68FirebirdAP

iTrader: (3)

So, I've got a SBC 406(400 bored .030over) that I built a few years ago. It is in my truck and really isn't very peppy. I dont really have a budget, but I am trying to spend as little as possible while still making the truck faster.

The truck weighs just under 6000lbs, I have a 4L80E trans, 4.10 rear gear and 28.5in dia tires. It has a 650CFM double pumper and shorty headers 1.675in tubes to 2.5in exhaust. Pertronix Distributor with MSD coil.

Engine specs:
Bore: 4.155in
Stroke: 3.75in
Dish pistons: 21cc
Head Chamber: 64cc
overall combustion volume: 101cc (including gasket and piston down bore)
Compression Ratio 9.26:1
Intake Valve Dia:1.94in
Exhaust Valve Dia:1.5in

Head flow(cfm)
Intake Exhaust
.050 40 .050 25
.1 70 .1 49
.2 139 .2 105
.3 190 .3 137
.4 227 .4 151
.5 239 .5 160
.6 290 .6 162

Cam: SUM-1103
Duration @ 50 214/224
LSA 112

It gets decent gas mileage(18mpg highway), but really lacking power off the line...

Any mod suggestions are appreciated.

68FirebirdAP

iTrader: (3)

2 more notes:

-I dont want to have to use higher than 93 octane(pump gas)
-heads are aluminum

pancherj

You can certainly run higher compression than that with 93 and aluminum heads...but the $$ might not be worth it. Long tube headers would help (I would go right for the 1 3/4" primary headers with a small collector...3" if you can find them for your vehicle).

You didn't mention what intake? What does the timing curve look like and are you using vacuum advance? I don't like the cam choice. If you have money for it, something in the upper 220's duration, less split and a tighter LSA would be better. Your fuel mileage will suffer some, but it will hit harder down low.

Lastly, the 4L80E has a tall first gear and you are running a pretty tall tire. More gear would help, but again your MPG would suffer some. What converter are you running?

68FirebirdAP

iTrader: (3)

I cant remember the exact intake, but it is similar to the Edelbrock Performer RPM intake. I will check if there is Vacuum Advance tonight, I dont think there is though. I don't recall what the timing is set at right now.

For cam suggestions, what do you think about Lunati LUN-10120301
http://www.summitracing.com/parts/lu...make/chevrolet

For the trans, I wanted something fairly stout, especially with how heavy the truck is. The truck is 4x4 so 4.10 gears front & rear. Additionally, the front and rear axles have different track widths, so the truck came with custom rims with different offsets. The only street tire I could find for the 16.5in rims were 28.5in dia. Any higher gearing will make highway cruising at a farily high RPM(right now it is 2600rpm @ 70mph).

pancherj

If there is no vacuum advance so that it runs a lot of timing advance down low, it will be sluggish. That cam you linked to is okay, but the Voodoo series is a more modern lobe. I'd go with a voodoo of around 280 duration (it is a 406... That's a lot of cubes to feed).

uxojerry

Have the heads and intake ported or go for bigger heads like an afr 210.

mr.beachcomber

Just some observations based upon what you've told us so far:

1) You need a distributor with both vacuum and centrifugal advance. Vacuum advance is important for street vehicles especially for stop and go driving. You also might want to check that your distributor's initial timing hasn't retarded over time. (Because of the CW rotation of the distributor shaft, a loose distributor clamp will allow the distributor housing will rotate in the same direction retarding the timing.)

2) The current intake and exhaust valves are too small to feed and engine that large. If you can't afford new heads with atleast 2.02 intake and 1.6 exhaust valves, try 1.6 rockers on the intake side to increase your flow there.

3) With an automatic transmission and stock stall converter, I would ditch the DP in favor of a 750 cfm with vacuum secondaries for a smoother torque curve and better pick up. (I've never seen a DP work well on the street despite many years of trying. It's better suited to a lightweight race car.)

4) The Lunati cam sounds like a step in the right direction if you get heads with enough flow to work with the cam. I'd check with Lunati tech to see what they think will work with your combination.

