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Big Block Not Being All It Can Be


phatTweaker
05-10-2005, 12:19 PM
Hi all.

I have a 1980 Camaro with a 454 I had a friend rebuild for me.
The specs of the engine is: standard bore and stroke, flatop pistons, oval port closed chamber heads with comp cams springs, retainers, and guid plates, and manley undercut race flow valves (2.19/1.72)..The cam is a solid lifter comp cam magnum 294S Duration @ .050'' Lift: 248° Intake / 248° Exhaust/ Lift: .595'' Intake / .595'' Exhaust, Lobe Separation Angle: 110°, ported ovalport perfromer intake, 750 Holley double pumper, 1.78" alumacote headers, 3000rpm stall converter, and a 12 bolt posi with 3.73 gears.

The engine sounds mean just tooling around town, but when I took it to the drags it was very inconsistant with times ranging in the high 14s to a best time of 13.57.

Some of the problems at the track was the engine would either stumble or stall after doing my burnout..Also During the runs about quater down the track I could see dropplets of gas comming up under the cowl induction scoop.

My questions are:
1. what is causing the gas to come out of the carb and up past the scoop?
2. Should I switch to a performer rpm or a victor jr. and an 850CFM Demon or profrom?
3. Should I go bigger on the headers?
4.If propperly set up and tuned how fast should this car go? My goal was high 11s.

thanks for any sugestions

chevytrucks92
05-10-2005, 11:12 PM
Well, the sputtering in the waterbox could be either too much fuel, or not enough OR your timing could be off. Timing will drastically effect your performance.

benchtest
05-10-2005, 11:42 PM
If you see fuel in the scoop, you've got at least two problems. 1) You're not running an air cleaner and the first backfire is going to burn your car down. 2) You may have an engine problem. You need to put a vacuum guage on it and see if it's steady or fluctuating. Cylinder pressure leaking up the intake will blow fuel out the carb. An exhaust valve not opening will blow back also. Does it feel smooth over 3000 rpm?

phatTweaker
05-11-2005, 06:45 PM
I think the timming is off because the car cranks slow after it's warmed up.
Your right no air cleaner..I was told by the guy that built the engine that it would be faster with out one.
Where should I place the vacuum gage..below the throttle plate or above?
It does feel pretty smooth over 3000rpm, but it sometimes bogs or stumbles before getting there....the time I saw the fuel come up from the scoop I was at about 4500rpm and it was cutting out big time..
The stumbling problems gets alot worse if I have to idle in the staging lanes for very long.. The temps never get above 180 so I dont think it's overheating..
Something strange I did notice is a few times I could hear a whistling noise comming from the engine..I'm starting to think I may have a vacuum leak.
Do you think 750CFM is enough carb for this engine?

thanks

AWP9521
05-13-2005, 01:20 PM
You may be geting a siphoning effect from the Float Bowl vent tubes as the air is rushing past the Carb. Try taking a couple of pieces of the apporpriate size rubber tubing about 4 or 5 inches long and insert them over the vent tubes and tie the other ends together with a tie wrap to the air cleaner stud if you still have one on the carb, make sure the tubing doesnt kink or is blocked by the hood so the Bowl Vents are not obstructed and see if that helps. You might also check out the float settings, they might be a little too high and causing the fuel to slosh out of the vents during hard acelleration, remove the plug screws on the side of both float bowls, if fuel runs out of either hole then the floats are set too high. Lowering the float level will also lean out the carb a touch and just may cure the stumble a little. Then again if your getting fuel slosshing from the Vents like described above then that would definitely cause the stumble too, even after a burnout.

If you are still stumbling then you may need to tune the carb, if you just bolted it on straight out of the box then that is a certainty. You need to look at the plugs right after a hard run without driving the car around after the run is over to see if it is running rich or lean, you may have to change the jets or even the acellerator pump cams or squirters to dial the car in. Holleys are a very tuneable carb and when properly set up will work quite nicely.

Not sure about the intake you currently have or the Performer RPM, I personally like the Victor Jr, they make decent power on the big end but because it's a single plane manifold you will loose some torque in the low RPM range, since you drive it on the street then you might want to stay with a dual plane design so you have the low RPM grunt and yet will flow decently in the high RPM's. Of course with that cam your running it probably done come on until at least 3000 anyhow.

Light car, big motor with lots of cam? Yeah if you can hook it up right and get the bugs out with some tuning you can possibly hit 11's

benchtest
05-15-2005, 09:53 PM
The vacuum guage is always on manifold vacuum. As AWP said, you need to check the basics and then move forward. Valve lash should also be checked.

500
05-18-2005, 09:16 PM
What distributor are you running ? What fuel pump ? Also, the stock fuel line is probably too small to feed a 454. An 80 camaro probably had a 5/16 steel line coming from the tank and you need a 1/2".

You might make the 11's. Your car is very heavy. Without slicks I don't think you have much chance.

I would put a 4" K&N air filter on it. Your rings and valve seats will thank you.

500

phatTweaker
06-07-2005, 11:28 AM
Stock distributor with curve kit and vacuum advance unhooked. Also stock fuel pump and line.
I havent had the vavles re lashed since it was built..I'm a lil nervous to mess with it myself as I dont know much about mechanics so I'll prob take it to the local speed shop.

thanks

500
06-07-2005, 12:09 PM
Stock distributor with curve kit and vacuum advance unhooked. Also stock fuel pump and line.
I havent had the vavles re lashed since it was built..I'm a lil nervous to mess with it myself as I dont know much about mechanics so I'll prob take it to the local speed shop.

thanks

You need to get someone with a distributor machine to check the curve. The advance kits for the HEI dist are a joke. You need to end up with 20 degrees at idle and 36 or 38 by 2500 crank rpm which means the dist only advances 8 or 9 distributor degrees. The limit slot will have to be welded up and then filed on until correct. It's a lot like running an engine on the dyno. Do a run, make some mods, do another run , etc until you get it right. Also the HEI module doesn't do good above about 5500 rpm. Even then you have to close the plug gaps to .030". You can use the HEI dist pickup coil to trigger an MSD ign.

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