, most reliable tune I’ve been able to put together so far that’ll get me around town and down the road on the highway, but the drop in rpms when going into gear tells me I’m not dialed in yet, idle rpms seem higher than usual, and total timing seems low to me.

Hoping I can tap into some knowledge of those who might have been here before and figure out the next phase of getting this thing dialed in. Or, maybe with as heavy as my RV is, this is actually a realistic landing spot and I’ve just been reading too much about what the timing curves of normal cars with 360s look like. RV weighs about 8,000 lbs.

F325C7BB-C68C-4663-90EC-9DD34B5CBFFA.jpeg


DF82BB55-6010-48ED-9466-92E446230523.jpeg


0A220425-A12F-4E9A-9BCA-038239C6A1B3.jpeg
 
Slow the all in to about 2800 rpm, if you have a adjustable vac advance try to delay it to come all in later.
 
halifaxhops said:
Slow the all in to about 2800 rpm, if you have a adjustable vac advance try to delay it to come all in later.
Click to expand...
Awesome, will give this a shot. Currently have vacuum advanced set to zero. Played around with 0-5 degrees of vac advance, but pulling it back to zero helped with backfiring. For some reason, anytime my timing started getting into high 20’s, I was getting backfiring.
 
How did you pull it back. The adjustment just does the "start" of the advance with the amount of vacuum if that makes sense.
 
halifaxhops said:
How did you pull it back. The adjustment just does the "start" of the advance with the amount of vacuum if that makes sense.
Click to expand...
With Edelbrock’s EFI setup, initial timing, total timing, all in rpm settings, and vacuum advance are electronic and adjustable via a tablet. Not nearly as cool as swapping out springs, but it’s been handy as hell as I’ve been learning the concepts and working to get this first project dialed in.
 
78DodgeRV said:
Awesome, will give this a shot. Currently have vacuum advanced set to zero. Played around with 0-5 degrees of vac advance, but pulling it back to zero helped with backfiring. For some reason, anytime my timing started getting into high 20’s, I was getting backfiring.
Click to expand...

I would put an old/another cap cut so you can check rotor phasing.
It sounds like your spark may be jumping around in the cap when the mechanical advances due to the rotor moving too far away from the terminals it should be firing to.
Check out my video on this:
 
78DodgeRV said:
So, I’m completely aware of the name of this forum, but...RV forums are a terrible place for engine advice and after a ton of research it’s clear you guys here know more about 360’s than damn near anyone else online. I figured, what the hell, I’ll give it a shot.

I’ve got a 1978 Dodge RV (B300 platform) with a 360 and a 727 transmission in it. Did a fuel injection conversion (Edelbrock EFI), engine is stock, and have been toiling around trying to tune the new setup. My biggest stumper so far has been dialing in the timing curve.

Right now I’m running 15 degrees initial, 21 degrees total, all in at 2200 rpms. Would like to run more total timing than this, but if I go higher I get some pre-firing and back-firing while under load.

With this current setup, idle in park is around 1050-1100, dropping to 850 in gear.

This is the best, most reliable tune I’ve been able to put together so far that’ll get me around town and down the road on the highway, but the drop in rpms when going into gear tells me I’m not dialed in yet, idle rpms seem higher than usual, and total timing seems low to me.

Hoping I can tap into some knowledge of those who might have been here before and figure out the next phase of getting this thing dialed in. Or, maybe with as heavy as my RV is, this is actually a realistic landing spot and I’ve just been reading too much about what the timing curves of normal cars with 360s look like. RV weighs about 8,000 lbs.

View attachment 1715545549

View attachment 1715545550

View attachment 1715545551
Click to expand...
You are spot on, pay close attention to a several of these guys as they are quite well versed in all things Distributors. One of them does a considerable amount of business in Distributors, he will never admit it but folks reach out to him from all over the globe for his expertise on Distributors. We call him Hoppy!
 
