Help with 360 timing

[rcuda022!]

I have a 72 Barracuda with a 360. I am having trouble getting the total timing to be in the mid 30s where I believe it should be.  At this point I have checked and double checked that the engine is at TDC on the compression stroke when placing the distributor in and have made sure that the rotor is aligned with the #1 plug and that all other wires are in the correct order. The engine will start on the first crank. When looking at initial timing I can vary it between 12-18 degrees however under load the total timing wants to climb past 40 and would keep going if I pushed it. As it currently sits the engine idles fine and has no hesitation for power when not under load (drive or reverse). When put in gear the engine stays idling fine however has very little power when given gas...almost feeling like its in a higher gear from the start. Just some background on the car it is a 360 street/strip engine (I did not build it and do not know all the internals) it does have a pretty beefy cam and the transmission is a 727. I have put a MSD 6al2 on the car and do not know if that is affecting it either. Any help is appreciated!

[73_Cuda_4_Me]

Factory distributor? What carb are you using? Are you running vacuum advance? What stall torque converter are you running with the moderate cam? What gearing are you running in the rear differential?

Would need to know some of this to help you out...

If you are running 12-18 initial, your all in timing will be mid-40's approaching 50 degrees, and more with vacuum advance! (If it is a stock dizzy)

You can install a limiter plate in the dizzy (www.4secondsflat.com), or weld the mechanical advance slots up a little on the inside edges, so that it only has about 15 degrees of mechanical advance total. Or go with new dizzy that has programmable advance curves.

Moderate cams need higher stall torque converters - they like higher rpm's to get into the power band at the get-go...

[rcuda022!]

1. It is a stock distributor
2. Holley double pumper 750
3. I have the vacuum advance plugged for the time being while trying to sort out the issue
4. I am unsure on the torque converter
5. 2.94

As far as the torque converter I know that the engine will perform because it was in a different vehicle prior to being in my barracuda and I know that it was performing well. Since putting the combo in the barracuda I had pulled the distributor with intentions of putting a MSD distributor in but ended up going back with the stock distributor and now am having this issue of what I believe to be to much total timing and lack of power. Also to mention I did not drive the car prior to messing around with the distributor.

[73_Cuda_4_Me]

First off, unplug the vacuum advance and cap the fitting at the carb it's hooked to.... That will keep the advance only running mechanical, about 30-35 degrees total on top of any initial you start with... so, limiting plate, welded slots, or another dizzy are your options there...

You state the engine ran well in another vehicle, but was that with the current torque converter? A stock torque converter will lock up at 1800-2000 rpm, and depending on cam, you may not even be close to the power band yet, so will be very 'doggy' taking off... especially with that rear gearing!

That gearing will only be good for cruising highways, and will really limit the torque taking off in street driving...

I have a 340 with medium cam and headers that had 727, stock TC, and 3.23 rear gears... felt sort of doggy till the engine wound up a bit, then snapped right up after 3000 rpm. I swapped the tranny to an SST A-41 Perfect Fit package, with a higher 1st gear (3.06:1) and overdrive (0.70:1), a 2800-2900 stall TC, and am not looking back!

I made my own limiting plate to solve the factory dizzy mechanical advance on mine...

[rcuda022!]

The limiting plate is a great idea if I cannot find another solution and I have the vacuum advance capped to eliminate that causing any factor.

And the torque converter is the same as it was in the other vehicle...it was literally transplanted into the barracuda with no change.

I agree with you about the gearing and plan for that to be next on the list.

I mentioned that the only other thing changed was adding the MSD 6AL2 and was curious if anyone has any insight as to if this can be the problem or if there is any other ideas that would cause the high total timing and lack of power?

73_Cuda_4_Me it sounds like you've got the perfect combo with that 340. I've never seen an A-41 but can imagine it is quite the upgrade.

[73_Cuda_4_Me]

The A-41 Perfect Fit Kit for Mopars is pretty awesome...

It's a GM 4L60E, Transmission Control Electronics, Flex Plate and Torque Converter, Drive Shaft, Throttle Position Sensor, RPM Pickup Sensor, Speedo cable, all the wiring, transmission crossmember, starter adapter, U-Joint and yoke, and a TCI EZ-TCU Handheld control/display unit.

https://shiftsst.com/blog/post/challenger-barracuda-1970-1974-perfectfit-kit.html

[Chryco Psycho]

Welcome to the site from Panama 
If you can weld the other option is to weld in the advance slots , I usually weld the inside of the slot toward the shaft to limit the curve .

[73_Cuda_4_Me]

If you need any assistance making and adding a limiter plate, let me know... A lot of members have added the 4secondsflat limiter plate because of the range of options in amount of advance it has, but the biggest problem with it is that it only changes the slot lengths on the upper end of the advance.

My stock dizzy had 'fluctuating' timing at idle with the cam I had... if you run 900-1000 rpm at idle, you are right on the beginning of the mechanical advance.. I was getting 5-10 degrees advance fluctuation at idle... the stock springs are just set that low...

