BBC upgrade.....Slow day at work;)

[dfarr67]

Never owned a vehicle with a BBC, nor driven one- a 366 doesn't count.
Current vehicle 1989 K1500 OD, 3:73 gears, 32in tires, 2400 stall/lockup, went from a 355 to a 385 TPI(FIRST) and have been happy with it's performance, towing and I would say without proof that I really haven't noticed a hit in the mileage.
Seems to be an uptick on the net in popularity with BBC builds and was wondering about 'what if', retain the built 700r as I am circumspect with it shortcomings and ever since finding a guy years ago who could build one- haven't had a lick of trouble. Find a good short block (gen6 ?) oe roller cam, I would spend the money on a cam (any firing order tricks here?) and AFR265 heads, would retain injection- TPI or ??. On the highway I think I am pulling 1800rpm in OD 115km/hr. wondering on how hard it would hit me at the pumps- and would it be worth it pep wise. Would like to retain capability to run 87 octain.

[mag2555]

If the current motor has forged pistons in it ( not just hypers) then why not drop a Paxton supercharger on it.

Even with 9.5 comp you can run a lower drive speed and make good use of like even 6 lbs of boost!

Besides you would have to as in the way that you’re talking about going up grade the fuel system for the big block anyway!

[travis]

Probably less mileage difference than you would think. 0-2mpg loss if the BBC is built right and driven like a sane person.

I’ve had mild 460 powered F150’s get 12 mpg highway with 3.50 gears, where a mild 351w in a similar truck would get 14. But, the 460 would tow drastically better.

[FloydODB]

489ci genVI block. 4 bolt. eagle crank/I beam rods, SRP pistons. 9.5:1. edelbrock e-streets with the bumps blended. comp behive setup. comp 11-460-8. howards lifters. matched vic jr. 615 carbed, 620 holley sniper

video kinda sucks. he says it'll smoke the tires continuously through (400) all three gears and then gets to squirrely. just got his new tremec last week.

https://www.facebook.com/10000048787181 ... 433489527/

[rustbucket79]

Why not re-top end your engine with a nice set of heads and maybe an EFI upgrade if your current tpi setup is maxed out?

[Schurkey]

I can't really help with the BBC part of your plan, but there's some other shortcomings you should be aware of. Well, you WILL be aware of them as soon as you boost the power and add front end weight.

1. An '89 K1500 will have seriously shitty rear brakes ("10-inch"/254mm rear drums with leading/trailing shoes.) They are almost universally out-of-adjustment because they adjust by using the park brake, and no-one does. The axle itself is likely an 8.5" ring gear, like they used to put under Novas and Camaros. Worked fine under lighter cars, not really suitable for a full size pickup. Common upgrade--find a 6-lug "Light duty" K2500 axle (9.5 semi-float) and U-bolt mounting plates from a GMT400-series truck in the right gear ratio. You'll need a conversion U-joint to go into the differential yoke, and fresh U-bolts, otherwise it's a bolt-in. The C2500 axle is a different width. The K2500 axle has bigger, 11.1 rear drums and Duo-Servo shoes. So you upgrade the axle and the brakes at the same time. The Rear Wheel Anti-Lock (RWAL) has a very poor reputation. Mostly, I think, because folks haven't bled the air out of it properly, and the leading/trailing shoe brakes just plain stink.

2. The front brakes may be a similar disaster. "Regular" cab trucks typically have JB3 brakes, narrow rotors, small pistons in the low-drag calipers, and a small, step-bore "Quick Take-Up" master cylinder connected to a crappy small power booster. If you have an extended-cab, you likely have the much-better JB5 brakes--thicker rotors, bigger pistons in the low-drag calipers, bigger step-bore master connected to a much-more-powerful booster. Converting from JB3 to JB5 requires the booster and master, calipers, rotors, and steering knuckles with the hubs from the extended-cab truck. My '88 K1500 started out with the horrible JB3 brakes, but now has the JB5 fronts and the bigger drums/9.5 axle in the rear. MUCH better.

