Where to set initial timing?? 10 degrees BTC?

I am putting a stock stroke 440 together and would like some advice on where to set up my distributor. Here are some specs:

stock stroke 440 (.060 over)
KB 236 pistons
lightly ported 452 heads w/ larger valves
Six Pack induction
TTI ceramic coated 1 7/8" headers
3" Full exhaust with H-pipe and Dynomax Ultraflows
Four speed with 4:10 gear
Manual brakes and manual steering
Custom hydraulic roller cam 294/302 (108 lobe separation) with a 0.510 lift

I have an electronic distributor with 26 degrees of mechanical advance. Should I set it at 10 degrees BTDC with a total of 36 degrees at full advance? Or do I need a little more initial timing?
I have got the distributor apart right now so it would be easy for me to weld the slots up a bit if I need to.

Anyone want to take a guess at what flywheel HP numbers I am looking at?


Thanks!
Stan

10 btdc would be a good start. I ended up running mine at 16 btdc.

It's going to like somewhere in the 20* range for initial.

Fix the mechanical advance in your distributor so the engine gets the initial it wants.

for every .015" that the advance slot is reduced in length one distributor degree will be taken out the distributor. i would reduce the slot by .090" and run 15 degrees initial with stock springs. lighter springs will increase the idle timing and the heavy spring will be useless so remove it. the next issue will be the 10.5:1 compression in conjunction with iron heads/pump gas and enough timing to make power.

After replying to your post I reread your build and saw you are using KB 236s. They have the "quench dome" design, it's the 237s which are flat top. With your 452 open chamber heads they are a step in the right direction, because they can create squish. It'd be really good to cc your heads and come up with actual numbers as 85cc can be quite low for a 452 which run all the way to 93. The block's deck height is another variable.

About here someone will jump in and tell you you'll have to mill the combustion chambers for equal clearance on the squish pads. That would be ideal, but more important is to mock up the engine and see what the clearance is with no head gasket. You'd like it to barely touch but it probably won't. You need 0.040 clearance when assembled, but 0.055 or more will still give you some benefits, at least it has on every Magnum 5.2 and 5.9 built over the years. Their pistons come within 0.095 or so of the head surface.

If the engine isn't assembled yet you could enlarge the chamber around the intake valve or other advantageous places.

I am thinking your engine will probably have to have total advance down around 32 degrees to run on pump 93. An FBO advance limiter plate would be a good investment.

R.

those FBO advance limiter plates do look like a good idea. i use 9.3:1 with quench dome pistons at .045" and 34 degrees total with 93 octane is about the limit. those kb236's do have a quench dome but '452's usually have one deep chamber on each head that can mess up quench if not dealt with.

I would set the initial with the vac gauge method after it is broke in then set the total (initial+slots) to ~36 (& the FBO plate makes it easy, $25 to your door). I'd mockup the short block & if you have plateau pistons & can get quench then I would mill the open chambers to equalize and level the quench area then mill as needed to set quench. On my 308's (sb) it is ~.095" deep (& varies alot)/milling needed

Thanks for the info! I can't believe I haven't heard of the FBO limiter plates before. I will be ordering one tomorrow!

Stan

I second the recommendation from rapidrobert.
After break in, use a vacuum gauge to set initial and use an FBO plate to limit total.

It helps take the guess work out.

its a fairly new addition and the only FBO part I have used that has not failed me. (2 coils, one leaked out the top and the other died). To Dons' credit (Bless his heart) he did send me the 2nd one for free after I sat on the 1st one for a year. The one that died (2nd one) backfired and blew up the muff & scared the Hell out of the driver next to me & he damned near hit the ditch, I think he thought he was being shot at! I'd have your dist man set the total at 35 when it fires plus what the can offers with the initial set to 18 or so just for startup then do the vac gauge method later on afterwards for a spot on tune up

I was always at about 18 and a total of 36 but now have the dissy locked at 36 and have a start retard ignition module

I would, and do, weld up the slots to shorten and then file the welded end flat so I get the initial timing set at 16 to 18 BTDC with 34 to 36 total advance Your rotor plate should have 13 stamp on the bottom so you can measure from the advance pin in the slot to the end of the slot to see how much each degree (22 crankshaft degrrees = 13 distributor degrees)is in thousand and shorten that rascal up to what you want Buying and changing the plate and rerriviting is a unneeded agrevation in my opinion

Actually with the plate all you have to do is lift it up & set it (the weight(s) 1/4" pins) in a different pair of slots, takes 5 seconds, no riveting needed & either way (weld/file or the plate) you do have to take the reluctor off. with a thin/long neck pair of needlenose pliers you are able to spread the clip enough so the reluctor can come up off of the shaft. A good habit to get into is always press down on the shaft as you are prying the reluctor up to keep the plate on the pins (A helper comes in handy as it takes 2 hands to work the screwdrivers opposite each other and sometimes even a tire tool after the reluctor is up aways on the shaft and you need different leverage. In addition I would reduce the lower shaft axial play to .005" and check rotor phasing & dial in the dist timing subsystems & I might add a cup oiler on the side like the 60's points oldies had, ALL for a spot on dist with nothing left on the table. EDIT also check/correct if needed intergear top slot/dist lower tang interface slop and reduce rotor metal blade tip to cap terminal clearance to ~.015"

i'll post this up in here since i searched it out yesterday to email to my brother...
this is your slot length to advance number for the plates.

dist degrees / slot size
6* = .340"
7* =.355"
8* = .375"
9* =.390"
10* =.405"
11.5 *=.420"
12* =.435"
13* =.445"
14* =.460"
15* =.475"
16* =.490"
17* =.505"
18* =.520"

What is the duration at .050 for that cam?

Im gonna say you will be in the 20 degree initial area.

You set initial timing where you get max vacuum at idle....

I agree on the 20 or more initial.

I think the duration at .050 is going to be in the 240-245 range on intake and 250-255 range on exhaust.

If so, it would run at 15* initial... it will run better at 20+ range.

Vacuum method works great as long as the initial setting doesn't kill your starter. Have to work within the limits of the starter/battery/battery cables.

Stan,

Bring your distributor over and lets see what is does initially and modify from there. I picked up a Sun distributor machine last year so it will be easy to verify exactly how the mods change it. I welded the slots on the Hemi dual point and adjusted the initial timing and it made a nice difference! I used the same chart as posted earlier.

Jim
68 Hemi Road Runner

there's a plan!

That is where its at.... We had a distributor machine in Auto shop ( high school 71-73) Really made working on a distributor nice...

Thanks for all of the feedback everyone. I really appreciate it. I think I have a pretty good starting point.

Jim, I will definitely take you up on that offer. I will probably get the car running and drive it down to your place. I will probably bring another distributor for my Hemi as well and we can set that one up too.

Thanks!

Stan