4bt cummins swap

[MYBAD66]

Hey all I know this is probably a quite popular topic but I'm looking to put a 4bt cummins in the 66 with an sm465 tranny maybe put in dana 40 4.10 geared rear end is there anything in particular I should consider? Cutting the firewall frame etc.

[1972RedNeck]

If you get one with a Chevy adapter plate an flywheel, it will mate right to a tranny from behind an inline 6/sbc/bbc.

The firewall and frame are fine.

It would be pretty cool to see a 478 toro-flow under the hood. It should bolt right in too.

[1972RedNeck]

[kieth]

Anyone know the spec's on this engine (hp) max rpm, peak torque. Looks like it would get better fuel mileage with a OD transmission instead a stock 4 speed granny. how about a NV3500 or NV4500.....????they should handle the diesel torque......I always shoot for 65mph at 1800rpm on a diesel engine....someone get me the specs on the engine and I will work up the performance information. Kieth


I looked up the spec's and this little engine will perform rather well, it has the torque performance of a 327 4 barrel engine but is only rated at 2300rpm with peak torque at 1600 rpm. Looks like it needs a transmission with very close gear ratio spacing to keep from falling off its torque curve. Will review and look for a good transmission for this engine........Kieth

105hp@2300 peak torque 265ft/lbs@1600 rpm

[TJ's Chevy]

I know this is big an bulky an expensive....but a Richmond 6 speed will give you 5 direct gears and a 6th gear od. It is pretty close ratio.

[Peanutbutter]

Originally Posted by MYBAD66

Hey all I know this is probably a quite popular topic but I'm looking to put a 4bt cummins in the 66 with an sm465 tranny maybe put in dana 40 4.10 geared rear end is there anything in particular I should consider? Cutting the firewall frame etc.

Hi, I have a 90 1500 swb 4x4, 4bta with 4500 and 342 gears. To do this swap I would not use the 3500 trans, only the 4500 with around 3.42 gears and remember if you use the GM bread truck block to bellhousing adapter you will either have to cant the motor or the trans I think 7 degrees. We normally get 25 to 28 mpg, one time we got 34 in mass, checked the figures 3 times and came out the same. One time we pulled our smaller two axle fifthwheel camp trailer about 100 miles with no negative effects running 55 to 60 mah. Our truck has at least 400K on the 4bt and never been touched. Getting ready to put one in our blazer chalet.

[dieseldude4bt]

Hey Peanutbutter, I know who you are.
The Dodge diesel NV4500 or even the Getrag G360 would be a good option and wil bolt right up with the Dodge parts.
I run the original SM420 with a Ranger overdrive, have no problems with it and it gives me more gear options for my heavy truck when towing.
I average 24 mpg in combined driving in a 6300lb 3/4 ton 4x4 and have got as goood as 30 on a trip to Denver.

[ky-donzi]

I've got a 4bta in a 61 gmc 4x4. I used a late model frame, it makes getting parts easy. I love mine. Dieseldude helped me a lot on my build. Unless you go with a add on OD drop the 4 sp and look for a 5 or 6 speed.

Don't let the numbers fool you they have all kinds of power! Enough to rip gas componates apart

[argonaut]

Guys I'm intrigued by the 4bt swap. How does it stack up against a big block for power? Obviously it gets double the mileage. I had considered a 6bt but it looks like they're big and heavy and hard to make fit. Sorry if I'm thread jacking!

[ky-donzi]

I would say my 4bt (pump is turned up and different turbo) is somewhere in between a hot SBC and a mild BBC. There is a big difference tho, until you drive a diesel you cant really understand what I mean. Even tho my engine probably puts out 400-420 ft/lb, but at 1600-1800 rpm. The HP is very low, so it doesn't feel like driving a BBC until you hook a trailer to it.... IDK if Im making sense.

[dieseldude4bt]

^^2x what he said.

[jmack91z28]

My opinion is this isn't a popular topic, at least not here.

My 6BT with NV4500 in my dodge is the slowest thing i've ever owned/driven. Gets good mileage, about 18 mpg average. Pulls decent. My old 94 chevy with a 454 pulled way better but at the cost of 8 mpg... Parts are far more expensive, my (indestructible P pump) injection pump went out last year, costed me $2200 for a rebuild. You can build a nice small block for that much.

