250 straight 6 engine.

Non-specific B-body discussion

250 straight 6 engine.

Postby Rare one » Sun Feb 16, 2014 11:35 am

Hi there.
I have a rare 78 Bel Air that has the unique 4.1 liter 250 cube straight six engine and I am wondering if anyone on here has had the experience of owning or driving one? I don't think many B cars were equipped with this engine and not to mention they only were available for 3 model years.
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Re: 250 straight 6 engine.

Postby theholycow » Sun Feb 16, 2014 12:46 pm

My car has the 4.1 V6, never heard of the inline. Sounds cool. Got specifications? Maybe post some photos? :D
1980 Buick LeSabre Limited 4.1 V6 T5 5 speed manual, 38,000 miles, family heirloom. (Up to 78,000 miles now, can't believe my work is holding up!)
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Re: 250 straight 6 engine.

Postby Rare one » Sun Feb 16, 2014 3:25 pm

Image
Here is a pic of my 78 Bel Air straight 6 engine. This engine returned for 3 model years in the downsized full size Chevrolet and Pontiac cars from 1977 to 1979. Rated at 110 HP and 190 ftlbs of torque. I'm curious about other peoples experience and stories. Ask any questions about this or my unique B body in general.
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Re: 250 straight 6 engine.

Postby theholycow » Sun Feb 16, 2014 8:55 pm

That is very cool. I bet it delivers a whole lot of that torque right from idle without complaining.
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Re: 250 straight 6 engine.

Postby rabidmadman » Mon Feb 17, 2014 12:01 am

That is very cool and very rare. I saw one of these with the same motor, but also equipped with a 3 speed manual on the column...was very interesting.
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Re: 250 straight 6 engine.

Postby Rare one » Mon Feb 17, 2014 6:39 am

theholycow wrote:That is very cool. I bet it delivers a whole lot of that torque right from idle without complaining.

And you would be very correct. Off idle torque is excellent right up to about (I'm guessing here, no tach) 2000 rpm and after that its just fan noise lol. I have thought about upgrading it for more performance but I really like how it isn't to bad on fuel. Plus if I remove the stock Carb, air cleaner in heated intake winter drivibilty and warm up would go right out the window.
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Re: 250 straight 6 engine.

Postby Rare one » Mon Feb 17, 2014 6:54 am

rabidmadman wrote:That is very cool and very rare. I saw one of these with the same motor, but also equipped with a 3 speed manual on the column...was very interesting.


I have always wondered this myself if any of the 1977-90 B cars, especially the 77-79 model years were ever built using a manual trans?

How cool would it be if there was a chrome stick with black ball shift knob poking out of the trans tunnel and 3 pedals to boot :) kinda like one of my fave cars the "Iraqi taxis"

My Canadian built car was not equipped with the dreaded TH200 it came with the TH350 and 2.73 8.5 "Buick" rear axle.
Weired eh? Talk about an over built drive train :D

Anyone have production figures on how many 77-79 cars came with the 250 I6 engine? Wagons would be excluded as they had the 305 2bbl engine as the base offering.
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Re: 250 straight 6 engine.

Postby theholycow » Mon Feb 17, 2014 9:12 am

Rare one wrote:Plus if I remove the stock Carb, air cleaner in heated intake winter drivibilty and warm up would go right out the window.

You're not kidding! I took my car to a shop to let them deal with my leaking exhaust manifold and they didn't put the heat shield back on, so the Thermac intake just pulls general underhood air instead of manifold-heated air. We're having the coldest winter since I've had this car. I have to sit there and feed it gas with my right foot to keep it alive after starting, I have to keep it revving really high to be able to drive for the first mile, it takes forever to warm up, and fuel economy is down more than it should be. I wish I could find another heat shield. I should at least half-ass one until I find a proper one, come to think of it.
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Re: 250 straight 6 engine.

Postby theholycow » Mon Feb 17, 2014 9:16 am

Rare one wrote:I have always wondered this myself if any of the 1977-90 B cars, especially the 77-79 model years were ever built using a manual trans?