TrailBeast said:
I would put an old/another cap cut so you can check rotor phasing.
It sounds like your spark may be jumping around in the cap when the mechanical advances due to the rotor moving too far away from the terminals it should be firing to.
Check out my video on this:
Click to expand...

Awesome. I’m gonna run with Occam’s Razor here and say that I bet my distro phasing is off because I probably misaligned it a bit when I installed it. I know with the slot that you can only be in or 180 out, but with this EFI kit I was supposed to be at 12 degrees BTDC on compression stroke of cylinder 1 when dropping it in in order to line up the Hall effect sensor a certain way. Gonna bet that I probably got the stroke wrong.

Super helpful. Will report back.
 
Trailbeast those vids should go into the how to section they are great!
 
Anyone know a clever way to confirm I’m at 12 degrees BTDC on the compression stroke of cylinder #1 without taking the valve cover off?

Last time I hand cranked the engine with a finger over the spark plug hole until I felt pressure, dialed it to 12/before on the markings on my balancer, and then used a screw driver to check it was near the top.
 
Most small blocks run well around 12-34, for timing.
Set your all in timing at 34, with vac adv plugged.
Now check your initial timing. What's it at ?

Also with your heavy vehicle, you want your timing to come in a little later. Say 2500-2800 or even later. Perfect use for a factory distributor, with stock springs.

Cool RV by the way.
 
Last edited:
Johnny Dart said:
Most small blocks run well around 12-34, for timing.
Set your all in timing at 34, with vac adv plugged.
Now check your initial timing. What's it at ?

Also with your heavy vehicle, you want your timing to come in a little later. Say 2500-2800. Perfect use for a factory distributor, with stock springs.

Cool RV by the way.
Click to expand...
Thanks man!
 
Great thread ! I have the cousin to yours but with a 440. I have been thinking about best curve for mine as well.
7F23A9AE-EAE1-47F3-A874-95C4B0F011DD.jpeg
BD992CC7-CC83-4E9F-917D-68F9A39D6F69.jpeg
 
78DodgeRV said:
Anyone know a clever way to confirm I’m at 12 degrees BTDC on the compression stroke of cylinder #1 without taking the valve cover off?

Last time I hand cranked the engine with a finger over the spark plug hole until I felt pressure, dialed it to 12/before on the markings on my balancer, and then used a screw driver to check it was near the top.
Click to expand...

Turn it to 12 on the balancer and then take the fist) dist cap off and see if the rotor is pointing at #1 terminal. If not, you're on the exhaust stroke.

If you're talking about confirming the balancer ring hasn't slipped, you'll need a piston stop.
 
78DodgeRV said:
Anyone know a clever way to confirm I’m at 12 degrees BTDC on the compression stroke of cylinder #1 without taking the valve cover off?

Last time I hand cranked the engine with a finger over the spark plug hole until I felt pressure, dialed it to 12/before on the markings on my balancer, and then used a screw driver to check it was near the top.
Click to expand...

All a screwdriver does is waste time. It's not accurate enough to confirm timing marks, and it does not determine the stroke. If you think the timing mark is wrong use a piston stop and confirm the mark is correct. To find compression stroke, just stick your finger in no1 plug hole and bump engine around. Or if this is one of those with rear timing marks (bellhousing) might be easier to use no6. Bump until you feel compression and stop. The marks should be "on the way up". Now bump or wrench the engine around until the marks are aligned on 12BTC. Then set up the dist. so the reluctor is centered on the pickup coil.
 
Question.....were the RVs detuned for emissions in the late 70s like the passenger cars ?
 
What stall, rear gear, and tire roll-out? this will play an important roll in avoiding detonation on a long pull. Detonation and it's sometime partner pre-ignition, is the enemy of your engine, and has to be avoided at all costs. They break things like pistons and rings and hammer out bearings.
I'm trying figure out why you would chose all-in at 2200; and no vacuum advance. That is a race-car tune, with a lightweight car, a big engine, and race gears.

