Chevy 267

[jknowles87]

I have a 1981 Chevy Impala sedan with the stock 267 V8 engine, TH-250C transmission, unsure of gear ratio in the rear. I want to rebuild this engine, with a better camshaft, and a 4bbl Q-Jet to replace the 2bbl. Any thoughts on the potential power and mpg gains, if any?

Also, I want to replace the TH-250C with a 200-4R so I can get better MPG. What would be the best gear ratio in the rear for this setup? (I want to say it has either a 2.73 or 3.08 based on how it feels on the highway, but I am not sure).

[MagicRat]

Originally Posted by jknowles87

I have a 1981 Chevy Impala sedan with the stock 267 V8 engine, TH-250C transmission, unsure of gear ratio in the rear. I want to rebuild this engine, with a better camshaft, and a 4bbl Q-Jet to replace the 2bbl. Any thoughts on the potential power and mpg gains, if any?

Also, I want to replace the TH-250C with a 200-4R so I can get better MPG. What would be the best gear ratio in the rear for this setup? (I want to say it has either a 2.73 or 3.08 based on how it feels on the highway, but I am not sure).

Do not bother rebuilding the engine. It is definitely not worth it. The 267 was built for 3 years only. It was a low-powered (110hp, I think), low-revving economy engine, intended for buyer who just wanted good fuel economy, but did not want the extra vibration associated with the GM V6 engines of the day.

I am not sure how you feel about performance, but the 267-equipped cars I have driven were so slow they were hazardous in todays traffic. You simply have no extra acceleration to safely cope with merging, lane-changing etc.

Pick up another carbureted V8 Chevrolet engine and rebuild it, like a 350 cubic inch version. Rebuildable cores are still pretty cheap. A 350 will cost the same to rebuild as a 267, but will be MUCH better for power and performance. It will also boost the resale value of your car more than a rebuilt 267.

Even if a 350 core is too much money, a 305 cubic inch engine would be better. 305 cores are still very inexpensive and easy to come by.

Either the 350 or the 305 looks the same on the outside as the 267, and will bolt in place perfectly. You can easily get one with a factory 4 bbl carb.

If you go with a stock rebuild, your mileage will be very similar to a 267. This may seem counter - intuitive, but a Quadrajet carb will actually get better mileage than the 2 barrel you have (when driven normally) because the 'primary' venturis of the 4 barrel are a more efficient design than the 2 barrel that came on the 267's (that I have worked on, anyways). Also, a more-powerful 350 or 305 can get your heavy car up to cruising speed more quickly than a 267, so you can get the benefits of top-gear mileage sooner.

For an overdrive transmission, I would suggest installing one with the rear end you have and see how it performs. You can go with a 3:23, 3:54 or 3:73 rear end and still get good highway mileage. But the 2 rear end ratios you list will work fine with an OD transmission, unless you really want a race car.

BTW the 267 was underpowered, not just because it had less displacement than a 305 or 350 but also because the cylinder heads had (comparatively) very small valves and small ports. The heads did not flow very much air. You cannot bolt-on better heads from a larger 305 or 350 engine because the valves will hit the cylinder walls.

[MrPbody]

All due respect to MR, but I think 267 isn't as bad as all that... The smaller valves and ports are designed for the smaller dislpacement. That's a GOOD thing, not a bad one. Unless the engine's performance range is expected to be above 4,000 RPM, the small heads are an asset.

Get an Edelbrock "Perfomer" intake (no, NOT "RPM"), a TINY 4-bbl (Holley 390 would be my choice, unless a '66 or '67 Pontiac OHC 6 "Q-Jet" can be found) and a Comp 240H ("High Energy" series, 192/200 @ .050" lift, .390" lift, 108 LSA) and this little engine will be "snappy" on the low-end and get as good mileage as it's capable of. We went through this
"exercise" a couple of years ago with a "Jimmy". 19 MPG from 14 with the 2.8.

TH700-R4 would also be a better choice. TH200-4R is a good trans,m but most aren't Chevy cases. Do you already have one? If not, the 700 should be a little less expensive, and will hold up fine behind the little V8.

Jim

[MagicRat]

Originally Posted by MrPbody

All due respect to MR, but I think 267 isn't as bad as all that... The smaller valves and ports are designed for the smaller dislpacement. That's a GOOD thing, not a bad one. Unless the engine's performance range is expected to be above 4,000 RPM, the small heads are an asset.

The valves are well matched for the engine:
tiny valves....tiny displacement......tiny power

My point was that the cylinder head design (and related components) are what limit the power of this engine. Many newer, sophisticated designs make much more power (up to three times the power, or more) from the same displacement, but such sophistication cannot be easily applied (bolted on) to this engine.

Jim, that is good advice for a parts combo for a 267, but respectfully, I cannot think of any convincing argument to rebuild a 267 when there are other , better choices available for the same rebuilding cost.

The 267 was not a very good engine. It was reliable and smooth, but a V6 provided the same performance and gave better fuel economy.

Even if one does not need the power and core charge for a 350, a 305 provides a better combination of performance and mileage than the 267.

The 305's bigger bore and shorter stroke is a better combination for lower friction, greater efficiency and better power characteristics.

GM made the 267 for only 3 years then replaced it with the 305 as the base-model V8. This was done because the 305 (with a bigger bore and shorter stroke) is better, more powerful and more efficient (as demonstrated by the fact it is cleaner, more efficient in burning fuel and produces lower emissions.)

I do agree on the transmission, though. If I were looking for this swap, I would get a rebuildable 305 (or350) / 4bbl with a THM700R4 already attached. I have seen many such combos available at wrecking yards or for sale privately, very inexpensively.

