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

[RevTheory]

Yep! Badass. That's going to be quite a little hot rod

[David Vizard]

Rev Theory,
you are not the only one who cannot wait to see this Cobra in action. I always reckoned this is a real mans car!!!!!
DV

[BigBlocksOnTop2]

That will be a hand full!

[427dart]

Very nice Cobra! This would look great on it too!

[groberts101]

Very nice Cobra! This would look great on it too!

lol.. that would look great in just about anything! Chevy.. datsun.. trike.. whatever.

[427dart]

It's running VERY well and just need some good Spring type weather to enjoy it more!

[mbrooks]

Well, fired it up today! Alternator belt was too short but I couldn't wait till the weekend. So a ride report will have to wait a few more days.

I think David hit a home run with this combination. I'll try to explain my observations in comparison to a couple other builds of similar c.i. I had a 406 3.80 x 4.125 with solid roller from Mike Jones that was a good runner also, this one was very quick, unfortunately other complications relegated this to a dark corner in leu of the current 408 with which I'll compare the DV 408.

The other 408 uses AFR205 heads and the cam is on a 5* greater LCA, 3* less intake duration, 6* more exhaust, and less lift on intake and exhaust though exhaust was close, than the DV engine which uses the 220 heads.

Off idle the DV engine is pretty snappy, the cylinders hit real hard and sounds like it has more compression, kind of choppy, up to about 3000 rpm then it changes tone and kind of smooths out would be the best way I could describe it. There was no detonation I could hear off idle with last years crappy pump fuel even though the idle was too low, and picked up off idle real well. Not what would I would expect with the narrower than norm LCA that seems to be spec'd so often. I was expecting the DV engine to be a little soft off idle but that wasn't my observation.

The other 408 never did sound like the MJ cammed engine, sounded like there was too much exhaust duration off idle and was never a snappy as the solid roller engine or the DV engine for that matter. Maybe the guy thought I was a sound man.

I'm happy! Might have to order another cam.

I'll hopefully be back with a ride report soon.

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[RevTheory]

I bet that car is an absolute kick in the ass to drive

[wyrmrider]

luv that front suspension but IDK about the rigid radiator "hoses"

[mbrooks]

I bet that car is an absolute kick in the ass to drive

It is! They stick way past the comfort level if you're not accustomed to it. The guy that designed them has a pretty good racing and technical background, good camber curves, low roll centers, you can adjust the front and rear sway bars from the cockpit with LED readout to tell you where they are at is pretty cool (think this was copied or similar to the Mercedes LMP car). The frame tubing is CNC cut on this one, real square and flat and uses shear panels throughout. I have an old alignment machine and I'm always amazed at the setback which was only .020 at the front spindles on this last alignment. Lot of interesting stuff about the car, which makes them kind of complicated and costly because of the bespoke parts, but well designed to withstand abuse, the A arms are 1.5" tubing. The tire sizes are same as the Dodge Viper.

Fortunately I have done everything I wanted to do, unfortunately the clutch disc is not releasing at the moment, parts mismatch or something overlooked I imagine. So delay again. The engine still sounds good!

[mbrooks]

luv that front suspension but IDK about the rigid radiator "hoses"

Rigid only on the long run, they are connected by hose to the radiator and thermostat housing.

[RevTheory]

I used to work for Silver State Motor Cars back in the early 90s and they did Cobra kits. About once a month, the owner would let us take them out and cruise the Vegas strip. Although they weren't as powerful as yours, they were still a blast to drive.

[mbrooks]

Finally got the car out today. All the little gremlins and bugs taken care of. Glad I switched the dizzys out, the vacuum canister makes all the difference in streetability and being a horrible loud beast. The engine pulls about 15" vacuum at cruise from the never pointing at zero vacuum gauge, so may be a little lower or in that neighborhood. Put my HP750 on it from the other 408 and this one is a little lean at the cruise rpm, doesn't know wether to accelerate or decelerate, so some tuning is on order. Auto ignite after shut down is going to be a pita, it idles at 1200 with the vacuum advance so I might be able to lower it but I don't think that is going to do it but I'll pursue that one. So a little carb tuning and fix the run on and should be good to go, maybe some better gas for sure. Definitely not hurting for power, hits about 2500-3000 and takes off, didn't have enough run off to floor it. We'll see how long the production block lasts.

DV, thank you.

[MadBill]

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.

[Calypso]

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