Have decided to go the 292 route in my second coupe (first one nailhead), to be different. They seem to be plentiful around here as I have found 3 locally among friends. These are all late 60s. Any year better than others?
The best 292 blocks were cast in Mexico. Thicker & less core shift. Really mostly important for a full race motor. Be honest with yourself about what the engine will be used for. Some of the racing mods cost money and don't do much for a road motor. Also think gearing & over drive. These are very different from a short stroke high rpm v8.
You'll love it! Don't go crazy on the cam & valves. Remove the intake boss but skip the lumps. Be sure to put a hitch on it so you can pull a travel trailer to events.
I'm thinking semi-conservative. 9.5 compression, 1.875/ 1.60 valves, 268H cam. Intake and headers. 700R4 and 3.50 gears. Should be a lot less of a headache to install than the Nailhead.
I agree. They sounds like a good plan. These engines have a reputation a gas guzzlers. I think a couple of the reasons are that they were put into vehicles that were worked hard and they were geared to get work bone and not as highway cruisers. I have gathered the parts for a truck motor for my '68 C20 flatbed. 9.5-10 to 1 compression. A near stock 194 head with stock valves. Looking for velocity over volume. The head hill flow well enough in the rpm range it will be running in and velocity will be better than with lumps & big valves. Twisted 6 gave me some pointers. I had a custom cam ground by Crower that is a bit more of a low end puller than stock. It will be doing it's heavy work at 2500 and below. With 3.55 gears and a 700 r4 it will do highway speed at low rpm and well. It will also run early '90s TBI injection. OT for here. If my head plan doesn't work I have a turbo setup for it.
The goal is 225 HP / 280 Ft. lbs torque @ 3500 rpm. Very doable I think with a little work. The engine compartment in the 40 is long and narrow since it had the straight 8. With the front motor mount bosses on the 292, the plan is a fabricated front mount to pick up the straight 8 front mount bolting. Mexican blocks are 84 up I think, so a harder find.
Yeah they are tough to find. look in the water pump hole and check the machining on the front cylinder. if it is even all the way across there is little core shift. You have a good plan. The 292 is just a couple of inches longer than a 216, about the same as 235s with the long water pump or a GMC. Lots of those are in '40 Chevys. Move the radiator forward 2 1/2".
Bangingoldtin The Lumps do make a difference in flow even with the stock valve (1.7) the stock valve flows right at 170 cfm with the lumps the head would flow right around 200cfm. But that is not something that you would really feel in the performance side of things. But there are many people that have them in pretty much stock daily drivers. But if you are upgrading the head, I tell most to stay with the 1.8 intake & 1.6 on the exhaust. for a daily driver. If they are wanting a little more getup and go. The 1.94 valves are if you want the head to do all that it can and not so much looking at the MPGs and looking at a bigger cam down the road.
@Twisted6 , thanks. I am not so much concerned with MPG, but more about torque at the RPM range I plan for. That is why the 1.8 valves vs. 1.94, looking for velocity. The vision is for something different in the car. Because the Buick had a straight 8, there is plenty of length room in the compartment for a good fit.
I don't know what the length of the bare 292 block is, but the 248 straight 8 block is 31-1/2". Plenty room, and I might have to use a short fan spacer.
This is an interesting thread to me. I hauled hundreds of thousands of bushels of grain with a 1966 C60 with a 292. I am planning a pickup project and plan to use a 292 to power it.
The bare block from bell housing flange to the timing cover face is 28.5 And do not forget the motor mounts are staggered.
^^^ thanks for that dimension. That is 3 inches shorter than the I-8. With the 700R4, the motor will need to be 1 inch more forward by my crude measurements. That gives me 2 inches to work with, and as I previously posted, I plan on a custom front of the block motor mount that picks up the original chassis holes. That will also give me more room for the split exhaust and clear the steering box.
Just measured one as pulled from truck. Rear bolt surface to the front of water pump pulley 33" front of fan with 1 1/2" stock spacer 36".
I know with the 250s there is like 3 different sizes for lengths, I'm not 100% sure about the 292 pumps
All of the pumps I have researched so far are the same length. I was looking into options for total engine length. This is going to be a fun project, and my first foray into "juicing" an I-6.
There was a Buick overhead cam version of the short deck size of these engines. I don't know if anyone has put one on a 292 or if it would even work.
Easier to put the 4.125” crank in the Pontiac and it’s not easy but gives you 303”. A engine guy I knew put one in my roadster. It came from Bud Meyers race boat from the late 60’s.
I have seen a 250 with a 292 crank. Is the 230 Pontiac block different from a regular 230? Never mind I found one on eBay. Very different and so is the head gasket.
I had an original 68 Chevy 1/2 ton 4x4 with a 4 spd and worn 250...got a 292 ,new set of higher compression propane pistons,mild Schnieder cam...Getting a tight piston to head quench was not the best with available head gaskets..Should have had one made by Cometic....With a good valve job, stock 250 carb and larger 292 exhaust manifold the engine ran well and got 18 mpg with stock 3.73 gears...A better flowing carb and intake would have been better I suppose..
Propane pistons are a really hard find nowadays, so the plan is Ross forged with a zero deck, and tailor the head with a stock gasket to get 9.5 to 1.
6 years ago I had a hard time finding propane pistons other than .060 oversize....but a .020 set just appeared like magic.... check on available head gasket thickness...winding up with .035 squish is very helpful on these engines...
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