Idle speed with a MAX-1

tubman

tubman

Well-known member
I have an Iskendarian MAX-1 camshaft in my freshly rebuilt 258" 8BA. The engine also has an old "flattop" Mallory dual point, a Rochester 2GC carburetor, headers, and a set of Edmunds heads with 165 lbs of compression. The engine will idle OK at 500 rpm, but seems to like 700 rpm better. It doesn't like anything under 500 rpm. I am satisfied with this. Does this sound right to you experts out there?
 
Thanks for confirming that Jack. I'm used to stock motors that idle at 450. I didn't know if the MAX-1 was that much more "radical" of a grind to require an increase in idle speed. (There's got to be a better word than "radical", but I can't think of it at the moment.)
 
The 258 flathead is my favorite engine. The Max#1 and a 2GC is anice combination. Now a sbc dist would make it perfect. Power and economy is a single package. God luck
I'm in the process of building one almost exactly like it.
 
Sorry Ron; I did have a converted SBC Mallory in it to start, but when I found a good "flattop" Mallory dual point, I had no choice but to use it. I love the looks of those things. I have one in my Olds Rocket and as well as the early Hemi in my race car. The 258" runs excellently; it revs to 5500 no problem, and it seems there's a lot left there. And, to further muddy the waters, the 2GC is just temporary too. I have a Navarro "Universal" dual manifold and a couple of 94's that are going on it because it's going into a car with no hood.
 
Well the Mallory will sure make power. I waz thinking of economy in a street engine. I have a dual Edelbrock super dual intake with 2 dash 5 Holley's (94's) that might go on, but I also have a 4bl intake and a 500 Holley. Right now I have nothing to put it in.
 
This engine is for a "Hot Rod", so economy isn't at the top of the list. I also have an Offy "Super Dual", and really like the looks of it. However, someone on here (I think it was you, "Ol' Ron") said that the Navarro duals and triples had excellent fuel distribution and were overall the best. Although Navarro did make a "Regular" dual manifold, this is the "Universal" that has the carburetors farther apart like a "Super". Speaking of 4 barrels, I have Fenton, Edmunds, and Sharp quad manifolds. I also have a rebuilt WCFB and two 4GC's. If I live long enough, I plan on evaluating all of these setups sometime in the future. I ran a 390 Holley on an Offenhauser manifold on the 276 incher in my old '36 3-window. It performed very well, but I like the looks of the older carbs better. (Just so you know, I am running a 2GC on the 255 merc in my '51, and think it's hands down the best carburetion setup for a flathead in a car with a hood.)
 
I have a very similar setup to your engine but with original heads milled .050, 94 carb and an all mechanical chevy distributor (Bubba's). Mine will idle at 450 with no problem. I do have quite a bit of initial advance setin which seems to smooth out the idle. No pinging while driving.


Bill
 
Bored&Stroked said:
Heck - my roller-cammed 284 "idles" at about 1000 RPM . . . and I like it! LOL

D
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For economy my 192.448 MPH Bonneville record setting 292 cube Flathead will idel at 800 RPM but when you push down on the gas pedal there goes that foolish economy thing just saying LOL.
 
I think I refer to economy, for a daily driver. Back when I was building engines the truck was used for everything, including taking parts to the machine shop, so running a rich mixture wasn't practical and bad for the rings. So I went for economy.
 
Bill Batson said:
I have a very similar setup to your engine but with original heads milled .050, 94 carb and an all mechanical chevy distributor (Bubba's). Mine will idle at 450 with no problem. I do have quite a bit of initial advance setin which seems to smooth out the idle. No pinging while driving.


Bill
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Bill,

How did you set your timing? What do you consider "quite a bit of initial advance"? I set my initial advance like I usually do; advance it until I get the highest reading on my vacuum gauge and then retard it just a smidge. My dial-back timing light gave up the ghost a while ago, so I don't have any specific numbers. BTW, I am using a mechanical only Mallory "flattop" dual point distributor.

The reason I am asking this is that, although I think the engine runs great, I'm not sure that the cam is "radical" (there's that word again) enough to affect the idle speed. From what you say, it's not. At this point in time with the way this thing runs, I don't think I'm going to chase 100 RPM on the idle by messing around with the timing.

Thanks to everyone for their input.
 
Ron

I really do not think that cam affects idle very much. As I mentioned I have a Bubba Chevy distributor (8BA) with only mechanical advance. I started setting the timing with the pointer right on the dimple which is about 2 or 4 degrees BTDC (depends on who you ask). Then slowly advanced the timing until the idle was the smoothest. Backed of a little and tightened it down. This was around 14 degrees of advance at idle.


Ran very well and strong at this setting with no pinging even pulling up a hill. Put the timing light on it and I believe its around 29 - 30 degrees BTDC maximum which was much more than the recommended 24 degrees. I'm into my third year running with no problems so I believe its okay. I do baby it quite a bit but so far its fine.

I believe you feel this cam starting about 2000 rpm - pulls strong up through 3000 and beyond. As I remember its mostly more lift with not much duration change. The more experienced fella's will know much more than I do.

Bill
 
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I don't think initial timing is very important anymore. All it does is let you start the engine. After that, the vacuum advance takes over and you have idle advance. adding throttle, brings in mechanical advance and removes vacuum advance. Once you establish your cruising speed, the vacuum advance returns and you have cruise timing. combination of Mech. and vac advance, Now when you want to accelerate. your vacuum advance is removed and the timing reverts back to the power setting. Each engine is a little different, but after spending a few thousand dollars building the thing, might as well as spend the time tuning it properly. All the tools are there.
 
"Ol' Ron" - Unfortunately, no vacuum advance in a "flattop". This is a new engine and I'm sure I will be getting a little deeper into fine tuning it later.
 
Bored&Stroked said:
Ronnie, you need a BIGGER cam . . . it idles WAY too low! LOL :)
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Dale I think your right SO some additional changes have taken place to see if more MPH can be gained this year with 292 cubes at the end of three miles from a standing start on the Salt Flats BUT I think maybe 850 RPM at Idle will not hurt the economy that much. LOL
 
700 sounds alright to me. The motor in my roadster has a Schneider cam and that idles around 700 or so.

Mart.
 
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