Unknown rebuild specs

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DusterDaddy

DusterDaddy

sledgehammer mechanic
FABO Gold Member
Joined
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Location
Holmdel, NJ
Over 10 years ago when I first began my Duster project I scored a rebuilt 74 dated 318 with a stock bottom, stock heads with a 1.88&1.6 valve job. The lifters and rockers are stock Chrysler parts. Camshaft is unknown however the lift measures just shy of .480 This motor was intended for another persons project. The guy who was supposed to use it wound up having marriage problems and had to sell the car and engine. It was never fired.

Someone bought the project car but wanted a big block so he had a speed shop build an engine and that speed shop pulled
The 318 and listed it for sale. I wore the guy down and bought it for $300.00!

My Duster project was super low budget so when it was time to drop in the motor, in it went. It runs nice and makes nice power and is fun to drive.

Recently the car developed a stumble that was never there when accelerating from a stop so I figured it was time to get the car in the hands of classic car shop to try to shake out the last few bugs.

I am running an Edelbrock Performer intake with an Edelbrock 1406 carb. Ignition is an MSD AL6 box and a Chrysler electronic ignition distributor reproduction that I bought from Classic Industries.

Exhaust is 340 factory manifolds with 2-1/2” dual pipes with an H pipe and Borla proXS mufflers.

Transmission is a stock 904 with a Transgo Shift Kit. 8-1/4 suregrip rear with 3.55 gears.

I saw others on the forum talking about slop in the repop distributors from Classic Industries, so I bought a nice billet electronic ignition distributor from Summit Racing. I also got the MSD matching coil for my MSD box and had the mechanic swap those in.

He said the car had way too much timing and he was worried that with that much timing the motor could destroy a bearing. so he set it up with only using the mechanical advance with 14*’initial and 36* total.

The car runs great and is very well behaved with no stumbles, however the car used to be able to torch the tires from a stop and give a strong chirp as it shifted into 2nd. Well that’s gone now.

The converter in the car is a stock Chrysler “high stall” unit.

The mechanic thinks I need a higher stall converter and that’s all well and fine but we don’t really know all the details of the cam. The guy who sold me the motor told me back then that he thinks the cam is a reproduction of what Chrysler was putting in the 70 340 cars with an automatic.

Short of dismantling the motor to determine what cam I have, are there any gurus that can help me navigate the unknown and regain my ability to destroy my tires?

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Nice looking car. But that doesn't answer your question. I think you have some choices which only you can make. If you want to destroy your tires as you say then bump the timing back up. You're mechanic told you the potential risk involved so it's up to you. If all your interested in is smoking the tires maybe get yourself some extra rims with smaller tires and when you're in the mood switch em out and burn some rubber. Smaller and skinny = easier to spin and burn. Might be a lot cheaper in the long run. Other than that it's the old "you wanna play, you gotta pay".
 
Sounds like you had a good curve in the previous ignition that matched the engine and now you do not.
 
That’s above my knowledge base. I do know that this new distributor is very friendly towards setting up a good curve. I do have another option for another guy to take a stab at setting it up.
What’s your opinion on the converter?
 
DusterDaddy said:
That’s above my knowledge base. I do know that this new distributor is very friendly towards setting up a good curve. I do have another option for another guy to take a stab at setting it up.
What’s your opinion on the converter?
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That there's nothing wrong with it. Wasn't it the same converter before you made all the ignition changes?
 
Yes the same. So how do I get back to where I was before and still eliminate the take off stumble?
 
DusterDaddy said:
Yes the same. So how do I get back to where I was before and still eliminate the take off stumble?
Click to expand...
Get a timing light and figure out what curve works best. You already know it ain't the one you have now.
 
The first thing I would do, is get a light, see where the timing is now, pull some more in it if it doesn't have any more than about 12 or so.....maybe try 16 or 18. If that makes a difference, you know it needs recurving. Beyond that, you're simply going to have to experiment with different curves. Maybe if you run a compression test and post those numbers, we can give you a decent starting point.
 
I have a light and I will find a compression tester. I’m away for a few days but I’ll get to it
 
RustyRatRod said:
That's a tic too much total, but if it's not spark knocking, send it.
Click to expand...


It may not be too much. Timing lights don’t all read the same.

Some are worse than others. It could easily be 2-4 degrees different than a different light.

Also, the GIANT elephant in the room has teamed up with the bull from the china store and they are playing around in the OP’s ignition.

Or, saying it how I should have said it at first, he may have 36 at 3k rpm or where ever he’s setting the total but at 6k it may be retarding 4-5 degrees or more.

He may be just right or at least very close at that 36 number for what he has.

Ignition retard with rpm is real.
 
Also it is a MSD box, the light might not be happy with the box. Really not sure what state the balancer is in either. Did the distributor come with a set of plastic “keys” to set the mechanical advance? You insert them in a window in the advance plate and adjust it so the key just fits. You can almost get it down to just about 7-8 degrees of mechanical if you want. If so, you can adjust the initial to what it wants and then play with the total.
 
