4bbl jetting and cfm??

[Ortie666]

Hey I was wondering what size 4bbl people use on these engines, and the jetting in them,??

[Arns85GT]

What I did to the 2.8 Fiero v6

Here is the running gear that was dyno'd.

2.9 liters (.050 overbored)
ported heads
re-cut valve seats
roller-tipped 1.6 rockers
Edelbrock Torker II intake
Holley 390 carb
Blazer distributor set to open vacuum
ported exhaust manifolds into 2.5" mandrell bent
Magnaflow muffler
MDS coil
Power Pulley
11* initial advance with 36* overall advance

.025 shooter with 19 cc cam NOTE: the cam had to be modified. see below
4150 secondaries conversion kit with .052 jets on the secondaries (stock is a .056 metering plate)
.512 primary jets (standard .51's are actually .50)
plain secondary vacuum advance spring
check ball in vacuum removed to open secondaries quicker

The car had a bad bog problem with the 390 cfm carb. Here is the fix.

In consultation with Scotty McLendon, I found the final answer to the chronic bog. It completely solves the problem and the car now has a whole lot of snap from any rpm. The answer is reducing the shot. I took the orange accellerator pump cam (19cc) but the white cam will do about as well. With the carb off the car, you remove the screw holding the cam in place. You then pivot the cam on the armiture so the #1 hole on the bracket is between the two holes on the cam. You then mark the cam with a magic marker and remove it. You then drill a hole the same size as the other holes through the spot you've marked. You then install the cam using the new hole on the #1 screw hole.

You then have to adjust the accellerator pump arm. If it is the metal one, you bend the tab until the arm returns to zero setting. If you have the plastic arm, you tighten the adjuster screw until there is some slack (very little) between the accellerator pump arm and the pump lever.

You will then have immediate throttle response with an overall shot of about 1/2 to 2/3's of the original cam. In my case, the new hole was about 40% of the distance between the two original holes. My shot is therefore reduced from 19cc to around 12cc.

Believe me when I say that this fix changes the response of the engine very noticably.

The plain secondaries spring that came on the carb seems to work well.

The engine dyno'd at 132 peak hp at the wheels. With the HO GM cam, it had a flat hp curve area at 130+hp from 4500 to 5800 rpm.

Hope this helps

Arn

[Ortie666]

Thanks, i may try that, i actualy finaly got no bog, i have a 450 tunnelram carb on it with 60s in the front and a .025 shooter, i am thinking of getting a .058 for the front and mabye reducing the squirter size, but now that i got it working a bit better im having problems with the topend clattering, kuss when it revs to 6200 i think some of the nuts loosten them selfs off..