Ok, now I need some carb tuning advice (Holley 4160 600CFM)

Rembrant wrote

...and wait for my distributor to get back...which will be a little while since it hasn't even arrived there yet.

Well after 5 weeks without, I finally got my new distributor. Since I was replacing my intake gaskets, I figured it was a good a time as any to send my stock distributor out to Scott at Parkland to have it properly set up and tested, etc. Turns out my old stock DSII unit had a bent shaft and a worn out upper bushing. He said that it wouldn't work 100% and he recommended a replacement, and here it is. I just stuck it back in the block last night. I put a little bit of engine assembly lube on the gear but I feel like I should put some more on it. He's got me set up for 15 deg initial, 17 mechanical, and 17 vacuum. I think that will be a nice combo. I was running the timing at 16 deg initial for a little while and it was running nicely there.



Now, to pick up some exhaust hose today so I can start the truck and run it without setting off the CO2 sensors in the house and making the fire department arrive for a visit...lol.

Unfortunately it snowed last night, and my clean and dry roads are gone, at least for a few days anyway, so no test drives. Bugger.

17* mechanical?  That's a pretty tight slot.

Scott seems to have it down, and if your reluctor was wobbling I can see a problem there.

I'm eagerly awaiting the road test (maybe not as much as you. )

ArdWrknTrk wrote

17* mechanical?  That's a pretty tight slot.

Ha, ya...the rotor button barely moves at all.

I guess when you know your stuff, you know your stuff! When I had the engine broken in and tested on the dyno, it made it's best power at 32 degrees. I didn't tell Scott that, but that is exactly where he set it...15+17=32. I was running it for a little while with 16 deg initial, and it was much better there than the 10-12 I was running it previously, so I think his selection is going to be bang on. I told him what heads and cam I had installed, and how I was using the truck, and he selected the timing set-up from there.

What I learned that I didn't know prior to this was that the mechanical curve is not linear. I thought that with careful set up and adjustment of the springs you could get a pretty linear curve, but he said no, not at all...it still ends up like a arc, no matter what. Still...I'm glad I sent the distributor to him. I wouldn't have known it was bad otherwise...not like I can watch it spin in the engine like he can on the Sun machine.

Yeah, the advance isn't linear because

A) the weights swing an arc that is not centered at the fixed end of the spring, and even if it was, action of the arm is like a crank and connecting rod.
Have a look at some graphs of applied torque, though the cylinder pressure varies too.

B) light spring and stiff spring, it's not summing or a simple average.

He obviously knows his stuff.
You COULD HAVE had a Sun machine, you chose not to....  

I looked back at the last page (for context) and realized I have .040" (and .024 + .032) safety wire in my drawer.

It's mil-spec so I'd assume that's accurate enough to set a choke plate.

ArdWrknTrk wrote

I looked back at the last page (for context) and realized I have .040" (and .024 + .032) safety wire in my drawer.

It's mil-spec so I'd assume that's accurate enough to set a choke plate.

I ended up using some stainless safety wire I have on the shelf. I believe it was .030" or .035", so that got me in the right range anyhow. So now I have my carb set-up a little better with the throttle plates in a good starting position (they were not closing far enough before). I have the idle mix screws out 1.5 turns each.
New carb spacer and carb gaskets (old one was warped and leaking). New Fel-Pro intake gaskets (Old ones were leaking), and new properly set-up distributor. I also have a new DSII module that I'm not going to install until after I test this set-up. I was seeing some ignition oddities that and figured I should have a new module on hand just in case.

I think she'll run much better now. Compression is good on all 8 cylinders and about 30 psi higher than the engine was stock.

The only other thing on my to-do/want list, and it probably won't be until spring now, is to swap out the 600CFM Holley for one of those Summit 500CFM carbs with the annual boosters. There seems to be a fairly general consensus that the little 302 will work better with that carb. It may not make as much peak power, but it will run better at the lower RPM's where it is 99% of the time.

It may not flow as much CFM, but "power" and Absolute Horse Power are not the same.

You should have better signal and metering with the smaller carb.

My '85 5.0 GT had a 4180 (600) and its factory tune was about perfect after I pulled the plugs and adjusted the idle mixture.

ArdWrknTrk wrote

It may not flow as much CFM, but "power" and Absolute Horse Power are not the same.

You should have better signal and metering with the smaller carb.

My '85 5.0 GT had a 4180 (600) and its factory tune was about perfect after I pulled the plugs and adjusted the idle mixture.

Ya know, those carbed GT's worked SO well for what they were. I had quite a few buddies that had them in the late 1980's...and then many more of the EFI versions after. I never did have one myself...I was rocking a *cough* 1984 Z28 *cough* in those days, before slowing down and buying my first Bullnose with a 351 2bbl and NP435.

