Do I rebuild my SBC or swap for an LS3?

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

DoubleDingo

Full Access Member
Joined
Jul 3, 2012
Posts
10,209
Reaction score
14,540
Location
Right where I am
First Name
Bagoomba
Truck Year
1981, 1965
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s; 65-C20 with 4:57 gears and Borg Warner Overdrive
Engine Size
Carb'ed Vortec 350; 1972 L48 350
I bet it runs good too. That cam kicks major ***
Thinkin about tryin that in the TBI.
Think it would run?
It runs real good! I didn't install the cam when I installed the vortecs. I did it a year or so later when I pulled the engine to reseal it. That cam definitely woke up that engine. The torquey vortecs and the torquey camshaft, it's a fun truck to drive. Without even trying I leave people at traffic lights all the time, and usually they're in one of those new fangled high performance tin cans.
 
Last edited:

OneShot

Full Access Member
Joined
Oct 1, 2014
Posts
91
Reaction score
50
Location
Indiana
First Name
Paul
Truck Year
1979
Truck Model
c20
Engine Size
350
After an unintended hiatus (I put a crack in the rear axle casting of my Jeep Wrangler, and swapped it with a Ford 8.8 out of an Explorer) I'm back on this project.

Been daily driving the truck since the Jeep has been down. Getting increasingly annoyed with the engine problems. It's more than just valve guides - I think the passenger side head gasket may be blown. I'm parking the truck and driving the Jeep again until I get this mess sorted out with the engine.

Anyhow, I found someone local with some 461 heads that need a valve job. Selling 'em for $200 for the pair. Gonna get a quote for a valve job from a local shop I trust. Yeah I know I would need to make custom brackets for accessories... I just can't find any better heads in my area.

The saga continues.
 

Rusty Nail

Full Access Member
Joined
Jan 29, 2015
Posts
9,790
Reaction score
9,690
Location
the other side of the internet
First Name
Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
Id keep looking.
Aftermarket brackets likely exist but I bet it's not worth it. Sounds like a headache to me...
Id keep looking.

How do you crack an axle housing anyway?
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
4,092
Reaction score
5,947
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
200.00 for 461s that you'll probably have to put hundreds into are not a good choice imho. They are going to need hardened seats to run on unleaded,they are approximately 60 years old. They are going to need different accessory brackets, guides,valve job,probably some valves.Technology has come along way. There are better heads out there for not much more money.Keep us posted please as to what they end up costing or estimated to make usable. There is a thread started by @ChuckN nov.. 24th title is power steering bracket for heads without accessorie holes. last few posts will give you bracket options.
 
Last edited:

Rusty Nail

Full Access Member
Joined
Jan 29, 2015
Posts
9,790
Reaction score
9,690
Location
the other side of the internet
First Name
Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
I picked up a 461 head for $20 on craigslist one time. Kind of just to have it sittin around. :shrug:
It's red I think.
No pix.

Seller dude says "what are you gonna do about another one?"
Keep lookin , I said.

Meh.
 

DoubleDingo

Full Access Member
Joined
Jul 3, 2012
Posts
10,209
Reaction score
14,540
Location
Right where I am
First Name
Bagoomba
Truck Year
1981, 1965
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s; 65-C20 with 4:57 gears and Borg Warner Overdrive
Engine Size
Carb'ed Vortec 350; 1972 L48 350
I picked up a 461 head for $20 on craigslist one time. Kind of just to have it sittin around. :shrug:
It's red I think.
No pix.
What?! No pix?! Ban him!
 

DoubleDingo

Full Access Member
Joined
Jul 3, 2012
Posts
10,209
Reaction score
14,540
Location
Right where I am
First Name
Bagoomba
Truck Year
1981, 1965
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s; 65-C20 with 4:57 gears and Borg Warner Overdrive
Engine Size
Carb'ed Vortec 350; 1972 L48 350
Gotta give ya crap for no pix.
 

Mogulmasher

Junior Member
Joined
Dec 8, 2022
Posts
18
Reaction score
44
Location
Rochester NH
First Name
Mike
Truck Year
1977
Truck Model
C15
Engine Size
350
Well this is an interesting thread, I'll be in same position next year. I just picked up a 77 c15 with a low mile crate 350 in it. My plan was to get it all running and on the road as is and then build the 5.3 I have sitting in corner of shop to swap in later. But maybe it isn't worth it. I plan to drive this truck in summer almost daily to work so I was looking for the increased mpg of the 5.3. Now I'm beginning to think unless someone says we're talking like 3-4+ mpg it might not be worth it.

