Hey, I've got a pre-86 350 with a comp 280 magnum, ported heads with 2.02/1.6 valves, etc, and it runs smooth, idles around 1000 RPM, revs well with no misfires, backfires, or hesitation, but it makes no power I've pulled the distributor and double checked that it was in right, changed plugs, and now I'm stuck. Everything looks and sounds good, but it's got no *****, my Toyota Tercel seems to move out quicker and that's really saying something I'm thinking it has something to do with the ignition, but I really don't know where to go from here... any thoughts or suggestions would be great! Thanks

Engine was also rebuilt 20,000 miles ago

 

Bump, would like to get this fixed on my last day off for a few weeks!

 

Have you checked the catalytic converter. See if it get all nice ang glowy. If it does, you just found your problem

 

It doesn't have a cat. I sprayed some carb cleaner around the base of the intake and it does drop the rpm slightly, so I'm going to take it off and drop it back on with a new gasket, but can that really cause it to feel so weak? That's about all I've found.

 

No i had 6 out of 8 intake ports blown and mine ran alright. Give me some more info is it carburetor, fuel injected, or what. Make a video of you accelerating. Is it computer controlled or not?

 

I would definitely change the manifiold gasket.. A quick question though. Have you check the trans fluid lately? Better yet, give me an idea of how this car used to run before this started happening. Has it ran this way since you rebuilt it, or is it a problem that's just started recently. Does it still have an egr system? Just thinking more info might help find the problem.

 

Sorry, been busy with work and driving my suburban, but I'm still having problems. The carburetor I have on is a 1406 edelbrock. No computer control, it was a v6 RS swapped to an older model 350 with no computer. It used to pull about 10 times harder, now it sounds fine but doesn't get anywhere.. the acceleration is really bad. It puffs a bit of white smoke out of the breathers at idle but not a large amount by any means. My old 87 LG4 was still a lot quicker before I got rid of it and it was running on 6 cylinders.. I did change manifold and carburetor gaskets, no luck though. I don't think there are any vacuum leaks in the lines, most hoses are new. I'm going to throw on an old Q-Jet I picked up to see if that's the problem.. Question about the 1406 Edelbrock though, when should the secondaries be visibly open, even at WOT they don't really open enough for the secondaries to pop all the way open.

 

Underneath the cap and then the rotor, do you have the swing weights with the little steel springs?

 

Yep

 

Leeme guess:

Stock 70s smogger short block with deep dog-dish pistons, deep 70s smogger heads with HUGE smogger chambers and poor flow (such as 882, 624, or 993 castings) that needed valves ANYWAY so the shop just jammed the bigger ones into them which doesn't cost a damn thing extra but sounds GREAT in CL ads so it sells quicker, typical stock exhaust?

No wonder it has no power. No compression, no head flow, crappy chamber design, restrictive exhaust, poor match of cam to engine.

Other than being the same mistake people have got sucked into making since the mid 70s, it's a complete mystery. Maybe the space aliens stole all the power?

 

Replace the springs and make sure those weights will fly out when the distributor is spinning. You would be amazed at the difference if the spring tension is worn out. Besides, it is cheap and easy item to rule out.

 

Haha, good point sofakingdom. It does have headers and 3" back, though. I just have a hard time believing that it's such a dog, again, my 1.5L 90hp toyota puts it to shame.

@jwande: Springs were switched out, no difference.

 

Anyone? It jumps off the line but falls flat after. Timing light showed 60* at idle. Took out dizzy and reinstalled a tooth over, still the same. Moved plugs a spot over, no change.

 

Have you changed the advance weights and springs? Check timing and set it at about 12- 16 degrees, whichever lets it idle but shouldnt be more than 18. Then watch timing as you rev the motor. Does it sweep about 24 degrees by 2,500? If not, buy a weight and spring kit and play with it til you find the place where you get maximum grunt without detonation, while still maintaining about 16 degrees at idle. The key is in centrifical advance and the rate at which it increases. For your motor, on the street, you want full lead by about 2,800. From there, vacuum advance adds about another 7 degrees as manifold vacuum increases.

