SBC in FJ60 questions. Power and fan.

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cruiser711

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Hi everyone. Can anyone tell me what kind of power to expect from a stock 350sbc at the rear wheels. Just had a 350 rebuilt and had it dyno tested. It put out a mediocre 92HP running on LPG and 107HP running on unleaded fuel. It has HEI and with standard quadrajet carb and manifolds. These HP figures seem too low for such a motor. I read elsewhere of a person with similar output figures and he found out that the toyota throtle cable was not pulling far enough to open the secondary barrels. How can you tell if the secondaries are open? Are these power figures too low?

Also can anyone advise me what type of radiator fans are being used after a sbc conversion? I've used the stock 2F clutch fan but the pulley ratios seen different on this moteor and this fan is probably spinning twice as fast and makes a hell of a noise? Would an electic fan do the trick? I also using the stock 2F radiator. I live in Adelaide Australia and temperatures here can get quite hot. I don't have any heating probs at the moment but this noise needs to be rectified? Any suggestions?
 
Niner

Niner

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To find out if the throttle is opening up all the way have someone floor the accelerator pedal, With it not running of course, then using your hand just see if you can get anymore out of the carb.

I wouldn't worry about the HP numbers, torque is what you need in a wheeler anyway!
 
Rice

Rice

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There are a lot of very tame small blocks out there due to the period they were being produced (i.e. energy crisis and emissions). That said, 107 at the wheels is still low.

Questions:
1. while on the dyno were they getting readings of fuel/air ratios?? If so, how close to 17 was it?
2. Did they make any timing adjustments. Iron heads and low compression should put your correct timing close to about 36 degrees.

With respect to your carb, what I might try first is simply having someone put your pedal to the floor while you watch what's happening under the hood. At least then you'll know if the cable is giving you full range.

Theo (on this board) knows much more about Q-jets than I. I think many of these carbs are Vaccuum secondary carbs which means they won't really open up unless the engine is under load (Theo??). That means just watching for secondaries to open while under the hood usually doesn't work so great.

Radiator / fans: I use a 30% overdrive on my water pump and fan to help with circulation while stuck in traffic. The fact that your ratio is spinning the fan so high may serve to be a good thing. Still, if it's noisy ALL the time it sounds like your clutch may not be releasing OR your engine is still running hot. There are others who swear by electric fans but I'm not one of them. They move less air and are not as reliable as a good mechanical fan. To be sure you're ready for real heat I'd suggest a heavy duty Thermal clutch (e.g. flex-a-lite P/N 5655) along with a high pitch blade. Get the fan to within a couple inches of the radiator (much closer and efficiency goes down) and use a shroud. In addition, be sure your timing is set correctly, otherwise unused energy will remain in the cylinders and that means heat.

Good luck.
 
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cruiser711

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Well to be honest the truck drives a lot better with the new engine but I still feel that the 350 should do better. I'll check the carby some more to try and figure out what happening there.

As for the fan. The car seems to run pretty cool. Even on a hot day the temperature shows about a 1/4 on the standard 60 guage. The fan does cut out sometimes but at temperatures above 25 degrees celcius it seems to remain on forever even on highway speeds. The fan becomes incredibly load.

Rice I have a similar water pump to you I think. The puley is very small so the fan it realy getting a work out. And the ange of the fan is bery aggressive. Hence the noise which at highway speed is load to the point that my ears ring after a few hours of driving.
 
T
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Thanks for the plug, Rice! But honestly I've read up on q-jets a lot. That's where a lot of my knowledge comes from.

I haven't messed with the secondaries much. But they're actuated by an air valve that responds directly to demand. Vacuum secondaries are different in that they are directly linked to a vacuum pot that "lets go" as vacuum decreases and/or as air flow through the secondary venturi increases. (I need to study this more!)

You can change the spring tension on the q-jet secondary air valve to get it to open sooner or later. Q-jets are also the only carbs with secondary metering rods and hangers (I think). You can tweak these also.

cruiser711, there were many subtle variations over the years in the way q-jets came from Rochester. Things like the length and taper of the secondary metering rods, hanger height, rate of engagement, etc. all varied depending on the application. (The primary circuit varied also.)

I guess what you could do is try to determine what vintage q-jet you have and what application it came from. That might give you an idea of whether you have a "low rev, trailer tugger", a "screamer", or something in between. I have papers written by serious carb tuner/tweakers that explain how to get the most from a q-jet. Could email them or even ask Woody to post them if you're interested.

More than you wanted to know, right? Sorry, I get carried away. :)
 
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cruiser711

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Dec 18, 2003
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Clare Valley, South Australia
Thanks Theo, More info is better than none. I would be interested in the material you have by e-mail if you don't mind the trouble.

I'm not sure what application it came from. The engine was purchased as an import. I think it's a late 80's. The carby was thrown in but I doubt it's from this motor. It seems in good condition. Is there a way to tell? Are there any numbers I can look at anywhere to determine the vintage/application?

Anyway maybe the carby is not the problem. Could it be my exhaust? I've got stock manifolds with a centre exit. The rest of the system is what i used with the 2F motor. 2 1/4 inches with a few bends along the way that restrict is even further. Could this be an issue?
 

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