And for people saying ls is more reliable....hmmmm not sure about that. From ages of 16-24 all I drove was a 79 k10 with a stout 355 and a 71 Nova with a HO 305 then a 327. I built all the motors. The truck towed snowmobiles every weekend in winter and drove me to work or school daily. None of these motors ever let me down. Then I had a couple trucks with Vortec 350 motors, so still sbc power. I never worried about going anywhere with any of them.
 

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
4,092
Reaction score
5,947
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
You must be registered for see images attach
You must be registered for see images attach
The difference in milage is comparing an old carburetor 350 with hei,to an injected ls with modern ignition. Look what happens when you level the playing field. Just for fun I checked on a 1995 suburban,tbi EPA 11 city and 14 higheay combined milage 12.
Check the link below for an mpg based tbi truck. 17 city 20 highway tbi 350

 
Last edited:

Rusty Nail

Full Access Member
Joined
Jan 29, 2015
Posts
9,790
Reaction score
9,690
Location
the other side of the internet
First Name
Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
I was recently looking for a 1996 Yukon GT because I thought that might be cool until I found out it doesnt have an LS1, it's flippin LO5 powered.
Big yawn. The gmt800 is a WAY crappier body than a GMT400 imo.

Really the only desirable difference (to me) would be roller cam vs hydraulic lifter. What does it say the difference is between say a 1988 and a ? Pretty tough to find an original equipment roller motor in a square body I reckon.. 1 mpg more is no where near the expense of all the trouble of switchin.
Bet chances of buying a 2 door roller motored YukonGT are slim to none.
NOT rollin 4 door anything.

Makes ya wonder why so many kids are so hot to LS swap or buy vortex heads.
Trendy I guess.
"Traumatic" experiences with 30 year old carburetors maybe sends em over the edge. :shrug:Mom taught em how to drive in a Corolla.

Takes all kinds I heard but not sure what for. Im over it already. The lookin wasnt even fun. I got the Blazer back today and NOW it's effing NUTS!
 
Last edited:

Mogulmasher

Junior Member
Joined
Dec 8, 2022
Posts
18
Reaction score
44
Location
Rochester NH
First Name
Mike
Truck Year
1977
Truck Model
C15
Engine Size
350
My real world mpg with ls motors hasn't been great, although everything I've had has been awd/4wd. My 6.0 in 1500hd/2500/2500hd trucks have got 10-12, my Yukon xl Denali with 6.0 was either side of 12, and current escalade with 6.2 is 12.5-13.5. Heck my current 2500hd with 8.1 and 6 speed allison knocks down anywhere from 10-14.

I suppose in a old c15 I might see 15 or so?
 

rpcraft

Full Access Member
Joined
May 31, 2016
Posts
1,330
Reaction score
509
Location
Texas
First Name
Robert
Truck Year
1985
Truck Model
Jimmy
Engine Size
LS 6.0 364 CID
If you have an engine to start with that is in good shape, good compression, and a 350, I would just put a cam and good matching intake on it, like one of the performer rpm packages. My buddy did it on his 1981 K5. I did a mild RV cam on mine and the difference was night and day. His was a beast and I would have done the same to mine if not for an offroad accident that flipped my rig.
 

OneShot

Full Access Member
Joined
Oct 1, 2014
Posts
91
Reaction score
50
Location
Indiana
First Name
Paul
Truck Year
1979
Truck Model
c20
Engine Size
350
Long story short, I was offroading in Moab, Utah and I screwed it up there. I spent a week doing intermediate to moderate difficulty trails and then drove it back to Indiana.

When I got back home it started eating axle shaft bearings. I went through two sets of driver's side bearings before I noticed a slow oil seep at the differential casting where the tube is pressed and welded in. Come to find out, the tube wasn't parallel with the passenger side tube, which was causing weird torque loading on the axle shaft bearing causing it to fail prematurely. That can only happen if the casting is expanded (cracked) to allow the tube to sit in the casting cockeyed. Oh and as an added bonus when the bearing failed it took my nice chromoly shaft with it...

So instead of straightening the Dana 44, I pulled an 8.8 out of a Ford Explorer which is a MUCH larger axle. To boot, I welded up a full-width truss and welded it to the tubes to reinforce the axle. So help me.... that axle will never break again. While I was at it I rebuilt the whole axle, and added adjustable upper control arms for better pinion angle control.

Pictures of the new axle:
 

Latest posts

Forum statistics

Threads
42,167
Posts
910,461
Members
33,660
Latest member
1987R10Man
Top