[MrPbody]

MR,

We've found that by enhancing the low-speed power potential of these engines, they really are "snappy" (leave a light well, good passing accelleration) and provide excellent mileage. It's true, in factory "form", quite anemic. But adding a cam, intake and small 4-bbl. make them up to the task. Not for a "hot rod", but an efficient little power plant. It's not unusual to get upwards of 25 MPG with them, in a fairly heavy car like an '80 Caprice.

No doubt a larger displacement will provide more power, but not everyone is looking for a hot car. Some just want a little more without sacrificing what little fuel economy they're getting. 262 and 267 foot this "bill" nicely.

Jim

[MagicRat]

Originally Posted by MrPbody

MR,

We've found that by enhancing the low-speed power potential of these engines, they really are "snappy" (leave a light well, good passing accelleration) and provide excellent mileage. It's true, in factory "form", quite anemic. But adding a cam, intake and small 4-bbl. make them up to the task. Not for a "hot rod", but an efficient little power plant. It's not unusual to get upwards of 25 MPG with them, in a fairly heavy car like an '80 Caprice.

No doubt a larger displacement will provide more power, but not everyone is looking for a hot car. Some just want a little more without sacrificing what little fuel economy they're getting. 262 and 267 foot this "bill" nicely.

Jim

Thank you Jim for your balanced argument and I do understand your point.

I think that jknowles can understand both sides of this discussion and I am sure now he can make an informed decision.

[jknowles87]

I appreciate the quick and complete responses to my inquiry. My 267 is underpowered, but not dead. I made an open element air cleaner setup for it, and that greatly increased my acceleration and mpg (18-20 right now).

My reasonings for keeping the 267 is a) i already have it in the car and b) it is an engine that not many people have. I found a cam made by crane that makes "brute low-end torque" for 267 and 305s, in the 500-3500 rpm range. I planned on have the motor rebuilt with that cam, a 4bbl intake and quadrajet from a 305 for extra air flow (if i go this way)

I initially had planned a 350 swap for it, and I may yet go that way due to a better source of parts and compatability. I know the 267 accessories work on a 350 sbc, but will the wiring harness work too? What about computer?

Overdrive would be nice, no matter what engine I choose to build. Keep in mind, I want a street cruiser, not a hot rod.

[jaqes]

I also using Chevy 267 and i continue enjoying with it.

[463]

use the service RPO sticker located on the inside of the trunk lid. the code should be something like a G80 that a posi rearend. a GU4 is a 3.08 gear. here is a decode link:http://cadillacfaq.com/rpo/index.php

[luxeryvic]

try headers and and exhaust, the stock muffler and cat will hold back some power

[454bigblock]

Of all my years as a mechanic, the 267 has got to be the worst engine chevy ever made. You can easily replace the motor with a 305 or 350. No modifications. If your concerned about fuel mileage then I would go for the 305. Dont put your money into a 267, my friend.

[firebirdman81]

I have a 267 Chevy in my 1981 Firebird. Reliable and fuel efficient in a lighter car such as the Firebird but as everyone says, underpowered! I bought this car in 1991 because is was equipped with the Chevy V8 and I had a 350 to bolt right in without complications.

I drove the car only in the summer for 5 years and due to marriage, mortgage and children, I parked the car for many years without installing the 350. Now the car is almost 30 years old and still a number's matching car for whatever that's worth.

Over the years, I replaced the original soft cam with a mild Energizer cam (427 lift- 204 dur.) a valve job and replaced the carb with a Q-jet. I even found a posi rear end with a 3:42 ratio out of an 81 Z28 waiting to go in.

Reading some info on 267's they all say the same thing. "Not worth building for performance" and I will be taking their advise. Appraisers say because it came with the Chevy V8, if I should install the 350, it will still be considered an original car just not a number's matching car. If I keep the 267 and install the 3:42 posi, I should be able to get a bit more get up and go out of it.

[Ol'Jim]

The cost of the parts to rebuild the 267 will probably be significantly more $$ than for a 305/350. Same labor/machining involved, but the sales volume of a particular component is a key factor in driving it's cost down. Not many people making (or buying) rings, pistons, gaskets for 267's these days... Still many thousands of 305/350 SBC's being rebuilt every day. Check it out. Also - you can find quite a few good, used, running 305's that will not require a rebuild. Often with the matching 700R-4 O/D transmission still attached, complete with carb & distributor. You could be in business with a more powerful, more fuel-efficient, more durable eng/trans for maybe $400-750, and a weekend or two of work swapping them out. Toss in the cost of a quick degreasing, some fresh Chevy Orange spray paint, and you're in business for far less work & $$ than rebuilding your 267, and with more power to boot. Just my $.02... Also I agree with whomever suggested headers, & I'd go with a pair of Dynomax turbo mufflers & dual exhaust for even more economy & power, with an awesome cruising sound, but not too loud.

[monte_nut]

I have an 81 monte carlo with a 267 in it and i am a chevy guy all the way but the 267 is nothing but a gutless turd. i would go with a 305 all the way. it will cost the same to build and parts are easier to come by. DON'T WAIST YOUR TIME WITH THE 267 IT'S NOT WORTH IT.

[MrPbody]

Monte Nut,

Please note the dates on this thread. It's been "dead" for a long time. Also pay attention to the poster and realize not everyone is after big power. Some just want a "nice" engine.

I've heard exactly the same argument against 305. A good friend has a 400 HP 305 in his IROC, runs 12s, gets 22 MPG and revs to 7,000 in HIGH gear... LOTS of head work and a "special" camshaft, but still a .030" over 305, stock crank and rods. 89 octane, to boot!

IMO, 350 and 383 are the "best" small blocks. No argument there, just a "reality check" regarding the smaller engines.

Jim