How cool would it be if there was a chrome stick with black ball shift knob poking out of the trans tunnel and 3 pedals to boot :) kinda like one of my fave cars the "Iraqi taxis"

My 1980 has a 5 speed, but it didn't come that way. Knob is a retired 8-ball (printing worn off), stick isn't chrome though. Everything is ugly because that's how I roll, but anyway...
https://sites.google.com/site/hackensteinberg/
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Re: 250 straight 6 engine.

Postby Rare one » Tue Feb 18, 2014 7:09 am

theholycow wrote:
Rare one wrote:Plus if I remove the stock Carb, air cleaner in heated intake winter drivibilty and warm up would go right out the window.

You're not kidding! I took my car to a shop to let them deal with my leaking exhaust manifold and they didn't put the heat shield back on, so the Thermac intake just pulls general underhood air instead of manifold-heated air. We're having the coldest winter since I've had this car. I have to sit there and feed it gas with my right foot to keep it alive after starting, I have to keep it revving really high to be able to drive for the first mile, it takes forever to warm up, and fuel economy is down more than it should be. I wish I could find another heat shield. I should at least half-ass one until I find a proper one, come to think of it.

Yeah up here in Canada we are having one of the harshest winters in a long time. It by far the worst winter my Bel Air has seen since I have owned it (Feb 2010). I currently have everything thermac related intact but my air cleaner vacuum temp sensor was bad and always allowing hot manifold air to be sucked in even in the middle of July and it would make the engine ping pretty bad on 87 junk fuel and factory timming settings. I have since rerouted the vacuum source from the exhaust heat riser but now when the engine block is fully warmed the thermal vacuum switch cuts off all vacuum to the thermac flap door and then I'm sucking in -15 air making the fuel economy suffer and a slight bog when you lay on it off idle. During the summer this is not an issue and having the intake heat riser flap fully open is probably what the air cleaner temp sensor would be doing anyway if it was functioning correctly. Trouble is they stop making them :? at least for my unique engine
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Re: 250 straight 6 engine.

Postby Rare one » Tue Feb 18, 2014 7:23 am

theholycow wrote:
Rare one wrote:I have always wondered this myself if any of the 1977-90 B cars, especially the 77-79 model years were ever built using a manual trans?

How cool would it be if there was a chrome stick with black ball shift knob poking out of the trans tunnel and 3 pedals to boot :) kinda like one of my fave cars the "Iraqi taxis"
i
My 1980 has a 5 speed, but it didn't come that way. Knob is a retired 8-ball (printing worn off), stick isn't chrome though. Everything is ugly because that's how I roll, but anyway...
https://sites.google.com/site/hackensteinberg/

I was just going over your build write up and I must say that this I very interesting and cool that you converted your B body to stick shift. I like how you did it on a budget and used GM parts to make it happen. So if I'm correct all the parts were sourced from an 80's era Chev S10? I have alot of questions and I would love to do this to my Bel Air but I would want it to appear factory. I think the pedal set up and removing the stock column shifter and changing it to a floor shift steering column would be the hardest part. Is a T5 trans have the same dimentions as a TH350, drive yokes the same and cross member location?
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Re: 250 straight 6 engine.

Postby theholycow » Tue Feb 18, 2014 10:03 am

Rare one wrote:During the summer this is not an issue and having the intake heat riser flap fully open is probably what the air cleaner temp sensor would be doing anyway if it was functioning correctly. Trouble is they stop making them :? at least for my unique engine

I bet a slightly wrong one would be way better than totally missing. Otherwise you could do some more creative vacuum routing and switch it around by season or just skip vacuum and manually secure the flap in the preferred direction each season.

Rare one wrote:So if I'm correct all the parts were sourced from an 80's era Chev S10? I have alot of questions and I would love to do this to my Bel Air but I would want it to appear factory. I think the pedal set up and removing the stock column shifter and changing it to a floor shift steering column would be the hardest part. Is a T5 trans have the same dimentions as a TH350, drive yokes the same and cross member location?