For you tho;
For fuel-economy reasons, as well as a bit of WOT power;
you will need to push the minimum cooling system temp up to at least 180*, Myself; I would try for 195. But your cooling system will have to be rock-steady without any hunting around. You will have to make it so. You cannot begin your tune until the cooling system is at a fixed and steady temperature; whether it be 195 or 180, or whatever it is; it has to remain stable for the tune. Later you can add temperature compensation.
And your engine will HAVE to have a source of fresh cold air. If the inlet air temp is bopping up and down, from 100* to 400*F you will have a big tuning headache.
Ok so, you should know that the more idle timing you give it, with no other changes, the higher the idle will climb. This is not necessarily a good thing. Your automatic transmission equipped engine will never be asked to pull at idle, so at the beginning of your tuning, it can be whatever. Later, much later, you can start to monkey with that. So, your engine doesn't much care about it's idle timing, as long as throttle response doesn't fall on it's face between idle and it's stallspeed. But beginning at the stall speed is where it starts to care. From there to ~3200 it is almost critical to not have too much, and after 3600 most engines fall to between 32* and 36*.
So,
Confirm your timing index mark.
reset the idle timing to 10 degrees advance.
reset your idle rpm to 600 in Neutral, or 550 in gear whichever is less.That stock engine should idle down to 600in gear, no problem.
Now increase your idle timing to 12/14* and leave it there.
Now program your computer with a linear power-curve to be 26* at 2800; and then change to a slower linear curve to be 34* all in at 3600. That is your starter POWER CURVE. It will only be near-correct at WOT. It will not be correct at any other throttle/load setting. I repeat; it will not be near-correct at any other throttle/load setting except WOT.
All other throttle settings and rpms are adjusted by the load sensor, AKA the vacuum advance. This timing is added to the power curve in direct proportion to manifold vacuum, which is 100%dependent on the load factor or throttle opening versus rpm, AKA speed-density.
So lets say you are cruising along at 50 mph in top gear at 2400 rpm. Your engine might like 56* of timing there; IDK, just saying. But if you give it any throttle there as in; you came to the bottom of a kill,then, at 56* and 2400rpm, it will only take a few seconds (15 seconds@2400rpm is 600 revolutions times 4 firings per revolution is 2400 hammer-blows, or 300 per piston)until the factory pistons may begin to fail; IDK how much they can take, but the rod bearings may fail first. Therefore,the "vacuum advance" will have to immediately start to decrease linearly with throttle opening (manifold vacuum), back to the power-timing,which might be 20/22*@2400( just guessing) which I purposely made weak for this reason. Once climbing up that hill, your "vacuum advance" will have to stay at zero, while the engine is stuck in top gear at 2400rpm, on the SAFE power-curve.
If you were to downshift,at this moment, with a 727, the Rs would jump from 2400 to ~4100, and the engine would be on the all-in timing of 34*@3600, and if you have sufficiently enough octane rating, it will pull itself along nicely. Perhaps nicely enough that manifold vacuum might rise high enough to again bring in some "vacuum advance". This might be a good thing but could just as easily be bad; that is for YOU the operator and tuner, to determine. To help you with this, your EFI may have a knock-sensor tune available, and I highly recommend that you use it.

So some of these things have already been mentioned, I just put them all in the same post, and added some reasons why, to help you understand.
 
Last edited:
AJ/FormS said:
What rear gear and tire roll-out? this will play an important roll in avoiding detonation on a long pull.

I can't figure out why you would chose all-in at 2200; and no vacuum advance. That is a race-car tune, with a lightweight car, a big engine, and race gears.
Click to expand...
With the backfiring issues I was having, I started to bring total timing down and could only get rid of it by getting down to 20 degrees total with no vacuum advance. I went all in much earlier after seeing some charts where the 360s were all outta torque by 2200rpms.

When I was dealing with the backfiring, I was at 16 initial, 30 total with 5 degrees of vacuum advance, all in at 3000 rpms. With these settings, I’d get consistent backfires at 27 degrees of advance or higher (even while in park) and lots of stumbling/backfires on acceleration.
 
You must log in or register to reply here.
-

Back
Top