408 SBF with AFR’s latest 220 cnc heads – what power?

General engine tech -- Drag Racing to Circle Track

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby Calypso » Thu Apr 21, 2016 2:47 pm

MadBill wrote:One fix for run-on is to use an AC fast idle solenoid from a '70s -'80s GM (and perhaps others) 4 bbl, preferably for ease of installation, a Holley-equipped one. They are designed to raise idle speed when energized, to better carry the AC load, but can be used powered on for the normal idle, allowing the butterflies to close nearly completely upon shutting down. Anothe 'fix' of course is to hold the brakes on, shut down in gear and drag it to a stop with the clutch.


Used that solenoid myself and it worked great. You can get everything for Holley new:
Holley part#
46-74 Solenoid
20-9 Bracket
26-57 nut

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby mbrooks » Thu Apr 21, 2016 4:41 pm

There's some good ideas. I have a dashpot I've been saving all these years, if I can find it. Next time I'm out prior to shut down I'm gonna unhook the vacuum gauge which should let the vacuum advance down along with the idle then see how it shuts down. Might try for a dash mounted vacuum switch if it works.

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby GARY C » Thu Apr 21, 2016 4:53 pm

mbrooks wrote:There's some good ideas. I have a dashpot I've been saving all these years, if I can find it. Next time I'm out prior to shut down I'm gonna unhook the vacuum gauge which should let the vacuum advance down along with the idle then see how it shuts down. Might try for a dash mounted vacuum switch if it works.

How much initial timing are you running?

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby MadBill » Thu Apr 21, 2016 5:35 pm

GARY C wrote:..How much initial timing are you running?


Yes, run-on is generally due to a combination of high idle speed and retarded spark timing, so if you can get away with more inital + vac....
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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby GARY C » Thu Apr 21, 2016 5:53 pm

MadBill wrote:
GARY C wrote:..How much initial timing are you running?


Yes, run-on is generally due to a combination of high idle speed and retarded spark timing, so if you can get away with more inital + vac....

I usually start by getting my total base lined around 34 to 36 with no vacuum hooked up and a med to light spring or a combo of the two, then with the vacuum advance I adjust to around 22 to 24 initial with full vac on an adjustable 10* vacuum pot then back my idle speed down adjust my mixture screws then recheck my initial timing back and forth, it usually makes the carb more adjustable and responsive.

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby mbrooks » Thu Apr 21, 2016 6:25 pm

It's the ford duraspark, dyno preferred timing was 32, my initial turned out to be around 10 or 12. Understand the high idle doesn't help, I'll try to turn that down tomorrow. Never checked it with the vacuum advance connected.

Another question, on the carb, since I prefer to run the floats a little lower to keep fuel slosh down, what happens if I plug the first emulsion and see if I can get a better draw at part throttle on accel. There seems to be a lean area right before the boosters start to draw. 5 hole emulsion from top to bottom would look like blank .028 .029 blank .031. HP factory was 28 28 28 blank 28. Ran good with the top at .026 but there was always that lean area. Rereading some old posts, it was suggested that the top should be plugged for whatever reason, they being surprised it worked with the .028 or whatever was in the top hole.

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby MadBill » Sun May 01, 2016 5:08 pm

Have you checked out the easy fixes first? The most common cause of an off-idle flat spot is too much transfer slot exposed at idle. Getting the RPM down via the idle speed screw, possibly cranking up the secondary idle stop a bit or drilling 1/8" or so holes in the throttle blades would result in the requisite 0.040" or less of slot showing below the TBs.
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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby GARY C » Sun May 01, 2016 5:43 pm

MadBill wrote:Have you checked out the easy fixes first? The most common cause of an off-idle flat spot is too much transfer slot exposed at idle. Getting the RPM down via the idle speed screw, possibly cranking up the secondary idle stop a bit or drilling 1/8" or so holes in the throttle blades would result in the requisite 0.040" or less of slot showing below the TBs.

That would be my first approach, I would not want to alter the carb circuits if I didn't have to. In the cpl of cases I have delt with getting the timing and carb settings properly dialed in solves the problem.

