Well last week I took my 86 Z28 to the new dyno right up the road from my house. Made the first run and put down 287 hp at the wheels and 337 ft lbs torque.

The second run....:
He started out through the gears all sounded good got it into third and starting bring the rpms up then hammered it and got it up to 5200 let off and started to put it in neutral when BAM car jumps back off rollers. We had no idea what happened i looked under the car and saw gear lube pouring out the rear end. so we jacked it up and pulled the rear cover, turns out the pinion nut backed off and jammed itself into the posi unit which locked both wheels.

Still kind of dissapointed with the HP was expecting atleast mid 300's. The last run showed 290HP. The motor specs are as follows:
406
Dart iron eagle 200 cc heads 64 cc chambers manley swirl valves
xe274 cam flat tappet
30 cc dish keith black pistons on 5.7 eagle rods/eagle crank
1.52 comp roller tip rockers
edelbrock eps intake
demon 650 mechanical speed demon
brand new mallory distributor
Holley mechanical fuel pump rated for 450 hp
TH350 trans with holeshot 2500 stall
lont tube hedmans with H pipe and 2 1/2 duals

what do you guys think... kind of low hp.... im not real sure where my total timing is at but the base is at about 14.


Link to video of dyno run when rear end breaks.....( right click and save as)
http://www.angelfire.com/ab8/camarokev03/car.mpg

 

pic of car apart

 

second run dyno sheet, the guy said when the car jumped off if must have messed up the torque reading

 

first dyno run sheet

 

ouch.
Time to get a 9 inch or 12 bolt.

as far as power.

u have a rather small carb,intake,low compression??,small camshaft.

 

is it POSSIBLE to get less than 300 out of a 406?

 

No mention of dyno air fuel ratio?

You must adjust timing and carb jetting, don't expect it to be optimal out of the box.

What is your compression?

 

no i dont have an oxygen sensor bung in my exhaust, and they didnt have any kind of attachment. The compression is in the low 9's i know that dosent help but i didnt figure it would hurt the hp numbers by that much. I havent messed with the jets or anything, i was thinking about putting in 50 cc accelerator pumps instead of the 30cc ones.....

 

I calaculate your compression at 8.7:1 with a .039" head gasket, pistons sitting .025" in the hole at TDC (stock, no block decking) and a true 64cc for the combustion chambers. I can send you the spreadsheet if you like (email me). That's pretty low for that cam. A set of Keith Blacks with the smaller 18cc dish would get you up around 9.6:1, which would work better with that cam.

I wouldn't worry about the HP reading too much. You're talking about a Mustang dyno and they usually show lower HP readings than an equivalent Dynojet. My brother had a Miniram injected 400 in his 87 GTA that would run 13.0000000001 @ 110.5 on street tires and it only showed 260HP on a Mustang dyno.

 

Next time you're up there ask the dyno operators what bone stock 6speed LS1 cars generally hit on their dyno. If I recall correctly with the way Mustang dynos read they're usually down nearer to 275-280rwhp. Figure you hit 290 on the MD, I'd think on the dynojet you'd be in the 310rwhp+ range, which isn't bad at all with an auto...

I bet you got 10-15 rwhp or more tied up in that performer intake too, I would think the Perf RPM would be much better on a 406...

Unless I'm mistaken CarCraft of CHP did a 406 buildup with mid 9s:1 for compression, a Perf RPM w/ a 750cfm carb, the Dart Iron Eagles, and the XE274 and got 450hp on a engine dyno (with few/no accessories). I bet you can upgrade the intake and get it tuned well and hit the 350rwhp range on a dynojet...

You need to get some A/F ratio numbers on the dyno though and not just start guessing at changes to the carb...

 

I would change to an RPM airgap and maybe try a 750 carb.

 

-carb tuning or sell the demon and get a standard holley 750dp
-bump the compresion up to about 9.5:1
-rpm air gap if you have the hood clearance

those all sound like good ideas to me

 

when i called demon i questioned them about the 650 carb and they told me that it would be plenty.... so i dont know the carb seems to work awesome real smooth ill have to see if its going lean or not though. as far as the intake i know that isnt helping things any, i was planning on going with a dart intake to match the heads i think they call it kool can or something like that its pretty much an air gap design.

 

Yep - done that. I still have mine, and I can't complain a bit about it's off-idle performance. I'm up to #80 secondary jets and #74 on the primary side, but it idles rich, and I just can't figure out how to lean it out. Still working on that.

Something's holding yours back. Yeah, your HP number is a bit low, but you should see more torque than that for sure!!

I've got basically the same setup as you except for pistons,intake, and I have the 70cc Iron Eagle heads and it was dynoed last year - but - keep in mind it was an "engine" dyno, not a chassis dyno like you had.

I'd still expect 320 HP or so at the rear wheels. Makes me want to get mine chassis dynoed to see what happens.

Try advacing the timing a bit further to see if it helps. Believe it or not, I have my initial timing set at 19-20 degrees and it runs best there...

Good luck with it, and keep us posted on how it's going! !

 

As Damon mentioned, your compression ratio is probabily much, much lower than you think. I get 8.66:1 assuming a 64cc head.

The head volume can easily be larger, around 67cc's resulting in even lower compression. This motor needs a Blower... LOL

A 406 ci motor with a fully divided dual plane manifold can tolerate a much bigger carb to get maximum power.
If you can get your hands on a 850 or 950 try it.

I would bolt a 6-71 on it with two 750's and 8-10LBS boost.

I built my 406 with 22cc dished pisons on a true 0 decked block with measured 64cc heads for a cr of 9.8:1 (conservative yes but plans include some spray.)

 

yeah i know a supercharger would be sweet but i dont have the good forged pistons or anything they are just the keith black hypertectic or whatever..... do you guys think some 1.6 ratio rockers would help any or would that just bleed off even more of the little compression i have? I was going to get a set of 1.6 full rollers when i change the intake manifold.

 

KB hypers will stand up just fine on a supercharged motor with the correct boost for the fuel you're using. they are plenty strong. They do require much larger top ring gaps when used for either supercharged or NOS.

1.6 Rockers are not going to do anything for you. You have a fundimental flaw in the combination. Low compression ratio.