Also, what is your jetting like? Are you getting enough fuel or too much to the engine? Low power, without black smoke from the tail pipe, usually means insufficient fueling. I wont discount what sofakingdom said about CR, heads and cam selection. At any rate, play with timing curve and AFR. You should be able to get some kind of power out of it.

 

The plugs were getting fouled up pretty quickly, originally, but I leaned it out a bit and they look alright, haven't fouled up since.
Yeah I know the cam isn't matched to the heads, but I bought it as-is, assuming I'd be buying new heads down the road, but it feels way too weak for what it is. I previously had an LG4 and that hauled *** in comparison. This is just lacking power everywhere throughout the RPM range. The carb is a stock 1406 performer, comes lean for economy from what I've read.


At around what % throttle should the air velocity valves be wide open for the secondaries? Right now, they don't get pushed down by air flow at all, not even holding WOT for a couple of seconds.

 

i would recommend a holley 650 dp carb. im running a 79 vette 350 bored .030 with the same cam (comp 212) 041 fully ported heads.

 

Yeah, I mean it's not my first choice in carb, but it's what I have to work with for the time being.. When I can afford it, I want to pick up bowtie vortecs, an eb RPM style manifold, and a QF 650, that should match up with the cam a bit better.

 

Ive put the Performer 1406 on a few beefed up small blocks. One recently with the same duration/lift cam as yours. It hauls ***. Now just need to get the owner to buck up for motor mounts that wont come apart on a full throttle 1-2 upshift. Your solution lies in your AFR and timing curve.

So you know, aftermarket carbs generally come jetted a little on the rich side. They dont care about your fuel economy. They dont want people burning up their engines by running them too lean on a carb that they just bolted on out of the box. That would be very bad for sales. However, I have been able to make good power with Edel Performers, without changing jets.

Along with timing and jetting, take a look at your ignition KV. You need to be producing at least 40K to make good combustion. Also, did you degree the cam? Is it straight up? Did you perhaps get it one tooth off? They'll still run but not right.

 

I played around with the carb a bit after getting off the phone with edelbrock tech, it's a bit better, but I think the timing is still off and so did they. The coil is a stock delco, just haven't had the money to pick up another one, and didn't think I had to. Cam is straight up. So back to timing, what reasoning would there be for timing at idle to constantly show 60* (max of timing light)? Even after the distributor has been pulled out and set back in a few times over to make sure it was in right and not a tooth off.

As far as AFR, if I'm not rich and I'm not lean, I think I'm okay for now, right? Plugs are fine, just checked for fouling, no smoke out exhaust, carb doesn't spit out anymore.. so I'm thinking it's back to timing.

Just checked Edelbrock Tech FAQ--

Q: I purchased your 1406 carburetor and it is too lean, what should I do?
A: The 1406 is calibrated lean for fuel economy. In some applications, re-calibration of the carburetor may be necessary for optimum performance. See page 22-23 in the supplied owner’s manual (download here). Step # 23 on the calibration reference chart is a good starting point for enriching the air/ fuel mixture.



I'll probably get the 1455 rods and stiffer step up springs

 

Hmm, that's interesting info from Edelbrock tech. Not what I was told some years ago. Oh well. Learn something everyday. If your timing is sitting at 60 degrees regardless of moving distributor then youve got a very strange problem. What timing light are you using? Are you actually seeing 60 degrees with the balancer and tab zeroed? If your light is like my Ferret Instruments, it calculates actual timing and displays this number when first turned on. This is not necessarily accurate. You need to match up the timing marks at zero while reading the light's display. If its a typical dial back type then you need to line up the marks at zero with the desired timing dialed into the light. Your timing has to change when you adjust the mechanical referrence of the dist to the cam, period. It cant not change.

Follow my timing map as shown above,(16 -18 at idle) + 24 at 2,500rpm. This should be a good starting point for you.