The Stovebolt Site Forums The Parking Lot Big Bolts 366 Opinions?

Hello all, I'm looking at re-powering my '69 C50. I was going to drop in a 307 that I have ready to go (in place of the original 350). I have access to a freshly built 366 (w/receipts) that the guy wants me to hear and see run before it's pulled. The only hitch is that he wants about $1500 for it and for that price I could put in a decent 454. I'm trying to save the time of buying a "core" and rebuilding it myself. I've never ran a 366, but was looking at the bore/stroke specs and it ought to pull a lot better than a 350 (I'm guessing because of the undersquare dimensions). Anybody have experience with these engines? I know that there's NO REPLACEMENT FOR DISPLACEMENT, but at a 1:1 drive ration between the SM420 and the split rear end in high gear, any engine will be turning the same rpm's on the highway. I don't need a top fueler, but am looking for decent power on the road and good lugging torque when I'm dragging trees and moving hay. Any advice/experience that could be shared would be much appreciated.

To address the obvious answer, if I keep it for much more than about 10 years, it will get a Cummins, Int'l or Detroit motor with suitable tranny. For now I'm looking for a cost-effective tactical solution. I'll address the strategic problem when I decide if I'm keeping it forever or not.
Thanks All!
-Bryan

The 366 is a good engine, and was built judt for the larger trucks. The company my Dad used to wprk for had a few Kodiak trucks with them, never had any problems with them. They are not built for speed, though.

One thing to consider when changing from a 350 to a 366 is all the bolt on stuff that is different. Brackets, hoses, exhaust system to name a few. If you change over to another small block you can re use everything from the current engine. If you go the 366 route you'll have a big shopping list that you'll need.

I like a 366, but the shopping list don is talking about can be very expensive. A 383 stroker might be a good choice to keep down all the extra stuff. You might like the 383 well enough to keep it forever.

I also like the 366 but not for 1500 bucks. For that kind of money you can get a real good start on a 383. I have a 366 in my C60 and it pulls great but with the same gearing a 383 would be just fine. And like crenwelge says you might be happy forever with the 383. IMHO don't replace the 350 with a 307. I think I would spend a few hundred dollars and find a running 350 and put yourself right where you started for the least amount of money. Then you could plan the long term strategy for your truck's drive train. Good Luck
SimS

Need more information in order to help you make a good intelligent decision. Lets take a look at what we know and don’t know so far.
We know
1. Your truck originally had or has a 350
We need to know
A. Is this 350 still in the truck?
B. Dose the 350 still run?
C. If you still have the 350 do you have all it’s accessories and are they still functional?
D. If the 350 dose not run is it still a good core?
We know
You have a line on a good 366 for $1500
We know need to know.
A. What comes with the 366 dose it come with accessories?
B. What type of shape is your exhaust in? Can it just be bolted right to another small block? Would it be easily altered to fit the big block or dose it all need to be replaced anyway.
C. What is the value of the 350 if you still have it? Many large trucks came with sought after motor that had such things as 4 bolt mains, steel crankshafts, high nickel content castings, and good flowing heads. You really need to know what parts you have and what condition they are in, like has the crank ever been turned, dose it need to be turned or will it polish out. I bring up the value of the 350 for two reasons 1. If you decide to go with the 366 the 350 could be good trading stock to off set the cost. 2. If you decide to go the way of a 383 stroker the block and heads could be a good starting point and if it has a steel crank the crank could be used as trading stock.

From what is known now if you have a 350 that is a good core and a good running 307 witch IMHO I don’t think you would like very much but you could use it to keep the truck on the road while you rebuilt the 350 possibly for more power and torque than it had stock or even step up and have a stroker kit put in it for that 383. But The first step to finding good options is to find out what exactly it is that you have.

If you decide to go the way of a 383 stroker there are three rod length options, the first was common when people first started building 383s this was to just fit a 400 crankshaft to a 350 block use the short 5.565” 400 rod and 350 pistons it worked but you miss out on a lot of power potential.
After realizing the potential of running a longer rod the aftermarket started building pistons specifically for the 383 with the pin positioned higher so the longer 5.7”350 rod could be used this worked out so good that they then added to the lineup pistons that would allow the use of aftermarket 6” rods and the 383 really came alive. What I am getting at is when building a 383 small block Chevy the relatively small cost of the longer rod is money well spent. GO WITH THE 6” RODS

Well, this is partially a non-issue for now, as the money I was intending to use to fix/partially restore the truck right now, is getting ready to be "re-distributed" towards new siding on the house (about $8.5K). But to answer the q's: the 350 that IS in the truck IS running and driveable, but it is leaking around the valve guides and somewhat lacking on the compression. All accessories are there (alternator). The truck is boosted brakes and armstrong steering equipped. The 366 DID have all accessories and exhaust, including the bellhousing and mounts (wasn't sure if they'd be needed or not. I don't think for now that I'm going to put the 307 in unless I have no other choice as I don't want to go down in power,... The current exhaust is mostly rotted off, so it will need to be re-done anyway. The truck will be used to haul firewood and Hay so speed isn't an issue (55-60mph necessary) but low-end power will be.

I now have a different opportunity with this truck that I need an educated opinion on: I am acquiring a '65 GMC 4000 for $300.00, that currently is not running due to rat-eaten spark plug wires. It is largely rusted beyond repair, BUT is has a functioning Hoist, good steel stake sides, Air Brakes and a solid V-6/5speed combo. I have three questions for you guys:

1. Can the steering rack off of the '65 4000 be readily swapped into the '69 C50? Would I lose any appreciable load capacity? It is a power steering rack and that would be nice if the wife has to use the truck, not that she isn't muscle equipped, LOL.

2. Would I need an adapter or different bell housing to mate the 350 (or 383) to the 5-speed tranny? I'd like to have 2 more gears that the 5 speed would give over the truck's current 4spd/split rear combo.

3, How difficult would it be to change from the current boosted brake setup to the airbrake setup (with all function parts in-hand)?

4. Sorry, I thought another question, Would it be easier find chevy style mounting brackets for the V6 equipped Hyd Pump and Air compresor, OR would I be money and time ahead to just swap the Good running V6/5spd combo into the Chevy? I have no idea of the displacement, but it ran great 6 months ago (neighbor's truck) before the rats consumed the electrical wires and has always pulled the truck with authority.

I apologize for the litany list of questions, but I'd rather learn from other's mistakes/first hand knowledge, and do it the right way the first time if possible. Thanks again for all of the replies and assistance.
-Bryan

Hy Locust_Cutter, those two trucks are different designs. The easiest way to do all that retrofitting would be to mount the 69 body on the 65 chassis. I'm not saying that without some adapting it isn't possible to do that work, but that is one heck of a lot of work, hope that helps.

I wondered if that was going to be the case,... I may forgo the entire project as a whole and go with trailer(s) instead. We'll see.

If you need to haul stuff and have a good pickup, a trailer is the most economical method to go. I have a 2009 2500 HD with a 6L gas that costs me about $75 a year for registration, $1300 a year for $1,000,000 liability and $500 deductible collision. I have 4 bumper pull trailers that are titled in Oklahoma and they cost $4 per year for registration and the pickup insurance covers them for liability. I am currently cleaning up my salvage yard and have hauled loads of as much as 9,000 with an 18 ft. bumper pull trailer. I like to play with old jalopies, but when it comes to actually working, I prefer late model stuff. I got my commercial drivers license in 1959 and I have had my fun of working with the old timers.