  • T5 (complete with shifter, boot, etc) was from a 1986 S10 2.5 I4 (though I received it in a 1994 S10 2.2).
  • Bellhousing was probably from a 1960s GTO or something. There are 3 or 4 part numbers of the same identical bellhousing that was used for all Buick, Oldsmobile, Pontiac, and Cadillac pattern engines, but it's kinda rare...nobody buying those engines wanted to shift, I guess.
  • Fork was a somewhat standard GM heavy duty fork.
  • Clutch release system (pedal, master and slave cylinders, and I think release bearing) were from the 1994 S10. 80s era would have been fine too. After 1994 they went to a concentric slave cylinder which, in hindsight, might be a bit easier.
  • Flywheel was a 10.4" 53 pound monster from a Jeep Dauntless 225.
  • Pressure plate was 10.4" from a 3rd gen Camaro, I think a 305.
  • Clutch was from a 1983 S10 2.8L. I could have used the 1994 2.2's clutch but the 1983 2.8's clutch is slightly larger. 9 11/16" vs 9 3/8" or something like that. No OEM 10.4" clutch exists for the 14-spline 1 inch input shaft, and the two or three aftermarket ones were prohibitively expensive for me. Considering the performance I've gotten, I bet the smaller one would have sufficed.

The T5 is not the same length as the TH350. If I wasn't in a hurry by that time, I would have found an appropriate donor driveshaft. Instead I had a driveshaft shop do a custom length for me using my original driveshaft. IIRC they shortened it.

Crossmember location is off by a couple inches. With care you should be able to drill a new hole in the plate sticking off of the crossmember where the transmission bolts to it. I was hacky and just guessed and re-drilled it a million times. Works fine but it's ugly if you look under the car.

I don't think the steering column would be very difficult. I've had mine most of the way apart to fix it (it was wobbly/loose); I posted a thread with photos and very detailed instructions. I think it's only a few more minutes work getting it the rest of the way off to replace it. I suspect that a similar year Camaro would make a good donor but I'm not sure. I've also seen where someone who is good at sheet metal/body work just modified the existing column to be smooth.

The clutch pedal was one of the hardest parts. I kept looking at it, trying to find a way to make it fit or another donor that would fit, the one day I had a Eureka! moment and figured out exactly how it would fit.

Brake pedal was a piece of cake, I just modified the existing one. I moved it right for easier heel-toe; it is mounted to a bushing, I cut off one side of the bushing and placed it on the other side. I trimmed the plate where the rubber pad goes and stuck on the appropriate rubber pad. You could just trim it and skip the mounting bushing adjustment.

Finding that flywheel was tough. I wanted one that was balanced for my engine but no such beast exists. I have read about "match-balancing" where they balance it based on the flexplate I removed but found nobody who could do it. In the end I settled for imbalance. Turns out it's not too bad, especially with 53 pounds of gyroscope effect. You will probably need a different flywheel...hopefully an easier one.

I had to create my own slave cylinder mounting bracket. That bellhousing was never used with a hydraulic clutch. A concentric slave cylinder would eliminate that problem.

Without opening the hood or looking under the car, the only thing that doesn't look OEM is the steering column, which has the mounting nub for the shifter. The shifter boot screws into the floor nicely and looks OEM. The pedals look OEM. (Ok there's plenty of other things that look modified, aftermarket, or hacked, but not relevant to this discussion.)

Open the hood and you see some messy craftsmanship and design where the clutch master cylinder pokes through the firewall and the clutch pedal mount is bolted to the horizontal top shelf of the firewall. You also see the clutch hydraulic line that accidentally got melted and repaired, and if you look deep down you can see the slave cylinder bracket.

Look underneath and you can see the perforated crossmember transmission mounting plate (hacky me, you could do better), and the half-assed covers on the bellhousing because I couldn't find proper ones that wouldn't break the bank. If your budget is better than mine then you can buy a nice, clean bellhousing that includes its covers.
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Re: 250 straight 6 engine.

Postby Rare one » Sun Feb 23, 2014 7:59 am

Thank you very much for posting and sharing all this information.