My truck only weighs about 50-75 lbs more than a fully loaded Foxbody Mustang (I'm talking the later GT's when the "old" GT style became the lighter LX). I'm only mentioning this because I know that the 302 is plenty engine for what I'm doing with the truck, and I'm hoping I can get it dialed in to get some good MPG as well.

I've read about lots of people getting 20+ MPG with the Foxbody Mustangs over the years, so hopefully I can get mine working well enough to at least hit 20, if not a little better with some extra effort. Now that I have an AFR gauge, that will certainly help in the fine tuning department.

ArdWrknTrk wrote

You should have better signal and metering with the smaller carb.

Oh, I forgot to reply to this comment. This is exactly what my goal/point is with the 500CFM carb.

The peak HP is of little concern to me. While I did pay extra to have my freshly built 302 run up on the dyno, my main reasoning for that was a proper break in. I wanted the the thing to be turn-key for when I got it back home, with no leaks or hiccups of any kind.

Oh,...another question:

When you guys are setting up a carb...as in setting the idle mix screws and idle speed screw, do you do this with no air cleaner installed? I assume yes...because I can't reach any of that stuff with my air cleaner installed...

Yes, no filter housing.
I do have a Stub Stack though.
https://www.jegs.com/i/K%26N/599/85-0200/10002/-1?gclid=CjwKCAiA3OzvBRBXEiwALNKDP3Mdrl8Jk5blmTmcSbwqg_WdKFBdRTkTGpQUvwj-TCSmdg0w4CFpEBoC7hEQAvD_BwE

Smooths some of the turbulence as the flow breaks over the lip and choke horn.

Ideally, tuning the idle mixture should be done with the air filter in place if possible but with a clean air filter should not make a huge difference. On my 300 six this is easily possible due to the off-set air filter housing my truck has and is how I tuned my idle air mixture.

Absolutely true.

Someone has "borrowed" my flex shaft carburetor adjustment tool, and I've had to make do.  😡

Rembrant, I like that air filter spacer you have on your carb. Is it metal?

Frank Wyatt wrote

Rembrant, I like that air filter spacer you have on your carb. Is it metal?

Hey Frank, yes sir it is aluminum. It is a nice little piece and has an o-ring seal on the bottom side. The only issue with it is that the ID is fairly snug and I had to grind a couple small spots where the choke plate rods move up and down. I've had it for a while, but I'm pretty this is it in the link below:

https://www.summitracing.com/int/parts/trd-2011/overview/

I also have a 1" thick aluminum spacer under the carb too.

The reason I'm using the spacer was that I was running a fairly large air cleaner (14", I think) and it interfered with the plug wire boots on the distributor without the spacer.



Actually, with the open air cleaner I was running a plastic spacer, but when I switched over to the Foxbody dual snorkel air cleaner assembly, it was loose and sloppy on the plastic, so that is when I bought the aluminum one.

Frank Wyatt wrote

Ideally, tuning the idle mixture should be done with the air filter in place if possible but with a clean air filter should not make a huge difference. On my 300 six this is easily possible due to the off-set air filter housing my truck has and is how I tuned my idle air mixture.

The reason I was asking is that I don't think I can reach any of the screws with the dual snorkel air cleaner on there. Maybe I'll stick the open element breather on there to get it set up...

Cory, just get a carb adjusting flex tool.

It's not hard to reach the base flange of a Holley -under the stock air cleaner- with one.

Mine was a hex handle that slid along a spring, with a slot bit on one end and a hex on the other.
It was also used for adjusting GM points distributors.
Iirc, I got it from one of those spinning racks of KD tools.

And posted a picture, back on FTE.

ArdWrknTrk wrote

Cory, just get a carb adjusting flex tool.

I'll see what I can find. Hoping to get her fired up tomorrow. I'm just gathering supplies to vent the dual exhaust outdoors so that I don't have the fire department here again (and a very angry Mrs. Rembrant)...LOL.

I didn't realize how expensive that garage exhaust hose stuff was until I went to buy some. Local shop sells them in 11' sections (3" hose) for $170 each (plus 15% tax of course). That was going to cost me $400, so that little plan got nixed quick. Anyway, brother in law had 20+ feet of an industrial 3" vent hose, so that should do the trick nicely. I even grabbed a couple rubber MJ couplings so that I can seal the tailpipes to the hose. Stay tuned...lol.

I think I mentioned how expensive that stuff was (Ray, said he was going to use dryer vent???)

But, yeah, it's not cheap.

I lied... 🙁
I found it in the back corner of the bottom drawer.