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Old 07-28-2013, 04:32 PM
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496 Stroker with 871 Blower - Basics?

I just recently picked up a 72 Camaro that has a fresh 496 in it. It also has an 871 blower. It is setup for prostreet as intention. I am not entirely new to BBC but it's been a while and I have never ran a blower. I've been in a different area (high HP turbo 6's) and am coming back to the good ole' BBC.

I am wanting to start from scratch on some basics and not just go off of the sellers "memory" or info he might have gotten from who knows where. Too much money to not cover the simplest basics first. After this then it is checking all other safety systems, wiring systems, and break in the motor.

The previous owner was running street gas and 20-50 engine oil. I usually use race gas (various VP fuels) in my other drag project(s) and feel the same on this but haven't deciding on which selections to narrow down as of yet. I also usually use a Redline Race Oil and had consider a 40wt race oil for in this engine. But am not sure and wanted to hear what others with similar engines/setups use.

Seller said he was told by where he got the car (see , we are getting into 3rd hand info now), to run 10 deg at idle then 28 at 2500. It has probillet MSD Dist in it but I am not sure what weights are installed.

Plugs in it are Autolight 65. I use NGK in all my other drag cars and have a deal for getting them but IIRC BBC can be finicky and not like NGK.

I am looking for the basics from other owners with similar setup and experience in a blown 496.

Like:
-preferred engine oil weight (not brand, just weight)
-fuel preferences
-spark plug preferences
-timing ranges

OK, below are the more detail specs. hope to hear from other 496/8-71 folks! Thanks in advance for any good tips or advice.

Cj


Engine details:

Mark IV 4 bolt main, 454 bored .060 over making a 496 stroker casting
Custom "one-off" oval port intake manifold also ported to match the heads.
Weiand 8-71 Polished Blower, and two Holley 750 double pumpers.
B-H-J 15900 Harmonic balancer (external balance) (Neutral)
Crankshaft SCA-445420 454 forged 4340 2-PC Rear seal External balance 4.25 stroke (Neutral)
Callies 4340 forged H-beam rods (Compstar)
SRP forged blower pistons
Total Seal rings
ACL "Race Series" bearings
JE Pistons (brand) Wrist Pins & Spiro Lock Retainers
Howards solid roller cam (.702 Lift, 308/314 Duration)
Howards solid roller lifters
Howards double valve springs.
Large GM oval port heads (3964290) ported & polished. The exhaust ports were also D-shaped for maximum flow.
Manley stainless steel valves, bronze valve guides.
Crane Gold 1.7 aluminum roller rockers and Manley guide plates.
Cloyes double roller timing chain
7qt oil pan, windage tray and crank scraper with 4.25 stroker clearance
high volume oil pump & pickup.
MSD Pro-billet distributor (not sure which weights/springs are in it right now)
MSD 7-AL box with a Stage-2 module (Rev-limiter).
Moroso high volume water pump
Dynomax headers 1-7/8" leading to 3" exhaust with 40 series Flowmasters. A.R.P bolts all around including main studs
Other:
Built 2sp Powerglide with a shift kit and a 3000 stall converter w/anti-balooning plates.
Hurst quarter stick shifter with a pistol grip handle
The rearend is a narrowed Ford 9" (with a back brace)
35 spline Strange axles, and 4.88 gears inside a locker center section.
Art Morrison ladder bars with a diagonal link

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Old 07-28-2013, 11:15 PM
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Any more information, piston dish volume in cc's, head combustion chamber volume, etc.? Exhaust ports D shaped for maximum flow???

Did the previous owner have a build sheet with clearances and specs? Do you know which pulleys you have, are the carbs boost referenced, any idea what the static c.r. is?

Can you explain what a "one off" custom blower intake is all about? What's custom about it?
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Old 07-29-2013, 06:03 AM
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Who built the engine? Find out and talk to them. get it running and IT will tell you what it wants as far as fuel, plugs and timing is concerned. Every build id different and no one here can tell you want the engine will need
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Old 07-29-2013, 09:29 AM
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The info posted is all I have at the moment and as supplied from the seller. I expect to obtain the build sheet next week along with other paperwork being assembled. Sorry I don't have that specific info right now though.

I know that along the way I will find the plug range and all but as mentioned I wanted to know that I was starting at a reasonable reference point on these basics. Or to make sure what to stay away from.

I figured it would be a good place to start to see what some similar setups were running.

Like fuel - lots of choices even from just VP. I use Q16 on one of my other turbo high HP cars but have considered C12 or C16 for this one. I'd thought maybe there was a fuel that some might have settled on for x,y,z reasons of BBC/Blower likes more than another. Or also useful, any fuels to stay away from.

