RV Cams?
I was wondering if anyone has upgraded their cam from stock and what effect it had on driveability and mileage. I have a 85 K20, 350 4b with a 4 speed manual (1st is granny gear) Im not sure what the ...
Forum Discussion
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I tend to agree with guys that say it's sort of a package deal. But there may still be a way to bump up power economically.
Your truck should have HEI ignition. One thing to try first would be to find a spring kit for ignition advance and allow the ignition to advance a little faster right off. Lousy for emissions, good for snap. The total high RPM advance should remain close to the same, but with the right springs it can come in earlier than the smog curve that it has now. This won't help much on a high speed hill, but the truck will run better in town stop-and-go and other lower RPM's.
At 80K you might find an earlier set of used higher compression heads, give them a valve job, regain lost performance and bump up compression at the same time. (As an alternative, there used to be some new cast iron heads that sold for a little over $300 a pair, but I suppose those days are gone.) Bumping compression ratio will depend on how the smog engineers robbed it though. If the pistons are dished, the earlier head chambers won't be much less volume. But if the pistons are fairly flat-topped, the earlier, closed chamber heads may bump up the compression quite well. Maybe up to 9.5:1 would be good for towing, as compression ratio mostly affects torque. As Turtle noted earlier, the intake runners will also be larger. Used early heads should not be too expensive, and it's mostly for regaining the lost pre-smog torque mind you.
I assume it has a Rochester Quadrajet carb, and almost all of them flow 750 feet. I think there were some 850 feet units. This is significantly higher than other carb brands, yet works because the front barrels are small and work well at low speeds. The rear barrels are humongous, but only open at high speed, so the carb does not stumble easy, even at the large total flow. They are also more fuel stingy than other carbs, until the back barrels open anyway. The current jetting is probably a little lean, and if you can enrichen the mix, you will find a lot of power by doing so. There is a richer happy medium, than you have, where both power and fuel economy actually improve before economy goes the other way again.
An RV cam should improve power if you can first bump compression and intake runner volume. But even an old 327 flat tappet cam would an improvement over what you have. If your engine has roller lifters, the cam can be improved a lot. But I don't think 1985 did offer rollers.
If you can get some older heads cheap, the "tow tune" should not cost too much. Revamping the 350 will still allow for better fuel economy than a 454, or even a 383 or 400 smallblock. Yet the power increase can be pretty remarkable.
Good luck in your quest.
Wes
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I tend to agree with guys that say it's sort of a package deal. But there may still be a way to bump up power economically.
Your truck should have HEI ignition. One thing to try first would be to find a spring kit for ignition advance and allow the ignition to advance a little faster right off. Lousy for emissions, good for snap. The total high RPM advance should remain close to the same, but with the right springs it can come in earlier than the smog curve that it has now. This won't help much on a high speed hill, but the truck will run better in town stop-and-go and other lower RPM's.
At 80K you might find an earlier set of used higher compression heads, give them a valve job, regain lost performance and bump up compression at the same time. (As an alternative, there used to be some new cast iron heads that sold for a little over $300 a pair, but I suppose those days are gone.) Bumping compression ratio will depend on how the smog engineers robbed it though. If the pistons are dished, the earlier head chambers won't be much less volume. But if the pistons are fairly flat-topped, the earlier, closed chamber heads may bump up the compression quite well. Maybe up to 9.5:1 would be good for towing, as compression ratio mostly affects torque. As Turtle noted earlier, the intake runners will also be larger. Used early heads should not be too expensive, and it's mostly for regaining the lost pre-smog torque mind you.
I assume it has a Rochester Quadrajet carb, and almost all of them flow 750 feet. I think there were some 850 feet units. This is significantly higher than other carb brands, yet works because the front barrels are small and work well at low speeds. The rear barrels are humongous, but only open at high speed, so the carb does not stumble easy, even at the large total flow. They are also more fuel stingy than other carbs, until the back barrels open anyway. The current jetting is probably a little lean, and if you can enrichen the mix, you will find a lot of power by doing so. There is a richer happy medium, than you have, where both power and fuel economy actually improve before economy goes the other way again.
An RV cam should improve power if you can first bump compression and intake runner volume. But even an old 327 flat tappet cam would an improvement over what you have. If your engine has roller lifters, the cam can be improved a lot. But I don't think 1985 did offer rollers.
If you can get some older heads cheap, the "tow tune" should not cost too much. Revamping the 350 will still allow for better fuel economy than a 454, or even a 383 or 400 smallblock. Yet the power increase can be pretty remarkable.
Good luck in your quest.
Wes
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