How much timing to flatheads like?

How far advanced should the timing be for my flatty with an isky cam? How much do they like??

 

I've run 30-33 degrees on the dry lakes with Edelbrock, Clay Smith cam, and Zephyr Ignition.

traderjack

 

To be safe, 4 to 6 initial, 26 - 28 total.

 

Our Bonneville engine on the engine dyno makes the best power with a total 28 degrees. We use 4 degrees intial seting and 24 degrees in the magneto.. all in at 2500 rpm

 

Our Clay Smith cammed V8-60's ran 30 to 32 degrees with a H-C locked out mag on Alcohol. The more advance you can run without detonation, the cooler they'll run.

 

How do you guys figure that you are getting 28 degrees since all that there is to go off of is a single mark on the crank pulley? It lopes pretty good when I advance it and listen to what sounds good in "my eyes", but I dont want to go too much. When i retard it enough it flattens out and purrs like a kitten, so im assumng I should set it right in between where it sounds mean and where it sounds nice?

 

Use a set back timing light.

 

the initial timing is what you set the mark at, with a timing light...the rest comes from inside the distributor, usually from centrifigal force or vacuum(i'm no flathead expert) the total timing is the two added together.....different engine combinations require different amounts of timing...the way i always found the sweet spot was to advance it till you get pingin under a load(while driving) then back it off a degree or 2 till it stops pinging.....then if you get slow cranking problems, A: get a better starter, or B: back the timing off a degree or 2 till it starts ok.....so what you get is a happy medium of, the engine still cranks over and has no pinging under load

 

Ok, what rpm is best to have the advance all in?

 

General consensus on all-in by 2000-2500.

In general, the least advance you can run and make full power is optimum - different for every combo.

 

Did you read gmcbubba or dean lowe?

 

And...what ignition are you running? That has an effect on how or whether you can get to where you want to be.

 

Yes I did read what they said. Those are bonneville engines (race engines) mine is not. Mine is a mild street motor. I am using the mallory dual point with mechanical advance. I bought an advance curve kit for the distributor, it came with springs and degree keys. I am going to try and set it up for 25 degrees total. I just dont want the advance to come on too soon and have it detonate on me. Thanks

 

I have a related question. There is a baby rattle sound coming out of my engine bay when I accelerate. What is that... the distributor? 49 v8

 

Another side of this question for you guys running blowers, what is your initial timing at what RPM and what RPM/full advance.
To be more specific, my 289ci motor, Joe Abbin setup with 6psi boost. I was thinking at around 4/6 initial and 800rpm and 22/24 full at 3000rpm. I am/will be using the BTM boost retard set at 1. Am using the Isky 400jr.

Thanks

 

I watched a blown dyno pull where total was limited to 18* at 5psi & 5200rpm. It made a couple more HP than 20* total. It was all in by 2200 IIRC, but the BTM pulled it out at 1*/1psi or thereabouts...

 

As long as you pull timing back out under boost, you can get away with that. I'd probably aim to have the full advance in by 2200 - 2400. I'd pull a degree of timing out for every LB of boost - at least as a starting point. You DON'T want to detonate it! Also, run it a bit rich when you're figuring it out . . . lean is BAD!

Under boost, you'll probably only be able to handle 16 - 20 degrees. (Depends on the boost, how rich you're running it, heat, etc).. I used to run by blown flathead with an HC mag - locked it out at about 16 degrees (1/4 mile full-race motor). I started it by spinning it up on a 6V starter running at 12V and then engaged the mag. Locked out mags are hard on starters!

 

Thanks Flat Ernie & Bored&Stroked,

I will be getting the motor back next month and should have it together for dyno break-in and tuning the middle of February.

I'm using a 625 Demon Jr VBM (with boost referencing power valve) and I'm hoping it should be rich enough for start up. The main jets are #70's and I think that's good enough to get her going, at least for break-in.

I have always had someone with me to help tune on the dyno and this time I'm on my own so I'm a little nervous.

The BTM will be set at 1 degree retard per lb of boost so I should be OK.
So the only other thing is making sure the motor doesn't backfire on the startup. I've done a lot of motor tuning with carbs, but this will be the first with a blower.

If Joe wasn't so far away I'd put it in the truck and head his way. I've spent a lot of time and resources and want everthing to go well..................coming down to the wire.

Thanks again

 

The distributor isn't making the sound but it's probably the cause.

Sounds like detonation. Back the timing off a bit until the "baby rattle" goes away. Are you running premium?

 

In starting a blown motor, a coupe tips:

a) Check all your valve adjustments - to make sure you have enough lash. They should all be somewhere around .015 (check the CAM mfgr's recommendations).

b) Check and recheck the plug wiring and cap - make sure you have everything in the correct firing order.

c) Check your timing on #1 cylinder - I'd set my initial advance around 6 degrees or so. (Depends on what ignition you're running).

d) Disconnect the ignition and/or coil and crank it with the plugs out to insure you have oil pressure.

e) Check your carb float levels and make sure you have a good fuel supply and that the fuel system is primed and ready.

f) Put plugs back in and if you have the ability to have a 'kill switch' or seperate ignition switch - this would be nice. The reason is that it is nice to pump the accel pumps 3 - 4 times with the engine turning over (but no spark), then you flip the kill switch and ligiht her off. It is nice to have the thing already spun up, fuel in it, etc -- then throw the spark at it. This tends to reduce the chance of a lean backfire. You'll notice that this is how all the top-fuel boys start their engines . . . for a good reason.

Using a kill switch, I never once backfired my SCOT blown flathead.

 

Thanks Bored&Stroked,

I am running an MSD distributor and think I can hook up a kill switch.

I'm starting to get excited all over again..................just talking about it, it's been a long
road.

 

Cool! There is nothing like a blown flathead . . . once you've had one, you'll always want one and you'll never want to go back to NA and carbs. I'm building a 4-71 setup this winter as a "mule" motor to use for development and testing. I really want to learn how to retrofit the traditional Hilborn blower injectors for EFI -- so I have much to learn (should be fun though).

I don't know what heads you're running, but you want to really pay attention to the torque settings. I torqued my aluminum ones to 55 lbs (I know - everbody says 45 is correct). Also, run the engine JUST enough to get it warm - then shut it down and retorque. Then run it again and get it to full temperature -- then shut down and retorque. You don't want to blow a head gasket. Don't run those POS Champion plugs . . . use Autolites or NGKs . . . run a couple steps colder than the old H-10 Champion.