71 Cutlass Supreme with 260?

Sturgeon · 10-14-2007, 10:11 AM

This is further to a post I started a week or so ago... The best I can tell now is that the 350 I thought I had is actually a 260. The front of the engine block has a casting stamp of 550355 5 right below the intake manifold and just to the left of the oil fill. Based on searches, this appears to be a 260ci engine (also is marked with a 10 on the left side right under the first plug).

So, if this is true... I have a 260 with an intake off a 307 (casting 22528212) and an Edelbrock 1405 4bbl carb with a TH400 trans. The car is not a total pig, actually does pretty good from 40 to 80mph...and it runs very well, but I was hoping for more.

Any opinions on path forward for this setup? Any sensible way to get more horsepower out of this setup short of replacing the engine.

GoldOlds · 10-14-2007, 11:15 AM

If what you've got really IS a 260, well, sorry, you're not going to get much power out of it; not exactly an engine born of great potential. If you insist on keeping it, replace the TH400 with a TH350 - you'll shed a few pounds (20?) and lose less hp between the flywheel and back tires. There's NO WAY a 260 can make enough power to require a TH400. Honestly, I'd find a 350 or a 403; they can both make decent power.

- GoldOlds

J-(Chicago) · 10-14-2007, 02:11 PM

Weird....
That's quite a setup you have there. Oldsmobiles......

every part goes somewhere and in some cases, everywhere.

If you like it, keep it.
I had a 260 with 195000 miles on it

Sturgeon · 10-14-2007, 02:48 PM

I'm posting a few pictures of the casting numbers (the only numbers I could find on the block). Maybe someone can help identify/verify what I have here. Of course, you'll notice that the engine is gold which confuses things... I thought it was painted.

The first picture shows the location of the main stamping, the second shows the numbers... they read 550355_5. The third shows a "10" stamped under the valve cover on the drivers side.

Can anybody help validate what this is?

Dapapadon · 10-14-2007, 03:28 PM

I did find this info. if it will help.

Small blocks from 1977 onward will have the CID or liters cast in large numbers right above the center core plug. The engine VIN number will also be cast onto the side of the block.

I'm not familiar with the later blocks. Generic name for core plug is freeze plug. Check both sides of the block above the motor mounts.

Number 10 heads sound like a 260 though.

Don

J-(Chicago) · 10-14-2007, 07:47 PM

A 260 should be
557751

But.... I found this quote on 442.com
"The 1977 and newer blocks will have the cubic inches cast in large raised numbers right above the right hand center freeze plug, eg. 403. The 307 will be in liters (5L), and a diesel engine will have the letters "DX" on it. The engine VIN letter will also be cast into the side of the block. Note that the 260 blocks sometimes have the last 3 digits of the casting number cast there, "355", which is rather misleading. "

All Olds 260 blocks 1983 and newer were painted black, so I'd poke around that gold paint and see what comes up.
Olds 260 heads are #10 or #2a

The 260 heads have water jacket holes in between the intake ports. The orig. 2bbl intake covers them. So if there is an old 4bbl intake on there They must have plugged them up somehow so coolant didn't go everywhere.

Sturgeon · 10-15-2007, 05:47 AM

Well, I found this post which clearly shows that block# 550355 is an Olds 260ci from '75-'76. Depressing.

http://64.233.167.104/search?q=cache...lnk&cd=4&gl=us

tons of other good info in here as well.

Sturgeon · 10-15-2007, 05:49 AM

here's another one...

http://64.233.167.104/search?q=cache...lnk&cd=3&gl=us

Oldsguy · 10-15-2007, 05:59 AM

This is what I would do if I were in your shoes. Do some research and find out what can be done with the 260 first. Ask, why is the discplacement 260 and are there any similarities with the 350 such as stroke or bore? Is there any way to produce more power with that engine? If so, you might want to pursue that, if not then you may decide to look for another engine for a suitable swap and just the drive the thing in the meantime. If you do the latter, you could rebuild a really nice engine as time/money permits and then make a swap one week when it is ready. Just my 2 cents.

Sturgeon · 10-15-2007, 08:00 AM

thanks Dan... very wise comments. I started to research the 260 a bit (how to increase power output), but haven't come up with anything yet. The idea of slowly rebuilding an engine is very interesting... I certainly don't have several thousand sitting around for a new crate motor.

The current set-up does run very well, but leaves much to be desired at the pedal.

Oldsguy · 10-15-2007, 12:02 PM

Well, that is essentially what I have done and it has worked well for me. I am still not driving it though. You have to learn patience and persisitence (or at least I did). Setting intermediate goals has helped too, i.e. this week....order rebuild kit, next payday send block to machine shop, next payday have heads done,,,etc. Good luck.

