I haven't seen any mention of tuning..... Did you get WB AFR data on the dyno, how did it look? How about your timing? I would go for a tuning session with Dean before I start replacing parts. Although it does sound like your single 2.5" would be the biggest restriction.

What rockers are you running?

Joe

 

Air Fuel was dead on. Never have had a timing light on it but if the dist is turned the slightest bit the car won't even start.

SStroker there wouldn't be a way to get one in there the way I would have to run it.

 

I would try adding timing rather than taking it away. Lowering the timing will cause it to be to low to start the engine. Raising it will cause more knock maybe, and might increase power. Engines can be very sensitive to timing so you might want to look at that.

 

You're down on power for sure. I was running 13.00000001 @ 108 with a 406 in my old 79 Malibu on street radials (2.2 60-foot) through a marginal TH350 trans with 2.73 rear gears using a LOT milder cam, heads and intake than you are.

I think you are giving up something to exhaust restriction but I'd be surprised if it's more than 20 HP. A small restriction for a short distance is NOT the same as having small pipe all the way back. Doesn't work like that.

You need to TUNE, pure and simple. What's your cranking compression? If it's below 165 or so, you have probably miscalculated your compression ratio or possibly gotten the cam installed "off" by a good bit. Is your fuel pressure steady all the way to redline? If not, that'll kill power for sure.

Ignition timing. What is your total advance? It should be around 34-38* for best power. Setting advance for what "feels good" or makes the engine easy to turn over while cranking is almost certainly not going to make best power. KNOW what your ignition advance is at all RPMs, don't guess.

Carb jetting and such. Just a wild guess, but did you have a low profile air cleaner on your motor while doing your runs? Try running with it removed and see if you get a much higher number. Not saying it's for sure a problem, but I've seen it before on tight hood clearance cars- like a 3rd gen with a stock hood and a tall intake (RPM air gap). Limiting the area above the carb can make WACKY things happen to fuel metering, besides just being a dead restriction.

More carb stuff..... vacuum secondary carbs can have problems getting the secondary bores open fully depending on a LOT of different things, including the fact that Holley puts much too stiff a spring in the secondary throttle diaphragm as supplied from their factory and that many people never get the primaries wide open due to limitations in the car's throttle linkage! While making a dyno run it's not a bad idea to manually force the secondary throttle wide open by hand to see if it helps (depending on whether they'll let you get near the motor while making a pull). You'd be surprised the number of times I've been stumped by a throttle that isn't opening fully. Jetting on an out-of-the-box stock Holley will, surprisingly, probably be pretty darned close for making max power.

Valvesprings. Did you use the ones recommended with the cam? Roller cams require MUCH stiffer springs than a flat tappet cam. I'm not sure if you got AFR heads that are designed for use with roller cams but I throw this in for what it's worth. Trying to run flat tappet springs with a roller cam will leave you scratching your head why you aren't making any power over 3500 and can drive you BONKERS looking for a reason. It's not really valve float in the calssic sense, more like gradula loss of positive valve control as RPMs rise.

A few things to think about. Hope it helps or at least leads you in the right direction.

 

good post

 

if you miscalculated your quench hight or something with the compression and a stroker with a relativly large cam (not a 401 or 406 - whateveryou have) it can bleed some off and your even lower.

Perhaps you should show us your dyno chart?

ps you have a baby cam

You probobly have a good 40hp to be gained in tuning and exhuast and little things. another few in rockers...
I really cant see much more from that cam since i cant see you revving very high on a 40x and hydro roller (HR right?). maybe i'm wrong.
TQ is there though

I'm personally shooting for 450FWHP or about 35-360 RWHP with a high stall and auto & steel driveshaft with a 236/242 cam with more lift and most likely steeper lobes revving to ~6400 rpms with heads flowing at 275cfm @.600 lift and long tube headers with true duals.
If i miss i'll just turn up the spray

who knows
we'll see what happens

 

trey your not shooting for much....
fwiw, i think im right around there with my stock shortblock, diy heads, and 230/236 cam.
jeremy

 

I am looking at my exhaust as the problem. Maybe I'll be one of those people that gain 50hp from a restrictive exhaust. I remember reading that no matter how long or where you put a restriction the motor will see the whole exhaust as that size. That would mean that its breatheing through a single 2.5" exhaust.

IT doesn't matter which way the distributor is turned, if it is moved the slightest bit, the motor will start shaking then eventually die. And it will NOT start unless it is returned to where it was before. So if it is timing I guess I will have to do without the power because I like being able to start it.

I really don't see how the cam could be that much of problem. Tehre was a 96 LT1 there that with a 218/230 cam and stage 2 heads made 380 hp at the wheels.

Somewhere along the lines you guys got the impression it was a stroker, its not its a regular 406.

I can't remember all the numbers but I remember buying forged pistons that would make 10.5 with a 70cc head. I bought the 68cc heads.

I am not sure about the secondaries opening, someone mentioned a Holley carb this is a Edelbrock do they have problems as well?

I don't see why I should try rejetting the carb if the Air/ Fuel was dead on throughout the whole RPM range.

 

have you looked at how the distributor is advancing the timing vs rpm?

 

BTW a 406 is a .030 over 400. The 400 is kind of a "stroker" because that's where the 383's crank came from, the orginal strokers were using 400 cranks with the main journals turned down.

If your A/F is fine then it's timing. You really need to get a timing gun on this thing and see where it is.

Bret

 

True but that is the stock crank stroke for a 400. It is only considered a stroker crank when it is put in a 350 block.

 

if you have no adjustment ability in your distributor, you have something wrong. did you install that cam straight up?
jeremy

 

There is adjustment it will just run like sh*t and be VERY hard to start. Yes the cam was installed straight up. Where it is now it fires on a half revolution and idles wonderfully, with the fans on in 90* heat it wouldn't go over 195*.