DusterDaddy said:
Over 10 years ago when I first began my Duster project I scored a rebuilt 74 dated 318 with a stock bottom, stock heads with a 1.88&1.6 valve job. The lifters and rockers are stock Chrysler parts. Camshaft is unknown however the lift measures just shy of .480 This motor was intended for another persons project. The guy who was supposed to use it wound up having marriage problems and had to sell the car and engine. It was never fired.

Someone bought the project car but wanted a big block so he had a speed shop build an engine and that speed shop pulled
The 318 and listed it for sale. I wore the guy down and bought it for $300.00!

My Duster project was super low budget so when it was time to drop in the motor, in it went. It runs nice and makes nice power and is fun to drive.

Recently the car developed a stumble that was never there when accelerating from a stop so I figured it was time to get the car in the hands of classic car shop to try to shake out the last few bugs.

I am running an Edelbrock Performer intake with an Edelbrock 1406 carb. Ignition is an MSD AL6 box and a Chrysler electronic ignition distributor reproduction that I bought from Classic Industries.

Exhaust is 340 factory manifolds with 2-1/2” dual pipes with an H pipe and Borla proXS mufflers.

Transmission is a stock 904 with a Transgo Shift Kit. 8-1/4 suregrip rear with 3.55 gears.

I saw others on the forum talking about slop in the repop distributors from Classic Industries, so I bought a nice billet electronic ignition distributor from Summit Racing. I also got the MSD matching coil for my MSD box and had the mechanic swap those in.

He said the car had way too much timing and he was worried that with that much timing the motor could destroy a bearing. so he set it up with only using the mechanical advance with 14*’initial and 36* total.

The car runs great and is very well behaved with no stumbles, however the car used to be able to torch the tires from a stop and give a strong chirp as it shifted into 2nd. Well that’s gone now.

The converter in the car is a stock Chrysler “high stall” unit.

The mechanic thinks I need a higher stall converter and that’s all well and fine but we don’t really know all the details of the cam. The guy who sold me the motor told me back then that he thinks the cam is a reproduction of what Chrysler was putting in the 70 340 cars with an automatic.

Short of dismantling the motor to determine what cam I have, are there any gurus that can help me navigate the unknown and regain my ability to destroy my tires?

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Click to expand...
Judt tailor the advance curve , starting with shortening it...so yoy can have 20 or more initial timing.
The stumble could have been a couple things, carburetor mainly.
 
Sounds like you need another mechanic. Get one that can read a service manual and not just Hot Rod magazine.
NO to the cam and higher stall converter. They are a PIA on the street.
Why no vacuum advance? Even the stock electronic ignition is very reliable.
In my experience, most "stumbles" end up being fuel related.
 
furrystump said:
Also it is a MSD box, the light might not be happy with the box. Really not sure what state the balancer is in either. Did the distributor come with a set of plastic “keys” to set the mechanical advance? You insert them in a window in the advance plate and adjust it so the key just fits. You can almost get it down to just about 7-8 degrees of mechanical if you want. If so, you can adjust the initial to what it wants and then play with the total.
Click to expand...
Get your Initial and mechanical done 1st then try your Vacuum advance. Not sure if that is adjustable but you want around 50' with it connected at cruise rpms. JMO You'll get better mileage on highway cruises.
 
Holmdel is very near sealevel. With 3.55s, it should rocket off the line.
IMO, put the previous distributor back in, set the timing back to what it was and increase the idle rpm 150 from where it used to be, which should cure your not-enough-Transfer-Slot-exposure-to-prevent-the-dreaded, Tip-in sag.
Now you have a base-line working ignition system.
You know it works so map it out.
Defeat the VA, then record the Timing Advance every 400 rpm from idle to whenever it stops advancing. Go find or make a graph paper. Graph your results; rpm along the bottom, advance up the left side. Connect the dots.
>>If the line is a curve you have a two-spring curve which is very good.
Find the highest advance number; you want that to be no more than 36*. This is called your Power-Timing.
Find the rpm at which that number occurs. You want that to be as low as possible but not causing detonation. This is part two of PowerTiming.
Find, as best as you can, where the two curves cross. You want that to be near stall rpm. This will be called your Stall-Timing, after you synchronize them.
The engine does not much care about any timing under stall, so long as it is low enough at idle, to not cause the tip-in sag.

