318la mild cam on holley DP 650.

[Beto0311]

How y'all doing gentleman. Back again in search of knowledge. Hopefully someone out there has the same set up or can just skool me up... on my 51 coronet I transplanted a mild 318 married to a 518OD, with posi 3.73s. Intake manifold is a holley street dominator with a holley DP 650cfm... 1st question, what should timing be at on the block ? (currently at 10°btc) 

2nd: Carb tuning? Set at 850rpm at 10inches of vacuum.. 

3: any recommendations for this type of set up... as far as timing degrees,  and carb tuning 

[48Dodger]

If the block is mild (slugs not zero at the deck and or stock valves) not sure a 650 dbl pumper is the best bet. If it's a spread bore vac/secondary it might give more back. Timing is dependent on vacuum....get that set first then find your advance.  What's the bottom end like? What is your conv/stall spec? What is your rear axle gear ratio? What is your final drive ratio? What is the vehicle weight? Just trying to get a feel for the drivetrain.

 

48D

Edited April 23, 2020 by 48Dodger

[Frank Elder]

I know 4bbl is what everybody desires but a well tuned holly 500 cfm 2bbl would probably be enough.

 

[plymouthcranbrook]

A lot of people over carborate and end up with very poor low end performance until the engine revs up. Unless you are spending a lot of time at high rpms and near full throttle you might be disappointed with the engine. Often times for street use a progressive set up works better as it does not tend to flood everything at slower speeds. And don’t forget manifold heating as it is necessary unless you are only driving in a warm dry environment to ensure gas turning into a vapor not staying a liquid. Used to see that in ancient times when everything was carborated and folks would put the biggest carb they could fit on a engine and not understand why the car ran like crap. 

[MackTheFinger]

Best thing to do would be to start with factory timing and go from there. For jetting you're sorta on your own. You'll also have to take accelerator pump shot into consideration. There are different acc pump cams available for Holleys and at some have different acc pump cam mounting spots plus the adjustment for when the pump starts working. It's more complicated than just jets. Your tuning is even more complex with mechanical secondaries and a secondary acc pump.

Your setup sounds like a good combination for a street car other than the intake/carb setup, not that it can't be made to work but it won't be simple. I ran an Offy Port-O-Sonic and a 780 Holley on a 283 SBC with a T-10 and 3:73s in a 57 Chevy and it ran great wide open. General driveability and throttle response was actually better with a WCFB or an AVS and a dual- plane intake.

Good luck!!

[48Dodger]

On ‎4‎/‎23‎/‎2020 at 4:09 AM, Frank Elder said:

I know 4bbl is what everybody desires but a well tuned holly 500 cfm 2bbl would probably be enough.

 

 

That's what we run in the Stockcar division, 4412 Holley.....of course they are 2bbl's on steroids...lol

 

48D

[Sniper]

Well, it's my opinion that the choice is never a double pumper on a street driven car.

 

And it is my opinion that the Street Dominator is never the choice on a race engine.

 

So you have a race carb on a street intake.  It works, after a fashion.

 

As for timing, it depends you give no engine specs other than "mild".  Been some changes to the 318 over the years that will also affect timing.  Cam specs will affect timing.

 

What distributor you are running will affect it too.  The amount of built in mechanical and vacuum advance will affect base timing.

 

Here's a good write up on figuring it out

 

https://www.firstfives.org/faq/timing/timing_for_modified_engines.PDF