3. The lower steering shaft "rag joint" failure is epidemic on GMT400s. Symptoms are perpetually having to saw the steering wheel back and forth to hold a sort-of-straight-line. There are a number of "fixes", but the easiest is to install a lower steering shaft that has a U-joint instead of a rag joint. GM had one, came in C3500 trucks. It's now discontinued, but I found one some months ago. Dorman makes a copy of that shaft. Other guys have scalped a Jeep Grand Cherokee steering shaft, then melted-out the plastic insert to make it fit. (A truck new enough for air bags needs a different shaft., but that didnt' happen until '95-ish)

[dfarr67]

Why not re-top end your engine with a nice set of heads and maybe an EFI upgrade if your current tpi setup is maxed out?

I don't know....AFR vortec eliminators and FIRST EFI TPI intake- I thought they were OK hardware

[dfarr67]

I can't really help with the BBC part of your plan, but there's some other shortcomings you should be aware of. Well, you WILL be aware of them as soon as you boost the power and add front end weight.

1. An '89 K1500 will have seriously shitty rear brakes ("10-inch"/254mm rear drums with leading/trailing shoes.) They are almost universally out-of-adjustment because they adjust by using the park brake, and no-one does. The axle itself is likely an 8.5" ring gear, like they used to put under Novas and Camaros. Worked fine under lighter cars, not really suitable for a full size pickup. Common upgrade--find a 6-lug "Light duty" K2500 axle (9.5 semi-float) and U-bolt mounting plates from a GMT400-series truck in the right gear ratio. You'll need a conversion U-joint to go into the differential yoke, and fresh U-bolts, otherwise it's a bolt-in. The C2500 axle is a different width. The K2500 axle has bigger, 11.1 rear drums and Duo-Servo shoes. So you upgrade the axle and the brakes at the same time. The Rear Wheel Anti-Lock (RWAL) has a very poor reputation. Mostly, I think, because folks haven't bled the air out of it properly, and the leading/trailing shoe brakes just plain stink.

2. The front brakes may be a similar disaster. "Regular" cab trucks typically have JB3 brakes, narrow rotors, small pistons in the low-drag calipers, and a small, step-bore "Quick Take-Up" master cylinder connected to a crappy small power booster. If you have an extended-cab, you likely have the much-better JB5 brakes--thicker rotors, bigger pistons in the low-drag calipers, bigger step-bore master connected to a much-more-powerful booster. Converting from JB3 to JB5 requires the booster and master, calipers, rotors, and steering knuckles with the hubs from the extended-cab truck. My '88 K1500 started out with the horrible JB3 brakes, but now has the JB5 fronts and the bigger drums/9.5 axle in the rear. MUCH better.

3. The lower steering shaft "rag joint" failure is epidemic on GMT400s. Symptoms are perpetually having to saw the steering wheel back and forth to hold a sort-of-straight-line. There are a number of "fixes", but the easiest is to install a lower steering shaft that has a U-joint instead of a rag joint. GM had one, came in C3500 trucks. It's now discontinued, but I found one some months ago. Dorman makes a copy of that shaft. Other guys have scalped a Jeep Grand Cherokee steering shaft, then melted-out the plastic insert to make it fit. (A truck new enough for air bags needs a different shaft., but that didnt' happen until '95-ish)

Fixed with 2005 Suburban 4 wheel disc set up with Hawk HPS pads, 2007- 2500HD hydroboost and disc/disc master, Lee steering gear and rebuilt rag joint- didn't like the feedback on the Borgeson u-joint, but I was shocked at the condition of the original rag joint. Anti lock long gone.

[rustbucket79]

Well you didn’t mention you had decent stuff now did ya?

How about a Vortec setup then?

[dfarr67]

BBC Vortec?
I don't think they lived up to the SBC vortec expectations and regardless I would go alum heads for the weight.

I was thinking 396cid but the bore size might be an issue- a 454cid is probably easier to find- even a good short block.