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby mbrooks » Sun May 01, 2016 7:20 pm

I had to get the mule car worked over, it has the a/f gauge. Put the 950 on it and it was rich, might have been alright for full throttle dyno pull but everywhere else was like the fat girl singing. I ended up putting some 110 unleaded in the car til I get things ironed out, shuts off like lights out. I did get the idle turned down with no problem to about 1000, shakes the shit out of the car, only weighing 2400# and lightly sprung. Got the 750 ironed out on the other car so just have to transfer the adjustments over and see how it rolls. Little different cam and vacuum should be the only difference so settings should be close. Take quite a bit of pavement to do a full throttle run. I'll check in later.

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby mbrooks » Mon May 02, 2016 3:21 pm

Forgot what this race cam stuff is all about. It did not like the t slot restriction and had to go down one size on the iab. Below about 2500 there better be a load on the engine or she is going to roller coaster. So all in, just peel em back and let the big dogs feed. Definite different driver than the same engine on a 110 LCA. Forward velocity is good on both. :mrgreen:

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby RevTheory » Mon May 02, 2016 3:25 pm

I either forgot or never heard how DV cammed that engine. I'm guessing she's a bit roudy :D .

You'll have to post up a video so us broke-asses can live vicariously through you, lol.

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby mbrooks » Tue May 03, 2016 1:41 am

Interesting thought. I'd have to do some figuring on that one.

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby David Vizard » Sat May 07, 2016 10:31 am

Got to visit at Chris Straub’s shop on Friday (22nd April) and was rather surprised at the extent of his operation. It seemed to me to be a very much ‘in the background deal. I was surprise to see how many products he made for big name companies. The best part of the visit though was that we got to talk cams and valve trains.
Although we had settled on event timing a few weeks back Chris held off with the actual profiles to be used as some new Glen Steyers profiles were just being finished off. Here’s the intake/exhaust profiles that will be used in the 427.
Lobe lifts 0.375/0.340
Duration at 0.004:- 302/309
Duration at 0.006:- 297/304
Duration at 0.050:- 240/248
Duration at 0.200:- 160/158
LCA 105
Intake Center line:- To be set up on dyno with Jesel adjustable belt drive.
So that those of us who are more used to seeing the seat duration quoted at 0.006 I have included both the 0.004 that Glen Steyers uses and the 0.006 used by most of the industry.
These profiles were decided on both for output and street reliability. Part of the requirements of a reliable hydraulic roller valve train is to use lifters that promote reliability. As far as reliable rollers for a performance setup Chris’s experience mirror’s mine. Unless you know what you are buying there is a very good chance you may end up with a set of lifters that just won’t take the loads seen in a 7000 rpm motor lifting the valves up to near 0.700. Chris’s choice here was to use the Morel lifters and that, from my own experience, was a choice I had no trouble going with.

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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby David Vizard » Sun May 08, 2016 8:12 am

Guys,
i should have posted this in the 427 thread. will fix.
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Re: 408 SBF with AFR’s latest 220 cnc heads – what power?

Postby mbrooks » Mon Sep 11, 2017 7:45 am

Update

Have an annoying rear main seal leak so the engine is out and getting a reseal. Only changes from the dyno are Holley 750HP and a Vic Jr intake.

Me and the neighbor had it out the other day and took it for a romp. The road has a pretty new chip and seal so traction was good which helps with the old tires. Made a 3rd gear run and the acceleration was awesome. With the car only weighing 2400# and the pull rod rear suspension the weight transfer is very good. You know the 1G feeling you get and all your innards move to the back, I've had a few cars approach that for a short time, usually at the top of the power band, or when making a turn on a road course. With both of us in the car, from the time I started the acceleration to when I decided things were unsafe that 1G feeling was continuous, I didn't mash the throttle but kept feeding it fuel and it just kept going. I was really surprised. The neighbor is an older gentleman who used to race dirt track motorcycles and probably other odds and ends, he let out a hillbilly holler like he'd won a pot of gold.

That was pretty good acceleration from the bottom of the power band up, didn't hit the rev limiter at 6500 or wherever it is at.

It also has that low rpm rumpity rump, have to be delicate on the throttle in turns, especially with the old tires. Going out making a turn the car hit the rump on the upswing and the car made a nice little 90 degree pirouette, neighbor thought that was pretty cool but totally unintentional on my part.

Lot of motor if it stays together.


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