I have a '80 1 ton daully I'm rebuilding. Would a build SBC be enough power to haul my K5 Blazer on a trailer? What can I do to the most torque out of it? Thanks for any info.
Depends on where you're towing, IMHO. If you're in a 'mountain' state and don't mind going slow up the hills, you'll be OK with a 350. If you want to crest the hills above 50 mph, a big block or a diesel swap (Cummins TD or ???) would be wise. I can't speak much for 'flat lands' or lower elevations as I don't have a lot of experience there. I have towed my Jeeps (Grand Cherokee, Cherokee and now a YJ) around Utah quite a bit with a carbed 350 ('77 GMC 3/4 ton--SM465, 3.55 gears 32" tires) and an '89 TBI 350-700 (3.73 gears and 31" tires). I can't keep up with the 'cool kids' on the hills (I want a Cummins TD Suburban or a full size Dodge CTD SUV), but have been somewhat satisfied overall. I just bought another '89 Sub, 2500, TBI 350, T400 and 4.10 gears (31" and 35" tires--kinda deciding which tire to go with for the best daily driver/towing performance) and haven't seen a significant improvement in towing ability over either of the other two rigs. I drag my junk on a car hauler trailer (say 6000 lbs for the trailer and Jeep item) to Moab quite frequently and the mountain pass between Provo and Price, UT is about 8000 feet with about a 4-5 mile 8% grade to the summit (from about 6000 ft. or so--guessing as I haven't ever checked the elevation where the grade starts). I'm at about 40 mph going up that hill and working the 350 pretty hard. The SM465 would pull that about 45 mph and I'd assume that to be the lighter weight of the pickup vs. the Suburbans. I usually get about 8-9 mpg towing between Salt Lake and Moab and get about 13-14 mpg around town with the older pickup and the 700 equipped Suburban. The T400 Sub is about 11-12 mpg around town and about 8-9 towing. Exhaust and intake mods help, but the 350 is not the 'king' of the towing engines. However, it's not to bad and can get respectable daily driver mileage and still do some work towing. If you wanted to build a towing small block for your dually, I'd go as big as you can (bored 400, or 383) with the appropriate Comp Extreme 4x4 cam for your engine size. Add some 'tri-Y' headers and a nice free flowing exhaust system and you'll be about as good as it gets for a naturally aspirated, pump gas, small block. However, there's no replacement for displacement if you are serious about towing and can come up with a 454 or have the budget for a RamJet 502 from your friendly GM dealer.
If the most your looking at is the K5 on a trailer, I'd do a 383 and go for it. Don't have to mess with the problems that come with putting in a different motor and it's a relatively cheap and easy build.
I have a 89 2500 350 tbi,700r4,373 extended cab and I live and tow in some "flat states" In., Ky., Ill. . It does a good job pulling my K10 long bed. But when it does get to some hills it does put a good butt-kickin on the 350. I can watch the speedo and gas gauge drop at about the same rate on some of the longer hills (longest I've been on are maybe 1 mile long).
Definitely bigger inch small block... 383, 406 etc..... if you already have the 350 block then go 383... its not hard at all to get 400 ft lbs out of a 383..... my .02 take it easy -j-rOd
Alternatively, consider finding a later model drivetrain complete. My bet is that you could find a later model 7.4EFI Big Block with 4L80 attached for less than the buildup below, and just freshen up the top end. For going small block, I agree with the above posters. -Get a stroker crank for the existing 350. -Go Comp Extreme cam maybe retarded 2 degrees for low end grunt. Depends how their grinding them nowdays. -Use a Quadrajet on it for the teeny tiny primaries (better unloaded MPG) and massive secondaries (more power on the hills). Better yet, get one of the bolt-on FI systems - Edelbrock, Holley, etc., and get the best of both worlds. - Use an MSD or other CD ignition box, does wonders for MPG. - You'll need to gear tall for the hills. If you're using a TH400, it will hurt mileage, but help towing. You might consider swapping an OD unit (4L80) or a manual with OD for better highway MPG.
I like this one. CHECK OUT THIS BAD BOY If I were to go with a gasser for my sub,id go with this motor. Unless I could swing a 502 waytogo
I have a mildly built 406 SBC in my K5 and it pulls great, suprisingly I used to tow with it a lot and about as heavy as a loaded K5/trailer combo every once and a while. It would pull it really well, but I never got into the hills with it. I have had my K5 on the dyno, roughly, 200HP and 300ftlbs to the ground. With a 38% drivetrain loss (38% is conservative it a big 4x4 with a 700R4) it is roughly around 315HP and 425ft lbs or so at the crank. I love 400's! The 400SBC is the ideal towing motor but the problem with 400's is keeping them cool, I am pretty confident that I would have a hard time pulling a big load up a hill for long without the temp getting out of hand, and I have dual electrics and a 4 core radiator. I'd build a 383 budget motor. Comp cams extreme energy 268H cam, merlin or vortec iron heads, 9.1:1, and the usuall Performer intake and Qjet. This is basically my setup minus the heads, mine are stock 400 heads, and I would think a 383 should make nearly as much torque, at a lower RPM range, and almost as much HP. A small block, especially built, will do just fine with a K5/trailer combo. A good 383 will probably even do well in the hills.