Ok job one is to get your PowerTiming worked out. If it is NOT 36*, make it so. If the engine detonates at above 3800, then decrease the PowerTiming to 34*. and try again. If it still detonates, use a higher octane gas and start over. If it still detonates, with highest octane gas, with 34*and 3800rpm, and the engine has the correct heatrange plugs, and the right jetting; sorry man, your combo is sick. Something will have to be changed. Let's assume this is not the case.
For arguments sake, lets say the PowerTiming is ok/no detonation at 35*@3400rpm. From now on, that will be your target. Reset your distributor to 35 at above 3400, and remap your curve. If there is no detonation below 3400, then Leave it there for several days, and get to know the curve. Idle it down until you get a Tip-in sag, then add 50 rpm If this is greater than 650 in gear, or the trans engages harshly, make a note of it. Keep driving for like a week. Make sure you have no detonation anywhere.
Next we are gonna home-in on your Stall timing.
Correlate your stall rpm onto the timing curve to see where it's at. I'm assuming here that this past week, you had no detonation. Are you happy with the power hit at stall? If yes, then that part is done.
But let's say you think the stall is a lil soft. Then; Increase your Powertiming by 3*. After this, do not run WOT if you experience detonation. Now go try some more hits. Just hits. If it gets better, GREAT, try 3 more! Keep adding 3 degrees at a time until you get detonation, or the power seems to fall away.
Lets say your convertor stalls at 2200, and it liked 26* for best hit.
Put your power timing back to where we started, 34*. Look on your graph and see what the current stall rpm is. Lets say it is 22*. You are gonna want that to be 26*, sooner or later.
Next, we are coming to Idle-timing.
Say it is 10 degrees. Say you have no Idle Tip-In sag, it idles nicely there, and the trans does NOT bang from N>in gear.
Why would you want to change it? You don't need to, so leave it there.
But say to eliminate the tip in sag, the rpm climbs up to 800, and the trans really jumps the car when you engage a gear. This is unacceptable. The only easy cure I know of is to retard the timing. So try less.
Find a combination of;
Transfer Slot exposure and
Mixture screw adjustment, and
Idle-Timing ,
that eliminates the Sag, and Minimizes the clang, Yet when you put the trans in gear, the rpm drop is 100 rpm or less and drive-away is a dream.
and don't care for a second what the timing gets to be, unless it goes retarded, lol, but I've never seen that happen. Your engine will tell you what it wants, don't try to force more timing than it wants. Don't even put a timing lite on it , until you got it worked out.
Ok so now, having worked it out, you find the Idle-timing to be 10*.
Finally, you might want to know about the Cruize-Timing.
Cruise-Timing
This is easy. with 3.55s and 26.5 tall tires, 65=mathes to 2927 rpm at zero-slip, so could be up to 150 rpm either way, depending on many factors.
So here's what you do; With the Vcan now engaged, and the distributor loose enough to tug on, and the engine warmed up; Rev the engine up to cruise rpm, ant try to keep it there. Then crank in a lil advance say 3*. If the rpm goes up, bring it back, and add 3 more, bringing the rpm back. Repeat until adding more timing does not produce more rpm. That's your ideal Cruse timing. NOW put the Timing lite on it and rev it back up to Cruize-rpm and read it. Whatever it is, subtract 3* for lack of load, and that is your target. Write it down. Sat it's 44*. I mean it could be a lil more or a lil less, this is just an exercise. Put the Power-Timing back to 34.

Synchronization.
Now we have the FOUR targets, namely;
PowerTiming of 34*,
Stall-timing of 26*, and
Idle timing of 10*, and Cruise-timing of 44*.
Those are the maximums that your combo will accept. But when you look at your curve, it looks nothing like that, so what do you do?
Well, IMO, you pull it out and ship it to a guy who can connect the dots for you, and for a modest fee, you're back in action, and forever happy.
Or, you ship him your spare and get that one modified. Your man doesn't care which one he gets. You tell him what you want, and he makes it happen. This will save you weeks to months of chasing the curve by yourself. Well worth whatever it costs.
So, when you get it back, you stab it in, set the Power-Timing to 34* and Drive.
RESIST the urge to experiment, just drive it.

If yur not happy with the hit at stall, get a new convertor, and adjust the stall-timing again to see if the D has to be recurved... or not.
If yur still not happy, maybe your cylinder pressure is down.
If yur not happy with the acceleration as a whole, below 65 mph, change the rear gear, or get a different trans, with lower or more gears.
If the engine is a slouch above 65 mph, yur gonna need, either
1) more cylinder pressure, or
2) a bigger engine, or
3) supercharger, or
4) a lighter car, or
5) aero.

Lunch-time!
 
AJ/FormS said:
Well, IMO, you pull it out and ship it to a guy who can connect the dots for you, and for a modest fee, you're back in action, and forever happy.
Or, you ship him your spare and get that one modified. Your man doesn't care which one he gets. You tell him what you want, and he makes it happen. This will save you weeks to months of chasing the curve by yourself. Well worth whatever it costs.
So, when you get it back, you stab it in, set the Power-Timing to 34* and Drive.
RESIST the urge to experiment, just drive it.
Click to expand...
If you go this route with your stock dizzy @halifaxhops is the man.
 
I always thought that adjustable mech advance was the way to go. I bought a distributor from Mancini and it has 20 degrees built in (as far as I can tell) which works fine. In the old days guys would weld the slots which was trial and error.
 
It is still done/ Some use limiter plates now as well. Here's a slot diagram that takes out some guess work.
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