J-(Chicago) · 10-15-2007, 12:15 PM

If you weren't in New york, I'd trade you for my 350. I spend a LOT of $ a month in gas to drive my Olds now.

90 mi per
day
6 days per week
=540mi per week
X4 weeks per month.
=2160 mi per month
/ 12 MPG
=180 gallons
X 3.08 per gallon
=$554 per month
Probably around the cost to lease a new BMW.

Sturgeon · 10-15-2007, 03:54 PM

more than a new BMW!

Olds64 · 10-15-2007, 04:33 PM

Check out the following website. I have looked at it a couple of times and it strikes me that the guys that post regularly might know a thing or two about the 260 (only because most of them seem to own later model Cutlasses).

http://www.oldspower.com/

Oldsguy · 10-16-2007, 05:15 AM

Quote:

Originally Posted by J-(Chicago)

If you weren't in New york, I'd trade you for my 350. I spend a LOT......
=$554 per month
Probably around the cost to lease a new BMW.

Yeah, but new BMWs are a dime a dozen.

Sturgeon · 10-16-2007, 03:14 PM

agreed! that's why I bought my Cutlass.

So, I read a few posts in that other forum... one guy was suggesting adding a turbo charger to a 260! interesting, but I never heard of doing that with a carburated system.

dar83501 · 10-17-2007, 12:43 AM

why in god's name is a t-400 sitting behind a 260? My impala and my 91 olds have a 231ci v6 for crying out loud! 29 cubic inches bigger and the strongest transmission made by buick, pontiac, and oldsmobile behind it!

Sturgeon · 10-17-2007, 05:05 AM

I'm assuming the TH400 is original to the car... the better question would be "why in god's name would a 260 be sitting in front of a th400??"

I'm bringing the car in to my mechanic (experienced Olds guy) end of this week... he's going to take a close look at the whole configuration.

joe_padavano · 10-17-2007, 07:13 AM

Quote:

Originally Posted by Sturgeon

So, I read a few posts in that other forum... one guy was suggesting adding a turbo charger to a 260! interesting, but I never heard of doing that with a carburated system.

Then you had better do a little research. The original Turbo Buick V6, the Turbo Pontiac 301, the Olds Jetfire, and the Corvair Monza Turbo were all carbed.

GoldOlds · 10-21-2007, 07:19 PM

Turbocharging would probably help, but it boils down to the same bottom line - anything you do to make DECENT power out of a 260 will make GREAT power in a 350. If I was considering a unique buildup like the 260, the first question I'd ask is "is the bore on this engine big enough for heads with decent-sized valves?" Alot of Chev guys think it would be great to see what they can get out of a virgin bore 283 until they realize it won't clear 1.95/1.50 valves. The 1.875/1.562 valves on the #5 heads would be REALLY close; FORGET about anything bigger (although you'd probably be boring the block anyway).
Sorry to keep picking at your 260 plan, but I honestly think you'll be disappointed with the performance result after spending significant $$$$. Keep in mind the pre-'78 Cutlass is NOT a light car!

- GoldOlds

Sturgeon · 10-23-2007, 07:25 PM

no worries... I'm at peace with my current situation (disappointed in what I have, but at peace). I'll just take my time and look for the right replacement engine over the next 18+ months... in the mean time, I've got the interior to take care of and some cool cruising to do.

J-(Chicago) · 10-23-2007, 07:41 PM

hahaha, I might have you beat here soon. I think I'm gonna put a 231/400 combo in this winter

I gotta work with whats laying around at the moment.
Stupid.....
but
I can't stand paying for the gas anymore, and I'm NOT getting rid of the Olds. It's my first car and I've been driving it everyday for almost 10 years.
Someone really screwed us with this 3-4 dollar a gallon crap.

J-(Chicago) · 10-23-2007, 07:45 PM

Thus revoking my racing stripe privileges.

I might just end up putting in a 260 because I'm not sure about mount changes for the Buick motor.

GoldOlds · 10-23-2007, 08:42 PM

Quote:

Originally Posted by Sturgeon

no worries... I'm at peace with my current situation (disappointed in what I have, but at peace). I'll just take my time and look for the right replacement engine over the next 18+ months... in the mean time, I've got the interior to take care of and some cool cruising to do.

THAT sounds like a very reasonable plan, although I doubt it will take 1.5 years to find an Olds motor with good potential (350, 403, 455 or whatever you'll eventually come across). As you just suggested, you can still do lots of cruising and by the sounds of it, your 260 will live up to that duty as long as it is required to do so. ALOT of guys use a lesser motor for cruising while saving up $$$$ to build a powerhouse.