I can come back with specs when I get them.
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Old 07-29-2013, 09:49 AM
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That's just it. Not knowing the compression ratio or the amount of boost is what will pop the cherry here. You need to know all of that info before you start asking "what do you use"... Nothing we say will be anything more then a guess on our part.
You may want to look into a bit bigger head pipe for the headers also. 1 7/8ths diameter may be a bit restrictive once you get it up and running...
Mark
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Old 07-29-2013, 10:00 AM
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Hopefully will have all that soon. I figured I'd ask now anyway since I am shaking it all out and running over it all in the shop.

I can look at the headers issue easy enough. Stans headers is only 30 minutes away. But that's still a ways down the list to get things sorted out on changes and fixes on the car.

I still have to change things like the exhaust (straight back pointed at and blowing right at the axle), some fuel line reroutes, and electronic changes and additions.

I do know it has very thick intake gaskets to lower AR (again, 2nd hand info from the seller, but you can see them). What the exact CR is I am waiting to confirm.

Thx
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Old 07-29-2013, 08:24 PM
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OK, so here is what I have,

CR is 8.15:1

Piston dome effective volume -3 cc's
Head combustion chamber volume 101 cc's
Deck Clearance .022
Pulleys: believe it is currently at -2.8% under driven with 35 teeth on the top pulley.
The carbs were rated for the blower

Other:

Bore: 4.310 Flat Top
Stroke: 4.250 Top Ring 1/16
Rod length 6.385 2nd Ring 1/16
Comp Height 1.270 Oil Ring 3/16 plus spacer
Piston Weight 538
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Old 08-06-2013, 11:18 AM
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Quote:
Originally Posted by astroracer View Post
Who built the engine? Find out and talk to them. get it running and IT will tell you what it wants as far as fuel, plugs and timing is concerned. Every build id different and no one here can tell you want the engine will need
The problem is that the seller was, how to say, less than honest. He professed to have the build info and promised to send when he found it. Now the supposed "machine shop" has a phone number that will not answer or disconnected. He also failed to "find" this build paperwork. So yeah, people lie. But there is karma

The engine is running but before I run again I have to fix some serious issues like fuel lines against power cable, melted starter cable, leaks, and so forth. Things like running a FP gauge of 0-100, alternator wire of 14 gauge back to the trunk, + cable from trunk rubbing against SS braided fuel line (no kidding), fuel pump above sump, and so on. Goofy crap like that.

So this is why I wanted to get a starting off point. At least in the ballpark for the BBC/871. While exacting will come later I have discovered the previous owner was basically an idiot and there is a chance something like the spark plugs are totally wrong for the application.

Just wanted to know what others with similar setup were using. Maybe not exact but as explained it would be better than way off like I have been running into while putting the car right.
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Old 08-06-2013, 01:14 PM
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20W 50 is what all the old school BBC guys used for high performance and I agree with the 20w 50 because this car isn't going to be driven in the winter and it will offer good protection on engine components.

the information sounds correct to be honest with you. they don't use a lot of advance in boosted applications to reduce the chance of detonation.

either way if you throw more timing at it be sure to use a higher octane fuel.

It sounds like your doing your homework and if you keep at it you will be just fine. who is the machine shop/builder??

Last edited by bigblocks; 08-06-2013 at 01:21 PM.
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Old 08-06-2013, 01:20 PM
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your total timing looks about right, your initial looks pretty low, 20 or so initial with 34 or so total, but take off a degree of total for every 1-2 psi of boost, and if you can run a vacuum advance. (this is where electronic timing control makes this a lot easier).
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Old 08-06-2013, 06:35 PM
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The timing curve is very safe for pump gas at 25DEG MAX under boost on pump gas.

But the distributor curve set up is way off for this motor to run best.
Start by getting a Boost tming master box. or same so you can set up a blower motor friendly complete timing curve.

Blower motors with huge cams need more than 10deg initial base timing. More like 38deg base initial.
Then when uder boost you need to reduce the timing under boost,,, a bit , even, on race gas.

A LOT when on PUMP gas. You can see the curve is actually backwards, from the engines needs... The distibutor is not set up for this blower motor at all.

8:1cr 8-10 PSI +/- blower boost on pump gas. More.... with high octane gas.

If you want to lean on it hard (boost), high octane race gas or methanol is your friend.

You can make a ton of street power with 7-8 psi boost on good street pump gas.
But not with that distributor set up.

But I don;t see 8:1cr with 496 cubes, flat top pistons and 101cc heads on it.

That don't add up.

That is 9.5:1cr area. OK on race gas. Not OK on PUMP GAS.
Great for Methanol.

This is a high compression ratio stricktly Methanol or 110++ octane RACE GAS gas blower motor.

Street pump gas will only allow very modest blower boost combined with a good dose of boost spark retard.
OK for cruising around, just know the difference.
Find a shop that can Engine dyno tune this motor for you.

