Engine Tech I have a 66 skylark convertible with a 340 4bbl and was wondering what newer type engine & tranny I could drop right in without changing motor & transmission mounts in case I want to put the original motor and tranny back in. I am trying to get better gas mileage. Right now I am getting 15-16 and would like to do better and be able to use reg gas. Thank you. Les What I forgot to tell you was that this vehicle has a floor shift and I was wondering if that will make a difference on what transmission I can use. Thank you, Les
Take a look around on this forum. You'll find some good info on this, as I seem to remember reading something similar to this not long ago. If I recall, a Buick 350 with a TH350 will pretty much just slide right in with little or no mods. Others here will correct me if I'm wrong. :grin:
Your best bet for fuel mileage and ease of installation is a 2004R trans which is a bolt in pretty much and then a 5.3L 2000+ Chevy LS engine with the fuel injection run off a megasquirt or factory computer. You can buy engine mount and even headers for the same year Chevelle as your Buick and they will make the install a snap. If you went with a 4L60E it would be a lot of work for a crappy trans in my opinion. The 2004R is a really good trans with the same driveshaft spine count, length etc making it an easy swap PLUS no computer needed.
Booo... 450 bucks gets you a master rebuild kit from Northern Auto Parts, including pistons, for '72-'80 years (as advertised) which is the low comp Speed Pro pistons. Pistons will sit .070 in hole, have 24.74cc dish, and at .060 over, will net 10.18 compression if deck is zero'ed and 10cc removed out of heads (about .035-.040 off or so). Other than machine work, it'll be super cheap, cam will be automatically indexed with the timing gear/chain that comes with the cam and lifters, so it's basically just a bolt-up build. 10.2 SCR = 8:1 DCR with that stock cam, meaning, 93 octane at sea level is all it will need. Engine will be pretty much the 1970 "Hi Compression" 350-4, with 315 HP and 410 ft. lbs. and it's a BUICK. :TU: Toss in some TA Stage 1 valves and some head and exhaust manifold cleanup with the 750 Qjet and HEI ignition and you may see closer to 330 HP and 425 ft. lbs. out of a 'stock' engine, getting well over 20-25 MPG depending on gearing. Or so that's the theory. :Brow: 3.23:1 rear and 200-4r trans it wouldn't surprise me if the thing got 27-29 MPG.
I agree go with the 2004r. Less cost then LS swap by far for mpg increase. add taller tires too.anything else would require a lot of work and/or modifications. Maybe add a megasquirt or mad atomic fuel injection. 15 still ain't bad for old cars .a lighter foot might help. tuning can help also. a little more timing and slightly smaller jets but read plugs so you're not to lean.the 4l60 will need a ecm speed sensor and tips just for starters and its basically a 700 which is not Buick bolt pattern you will need adapters.and shorter driveshaft. With cross member work. call bowtie overdrives for a 200r4jusr set carb cable before running engine so you don't damage trans. ---------- Post added at 06:46 PM ---------- Previous post was at 06:38 PM ---------- With engine swap you will do a lot of rewireing and entire fuel system redo and your gain might not gain much mpg not to mention the programmed rear gear the you should be matching to engine
Maybe this isn't the answer you're looking for but is this car your daily driver? If not, why worry about gas mileage. My second wonder is if the 340-4 is the original engine and runs good, why would you want to remove it for a few mpg? The cost of swapping in something else would probably buy you more gas for years with what you have right now. I can understand if you were seeking more horsepower, but gas mileage? I'd leave it alone and go buy a cheap little 35mpg Honda or Toyota for a daily driver and save the Buick for part time enjoyment. If you're still headstrong on better mpg, I go with Sean's suggestion, either a 4.8 or 5.3 out of a late model pickup would probably get you nearly 25mpg highway in your car. But spend some time with a calculator before you do it, you might be surprised/disappointed at the cost per gain.
It's "well said" when someone agrees, and "absolutely disgusting" when someone disagrees. :laugh: No harm intended, just a small jab, and I think it's pretty funny. Having said that, it's true. A few more mpgs over the years from a car you don't intend on driving every day is pointless. I support the idea of keeping your Buick all Buick, but whatever floats your boat. The (Buick) 350/350 is probably the easiest and cheapest swap, if you swap at all.
No The 350/350 combo would give more power, better off the line acceleration due to better gearing. And likely the same MPG 2004R with either engine would have some serious MPG gains.
I had a 67 Skylark 340-4barrel, and I swapped the 2 speed 300 tranny for a 3 speed 400 tranny. Cheap. I then installed a type O, 8.5" 12bolt, Olds posi rear end with a 2.56 gear for cheap. These are cheap because they can't be geared down, but they're very strong. Tall gear is a poor mans' overdrive and easy to do. Wonderful car to drive, and so smooth at any speed. I loved that car.
As for fuel mileage; I did't check my Skylark closely, but it was close to my 67 Elcamino 327 with 700r4 that got up to 24 on long trips. This is accurate by checking the speedometer to the interstate mile posts for a long stretch and factoring in the percent difference. A friend had a 57 Chevy with same engine & tranny got 24 mpg as well. I believe the 340 will be better than the Buick 350, and I think you'll see 20 mpg from one with tall gears or o/d.
:laugh: ---------- Post added at 06:35 PM ---------- Previous post was at 06:20 PM ---------- Ehh...I'd like to add a little more here on MPG. The Qjet (750) and a good tune is the secret to the 350's superior fuel economy, methinks. Highway gear, 3 speed trans, 350 with aforementioned carb and well tuned should get better mileage than the old 2g or 4g 340 setup. Nice thing about the Qjet is that even at higher RPM cruising speeds, it will get better mileage (this is another in-depth conversation altogether that is likely to cause some flame wars, but I'll risk it anyway because it's true :laugh: ). An example taken from a fellow board member is his Buick 350 with a Crower level 3 camshaft and 3.42:1 gears (no overdrive) and says he gets 20 MPG at 70 MPH, and turns 13.77 in the quarter. "Big block torque," he says. Standard valves, all cast iron stock manifolds, smooth idle, pump gas.
Get the 300 trans out of there.find out what gear you have in rear.2 series would be great.I would bet it needs tuning also.
To add to the confusion even more (not to be a badger in the chicken coop or anything, but here it goes)... The ST300 is an old trans that I have fond memories of... Statistically, 1st gear is 1.76:1 ratio and so is more like taking off in second gear vs the 2.74:1, 2.52:1, and 2.48:1 ratios for the 200-4r, TH350, and ST/TH400, respectively. So why would anyone consider keeping the evil old ST300? Short answer: more mid-top end performance. Parasitic power loss is greatest with the ST/TH400 at 44 HP lost from the flywheel, and goes down to 36 HP with a TH350. The ST300 only loses 18 HP. This is HALF the power lost from the next grade up 'replacement' TH350 that Buick and Chevy engineered to replace their 2 speed trannys in '69. It is a very durable trans (I've had one behind a 1970 455 and it held up just fine with zero problems) and will improve gas mileage over other transmissions with more parasitic power loss. With all that said, overall performance, all things considered, the TH350 is a nice replacement because of multiplied torque output for 1st gear, though 2nd and 3rd gears will suffer vs the ST300. So it's a tradeoff in regards to stoplight to stoplight performance vs cruising and highway performance. Something else to chew on.
