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Discussion Starter #1
OK gents...school me a little.

I recently did a cam swap to something much milder.

Cam Style Hydraulic flat tappet
Basic Operating RPM Range1,500-4,000
Intake Duration at 050 inch Lift 204
Exhaust Duration at 050 inch Lift 214
Duration at 050 inch Lift 204 int./214 exh.
Advertised Intake Duration 262
Advertised Exhaust Duration 272
Advertised Duration 262 int./272 exh.
Lobe Separation (degrees)112

I put on a 4 bbl edelbrock 1407 with electric choke (that I rebuilt myself... so that can be an issue) and intake. Reattached everything but now I seem to have issues. The car sounds as though it's skipping a beat randomly. I checked the plugs with a plug light attachment and they all seem to be firing normally. I've used the dizzy (Pertronix flamethrower and coil) before with my old 2 barrel and it ran fine (didn't have this problem). I checked the timing... 14* initial, 36* total, 44* total+vacuum. The light shows timing steady but drops (retards) 10* randomly every few seconds for just a split second. I idle at 750 RPM in gear and 950 RPM in park. It takes off from a stop just fine but the engine stalls (almost dies) at higher RPM about (3500-4000) when driving only and the carb backfires (actually looked more like a reverse spray of fuel). I have the dizzy vac set at manifold vac. However, I just noticed the harmonic balancer has a slight wobble to it... maybe a 1/32" wobble (it's real noticeable also causing pulleys to wobble a bit). And the engine shakes a bit. What the heck is up? Anyone have a clue? Is the balancer causing these issues? Can it do that? Has anyone encountered this? That's about as much info as I can think of that might be of help. Can anyone suggest a possible cause for the problem and a solution?

Thanks
 

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If the harmonic balancer wobbles on the crankshaft, you should bolt it on.

Before you can do this, having a 210 HP V8, the crankshaft snout may or may not have been drilled & tapped for a bolt. Check to see and buy the bolt/washer combo from the parts store Help aisle. If the h/bal has a loose rim on the hub and tight on the shaft, get a new h/bal. They are under $60 each.

If losing 10° of timing while idling, I'd check the carb setting of mixture screws along with maybe unhooking full time manifold vacuum. As engine slows down, so does vacuum, vac timing changes also. Once carb is adjusted for smooth running, and it reads like its doing good otherwise, hook manifold vacuum back up.

Could be fuel starvation either to carb from the fuel pump as in bad f/pump or new gas cap needed as it is not venting, or weak valve springs - built-in rev limiter has kicked in.
 

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Discussion Starter #3
The balancer is already bolted to the crankshaft. I drilled and tapped a hole for the bolt when I had to reinstall it because otherwise I would not have been able to use the installation tool and that would have required beating it in.

I'll try and unhook the manifold vac line from the distributor again but I would swear it was doint it with and without vac advance.

The engine had been freshly rebuilt with new valves, valve springs etc etc... the cam that was installed was just too hot for my tastes and driving style.

As for the fuel cap... The car is in pieces right now. No gas cap installed... taped off the openning with something called speed tape we use on airplanes. It's aluminum tape rated to stick up to about 400 mph. And it sticks like crazy... maybe that's the case... I'll check it. I'm thinking it's the balancer but having a hard time thinking it's causing all the timing, shaking, rough idle issues, and some sort of tapping/clacking noise that can be heared resonating inside the long tube header collectors. Out the mufflers...well what can I say. It sounds killer! No other noises.
 

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The abrupt change of timing may be due to a sticky oil pump relief valve. I had this action happened to me and the next time I had the oil pan off, I removed the pump cover, pulled out the pin and spring and plunger and crocus clothed the plunger and reinstalled everything and timing problem went away - steady.

Not saying this may be your problem, but cured mine.

Headers are noisier than cast iron manifolds and exhaust noise is louder, might check valve lash again on exhaust side and intake while you're there. What you're hearing is probably the air collapsing back together inside the header tube, kind of like a sonic boom - same principle. Firing order is correct, I'm sure you've checked it several times just to be sure.

Too much advance may cause fuel reversion through the carb at high RPM's.
 

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If your tape job on the gas filler is a solid seal, you need to poke a small hole in it. There needs to be a small amount of venting to let excess pressure out of the tank and so that the fuel pump is not trying to pull through a "straw with a finger over one end".
 

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The wobble in your balancer could be the outter ring starting to seperate. This could also cause the tdc mark to be inaccurate as the outter ring rotates on the inner hub. I would buy the best balancer I could afford. Stay away from the cheapo chinese crap.
 

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Discussion Starter #7
Well I changed out the harmonic balancer. I found the outer ring was not aligned with the inner portion. I also found the polymer between the layers oozing out in several spots. The wobble has now stopped and most of the car shakes have stopped too but I still have issues. I'm going to post up a new question for the problems that still exist. Thanks guys.
 
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