I dunno, I don't buy into the cummins hype even though I own one. A swap would be very expensive, around 6-8 thousand? You can buy a lot of gasoline for that, years and years and years of gasoline.

4BT's aren't balanced, so they'll rattle your teeth at idle. I've seen many a 4bt swap that ultimately ended in the owner selling the vehicle because of the harmonics and vibrations.

You want good mileage and torque, and affordability? Why not an older stovebolt 261 or so. It'll produce more power than a 4bt at less weight and costs and with fuel that costs 50 to 70 cents cheaper a gallon.

Just my opinion and experience on it.

[ky-donzi]

Jmack

I agree with a lot that you a have said except for

"You want good mileage and torque, and affordability? Why not an older stovebolt 261 or so. It'll produce more power than a 4bt at less weight and costs and with fuel that costs 50 to 70 cents cheaper a gallon."

I doubt that a 261 would pull anywhere near as well as my 4bt, nor get the mileage.

[jmack91z28]

No, you're right, it wouldn't get near as good as mileage as a 4bt. But when you factor in cost difference in fuel, it's not quite as good a deal you know? For the money and time spent that is.

I think a 261 or 292 will put out as much torque as an old 4bt, and a lot more hp. But then it has to do with where the two engines are making torque, how the truck is geared, transmission, etc.

My 6bt doesn't feel like it's really making any power till about 1700 rpm, then after 2300 rpm it's basically making a bunch of noise and not doing anything haha. So you've got such a small powerband. I know you can mess with the governer spring and all that fun stuff in the IP and "turn the fuel up", but I just haven't yet.

A good running stovebolt with a newer style HEI ignition and the such, coupled with a 5 or 6 speed, geared correctly should produce respectable power numbers, tow what you'd need within reason and probably get 20 mpg highway.

I'm not knocking the cummins option, just giving an alternate view.

[TJ's Chevy]

A stock 292 inline 6 makes 153 HP and 265 Pound feet of torque...these motors were lucky if they were getting 15 miles per gallon. I am not sure if your 4bt is turbo charged are not...I forgot. lol. Anyhow, If you turbo stock 292 to 8 pounds of boost your power will increase to around 300 hp and over 300 pound feet of torque...a 261 is not the best motor for 1...parts are scarce...2 trying to find performance parts are nearly impossible. If you were going to do a 6 cylinder a 250 or 292 would be your best bet. Note that many parts aren't interchangeable between the two...a 292 crank will fit a 250..or a 250 head on a 292. The 292 will get much better rpm rang then your cummins will...I can rev my 292 to 4,500 rpm between shifts...and the bottom end is stock...but my carb and manifolds and ignition aren't. The 292 peaks torque around 1,600-2,000 rpm...and hp around 4,000 according to factory. Now if you do a 6bt 5.9 turbo cummins you'll put us all to shame! LOL!

[jmack91z28]

Originally Posted by T.J. MCCAULEY

A stock 292 inline 6 makes 153 HP and 265 Pound feet of torque...these motors were lucky if they were getting 15 miles per gallon. I am not sure if your 4bt is turbo charged are not...I forgot. lol. Anyhow, If you turbo stock 292 to 8 pounds of boost your power will increase to around 300 hp and over 300 pound feet of torque...a 261 is not the best motor for 1...parts are scarce...2 trying to find performance parts are nearly impossible. If you were going to do a 6 cylinder a 250 or 292 would be your best bet. Note that many parts aren't interchangeable between the two...a 292 crank will fit a 250..or a 250 head on a 292. The 292 will get much better rpm rang then your cummins will...I can rev my 292 to 4,500 rpm between shifts...and the bottom end is stock...but my carb and manifolds and ignition aren't. The 292 peaks torque around 1,600-2,000 rpm...and hp around 4,000 according to factory. Now if you do a 6bt 5.9 turbo cummins you'll put us all to shame! LOL!

Yeah that's all pretty much accurate. A 261 would produce about 150HP at 2,000 and 230 ft lb at about 4,000.

What transmission and rear end are you running in your truck TJ?

[TJ's Chevy]

Originally Posted by jmack91z28

Yeah that's all pretty much accurate. A 261 would produce about 150HP at 2,000 and 230 ft lb at about 4,000.

