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We're back up and running! Clogged fuel filter was the culprit. Gotta hate the stupid stuff lol. I drove it up to the Butler Farm show tonight. About 20 miles each way. Got on it once. Looks like the mystery converter is flashing to 3700 rpm or so. Hooking up is going to be impossible without slicks. My PCV valve kept popping out of the gromit and dumping oil everywhere, so I duct taped it back on for the ride home lol. That fixed it for the ride back. I'll get a new gromit tomorrow, put the driveshaft loop on and try to get the idle sorted out so I don't have to feather the throttle in gear.

Temp: 190-195 @ constant 60 mph, 185 idling
Oil pressure: 20 psi at hot idle, 50 driving, couldn't look at the gauge when I got on it!
Alt: Okie Dookie.

Seems like there's a funny bend in the powercurve around 4500 rpm and then charges back at 5500 up to 6000. Might be a total timing problem or more likely a carb issue.

Kev :D :D :D
 

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I've got a breather on the passenger side with a baffled grommit and baffled valve cover. On the drivers side I have a baffled PCV running into the back of the carb through a vacuum line. Does that sound okay to everyone?

Kev
 

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Seems like there's a funny bend in the powercurve around 4500 rpm and then charges back at 5500 up to 6000. Might be a total timing problem or more likely a carb issue.

Kev :D :D :D
You could be going lean so you may need to adjust the jets up. Before you monkey with jets, 1st make sure your fuel supply is adequate. A fuel pressure gauge on the cowl would help diagnose that scenario.
However,
Sounds like the problem is occuring at or around peak torque. This is also the point of max VE... cylinder filling is the highest, but peak fuel demand is at peak power. That leads me to believe it's not fuel related.

An improper spark curve could cause a lay down. You may have adjusted it for high and low rpm but it could be over advanced at peak torque. This is a very plausible scenario. Your VE is likely over 100% at 4,500 considering that cam and heads. This means the pressure in the cylinders may exceed spark timing requirements. Just for giggles, try boosting the octane to 100 and see if that helps.

In any event, I'd try running full advance "all in" at 3,500 and reduce the overall timing to 36 or 34 and see if the problem goes away. Initial is what ever it wants to idle. With that cam and low SCR you may need to be over 12 initial. You may have to restrict the advance to get both the top and bottom advance numbers.



A third possiblity is the trans is slipping at peak torque. You may have over 400 ft/lbs @ 4,500. Is the trans up to it?
 

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Discussion Starter #1,408
I'm a little concerned about the trans, as it's a stocker with a shift kit. Okie dookie for 307's and 283's, a little frightening behind that monster.

Kev
 

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I guess to re-phrase my question:

Does it feel like the transmission could be slipping when the dip in accelleration happens? If so then I think you've found your problem.

I'd also consider putting in new u-joints when you install that drive shaft loop.
Might save you a tow bill home.
 

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Discussion Starter #1,410
Well the transmission feels slippy navigating the parking lot, but that's the converter. It doesn't really "feel" like the transmission's slipping on hard acceleration. At about 2600 rpm while driving around it feels nice and locked up throughout the band. Tough to tell with one test sample though. I might go out and play a little tonight and think harder about it.

U-joints are less than a year old.

Kev
 

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Okay, the power seems smooth now up to 6000. I pulled the total timing back to 32 degrees. I guess the efficient heads like less advance. Now it won't idle though, guess I'll have to add lots of initial and lock it out.

Next problem, I'm chucking fan belts like it's nobody's business. I have a 6 cylinder power steering pump, so there's no adjustment on it. I'm just using the alternator as the adjustment. It goes like this....

Long belt - outside crank pulley to pwr steering pump just touching the water pump pulley and over to the alternator.

Really short belt - inside crank pulley to waterpump/fan pulley.

This ghetto set up has worked for 5 years, but the BLS keeps flinging the long belt every time I dig half way into the throttle. Tonight, it finally snapped the inside belt, luckily I was about a quarter mile from my house.

Any suggestions on how to get this thing to work? I want to use a traditional two belt set up, but A) pwr steering pump and alt both line up on the same pulley and B) pwr steering pump has no sliding adjustment for an extra belt.

Hmm.........

Kev
 

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So I was right. It was border line detonation causing the lay down around peak torque. You need to restrict the total advance so you can bring the initial back up. I noticed there's a "how to" in those Tunnel ram articles. I'll bet that thing want's to run past 6k! I wouldn't do that, at least for now.
As far as the belt tossing. Get some deep groove pullies. Make sure they line up. You might be able to get away with just a deep groove alternator pulley. If not, you may have to shim or maybe replace your brackets. 4th gen V-8 brackets shouldn't be too hard to find.
 

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Kevin, are you sure the balancer is on the whole way? That would cause the crank pulley to be out of alignment with the other pullies. Also, you may need to get a different vacuum advance can. There's an extensive list of can part#s in the Best of Tech section with their corresponding vacuum ratings.
 

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I went thru a belt tossing ordeal a while back. My neighbor at the time told me to try a belt with ribs on the outside. I have never had a problem tossing belts since I changed it.
 

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Balancer is on the whole way. Triple checked it with the issues I was having before.

The ribbed belt I just bought last week got flung tonight. I think there's definately an alignment issue (I can see it!). I'm going to get an adjustable bracket for a V8/long water pump car. If I need to change the power steering pump pulley to a V8 one as well, I will.

Kev (Gonna fix it the right way)
 

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Okay, the power seems smooth now up to 6000. I pulled the total timing back to 32 degrees. I guess the efficient heads like less advance.

Kev

I might add that your theory about the heads isn't accurate. The heads are efficient at flowing air but the S/R chambers aren't "fast burn" like Vortec's. The minimum port cross section helps keep the velocity high. The inertial ram effect coupled with high air flow is essentially "supercharging" the cylinders. That's the midrange rush you feel.
The reason that less advance helps is because the cylinder pressure is highest at peak torque. You have to retard the spark to get through this part without detonation (apparently inaudible or your engine is too loud).
This does not mean that 32 degrees total is optimum timing for best power.

Is the carb jetting the same as it was for the 307? If so, then it needs to be jetted up for it's new home on a bigger, more powerful engine. How much I don't know, but remember... since you are consuming more air, that means more fuel is needed. Too lean and it's going to be prone to detonation. That could be the root cause. I would check what's in there and step up slowly in small increments. Read the plugs and have someone watch for black smoke.
You'll know when you gone too high. Then back it down.

You'll be able to restore total timing once the fuel curve is correct to get you through the tight spot.
Get the adjustable vacuum advance and the advance curve kit. SBC experience says it may run best at 36-38 but I wouldn't go past 38 degrees. However, if it only wants 32-34 then so be it.
Keep a log book with changes and only change on thing at a time.
 

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Kev... I'd strongly recommend just running the OEM V8 belt arrangement. I'll bet you can get a V8 pump, brackets, the whole deal from a boneyard for CHEAP. Pretty much any 75-85 SBC equipped car will work. Grab your tools and hit the yards!
 

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Discussion Starter #1,418
Thanks for clearing that up, Paul. Great info, as usual.

John, I'm almost positive I'll be up at the boneyard tomorrow.

Kev
 

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Kevin, take a look at the ground strap on a few of your plugs. You should be able to see a line going across the strap which indicates your total timing. Ideally, you want the line to be right in the middle of where the strap bends.
 
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