When I made my limiter plate, I shortened the length of the slots on the inside edges, so the springs were actually tighter at idle, and hold the advance rock steady until I hit about 1200 rpm...

My dizzy has a 30 degree mechanical advance, and I run about 16 degrees at idle for initial, so I needed just a little more than half of the slot length in the stock dizzy, for about 16-18 degrees total more.

Here is a picture of the plate installed after making it...

[rcuda022!]

The idea of making and adding the limiter plate like you have sounds great. As you mentioned I was a little concerned about the mechanical advance coming in to early and it sounds that by your design you have eliminated that problem. How does holding the advance off until around 1200 rpm effect the response from idle? Also if its not to much trouble I would love some guidance in making the plate (length, slot hole lengths, and such). And finally the more I am looking and seeing in responses it seems that the higher total timing numbers is "normal" in these small blocks is that the case?

[73_Cuda_4_Me]

The response from idle is not affected with advance starting at 1200... the advantage of having rock solid timing at idle so you know exactly what you are starting with helps out when timing a bigger cam.

I've never seen or heard anyone calling for more than 34-36 degrees all in on mechanical advance... there are some, including me, that like to have additional vacuum advance for mild cruising, so when there is no load on the engine, the vacuum advances to help get cleaner burn and slightly better mileage, along with lower engine and engine bay temperatures... but I didn't worry about vacuum advance at all for 15 years.

We'll get you set up with some pix of what I did...

[MoparLeo]

Why do you "believe it should be in the mid 30's" What did you base that assumption on ? You set the timing to what your engine wants. It is no longer stock and you are unsure of the mods so you can't assume a correct amount of advance. The engine will tell you when it has too much advance. Pinging etc... 2 ways to set timing, for the strip. or the street. Street needs advance to constantly vary with the engines rpm and needs low to mid range torque. Strip is pedal to the floor with little regard for any curve, just total advance. A curve is just that. Advance changing according to the engines demand. Like said above, it is hard to give proper advice and to diagnose something with unknown variables. One thing for sure, any mods done to the engine are geared towards moving the powerband higher up the rpm range and your rear gearing is a torque killer.  Plug the vacuum port on the carb, rev the engine to 3500 rpm, hold it there and advance the timing until it starts to lose power. Back it off slightly and go for a ride. If it runs smoothly as you accelerate, you have hit it. Any time you make a mod of any kind, there are always side effects. Then you have to deal with those and on and on.. An unknown engines mods is like eating someone elses cake and wondering why it tastes the way it does. Without knowing the ingredients and proportions used, you will never really know.

[rcuda022!]

I understand that I can't assume the correct amount of advance due to not knowing all the internals of the engine; I was basing the mid 30's mark on things I have read and seen. The way the engine currently sits I can take the initial down to about 8* before stall and the total still ends up being in the mid 40's to 50. Possibly to being naive I was assuming this number was still to high. Either way I set the timing it has extreme lag on acceleration...for reference it feels like pulling a weight behind the car. So to better understand the curve, under load in drive is the curve going to be different based on the accelerator input or will it remain constant like it is when it is sitting still running a timing light? Also what we be the appropriate method in order to find what mechanical advance my distributor has?

[73_Cuda_4_Me]

@rcuda022!  - I, along with so many other members on this site, support new members in their quest to understand all the things we have to deal with when trying to improve our 'babies' to get them where we want...

I would NEVER be demeaning in trying to answer another member asking questions...

There is an awful lot of information here, learned over many years and years of working on, in, under, over, and inside our vehicles... and all you have to do is ask!

I would hope that every member on this site would look forward to HELPING others obtain the knowledge they seek, in a manner that SUPPORTS and promotes our pastime and love for sharing information we've learned over the years.

EVERYTHING I've ever read on small blocks puts recommended starting 'all in' timing around 35 degrees, so that is a safe place to start. PERIOD

[rcuda022!]

@73_Cuda_4_Me    I certainly appreciate that! I look forward to asking more questions in the future and getting good feedback. I will heed your warning and remain with the same thinking that small blocks should 'typically' not exceed 35 degrees...and go from there.   

[73_Cuda_4_Me]

It is a good starting point to shoot for, and then the components of the whole package will determine where things can be improved...

I'll gather my photos of my dizzy mod, and start a little show of what I did... what I used, things to look out for, etc...

Main thing for a limiter plate is knowing where your cam likes to start and idle best... usually determined by fastest idle speed...

Start engine, check timing, try advancing or retarding to increase idle speed, adjust idle screw to get back below 900 or so, advance or retard to get fastest idle timing. If starting it suffers, back off on whichever direction you went, until you get good starts and good idle.

That determines best initial timing...

NONE OF THIS IS SET IN STONE AS FAR AS CARB ADJUSTMENTS, which also have a major impact on idle, too... it's all interactive. It just sets timing for the current setup... gives you a starting point for advance requirements.