Build 454 BBC for street blower
I've finally got my 454 delivered to the machine shop for rebuilding, and it's decision-making time...
While taking the screwed-up (seperating) harmonic balancer off, I discovered that the previous owner had cross-theaded the bolt in, which resulted in galled threads in the snout of the crank.
I've decided to discard it and replace it with a Scat 9000 crank (quoted $360 CDN) It was going to cost $140 to grind the cast one, plus whatever it costs to repair the threads, so I thought it was a worthwhile "upgrade"
I'm going to have the engine balanced ($300 CDN) to my new (NAPA stock) harmonic balancer and flex-plate.
My NAPA supplier sells us Clevite brand at Jobber prices, so I'm inclined to buy my parts from them ... even though I'm a Sealed Power/TRW piston fan.
I'm trying to build the short-block with an upgrade path to include a street blower.
This plan includes using some forged flat-tops (#224-2519.030), Plasma/Moly Rings, Clevite 77 rod, main,and cam brgs, and ARP rod/main bolts. Of course I'll add a HV oil pump, pickup screen, drive, etc as well.
Heads & Induction
I've got a set of freshly-rebuilt (stock) 781 heads, and a used Torker II intake. A friend is offering to "port-match" those heads to the intake. I plan to order one of those Edelbrock Thunder AVS (800 CFM) carbs or perhaps a Holley Street Avenger 770 CFM?
Headers, 2-1/2" dual exhaust, turbo mufflers, and tailpipes are planned.
1966 GMC 910 2WD, 127" W/B Fleetside.
Weight: 3,000 lb?
Axle: 12-bolt (will be converted to posi) 3.73 gearing
Trans: TH400 - stock, freshened with Raybestos clutches/steels and a shift kit.
Convertor: Plan to purchase a B&M Nitrous Holeshot 2400 stall (w/anti-ballooning) or equivalent.
I'm planning to rev this thing to a max of about 6000 to 6500 (?) and to take it to the track (bracket racing) very occasionally ... just for fun. It will be a "good-weather daily driver" and will see short highway trips 10 miles each way back and forth to work.
I'm looking at a Comp Cams 280AH (Blower/Turbo grind) 232/237° @ .050, .547/547 lift, 114° Lobe Seperation
A Clevite #229-2305 "Performer" 224/234° @ .050, .529/.553 lift, 114 "Lobe CL" (is that the same as "Lobe Seperation Angle"?)
Am I going to need to upgrade the valve springs/ rocker arms/ pushrods?
I'm thinking Weiand/B&M street blower (5-10 PSI boost ... nothing too radical ... more for looks.)
I've read some articles that advise against buying used (6-71 / race) blowers as they are likely to be worn out "beyond rebuilding". By "worn out" do they mean that they are incapable of 20 PSI boost levels, or is it metal fatigue and grenading that they're talking about?
I'm heading to a swap meet this weekend, and may keep my eyes open for a "bargain" blower.
Any comments / suggestions as to my planned build?
This article mentions some very impressive dyno numbers, but I didn't see any mention of how much boost was involved. By my calculations, it looked like about 7.5 PSI (?) yielding an average 609 TQ / 523 HP! WooHooo!
The reason people advise not to buy used blowers (race or not) is because if you don't know what you're looking for you will end up buying an expensive door stop. Cracks and scratches are probably the biggest issues. If the rotors are stcratched or the inside of the case is scratched or damaged, the blower could be no good. The problem s trying to find the problems with the blower assembled, you can't really see exactly what you have. I wouldn;t be afraid to buy a "used" blower from a person I "REALLY TRUSTED". The issue of being used is no big deal, the issue is damage.
I don't know what your goals are so suggesting a blower size/boost level is impossible. I will add a link to another blown big block article for you to look over. Feel free to ask questions if you have any. I will help if I can.
Hi Royce, and thanks for the reply.
Yes, that's a good article ... and in line with what I'm thinking about, which is moderate levels of boost (5-10 PSI) on a budget-built engine.
My 781 heads still have stock valves (2.06 / 1.72) and I'm thinking single 850 CFM carb which I'm sure won't flow quite as well... and won't get quite as high of HP/TQ figures.
The lower HP/TQ will likely be more than the traction that I'm expecting anyway. I'll be running P255/70R15 BFG Radial TA's on all 4 corners, and pickups are pretty light on the rear.
That 8-71 blower is pretty huge ... looks like the stock HEI dist won't fit. What about a 6-71 or even a Weiand / B&M 174? Will they allow for the stock HEI?
I've been reading a lot of stories about piston / head incompatibility on BBC's, but I should't have any issues like that using flat-tops ... right?
That Comp Cams 280AH blower cam sounds like the ticket IF I do go the blower route. I wonder what it will be like on a naturally aspirated engine until I do? I'm not real concerned with vaccuum, as I'm going to be running hydroboost brakes and a 2400 stall convertor.
As far as the pistons and head situtation, I will let another big block guy help you with that. I am a small block guy.
A blower cam on a N/a engine will be fine, you will not make as much peak power but, you should have a nice wide power band. This is due to the wider LSA.
I have never tried to run an HEI with a blower so I don't know how big of a blower will fit with an HEI. I am sure someone here knows how much room a big block has. With my 8-71 on my small block an HEI wouldn't fit but, a normal points "size" distributor clears with ease.
I think a small blower will get you where you are trying to go. You may need more carb than an 850 though. The small blower will give you plenty of grunt down low. Take a look at the 193ci blower from The Blower Shop www.theblowershop.com it's a little bigger than the 174 and is a better unit. If you want to make more power then step up to a 6 or 8-71. It will cost you more, extra carb, linkage, scoop, plumbing, etc.. adds up fast.
The small blower is not going to get you in the 10psi range. It might take you to 6 or 7psi on a engine of that size. If you think you want to get close to 10 psi, you might want to think about an 8-71. You really don't want to overdrive the little blower to get your boost, that will create too much heat and hurt power and increases the chance of detonation. If your goals are to have a decent running street truck with a few 1/4 mile passes then the small blower will work. If you only plan to run the regular street radials then no need in getting a bigger blower or turning up the boost because those tires aren't going to hold a small blower let alone a big one on a big block in a truck.
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