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Old 01-31-2012, 10:58 AM
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My blown BBC has glowing red hedders

Bbc.489 8-71 tbs blower.2.demon blower.carbs.750's
Cam is.solid.roller.blower.grind.c.cam.255/262@ .050..652.lift.114.ls
8-2 to.1.comp. Heads are.darg.pro 1's with.2.30 190.valves.with. 345.cc.intake runners cranking comp is.130.psi.
With.timing set at.8 and 28total idles smooth.no sugre.headders.glow.red.if held at steady rpm.of.2500 rpms.for.30.seconds.my heat.gun goes.of.the.scale.at 800 .so yes.hot Had.some.reading.of.780zo i know.the.gun is.working
i tryed messing with the.timing.if.had.it.locked.out.set.at28 it.surges.so bad at idle.i dont have a boost.retard.box.just msd dist al6 box with the.big blue coil.
These.carbs.are.boost ref.so the.nipple.in the front even booked.uo to a.vac.gun sucked.down theres.no chane still no chaneis i pit.preesure.on them
should.the.headders.glow.red?

Plugs.are.black. And.when i snap the thorttle.lkke.half.way quick.it.backfires.ouf the.exhast.sound.like.a.gun .i habent.drove.it yet.what should i do or.cheack or.should.a.call.don hampton maybe .
Thanks.everyone.bout.to go crazy

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Old 01-31-2012, 11:27 AM
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Only 2 possible causes: Not enough fuel, or way wrong timing.
Locking the timing at 28 degrees might work at idle and at higher revs at WOT, but may be too much when near WOT in the lower RPM ranges.
If the carbs are atop the blower, then they don't need to be boost-referenced. That's for blow-through carbs that aren't enclosed.
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Old 01-31-2012, 12:06 PM
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Quote:
Originally Posted by whyholdback
Only 2 possible causes: Not enough fuel, or way wrong timing.
Locking the timing at 28 degrees might work at idle and at higher revs at WOT, but may be too much when near WOT in the lower RPM ranges.
If the carbs are atop the blower, then they don't need to be boost-referenced. That's for blow-through carbs that aren't enclosed.
so did the blower shop.sent me.the.wrong.carbs.
Then?.i got the blower.and the.carbs.at the.same.time.i do know.rhay there texh support.sucks.they.tell me.we.just biuild.them.and.ge the carbs.from barry grant
should.i call don hampton i would.have.gottn mine from hin but i got the.blower.ect.ober 6years.ago ans dixnt k.ow about hi
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Old 01-31-2012, 12:16 PM
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You timing is way to low. I would start by advancing the base timing and limiting the total. Not sure on a BBC what a good starting point would be but I would go at least 16-20 initial with 30ish total I would think.
Your carbs could also be too lean or you could have a vacuum leak. Fix the timing first and go from there.

This is from the BDS Website tech section


Why are my exhaust pipes red-hot?

Exhaust pipes get red hot for two basic reasons. Either the ignition timing is incorrect or the engine is running extremely lean. There are other causes but these are the two most common, ignition timing is extremely critical. Blown motors love advance. Without enough initial timing advance, blown motors will run hot and the exhaust pipes will glow in the dark. Blown motors should run as little as 16 degrees or as much as 26 degrees initial advance with the total advance of about 32-36 degrees at 2500 RPM to 3000 RPM. Specific timing requirements depend on compression, blower drive ratio, engine load, camshaft, and fuel octane.
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Old 01-31-2012, 12:37 PM
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Quote:
Originally Posted by T-bucket23
You timing is way to low. I would start by advancing the base timing and limiting the total. Not sure on a BBC what a good starting point would be but I would go at least 16-20 initial with 30ish total I would think.
Your carbs could also be too lean or you could have a vacuum leak. Fix the timing first and go from there.

This is from the BDS Website tech section


Why are my exhaust pipes red-hot?