Last edited by F-BIRD'88; 08-06-2013 at 06:49 PM.
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Old 08-06-2013, 06:54 PM
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Get and install the starter motor brace bracket and get and install a ignition power interupt switch
so you can start your BBC blower motor easily, with 38deg intial base timing, instead of 10deg base inital , which is not near enough for this motor.

This motor should run real good when properly dialed in on race gas.

3964290 cylinder head. This is a odd ball 1970 head that came with both old style and new style (peanut plug) spark plugs
Verify which you got. They are not the same. The plug heat range will depend on how you will be using it at the time.
Look at BOTH HEADS.

race tune up..for racing it .... light duty street tune up lots of idling, not much WOT under boost and tame boost and timing...They are not the same.

Last edited by F-BIRD'88; 08-06-2013 at 07:00 PM.
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Old 08-06-2013, 07:58 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
The timing curve is very safe for pump gas at 25DEG MAX under boost on pump gas.

But the distributor curve set up is way off for this motor to run best.
Start by getting a Boost tming master box. or same so you can set up a blower motor friendly complete timing curve.

Blower motors with huge cams need more than 10deg initial base timing. More like 38deg base initial.
Then when uder boost you need to reduce the timing under boost,,, a bit , even, on race gas.

A LOT when on PUMP gas. You can see the curve is actually backwards, from the engines needs... The distibutor is not set up for this blower motor at all.

8:1cr 8-10 PSI +/- blower boost on pump gas. More.... with high octane gas.

If you want to lean on it hard (boost), high octane race gas or methanol is your friend.

You can make a ton of street power with 7-8 psi boost on good street pump gas.
But not with that distributor set up.

But I don;t see 8:1cr with 496 cubes, flat top pistons and 101cc heads on it.

That don't add up.

That is 9.5:1cr area. OK on race gas. Not OK on PUMP GAS.
Great for Methanol.

This is a high compression ratio stricktly Methanol or 110++ octane RACE GAS gas blower motor.

Street pump gas will only allow very modest blower boost combined with a good dose of boost spark retard.
OK for cruising around, just know the difference.
Find a shop that can Engine dyno tune this motor for you.
I have a good shop all lined up once I get things squared away and the right components installed. All I have is the word of the seller on the timing being 10 at base and up to 28. I have not ran the engine yet to verify anything because of finding a lot other wrong to fix before starting up again. I've no idea what the distributor curve is. Just that it is MSD pro billet.

I definitely plan on running race gas and not pump. C12, C16, or maybe Q16 (which I already use and order in qty on a V6 turbo car).

I have looked at the MSD PowerGrid. Maybe that will do the same as Boost timing master box. Haven't checked but it seems to be able to control those aspects.

I am a bit confused when you talk about the curve. I don't have any idea what the curve is, only what I was verbally told on base and at 2500. Do you mean that I should have the higher advance at idle (ie - 28) and less at boost? Or rpm?

You've given me a lot of info. Appreciate it. As for the CR, yeah, I've no idea at this point what's what on that.
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Old 08-06-2013, 08:01 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
Get and install the starter motor brace bracket and get and install a ignition power interupt switch
so you can start your BBC blower motor easily, with 38deg intial base timing, instead of 10deg base inital , which is not near enough for this motor.

This motor should run real good when properly dialed in on race gas.

3964290 cylinder head. This is a odd ball 1970 head that came with both old style and new style (peanut plug) spark plugs
Verify which you got. They are not the same. The plug heat range will depend on how you will be using it at the time.
Look at BOTH HEADS.

race tune up..for racing it .... light duty street tune up lots of idling, not much WOT under boost and tame boost and timing...They are not the same.
Starter brace has been ordered. By ignition interrupt you mean crank and then kick in ignition power? I can manually do that now as it has separate switches for starter and ignition. I did a search to better understand the benefit. Just faster start and less strain on starter this method?

Thanks for info!! Any and all tips like this are much appreciated for sure
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Old 08-07-2013, 03:37 AM
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On this engine , on race gas I would run no advance curve in the distributor at all.
Lock the distributor advance curve and then take out timing as boost builds with a retard box.

Ya easy starting with locked out timing (38deg BTDC) using a separate spark power switch.
You got the idea.

The amount of "boost retard" timing that needs to be taken out under boost depends on the fuel used
and the amount of boost and the real engine compression ratio and the air fuel ratio, when under boost.
Thats what the dyno testing is for.

With the big big Howards cam it will want a lot lot of timing at idle. This is normal for a roots blower motor
with a cam in it that is this big. It will start up, warm up and drive and respond to the throttle much better
with generous initial timing.

A lack of basic timing makes it tend to spit, pop, backfire and protest, especially during warm up.

Last edited by F-BIRD'88; 08-07-2013 at 03:51 AM.
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