A buddy back in the day replaced a 318 because it ran like sh¡t. The replacement ran the same.
Oops, he reused the same distributor..
Diagnoses trumps the cash shotgun effect every time.
Stutters at 2500 rpm
- Thread starter 78cordoba
- Start date
A buddy back in the day replaced a 318 because it ran like sh¡t. The replacement ran the same.
Oops, he reused the same distributor..
Diagnoses trumps the cash shotgun effect every time.
It's going to run better with #6 firing.
I'd start with a new plug in #6.
Put a thin piece of tape on the balancer at 35 degrees BTDC.
You don't need vacuum advance for cam break in.
Just start it and get it to 2,500 steady and set the timing to your mark.
Then vary it occassionally up and down.
Let it cool completely.
Then you can try other parts, vacuum advance etc...
I'd start with a new plug in #6.
Put a thin piece of tape on the balancer at 35 degrees BTDC.
You don't need vacuum advance for cam break in.
Just start it and get it to 2,500 steady and set the timing to your mark.
Then vary it occassionally up and down.
Let it cool completely.
Then you can try other parts, vacuum advance etc...
78cordoba
Well-Known Member
That is exactly what I'm going though 2nd motor on this one but never replaced ecu or dizzy so I figured it doesn't hurt to replace them as well
A buddy back in the day replaced a 318 because it ran like sh¡t. The replacement ran the same.
Oops, he reused the same distributor..
Diagnoses trumps the cash shotgun effect every time.
78cordoba
Well-Known Member
The coloring on 5 and 6 is about the same im not sure if 5 isn't firing either. This is the same way the old engine ran with a different set of plugs. But the old engine had other issues too due to bad experience with a bad engine builder. Needless to say I wound up rebuilding this one myself.
You don't by any very slim chance have plug wires 6 and 5 swapped???
1-8-4-3-6-5-7-2
1-8-4-3-6-5-7-2
78cordoba
Well-Known Member
Well between the distributor and the ignition module it solved it. Thanks guys!
but now I have an issue with the carb the idle mixture screws still don't function properly and if i put it in drive and step on it, it dies when I let off the gas, but only when from a stop. in park I can give it as much throttle as I want.
but now I have an issue with the carb the idle mixture screws still don't function properly and if i put it in drive and step on it, it dies when I let off the gas, but only when from a stop. in park I can give it as much throttle as I want.
Geoff 2
Well-Known Member
Do you mean the mixture screws have little affect on idle quality?
[1] Make sure your PCV is working, not blocked up. It should rattle when you shake it.
[2] Remove carb & see how much transfer slot is showing at idle. it should be 020 - 060. I am guessing it is going to be a LOT more, which means there is a problem.
[1] Make sure your PCV is working, not blocked up. It should rattle when you shake it.
[2] Remove carb & see how much transfer slot is showing at idle. it should be 020 - 060. I am guessing it is going to be a LOT more, which means there is a problem.
78cordoba
Well-Known Member
Yeah It was closer to 090
Geoff 2
Well-Known Member
What is the initial timing?
You probably need a LOT more; that will increase idle rpm, allowing the t/blades to be closed more; may still need some bypass air, but idle timing FIRST.
78 400 had a 8.2:1 CR. If it is still 8.2, that is not helping...
You probably need a LOT more; that will increase idle rpm, allowing the t/blades to be closed more; may still need some bypass air, but idle timing FIRST.
78 400 had a 8.2:1 CR. If it is still 8.2, that is not helping...
78cordoba
Well-Known Member
I had it at 10 on initial
Geoff 2
Well-Known Member
Timing at idle needs to be a LOOOOOOOOOOOT more than 10*. For three reasons:
- factory #s are always conservative
- low comp ratio burns slower, needs more ign advance [ timing ]
- more cam overlap, more idle timing needed.
This is also going to be part of the problem.