- GoldOlds

Oldsguy · 10-24-2007, 04:41 AM

J, if you aren't using a Rochester Quadrajet I would consider it. If you stay out of those you get as good to better mileage than you would on a 2bbl.

J-(Chicago) · 10-24-2007, 07:18 PM

I'm using the stock 4 bbl carb &
an 85 307 at the moment

I set the tps voltage, and adjusted the secondary needles, & timing, and my mileage is still only 13 mpg at best. The computer is getting silly on me lately and keeps advancing the timing

it's about time timethat i take
it off and totally rebuild it again, but rebuilding a 4 bbl 307 setup seems like trying to piss in the corner of a circle room.

I mean.... It's already a dog, might as well keep it that way now.
I had a 73 smogger with # 8 heads in it, but I yanked it back out for upgrades and put the 150000 307 back in.
Then.... my job of course moved from 15 miles away one way, to 50 miles away one way and both of these motors are like fingernails on a chalkboard to me at the moment.

I got a 97 FRODD escort , but it's PURPLE!!!
It needs a shifter cable, brakes, a battery, 2 tires and the 200 dollar registration fee. I think I could find a low mileage 260 2bbl setup for that price

and save myself a headache.

I guess what I'm getting at is..... The 307 is beat and crappy on mileage to boot.
and the smogger 350 isn't the most ideal thing to put back in.
after that, I only have a 1971 350 or a 72 455 to put in a daily driver

I need some efficiency STAT. I don't make a lot of money.
What do you think will be the easiest combo to burn 600 miles a week in?

J-(Chicago) · 10-24-2007, 07:26 PM

Don't make me yank the Iron duke out of a firebird though.
Pretty please!!!!???

10-14-2007, 10:11 AM	#1 (permalink)
Sturgeon 71 Cutlass Supreme Join Date: Oct 2007 Location: Rochester, New York Posts: 14	71 Cutlass Supreme with 260? This is further to a post I started a week or so ago... The best I can tell now is that the 350 I thought I had is actually a 260. The front of the engine block has a casting stamp of 550355 5 right below the intake manifold and just to the left of the oil fill. Based on searches, this appears to be a 260ci engine (also is marked with a 10 on the left side right under the first plug). So, if this is true... I have a 260 with an intake off a 307 (casting 22528212) and an Edelbrock 1405 4bbl carb with a TH400 trans. The car is not a total pig, actually does pretty good from 40 to 80mph...and it runs very well, but I was hoping for more. Any opinions on path forward for this setup? Any sensible way to get more horsepower out of this setup short of replacing the engine.

10-14-2007, 07:47 PM	#6 (permalink)
J-(Chicago) Seasoned beater pilot. Join Date: Jan 2007 Location: Chicago Posts: 1,583	A 260 should be 557751 But.... I found this quote on 442.com "The 1977 and newer blocks will have the cubic inches cast in large raised numbers right above the right hand center freeze plug, eg. 403. The 307 will be in liters (5L), and a diesel engine will have the letters "DX" on it. The engine VIN letter will also be cast into the side of the block. Note that the 260 blocks sometimes have the last 3 digits of the casting number cast there, "355", which is rather misleading. " All Olds 260 blocks 1983 and newer were painted black, so I'd poke around that gold paint and see what comes up. Olds 260 heads are #10 or #2a The 260 heads have water jacket holes in between the intake ports. The orig. 2bbl intake covers them. So if there is an old 4bbl intake on there They must have plugged them up somehow so coolant didn't go everywhere. __________________ I'd rather have a numbers matching poker hand. Last edited by J-(Chicago) : 10-14-2007 at 08:14 PM.

10-15-2007, 05:59 AM	#9 (permalink)
Oldsguy Administrator Join Date: May 2004 Location: Lees Summit MO Posts: 2,967	This is what I would do if I were in your shoes. Do some research and find out what can be done with the 260 first. Ask, why is the discplacement 260 and are there any similarities with the 350 such as stroke or bore? Is there any way to produce more power with that engine? If so, you might want to pursue that, if not then you may decide to look for another engine for a suitable swap and just the drive the thing in the meantime. If you do the latter, you could rebuild a really nice engine as time/money permits and then make a swap one week when it is ready. Just my 2 cents. __________________ Dan '46 2 door

