I have a 454 bored .30 over with 10.5 pistons. I'm running large oval port heads that have the recomended comp valve train in them. The cam I'm running is a 268 extreme energy. I have a edelbrock 2-0 intake, dynomax headers, 3" exhaust with flowmaster mufflers. An accel blue print HEI distributor, with an accel coil and wires. I'm also running a 650 holley carb. The problem I'm having is the motor has NO power. Like it will not even spin the tires on the dirt and I'm running 4.10 gears. The compression is fine (180 psi). Fuel pressure is fine (6 psi). Timing (4 degrees) vacuuum advance and mechincal advance are working. I tried swapping on a q jet carb with no avail. I'm running 110 octane. It's hitting on all 8 cylinders, and it seems to have good response, but when you put it in gear and gas it, nothing is there!! It does have a sporadic backfire in the exhuast at idle, I was thinking maybe I had a bad valve but it seems like it would show up in a compression test... And it's strange if you unhook the pcv valve the backfire gets worse, I thought maybe it was running too lean but I bumped up the jetting by 6 sizes but it didn't make a difference. Any help would be very greatly appreciated.

Try advancing your timing to around 10-12 initial and see what happens. If you're running 110 octane, you should have no trouble with plenty of advance.

4 degrees initial is lower than I've ever run on anything.

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Chad Landry
TC Member #643
ACES Member #04556
'68 El Camino, 357, L31 Vortec heads, 700R4, 3.55 posi.

Well...I found out it runs best about 35 degrees initial timing!! I thought maybe my timing tab was off, (nope). Or that my timing chain skipped a tooth, (nope) If I run anything less that about 35 degrees it backfires and if I advance it that far it smooths out, BUT if I try to restart it the starter drags, Any suggestions?

[This message has been edited by Josh454 (edited 04-28-2002).]

35 degrees initial is to much. It will be real hard to start. Maybe even try 16. Is this distributor vacuum? Try hooking it up to manifold vacuum. If it were mine I wouldn't run anything smaller than a 750 on it.

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KJ
I don't make the rules I just play the game!
1968 Chevelle (http://home.attbi.com/~kjpartzman/kjcars.htm)

If I try to run anything under 30 degrees initial it backfires out the exhuast, I've tried different mechanical advance springs and weights. My distibutor is an accel blueprint with an adjustable vaccuum advance hooked up to ported vaccuum. I'll have to try manifold vaccuum but right now the front of my motor is torn apart where I checked the timing gears. (LOL)

Thanks,
Josh

[This message has been edited by Josh454 (edited 04-29-2002).]

Sounds to me like a timing issue also. Try moving the distributor gear over one tooth, the reset to about 14 degrees initial. By the way, you'll know if you go one tooth in the wrong direction. It won't run at all. I also think you need at least a 750cfm carb.

One tooth off won't do anything. That can easily be compensated by adjusting the distributor position. Check for vacuum leaks while you're at it. That exhaust "popping" sounds like a lean miss.

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MalibuJerry350
TC Member #1279
Original owner '70 Chevelle.
576,000+ miles on car.
Hey, if it's got wheels, DRIVE IT!
My Chevelle: http://hometown.aol.com/erie614/myhomepage/index.html

Well I just got in from pulling my heads off, I know for sure know it's not a bent valve!! Man, I'm just about to get rid of my car and buy a set of golf clubs.

Josh,

I too had a similar problem with my 454 popping through the exhaust. After some advice from TC and some electrical and mechanical help I discovered my plugs were fouling due to several things. The 850 CFM QJet power valve spring had to be changed to a weaker spring (due to my cam, this change also allowed us the ability to adjust the A/F mixture ), the jets had to be replaced with smaller jets, the metering rods adjusted and last the ballast resister had to be removed since I was using a Mallory promaster coil. The initial timing is 16 and 40 is the total. The car runs great now and can easily roast the tires. Good Luck.

I can't believe you yanked your heads. http://www.chevelles.com/forum/eek.gif
Are you sure you have the timing light on #1?
These guys are right, a 650 is too small.
If you buy a new carb, get an 800. A 750 should be good up to 6500 rpm or so, but an 800 removes all doubt.
A backfire means the there is unburned fuel in the exhaust that is ignited by an exiting exhaust flame. This could mean your plug wires, plugs, distrib cap, rotor, coil and or wiring are the culprits. Check them 1 at a time. Make sure you have 12 vdc to the HEI.
Since you have the heads off, check for TDC on #1. Be sure the harmonic damper timing mark is ok. Check your firing order on your wires. A buddy of mine has a red face right now because of this. He was timing the car for two days. I went over to "help". He had 6 and 7 crossed. DOH!

Hope this helps.
Don't give up!

Dave

Hehehe, my buddies razz me that I pull a motor to change my oil, so it's no biggie. Besides what better way to check for TDC? LOL, anyhow the mark on the balancer does line up. My wires, cap, rotor and coil are new, but wouldn't be the first time I got a defective product for sure. 18436572 right? I think I'm gonna try to degree my cam to make sure something isn't right in the chain. (SSHH I bought a cheapie)

Thanks,
Josh

Have you considered that your lack of power could be due to another component of your drive train not working properly? Such as your transmission? Just an idea.

Mike

Is there a sure fire way to check the trans? I've checked to make sure the rear brakes aren't locked up. I also recently installed a Detroit locker, and everything looked/seems to be working good. The trans fluid doesn't seem to be burnt and it's shifting. What are some other things I could check for in the trans?

Josh

Josh, I'm just suggesting to check the trans since you say that your motor seems to be running fine, except for the backfiring(which isn't good). I would check the fluid level and test to see if your converter is stalling at the right speed. This is assuming it's an auto, most likely a turbo 400(I hope). I hope I'm not steering you down the wrong road but if you can pull your heads off to check your valves, I think you can figure out how much timing your car needs to run right. If you can figure out how to get somewhere between 30 and 40 degrees total advance, the thing should make some kind of power.

Mike