It is a veeeeery simple test to see what the engine wants at idle. Warm up engine, idling, put into gear if auto, [ chock wheels ]. Loosen dist clamp & slowly turn dist CW. This advances the timing. Idle will get smoother, rpms increase. Keep going until you get the highest rpm. Then check the timing. Do not be surprised if it is near 30*!!
Perform this test & report back. Cheers.
- factory #s are always conservative
- low comp ratio burns slower, needs more ign advance [ timing ]
- more cam overlap, more idle timing needed.
This is also going to be part of the problem.
It is a veeeeery simple test to see what the engine wants at idle. Warm up engine, idling, put into gear if auto, [ chock wheels ]. Loosen dist clamp & slowly turn dist CW. This advances the timing. Idle will get smoother, rpms increase. Keep going until you get the highest rpm. Then check the timing. Do not be surprised if it is near 30*!!
Perform this test & report back. Cheers.
78cordoba
Well-Known Member
It is like 36 still doesn't buck the starter but that seems really high
78cordoba
Well-Known Member
Some details about the car I should have mentioned its been converted to electronic ignition. It has a lunati cam grind VDBCR-258. Keith black 240.040 pistons, been bored .040 over. It has edelbrock 75 cc e street heads and an edelbrock 1407 carb with manual choke.
Geoff 2
Well-Known Member
So you did the test in post #35 & 36* was best idle? Does not surprise me at all. My engine idles at 48*.
[1] Did idle rpm increase with 36*?
[2] Was idle smoother?
[3] This [ ign timing at idling ] is a hugely misunderstood subject....& a lot of ignorance about it.
[1] Did idle rpm increase with 36*?
[2] Was idle smoother?
[3] This [ ign timing at idling ] is a hugely misunderstood subject....& a lot of ignorance about it.
78cordoba
Well-Known Member
Yes idle rpm increased up to 36 and with ran smoother and seemed like the throttle response was smoother. So how much is too much total timing. Seems like most post I see people are looking to achieve roughly 20 initial and and any thing over 38 total is to high. Is that not correct?
Geoff 2
Well-Known Member
Did you read the link in post #38? Up to 50* of idle timing!!! [ See another link, below ].
With your combo, I would do this:
- you have an adj VA unit on your dist. Turn The Allen Key fully CW [ softest spring setting ].
- set init timing to about 15* [ not critical ] with VA disconnected.
- you want 17* added by the VA unit, so you will probably have to fabricate a stop to limit the travel of the plunger to 17*.
- you may have to modify the centri curve in the dist. With the low CR, 36-38 total timing [ this does NOT include the VA which goes to zero @ WOT ] is a good number to aim for. So if you use 15* init, centri curve would be 21-23*.
- this is all part of the tuning process for a modified engine. It always amazes that people buy the Holley/clones with removable air bleeds & emulsion jets....but never bother to dial in the ign timing. You are at idle cruise MUCH more often than you are at max rpm....
- the idle speed & mixture screws can NOW be reset. This, on it's own, may get the t/slots where they should be & completely cure the problem. If not, some bypass air might be needed. But I would do the above first & report back.
With your combo, I would do this:
- you have an adj VA unit on your dist. Turn The Allen Key fully CW [ softest spring setting ].
- set init timing to about 15* [ not critical ] with VA disconnected.
- you want 17* added by the VA unit, so you will probably have to fabricate a stop to limit the travel of the plunger to 17*.
- you may have to modify the centri curve in the dist. With the low CR, 36-38 total timing [ this does NOT include the VA which goes to zero @ WOT ] is a good number to aim for. So if you use 15* init, centri curve would be 21-23*.
- this is all part of the tuning process for a modified engine. It always amazes that people buy the Holley/clones with removable air bleeds & emulsion jets....but never bother to dial in the ign timing. You are at idle cruise MUCH more often than you are at max rpm....
- the idle speed & mixture screws can NOW be reset. This, on it's own, may get the t/slots where they should be & completely cure the problem. If not, some bypass air might be needed. But I would do the above first & report back.
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