Good luck with your project!

warriorcustoms

iTrader: (10)

A Straight Pattern cam like the Lunatti is a step in the Right direction because they Make More Torque!!!
Heres a cam Im gonna use in My next Motor... Itll be a 396 stroker Vortec or LT1 for a 4x4...
http://www.superchevy.com/how-to/0607ch-383-chevy-engine/

The straight pattern 206 @.05 .480 lift on a 110 cam makes 495ft lbs of TQ
On My build Im gonna use 1.6 roller rockers though to help TQ even More
That said a straight pattern cam close to the split pattern You Already have is this one...
http://www.jegs.com/i/COMP-Cams/249/12-206-2/10002/-1

But to get the lift up where it needs to be get some 1.7 roller rockers & You should make More TQ for off the line Acceleration But like others have stated You need a distributor like an HEI with Vac. Advance plus Mechanical Adv thats set up properly to work good on the Street... Then if You can do all the work Yourself get the Compression to 10.5 to 1 with those aluminum heads!!! A 1.94 valve will flow right around 260 to 280 cfm if the ports good so I wouldnt bother with heads Unless You think it Needs More afterwards Then save up for something like an AFR 195 , Dart Pro 1 200cc 210cc or 215cc with 2.05/1.6 valves or even more flow on the same heads would be 2.08/1.6 valves like My Dart Pro 1 200cc heads that have been ported to 208cc with 2.08/1.6 valves and flow 311cfm those are goin on a 396 stroker LT1 nitrous motor...
Ohh You may also wanna try a lil bigger carb too... I had a sweet dual line double pumper on My 355 I built for an 84 Z28 that was bench flowed ported divorced choke horn type of carb that flowed in the 730s that had 4 corner idle screws & never had an issue with it on the street
Just remember the Cam , Heads & Intake RPM range ALL Need to Match & Work Together!!! IF You want more Duration theres a 230 @.05 .480 lift 109 cam that works great in 406s & a 1.6 roller rocker helps get it in the right flow spot of the heads...

warriorcustoms

iTrader: (10)

Also get some Long Tube headers!!! 1.75 into 3in would be good then atleast 2.5 Ypipe into a 3.5in single or just 2.5in all the way out if you like duals... But remember this... A single free flowing exhaust system Makes More TQ & is better for Most Street Cars & Trucks... My S10 Ext Cab with an LT1 has 1.75 into 3in swap shorties to a 2.5in Ypipe to a 3in single with a Magnaflow muffler no cats & it does great... When I put the Ported Aluminum heads on & swap to that same 206 @.05 .480 110 cam I will get the single Upgraded to 3.5in because its right at that cutoff where its at with a single 3in... Hope My 2cents Helps!!!

wht/73

All good advice mentioned above.
Heads do "seem" kinda small , but I've been told my AFR 195's on my 406 are small but they seem to work ok.
Also, a converter change might be in order also.
I'm days away from installing a 80E in my Nova and just had Circle D (who is down by you) build a custom 5C converter for it.
It should have the same characteristics as the 8" ATI treemaster that's in my Nova now with a th350 which BTW, has almost the same gear ratios as the 4l80e!
TH350 2.52 1.52 1.00
TH400 2.48 1.48 1.00
4L80E 2.48 1.48 1.00 0.75

So the 1st gear change for me would be .04 not noticeable
2nd gear change for me would be .04 not noticeable
400 exactly the same!

Kevin Roche

Before you spend slot of money, d-port your exhaust in heads and 1/4" flange to headers, 1.6 rocker arms is plus with 310" cam rise 106 & 110 degree centerlines 2.02 & 1.6 are required, and Holley with 50cc pumps using 700 main body and 750 base plate then taper the throats and a MSD 6A choose equal length headers

wht/73

I still say converter change would be in order to help it out of the hole.

Kevin Roche

From my experience with 3 ton vehicle, use a Holley 500cfm 2 barrel with a 50cc pump, use the big lobe plastic cam lobe for accelerator pump arm off a 660 center squirter, and make sure it has movement all the way through the throttle range. That will get rid of the sluggishness that Holley's have. Believe me a 500cfm will work perfectly, just use the 2b to 4b adapter upside down on your 4b manifold. If your pump nozzle screw has a hole in it, restrict it with 3/4" long wire half the diameter of the hole (.030), this keeps the pump pressure up when you use weaker pump spring, with a 50cc pump.

ironmanLS1

iTrader: (9)

Disagree with the MSD 6A reference. I'm a big fan of a solid HEI set up. I don't know what Pertronix comes with but usually a couple good hard parts in an HEI make for a respectable ignition. In my bracket car, I have switched from an HEI with a heavy duty module and high voltage coil to a full MSD set up, MSD billet distributor / 6AL and seen no performance difference. It ran a little smoother with the MSD but track performance was the same. Just my .02.

And for carb for a street vehicle I always preferred a 750 vac sec, 3310 carb.

Kevin Roche

400 Mods suggestions​ is a 6000lb vehicle and on a budget. I believe a 3310 is 780cfm and if it is track performance your looking for, a MSD Programmable Digital-7 Plus
(P 7530) and a Profogger w/annular discharge nozzles
sure does the 650HP trick.

ironmanLS1

iTrader: (9)

Yes, my recommendation is budget cheap and gets the job done.