340 ignition timing.

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plumkrazee70

plumkrazee70

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Hello everyone.

I need some advice on my ignition timing. It's a 68 340, steel crank. I put a new harmonic balancer on, because the old One spun on the rubber.. I replaced it with a summit OE 7.25 dia. http://www.summitracing.com/parts/sum-163273/overview/make/dodge



Set the initial timing this morning, by advancing until starter kicked back and backed off a few deg. Came up with 34* initial. To me this seems really high.

I have a MSD billet dist. No vaccum advance, with 6a box.

My first thought is that the weights and springs are worn in the dist. (Dist. Is old, came off 318 that was in car.

Cam: http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=619&sb=2


Can someone point me in the right direction?
 
Did you remove the distributor vacuum advance hose and plug it off to the the carb side?
 
plumkrazee70 said:
Hello everyone.

I need some advice on my ignition timing. It's a 68 340, steel crank. I put a new harmonic balancer on, because the old One spun on the rubber.. I replaced it with a summit OE 7.25 dia. http://www.summitracing.com/parts/sum-163273/overview/make/dodge



Set the initial timing this morning, by advancing until starter kicked back and backed off a few deg. Came up with 34* initial. To me this seems really high.

I have a MSD billet dist. No vaccum advance, with 6a box.

My first thought is that the weights and springs are worn in the dist. (Dist. Is old, came off 318 that was in car.

Cam: http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=619&sb=2


Can someone point me in the right direction?
Click to expand...





i dont think 34 is high,hell ,my 360 likes 38,and it dont ping or kick the starter back.but thats all in,and i dont run any advance
 
When I set mine I set the engine at 10 degrees BTC and put a plug in the number wire, then turned the distributor until the plug sparked. This was good enough to get me running, then I set the engine for 36 total since that was where the engine performed best on the dino.
 
If it was mine.

I'd put the black bushing on it, light silver/blue spring combo and set initial at 16-20. That should give you a total in the 34-38 range. As long as it doesn't ping/detonate, you should be good to go.

That engine shouldn't require a locked out distributor. It's a smallish camshaft.
 
I guess I wasn't being clear based on the responses... Its at 34* initial ( at idle) not all in. The dizzy does not have vac. Advance.

Trying to set initial before I try and figure total.
 
crackedback said:
If it was mine.

I'd put the black bushing on it, light silver/blue spring combo and set initial at 16-20. That should give you a total in the 34-38 range. As long as it doesn't ping/detonate, you should be good to go.

That engine shouldn't require a locked out distributor. It's a smallish camshaft.
Click to expand...

I thought 16-20 would be good also. But I read in another
Thread that to find initial was to find where starter kicks back then back off? Maybe I'm wronh?
 
Yes-that's a decent method for getting the best idle, but you also have to consider the timing curve...unless you're running a purposed engine with locked timing, 34 is too much initial...it'll wind up somewhere north of 50 degrees when it's all in-and that'll end up hurting parts.

Since you have the light on it though, map out your curve like these guys are saying and see how it drives, then modify as necessary to get best performance and drivability.
 
txstang84 said:
Yes-that's a decent method for getting the best idle, but you also have to consider the timing curve...unless you're running a purposed engine with locked timing, 34 is too much initial...it'll wind up somewhere north of 50 degrees when it's all in-and that'll end up hurting parts.

Since you have the light on it though, map out your curve like these guys are saying and see how it drives, then modify as necessary to get best performance and drivability.
Click to expand...

Ok, I mis-understood the other threads. I don't have the springs/bushings that came with the distributor so I will have to order another set. I am ordering a new set of tires, so it will be a little bit before I can take it out for a drive.

When the tires get here, I will make the adjustments and take it out for a drive and report back.
 
I don't think any of us asked-what's your idle RPM? Once you get to a certain idle speed, it may be getting into your advance window...if your MSD is using the light weight springs, you may be getting into it above about 800rpm. Did you check to see when it's all in and how much you have?
 
Mine runs best at 34 with no advance hooked up. I tried lowering the timing and hooking up the advance and it ran like a POS. JMO
 
The mopar performance book recommends 35 degrees total for a small block with cast iron heads.

And knock off 2-3 degrees for aluminum heads

I run my aluminum headed 340 at 32 degrees total
 
I guess I should've put it up before...every engine is different and even two engines built similarly will behave differently with different environments...especially DA, humidity, and temperatures.

Cylinder fill, cam timing, induction all play into that party and if your engine runs well with locked out timing-awesome, not everyone's does.
 
This thread is all over the place. Half of you are talking about initial and half of you are talking about total.
 
Johnny Dart said:
This thread is all over the place. Half of you are talking about initial and half of you are talking about total.
Click to expand...


that's because some engines need more initial than others, and have to tested to see what they want for initial.

Total timing is what best works with the cylinder heads in question , per the mopar performance manual 35 degrees total for a cast iron engine
 
txstang84 said:
I don't think any of us asked-what's your idle RPM? Once you get to a certain idle speed, it may be getting into your advance window...if your MSD is using the light weight springs, you may be getting into it above about 800rpm. Did you check to see when it's all in and how much you have?
Click to expand...

I lowered the initial to 18, and reset the idle to 900 rpm. I have not checked what rpm total comes in at or what total is yet. I still need to look under the cap on the dizzy to see what springs and bushing are currently there.

I had the same thought about the advance coming in too early. I am going to order a set springs now (since they're so cheap) and check it out this weekend.

I am still working on getting my wheels painted, so it may not be until weekend after next before I can drive it. Looks like rain is coming.

Thanks again for the advice and staying on track. :D
 
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