383 timing

[MRB1966]

On my 383 with the "thumper cam". What should I set my timing at? I'm sure I'll get a few different opinions but I thought I'd throw this out there.

Thanks ,Mike

 

[Rusty knuckles]

The maximum total timing you can without causing it to knock. My stock cam is about 33 I think.

 

[Cranky]

Yup, give it what it likes. I've found that the lower compression engines generally like more...initial and total.

 

[Cranky]

Thread moved to the tech forum.....

 

[65-440]

No definite number there ... my 9.44:1CR .030" over 383 likes 16 initial/ 36 total ....runs very well ... I like to find the initial that gives me the best startup and then the most total before detonation...

 

[RJRENTON]

On my 383 with the "thumper cam". What should I set my timing at? I'm sure I'll get a few different opinions but I thought I'd throw this out there.

Thanks ,Mike

IMO.....Not enough info to make a recommendation. BTW....A "thumper cam" means nothing....unless you're referring to "Dominic Thumper"....then it depends on whether your like or dislike..... Cams are usually discerned by manufacturer by degrees intake and exhaust duration and lobe lift @ a specified degree, lobe centerlines, rocker arm ratio, etc. and engine comression ratio, transmission....if automatic the converter stall ratio, and other vehicle dynamics..... without accurate information at least initially, its like trying to determine how high is up or why is there air? Go with the suggestions that say the,engine will let you know by detonation or "spark knock" noise during hard acceleration. Contributions numbers 2,3,5. Just my opinion of course....
BOB RENTON

 

[PRHeads]

Those cams have a lot of overlap, so it’s likely going to want plenty of initial timing.
I’d be shooting for 15-20 initial as a starting point........ and total timing of somewhere between 32 and 40.

A "thumper cam" means nothing

Well....... that’s not really the case:

 

[MRB1966]

On my 383 with the "thumper cam". What should I set my timing at? I'm sure I'll get a few different opinions but I thought I'd throw this out there.

Thanks ,Mike

On another note on this cam swap. I have a Edelrock 650 carburetor avs 2. The cam cards reads as this... comp cams lift .484 intake and exhaust, duration @ .050 239 and 246, lobe separation 108.00. I'm thinking I need a bigger carburetor. More like a 750 dual feed
I did my cam break-in but I was having issues with it getting too hot. Pretty sure timing isn't perfect not sure if the timing is the issue or just not enough fuel.

Anyone else having these issues after a cam swap?

Thanks Mike

 

[Geoff 2]

Those horribilis cams. It will need a TON of initial timing, & probably why it is running hot.
Try this simple 5 min test: warm up engine, have it idling [ in gear if auto, wheels chocked ] loosen dist clamp. Turn dist SLOWLY to advance timing. RPM will increase, idle will be smoother. Keep going until you have the highest idle rpm. Now check timing. My guess is that it will be 30+ degrees, maybe as much as 40 deg.

 

[Geoff 2]

If the intake is a single plane, 650 AVS is ok. If dual plane, 800 AVS would be best.

 

[Outlawd]

Every motor is different even if its the exact same build. You just got to be patient and make small adjustments and run it each time on a road with a decent hill so you got some load on it after a few runs you will know when you found that sweet spot then put a light on it just to see and know where your at. jmo

 

[PRHeads]

My experience with Ede carbs is, they aren’t great with lumpy cams that produce low vacuum.
Look for something with 4-corner idle.

 

[Bakerda408]

Not trying to hijack this but i have a similar issue. 383, roughly 10.5:1, Edelbrock 750 and performer intake, Hughes SMC2942BL cam. I'm also around 5200ft in elevation. Initial timing is set at 22 and idles right around 900rpm, and it seems pretty happy there.

I'm new to the 383 but that seems like a lot of initial advance to me, but maybe not based off what i've read here.

 

[Cranky]

Not trying to hijack this but i have a similar issue. 383, roughly 10.5:1, Edelbrock 750 and performer intake, Hughes SMC2942BL cam. I'm also around 5200ft in elevation. Initial timing is set at 22 and idles right around 900rpm, and it seems pretty happy there.

I'm new to the 383 but that seems like a lot of initial advance to me, but maybe not based off what i've read here.

Initial and total depends on lots of things. The gas today plays a part too and so does the combination of the engine. The factory timing back in the day doesn't pertain to today's fuel for the most part.....and well, it wasn't exactly the best for performance back then either especially as we got closer to 1970 and later.

 

[Bakerda408]

Initial and total depends on lots of things. The gas today plays a part too and so does the combination of the engine. The factory timing back in the day doesn't pertain to today's fuel for the most part.....and well, it wasn't exactly the best for performance back then either especially as we got closer to 1970 and later.

100% agree, I run 87 ethanol free in it (seems to run best in old iron and small motor stuff) and the motor (pulled from a 73' C-Body) is stock minus the intake, cam, and carb. Just looking to see if i'm in the ballpark before I dive in completely.

 

[roadrunnerh]

'73 anything would not have a "stock" 383, unless someone installed it. Do you have a 400?

 

[Cranky]

Yup, 383 production ended in 71 and even if it had continued, the compression would be down a LOT by 73. The 400 is low from the factory too.

 

[Bakerda408]

100% agree, I run 87 ethanol free in it (seems to run best in old iron and small motor stuff) and the motor (pulled from a 73' C-Body) is stock minus the intake, cam, and carb. Just looking to see if i'm in the ballpark before I dive in completely.

Apologies, you are all correct. The motor did get pulled from a 73' C-Body but was not original to that car either. Casting number is 2468130-11 and stampings under the distributor of G383, 3 2, E. Which should be a 71' 383 made March 2nd with a cast crank. If my research is correct.

 

[cdr]

my STOCK 68 383 loved 24 initial yours should be happy there for a start & go from there

 

[Cranky]

my STOCK 68 383 loved 24 initial yours should be happy there for a start & go from there

Hey Charlie, how are you and yours doing? Is Brain Damage still running good?