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Old 07-11-2009, 11:43 AM
RamAirZ RamAirZ is offline
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Originally Posted by cobalt327
I'm thinking w/a 307 SBC in a 4000 lb. car, pulling another 4000 lbs-plus of car and trailer, a big cam isn't what would be usually called for. A small, short-duration "torque" or "RV"-type cam is what will usually work for towing, then an aftermarket head might serve no useful purpose. Unless the aftermarket head was carefully chosen, it could actually hurt the engine's ability to make as much torque down low as possible because of the valves and ports being too large.

That said, another option would be to go ahead and cam up the 307, add some mild aftermarket heads, and then gear it w/4.56's. Add a 700R4 (or an OD stick tranny) for the OD to bring the final drive ratio back in the area where the engine won't be buzzing on the freeway (ratio would be 3.2:1 in OD with a 4.56:1 rear gear).

But this will require the engine to be spun up good to make its power, obviously. The easiest way to cure all the probs would be a bigger engine to begin with, IMO.

But for a budget deal, I would still opt for the 416's w/stock valves along w/a good 3-angle valve job and headers, over the PP heads and 1.94" valves.
The car has 3.08's right now and gets around REAL good. The X4262H has 218/226 duration. I think it's a little bigger than an "RV" cam but should still make plenty of low-end torque (it's designed for 4x4's). In a simulation on DesktopDyno , it had at least 330 ft/lbs for a little over 2000rpm (2-4K) and pulled about 270hp. I think it's feasable to get near this power level using mostly stock parts don't ya think? With some minor work. The 200hp 307 was rated at 300 ft/lbs of torque originally anyways. I don't see a point in an aftermarket cylinder head for this, like you said it could hurt performance where I want it. The 307 runs good and I see no need to pull it at the time. Down the road it will get something bigger but for now I figured I could hop it up just a little using some parts I already have lying around lol (qjet, aluminum qjet manifold). Running 4.56+ gears isn't something I want to do either, when I redo the rear it will probably get 3.36's. Like you said, budget on this one is low for right now as I have other projects that need much more motor work lol. I wonder if the 520's are worth anything to someone.
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