10-15-2007, 12:02 PM	#11 (permalink)
Oldsguy Administrator Join Date: May 2004 Location: Lees Summit MO Posts: 2,967	Well, that is essentially what I have done and it has worked well for me. I am still not driving it though. You have to learn patience and persisitence (or at least I did). Setting intermediate goals has helped too, i.e. this week....order rebuild kit, next payday send block to machine shop, next payday have heads done,,,etc. Good luck. __________________ Dan '46 2 door

10-15-2007, 12:15 PM	#12 (permalink)
J-(Chicago) Seasoned beater pilot. Join Date: Jan 2007 Location: Chicago Posts: 1,583	If you weren't in New york, I'd trade you for my 350. I spend a LOT of $ a month in gas to drive my Olds now. 90 mi per day 6 days per week =540mi per week X4 weeks per month. =2160 mi per month / 12 MPG =180 gallons X 3.08 per gallon =$554 per month Probably around the cost to lease a new BMW. __________________ I'd rather have a numbers matching poker hand. Last edited by J-(Chicago) : 10-15-2007 at 12:26 PM.

10-14-2007, 11:15 AM	#2 (permalink)
GoldOlds Senior Member Join Date: May 2007 Location: Chatham-Kent, Ontario Posts: 116	If what you've got really IS a 260, well, sorry, you're not going to get much power out of it; not exactly an engine born of great potential. If you insist on keeping it, replace the TH400 with a TH350 - you'll shed a few pounds (20?) and lose less hp between the flywheel and back tires. There's NO WAY a 260 can make enough power to require a TH400. Honestly, I'd find a 350 or a 403; they can both make decent power. - GoldOlds

10-14-2007, 03:28 PM	#5 (permalink)
Dapapadon Senior Member Join Date: Jan 2007 Location: Portland, OR Posts: 311	I did find this info. if it will help. Small blocks from 1977 onward will have the CID or liters cast in large numbers right above the center core plug. The engine VIN number will also be cast onto the side of the block. I'm not familiar with the later blocks. Generic name for core plug is freeze plug. Check both sides of the block above the motor mounts. Number 10 heads sound like a 260 though. Don

10-15-2007, 05:47 AM	#7 (permalink)
Sturgeon 71 Cutlass Supreme Join Date: Oct 2007 Location: Rochester, New York Posts: 14	Well, I found this post which clearly shows that block# 550355 is an Olds 260ci from '75-'76. Depressing. http://64.233.167.104/search?q=cache...lnk&cd=4&gl=us tons of other good info in here as well.

10-15-2007, 05:49 AM	#8 (permalink)
Sturgeon 71 Cutlass Supreme Join Date: Oct 2007 Location: Rochester, New York Posts: 14	here's another one... http://64.233.167.104/search?q=cache...lnk&cd=3&gl=us

10-15-2007, 08:00 AM	#10 (permalink)
Sturgeon 71 Cutlass Supreme Join Date: Oct 2007 Location: Rochester, New York Posts: 14	thanks Dan... very wise comments. I started to research the 260 a bit (how to increase power output), but haven't come up with anything yet. The idea of slowly rebuilding an engine is very interesting... I certainly don't have several thousand sitting around for a new crate motor. The current set-up does run very well, but leaves much to be desired at the pedal.

10-15-2007, 03:54 PM	#13 (permalink)
Sturgeon 71 Cutlass Supreme Join Date: Oct 2007 Location: Rochester, New York Posts: 14	more than a new BMW!

10-15-2007, 04:33 PM	#14 (permalink)
Olds64 Landyacht Club President Join Date: Jul 2007 Location: Lawton, OK Posts: 1,587	Check out the following website. I have looked at it a couple of times and it strikes me that the guys that post regularly might know a thing or two about the 260 (only because most of them seem to own later model Cutlasses). http://www.oldspower.com/

10-16-2007, 03:14 PM	#16 (permalink)
Sturgeon 71 Cutlass Supreme Join Date: Oct 2007 Location: Rochester, New York Posts: 14	agreed! that's why I bought my Cutlass. So, I read a few posts in that other forum... one guy was suggesting adding a turbo charger to a 260! interesting, but I never heard of doing that with a carburated system.

10-17-2007, 12:43 AM	#17 (permalink)
dar83501 Brewsmobile > Bluesmobile Join Date: Sep 2007 Location: Lewiston, Idaho Posts: 272	why in god's name is a t-400 sitting behind a 260? My impala and my 91 olds have a 231ci v6 for crying out loud! 29 cubic inches bigger and the strongest transmission made by buick, pontiac, and oldsmobile behind it!

10-17-2007, 05:05 AM	#18 (permalink)
Sturgeon 71 Cutlass Supreme Join Date: Oct 2007 Location: Rochester, New York Posts: 14	I'm assuming the TH400 is original to the car... the better question would be "why in god's name would a 260 be sitting in front of a th400??" I'm bringing the car in to my mechanic (experienced Olds guy) end of this week... he's going to take a close look at the whole configuration.