What transmission and rear end are you running in your truck TJ?

You mean 150 HP at 4,000 rpm and 230 ft lbs 2,000. I am running the stock transmission( 4 speed on the floor) and the stock C-10 axle. GM 12 bolt rear axle...gear ratio probably 3.90 or 4.11. The only reason I rev it to 4,000+ between shifts is the rpm travel between shifts...2nd to 3rd is almost a 2,000 rpm split..if I was to rev it to 4,000 in 2nd then shift to 3rd my rpms would start just around 2,000 rpm....3rd to 4th is worse, But hey...these weren't made for speed. lol...which I am going to change to a richmond 6 speed...5 direct gears and a 6th gear overdrive. Spendy, but worth it.

[jmack91z28]

Originally Posted by T.J. MCCAULEY

You mean 150 HP at 4,000 rpm and 230 ft lbs 2,000. I am running the stock transmission( 4 speed on the floor) and the stock C-10 axle. GM 12 bolt rear axle...gear ratio probably 3.90 or 4.11. The only reason I rev it to 4,000+ between shifts is the rpm travel between shifts...2nd to 3rd is almost a 2,000 rpm split..if I was to rev it to 4,000 in 2nd then shift to 3rd my rpms would start just around 2,000 rpm....3rd to 4th is worse, But hey...these weren't made for speed. lol...which I am going to change to a richmond 6 speed...5 direct gears and a 6th gear overdrive. Spendy, but worth it.

Yeah, my fault haha.

[dieseldude4bt]

4bt vibrations are over exagerated, I have 3 trucks with them and they vibrate no worse than a lot of the 6.2L trucks I have driven.
I also have 4.10 gears and the sm420 and I don't have to rev to 4000 rpm between shifts so there must be a large differance in toque down low between it and a 261.

[ky-donzi]

If the diesel thing bothers you, you can get good numbers out of the newer LS
style engines. They would give good mpg, and power...

I can't stand computer controlled engines tho... This was the biggest appeal to me... My 4bt is completely mechanical...

It doesn't require any electrical connections at all. Matter of fact, if you push it hard enough it will start and take off down the street.

[BigSix]

Originally Posted by dieseldude4bt

Hey Peanutbutter, I know who you are.
The Dodge diesel NV4500 or even the Getrag G360 would be a good option and wil bolt right up with the Dodge parts.
I run the original SM420 with a Ranger overdrive, have no problems with it and it gives me more gear options for my heavy truck when towing.
I average 24 mpg in combined driving in a 6300lb 3/4 ton 4x4 and have got as goood as 30 on a trip to Denver.

dieseldude - with the ranger overdrive how did your sticks work out? Is there room in front of the bench to put the SM420 stick still?

[dieseldude4bt]

The 420 stick moves back 7 1/2 inches and the ranger stick is to the left and in front of that. as is my transfer case stick.

[66LSx]

The 4BT.....

gobs of torque, fuel efficiency, and even a bit of noise on the side....

It won't go anywhere fast..... but it'll keep going and going.....

I know a few things about that motor.....and its big brother 6BT....

(my last project 1947 Ford 1.5 Ton on hydroboosted disc brake, 4 link air suspension)

[61_FL_Apache]

That looks like a cool project!!

[66Submarine]

I'll have to agree that the light duty Cummins diesel thing was also a little bit of a letdown to me when I really looked into it. Still cool, but not nearly as cool as it looked at a glance.

TJ; FWIW, your truck should have 3.73 gears. 3.90 was the earlier (pre '63) Eaton ratio. Could have 4.11's, but I doubt it.

I'll also add that IME/IMO 4,000RPM is a really excessive shift point for normal driving with the SM420/inline six. I have a weaker 250 in my one ton and normally shift @ something like 2,200-2,500RPM (most of the time). It's certainly not necessary.

FWIW, 292 GM spec is (net) 153HP @ 3,600RPM and 255ftlbs @ 2,400RPM in '65. (I'll post the dyno sheet as an attachment).

So, (in stock form) the 4BT and 292 will probably pull similarly up to 2,000RPM or so, but the 292 will have another 50HP available higher up. That ability to wind it up a little and get half again as much power is kind of nice...