Foxy Green Foxbody Build

[BOSS#1540]

Does anyone have an msd bushing kit they can measure the bushings that come with them?

Yep!

 

[BOSS#1540]

I ran a fraction over 11 on a aluminum headed small block pump gas no problem eons ago but I am sure there were/are limits. They also use to say 8:1 was where it was at for a blower. I don’t know anyone who runs that low compression slug anymore. Carburetor or FI. Times have changed just like the fuel.

I assumed AI would say no, but it actually said yes and mentioned several of the conditions needed to do it.

 

[CCSguy]

Fox does not want the advice from a couple of you. You’ve worn out your welcome. JFC, read the room.

 

[Steve439]

Does anyone have an msd bushing kit they can measure the bushings that come with them?

I'll try to find them, it may be hopeless...

 

[Steve439]

These are 25-30 years old, hopefully they haven't changed.

Red .280

Silver .310

Black? .341

 

[89 Fox 427]

These are 25-30 years old, hopefully they haven't changed.

Red .280

Silver .310

Black? .341

Thanks. I believe something is different. My current one is 0.370 ish and I think that's the 18 degree.

 

[89 Fox 427]

Loading…

www.chevelles.com

 

[Steve439]

Thanks. I believe something is different. My current one is 0.370 ish and I think that's the 18 degree.

Oh yeah, those guys are in the distributors... D'oh!

I remembered one was black, but the one I said was black is probably blue.

I'm trying to find the 4 Seconds Flat ones, I'll keep looking.

 

[Raidmagic]

THAT FUCKING SHOW!!!!!!!!!!!!

I set my DVR to record drag racing one day, I saw that show, never heard of it, figured why not record it and watch it when nothing else was on. Figured it was another gay-ass no-prep bullshit show. Well, the GAY ASS was fucking correct! My daughter was laughing her ass off at me when I was yelling at the fucking TV when I started to watch it. WHAT THE FUCK!!!!!!!!!!!

Killed the recordings as fast as I could! She still makes fun of me to this day.

This might be the funniest thing ever posted on this site.

 

[SteveTX]

I assumed AI would say no, but it actually said yes and mentioned several of the conditions needed to do it.

Its been a month probably since I asked it to plot a graph for me. I tried 4 or so times it never ever could get it. It came sort of close to making a graph one time but none of the numbers were correct. I gave up. If I get extremely bored I may see if it has the ability now.

Thanks. I believe something is different. My current one is 0.370 ish and I think that's the 18 degree.

The Black is the 18°

Source >

Loading…

documents.msdignition.com

 

[SteveTX]

Loading…

www.chevelles.com

Oh my bad I see they had the info. I was trying to get some info to help and didn't see you had went there.

 

[Steve439]

I give up!

Trust the Chevelle guys...

 

[89 Fox 427]

I give up!

Trust the Chevelle guys...

Still leaves me guessing..

BUT...

30 degrees timing is safe as you stated before.

I'm going to file down the extra 0.410 bushing I have to somewhere between .390 and .400 and just get the thing to idle where I want it, cruise around town, check if it hard starts, and then worry about total timing later.

 

[89 Fox 427]

I don't like that the bushing is aluminum, so eventually I'll have a steel one made.

It looks to me (math thread) that every 0.009" diameter limits 1 degree of advance. I don't know if that translates linear like that, but if it does, then the bushing I have that measures .410" would actually be 13.5* if in fact the .280 bushing is 28 degrees

 

[89 Fox 427]

As I lay here thinking more... I can put a 10-24 nut in that slot instead of a bushing and just file the points of the nut down to whatever number makes sense once I start testing total advance

 

[Steve439]

I don't like that the bushing is aluminum, so eventually I'll have a steel one made.

It looks to me (math thread) that every 0.009" diameter limits 1 degree of advance. I don't know if that translates linear like that, but if it does, then the bushing I have that measures .410" would actually be 13.5* if in fact the .280 bushing is 28 degrees

That Chevelle thread brought up the idea that it's not linear.
Does it work out for the four whose diameters we know?

 

[Lowrider]

Still leaves me guessing..

BUT...

30 degrees timing is safe as you stated before.

I'm going to file down the extra 0.410 bushing I have to somewhere between .390 and .400 and just get the thing to idle where I want it, cruise around town, check if it hard starts, and then worry about total timing later.

Good idea, because you don't want to be embarrassed if the turd don't start after you take the Ukrainian
girl out for ice cream.

 

[89 Fox 427]

That Chevelle thread brought up the idea that it's not linear.
Does it work out for the four whose diameters we know?

Yes it does very closely for the ones we know, especially given Chinese machining tolerances. If we know .280 = 28* and .370 = 18* we can extrapolate

.280 = 28*
.289 = 27*
.298 = 26*
.307 = 25* (within tolerance)
.316 = 24*
.325 = 23*
.334 = 22*
.343 = 21* (within tolerance)
.352 = 20*
.361 = 19*
.370 = 18*

AI originally told me I needed a .442" bushing for 10 degree limit and I thought it was wrong, but now I'm thinking it might have been on to something.

 

[89 Fox 427]

AI at least can sound like it knows what its talking about. Here's the answer I got to a detailed question about timing when I described my setup. Nothing groundbreaking in its answer:

If the engine is cranking easily at 18 degrees, you likely have plenty of room to experiment.

With that custom bushing, I suggest setting your initial timing at 20-22° BTDC. It allows you to run a much higher initial timing without over-advancing the engine at high RPM

That big 295/309 cam creates a lot of exhaust dilution at low RPM. Giving it 21° at idle will significantly increase combustion efficiency, crisp up the throttle response, and help the engine carry the load if you're running accessories like power steering or A/C.

Most 427 Windsors with modern aluminum heads like the Promaxx you have, find their peak power between 32° and 35° total. The 13° bushing let's you "shove" more of that timing into the idle/low-RPM range where the big cam needs it most.

The extra 2-3 degrees at idle will likely:

•Increase idle vacuum slightly
•Allow you to close the throttle blades a bit more at the carburetor, which helps prevent nozzle drip and keeps you on the idle circuit rather than the transition slots.

The Test:
Bump it to 21°, let the engine get up to full operating temperatures (180-190°F), shut it off for 5 minutes, and then try a hot restart. If it fires right up without that "labored" or "thumping" sound from the starter, leave it there.

One final check: is your vacuum advance currently hooked up to manifold vacuum (full vacuum at idle) or ported vacuum (no vacuum until you touch the throttle)? Depending on which one you use, that 21° base timing will behave very differently at a standstill.

 

[Steve439]

Holy shit, that's about as good as what a guy who understands it would post.