I would really love to do this to my 78 Bel air but its a big undertaking and the only way I would consider doing this said swap is if I didn't have to make any perminant mods or get wild with backyard hackery lol.

How did you configure the steering column steering lock lever? Did you just leave it in the drive position?

Reverse light and neutral safety switch is another thing that's popping up in my brainstorming state lol.

I think my engine would be easier to find a flywheel and bellhousing tho as these engines were always avalible with a manual trans behind them in other GM vehicles. Again the steering column and clutch pedal setup without disturbing the fuse junction box are the head scratches for me but that's half the fun.

Your right about the over the input shaft style release bearing setup, much easier to install and adjust.

How dose your Lesaber drive and how is it in 5th gear on the highway?
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Re: 250 straight 6 engine.

Postby theholycow » Sun Feb 23, 2014 1:07 pm

I left the lock lever in place and leave it in the P position at all times. It wouldn't be hard to take it apart and permanently fix it in place.

Neutral safety switch is a non-issue. I don't think it existed back then. If equipped, you could connect it to the clutch switch I guess. I prefer unsafety and removed the clutch switch...I'll never run anybody over starting the car, but you know the old cliche, if I stall on railroad tracks at least I can electric drive off of them like a Prius.

Reverse lights are a piece of cake. The connector goes to the steering column. I just fished it out and spliced it to the OEM reverse switch pigtail on the T5. Even the wire colors are the same.

The fuse box turned out to be easy after I struggled to place the pedal for a while. The pedal arm just barely clears the fuse block -- but I did have to remove a tail light harness whose plug was clipped to the side of the fuse block. I placed it back behind the pedal's stroke. Be sure to secure yours better than I did. GM put solid aluminum wire in that harness. Repeatedly beating it with the clutch pedal arm fatigued it until my tail lights stopped working. I bypassed that connector to fix it for that one wire and may eventually reroute the whole thing.

I love how my car drives. The gearing in my T5 turned out just about right, though a slightly taller 1st gear would give me closer ratios. You can get T5's with all kinds of gearing or even assemble one with your choice of gears.

I have a heavy clutch, probably similar to a race car with a multi-puck clutch. It's partly my engineering but I suspect it's partly the pressure plate I used, for which little data was available. I like it heavy but you would probably end up with a more regular feeling clutch.

Also due to my engineering, but more so my craftsmanship (the specific T5 I used had the input shaft and quill too long so I had to cut both back and the cut the splines along more of the input shaft; and I suspect my hacked inspection cover lets water in to wash the grease from the input shaft) the clutch can get a little sticky on the input shaft and drag. If I ever take the transmission down I might dremel those splines some more.

Anyone who can drive a manual can get in my car and go. Despite its hacks and weaknesses it operates like any manual. The clutch, although very heavy, is much easier to use than my 2008 VW was. There's a nice wide range in which it engages gradually, but that range is neither at the bottom nor the top. It's right where it ought to be.

My 5th is just right for my engine and rear end and my preference. It's almost as tall as it can reasonably be, and I like that. I can get into it and accelerate glacially at 45mph but that's probably not good for my engine (upgrade my oil pump and ignition system, then it'll be fine). By 55 it's good, I won't lose speed on the steepest hill. At 65, which is most of my freeway driving, it's perfect; I can accelerate reasonably, though if I feel like a fun downshift I still have a good excuse to do so.

Here's a video from a year ago, just 20 minutes of my shifter, knee, and pedals as I drive...it's 1 minute in before you see a shift (just to neutral), and 3 minutes before you see any real shifting action. I'm just lazily driving home from to work, not racing around or anything.
http://youtu.be/Dp6jFsBhYIA
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Re: 250 straight 6 engine.

Postby Rare one » Mon Feb 24, 2014 6:09 pm

That vid is neat. Looks like it drives great and the clearence to the dash and bench looks good. I believe the T5 didn't have a long throw with the S10 shifter. I am really wanting to do this to my Bel Air now lol. Any strange or annoying engine or diveline vibrations to speak of?
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