Have a street 408 that I’m trying to make a little more tame and smooth at idle
4 speed 3:55
408 eddy head
239 243 hydraulic roller on a 112 lsa - mrl grind
Vacuum is about 12 at 1000 rpm
89 la roller block 10:1
Timing is 20 initial 32 all in
Hughes makes a fast bleed magnum style lifter, I was thinking of using them on the intake side only to knock the edge of at idle and allow me to set a 900
Any experience with this ?
Just so you know;
The first cam in my 360HO, back in 2000 was a FTH, @292/292/108@.008 tappet, and
248@050
The Scr was 11.3 with alloy heads.
That cam ran mostly at +4, so, the Ica was ~70*, and she ran 1.6arms.
I ran this on 87E10@12 to 14 Idle-advance with the Orange box, an Accel square-top Super Coil, and a factory distributor, which I recurved as was necessary.
The induction was an ancient 750DP on an Airgap. Primary throttles drilled to sync the transfers. Yes on PowerBrakes.
I was able to tune this down to idle at under 800 unloaded, and to 550/600 in gear and pulling itself on flat, level, hard ground, by retarding the Idle-timing to 5*Advanced.
The car runs a manual trans, at the time with a 2.66 low, and with 3.55s.
Just so you know.
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My guess is this;
Your cam is what?
284/288/112 and with an Ica of 69@ Plus4
With 20* idle timing, your transfers are too far closed, and your mixture screws are too far open, your bypass is too much, and I bet your secondaries are probably sucking air.
and, Ima thinking she's might be running cold? that's a guess, cuz too hot will run crappy too, but for a different reason.
IMHO, you just need a tune
and maybe a looser convertor, IDK.
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Just so you know;
I got rid of that cam at the end of the first summer, cuz it didn't like 3.55s and that was all I wanted to run, cuz she was my DD.
What she didn't like about 3.55s was this;
1) I couldn't drive slow-enough. If I wasn't careful, she'd get jumpy down at 550, and
2) Top of First gear was over 60mph, and the 275s were still on fire after the shift. For a DD, she just had too much top-end power, and not enough torque down low, and
3) she ran hot all the time; which I later found out was NOT entirely the cam's fault.
Just so you know.
this combo was fine with 4.30s, except it was real hard on fuel, driving 30 minutes each way, to and from work every day.
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Here's what I suggest; and it's just a suggestion;
Take the carb off.
>reset the T-slot exposure to a little taller than wide.
>reset the mixture screws to in the center of their adjustment range
>Close the secondaries up tight but Not sticking
Put the carb back on.
>Make sure the WET float level is correct and stable.
Set the Idle speed with Idle-timing.
> You must run a PCV system, and
> I had no problem running the VA on the sparkport, Mine ran about 8 inches at idle.
>For a streeter, I would get the coolant temp up to at
least 185; My car went 93 in the 660 at a steady 207
> Now I would fine tune the Idle-Air bypass. 7/64ths is what I ended up at, for pulling at 550 rpm in gear, but every engine is a lil different.
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Here are a few things that you may need to know;
>The more idle-timing you give your engine, the more idle-power it's gunna make and so, the faster it's gunna want to run. It's just that simple.
>In my experience, cracking the secondaries for bypass-air, on a Non-4-corner carb, is an exercise in futility, two or more rear cylinders will run lean at idle, and then she got jumpy on me.
>Same will happen if you try to run a brake booster off just one of the runner. I rerouted mine to the Plenum. >The PCV MUST be run under the primaries, coupled to both bores.
>If your ring gaps are too tight, or your skirts are, it's gunna show up at idle, as an engine that labors to tick over; it needs more Idle-power. It may run easier when cold; that's yur first clue.
I first ran my Hypers at the KB recommended clearances; man I worked so hard on the tune that summer, you wouldn't believe. At the end of the summer, I swapped engines to my sweetheart 318 for the winter, and so, I tore that 367 down. I increased the skirt clearance and opened up the gaps on the compression rings. With a new, much smaller cam (276/286/110, 223@050) that engine had a whole new personality. I'm not talking about just Power and torque; She ran so sweetly, I increased the coolant temp, first to 185, then 195, then 207, which was magic.
> In my experience, I discovered that the Eddies liked heat. The following winter, at the freshening, I painted the heads, several coats of enamel in an effort to keep the heat in. and I slowed the pump down. I painted the AirGap too. I painted it all!
If you must know, "Hugger Orange" a Chevy color, lol.
> on the street, I can't tell the difference in power between 32 to 36 degrees advance. I mean any setting will roast BFG 295s so, she's usually down at 32/34 on 87E10.
> I bought and installed a dash-mounted, dial-back, timing module that has a range of 15 degrees. I set the timing with the device already advanced some, so I can retard it, on the fly. The range ended up for up to 6 advanced/9 retarded. So, from the front seat, I can retard the timing from 14 to 5, which totally kills idle power, or I can add up to 5* for fuel economy while cruising.
But there was a time that I used it just for fuel economy. I can tell you that there were times that my engine liked a ton of cruise-timing. Most of the time she is set to 56 degrees @2240 in overdrive, but there was this one time she liked more than 60.
If you use your VA for idle-timing as is so often suggested, what will your cruise timing end up at?
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>BTW; You absolutely cannot give your engine the amount of idle-timing that it wants, and still drive the thing ....... because, the idle-rpm climbs out of sight. Prove me wrong. Go ahead, try 25, or 30, or 35, just keep throwing timing at it without resetting the throttle position, until the idle-rpm stops increasing. Now read your timing. What does yours like? 42 degrees? More?
Now put it in gear. Bam! Ok don't put it in gear again. Instead, idle it down with the speed screw. Now put it in gear. I bet it stalls. But if it doesn't, try to drive away. I bet it stalls,......... cuz the T-slot sync is way out to lunch.
The point is this; Since you cannot simultaneously give her what she wants, and still drive it, why should you care at all, what the Idle-timing is? Just set the sync , followed by the Timing-controlled Idle-speed to something slow enough but that doesn't cause a tip-in sag. If the engine labors down there, it most likely has other issues.
The first time the engine cares about power-timing, is at stall. Too much and she is likely to detonate. Too little and she gets lazy. You will not hardly be able to tell between perfect timing and up to three degrees not enough. But ONE degree too much and there is your piston-shattering detonation.
The point is this. Your street-driven engine is not a race engine, so don't let the internet bully you into trying to force your engine's timing. EVEN at WOT and at the power peak, that last degree might only be worth 7 stinking horsepower, and tell me how yur gonna feel that with a stroker at any street-legal speed; You can't hardly even run Second gear out to the Power peak with 3.55s; which will top out at 65 equals about 4400rpm.
Just saying, lol
End timing-opinion rant.
Happy HotRodding
PS
holes in the primary throttles do the same thing as changing idle bleeds. It's not rocket science. If your carb has screw-in bleeds, fine, use them. But if it doesn't, then the holes are, IMHO, a better option than cracking the secondaries. Theoretically, you could bring extra air in thru the PCV circuit, and I have at various times experimented with that. But, I am quite comfortable drilling my throttles. And yes, one time, as I was learning, I went too big. I just soldered the holes shut, moved over, and started again with smaller holes. How did I know that I had drilled too big?
Cuz the idle-speed went too high at my chosen T-slot sync. and Idle-timing. I didn't want to drill, but I had to know.