10-21-2007, 07:19 PM	#20 (permalink)
GoldOlds Senior Member Join Date: May 2007 Location: Chatham-Kent, Ontario Posts: 116	Turbocharging would probably help, but it boils down to the same bottom line - anything you do to make DECENT power out of a 260 will make GREAT power in a 350. If I was considering a unique buildup like the 260, the first question I'd ask is "is the bore on this engine big enough for heads with decent-sized valves?" Alot of Chev guys think it would be great to see what they can get out of a virgin bore 283 until they realize it won't clear 1.95/1.50 valves. The 1.875/1.562 valves on the #5 heads would be REALLY close; FORGET about anything bigger (although you'd probably be boring the block anyway). Sorry to keep picking at your 260 plan, but I honestly think you'll be disappointed with the performance result after spending significant $$$$. Keep in mind the pre-'78 Cutlass is NOT a light car! - GoldOlds

10-23-2007, 07:25 PM	#21 (permalink)
Sturgeon 71 Cutlass Supreme Join Date: Oct 2007 Location: Rochester, New York Posts: 14	no worries... I'm at peace with my current situation (disappointed in what I have, but at peace). I'll just take my time and look for the right replacement engine over the next 18+ months... in the mean time, I've got the interior to take care of and some cool cruising to do.

10-23-2007, 07:41 PM	#22 (permalink)
J-(Chicago) Seasoned beater pilot. Join Date: Jan 2007 Location: Chicago Posts: 1,583	hahaha, I might have you beat here soon. I think I'm gonna put a 231/400 combo in this winter I gotta work with whats laying around at the moment. Stupid..... but I can't stand paying for the gas anymore, and I'm NOT getting rid of the Olds. It's my first car and I've been driving it everyday for almost 10 years. Someone really screwed us with this 3-4 dollar a gallon crap. __________________ I'd rather have a numbers matching poker hand.

10-23-2007, 07:45 PM	#23 (permalink)
J-(Chicago) Seasoned beater pilot. Join Date: Jan 2007 Location: Chicago Posts: 1,583	Thus revoking my racing stripe privileges. I might just end up putting in a 260 because I'm not sure about mount changes for the Buick motor. __________________ I'd rather have a numbers matching poker hand. Last edited by J-(Chicago) : 10-23-2007 at 08:00 PM.

10-24-2007, 04:41 AM	#25 (permalink)
Oldsguy Administrator Join Date: May 2004 Location: Lees Summit MO Posts: 2,967	J, if you aren't using a Rochester Quadrajet I would consider it. If you stay out of those you get as good to better mileage than you would on a 2bbl. __________________ Dan '46 2 door

10-24-2007, 07:18 PM	#26 (permalink)
J-(Chicago) Seasoned beater pilot. Join Date: Jan 2007 Location: Chicago Posts: 1,583	I'm using the stock 4 bbl carb & an 85 307 at the moment I set the tps voltage, and adjusted the secondary needles, & timing, and my mileage is still only 13 mpg at best. The computer is getting silly on me lately and keeps advancing the timing it's about time timethat i take it off and totally rebuild it again, but rebuilding a 4 bbl 307 setup seems like trying to piss in the corner of a circle room. I mean.... It's already a dog, might as well keep it that way now. I had a 73 smogger with # 8 heads in it, but I yanked it back out for upgrades and put the 150000 307 back in. Then.... my job of course moved from 15 miles away one way, to 50 miles away one way and both of these motors are like fingernails on a chalkboard to me at the moment. I got a 97 FRODD escort , but it's PURPLE!!! It needs a shifter cable, brakes, a battery, 2 tires and the 200 dollar registration fee. I think I could find a low mileage 260 2bbl setup for that price and save myself a headache. I guess what I'm getting at is..... The 307 is beat and crappy on mileage to boot. and the smogger 350 isn't the most ideal thing to put back in. after that, I only have a 1971 350 or a 72 455 to put in a daily driver I need some efficiency STAT. I don't make a lot of money. What do you think will be the easiest combo to burn 600 miles a week in? __________________ I'd rather have a numbers matching poker hand.

10-24-2007, 07:26 PM	#27 (permalink)
J-(Chicago) Seasoned beater pilot. Join Date: Jan 2007 Location: Chicago Posts: 1,583	Don't make me yank the Iron duke out of a firebird though. Pretty please!!!!??? __________________ I'd rather have a numbers matching poker hand.