Exhaust pipes get red hot for two basic reasons. Either the ignition timing is incorrect or the engine is running extremely lean. There are other causes but these are the two most common, ignition timing is extremely critical. Blown motors love advance. Without enough initial timing advance, blown motors will run hot and the exhaust pipes will glow in the dark. Blown motors should run as little as 16 degrees or as much as 26 degrees initial advance with the total advance of about 32-36 degrees at 2500 RPM to 3000 RPM. Specific timing requirements depend on compression, blower drive ratio, engine load, camshaft, and fuel octane.
i now my base.timing.os.low at 8but id i.set.it at say 16 my advance.gose.up to36 o thouht the blower.shop said.my timing.should.habe.a.total.of.22/28 deg.
12%.under.driven on 93.pump.gas bost.shojld.only be 8psi they said ?.i think the blower.shop.as not.got.a.clue.?.so i should.ser.it.at say 14 at idle.and 34 total i need.to buy a.spring.kit.i dont have a vac.advance msd dist either. It.got.a.20deg curve in it

keep the.answers.coming.whay should be.my.max.headder temp at..3000 rpms.should the.headders.not.glow.red.at all.?
I got to look.on the.demon box.again and let.yoy know.jet sizes

Thinking..there.75/83 w.6.5 pv in.front. Bit.mt.short.term is.bad
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Old 01-31-2012, 01:08 PM
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The curve can be changed with springs and bushings to accomplish more initial and less total. It is always a good idea to be conservative with total timing but initial needs to be about 8* more than what you are running now.
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Old 01-31-2012, 01:22 PM
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Lock out the spark advance 28-30 deg. Fix the carbs. Its either way too rich or way too lean at idle. verify timing tab TDC location.
Get your self to a engine dyno shop that is experienced with blower motors.

Lots of people have lots of trouble with BG carbs.

A damaged motor will cost far more than a carb setup and engine dyno session.
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Old 01-31-2012, 01:39 PM
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Fixing to sell this blower stuff get i super victor intake with a1250 carb and get a Pro shot fogger kit wirh 600 jets
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Old 01-31-2012, 09:45 PM
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I agree with T-bucket23. I've started on a Blown 468 BBC build and I read up everything I could find for the last year+. Total timing should come in pretty quick and be 30-34. Bob
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Old 01-31-2012, 10:10 PM
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I have a procharged 496 which is a little different but the same. I use a mallory hifire to control the timing so it is at 36 total pulling out timing under boost. It retards the timing under 800 rpm so starting is not an issue. I have a C&S carb a bad a family illness has caused me not to have the money for a dyno session. Roger(owner of C&S) has been a saint and has helped me dial it in on my own. Mallory makes a timing box too. I would not throw in the towel on the blower so fast nitrous is another animal. ALL good suggestions from these guys. Get that timing advanced then tune the carb. What f-bird said is critical find the proper timing mark. I used a piston stop. All plugs out turn clockwise put in stop gently hit stop (I used ratchet on the vibration dampner bolt) check where it stops on timing mark then reverse the procedure counter clockwise and make sure the timing marker is dead on center of both. Hopefully the vibration dampner has 360* marks on it. Don't throw out the baby with the bath water
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Old 01-31-2012, 10:26 PM
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Quote:
Originally Posted by whyholdback
If the carbs are atop the blower, then they don't need to be boost-referenced. That's for blow-through carbs that aren't enclosed.
Take that advice you will be replacing more than just pistons. You do need to boost reference your carbs.
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Old 01-31-2012, 11:47 PM
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2 X on that. Run Holley style carbs without boost reference is a sure fire way to cause problems.
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Old 02-01-2012, 06:39 AM
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Quote:
Originally Posted by whyholdback
If the carbs are atop the blower, then they don't need to be boost-referenced. That's for blow-through carbs that aren't enclosed.
This couldn't be more wrong.
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Old 02-01-2012, 10:56 AM
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Red hot headers seems pretty normal to me, zero airflow as it's not moving and takes about 30 sec.
Your using tube exhaust manifolds which are pretty thin, normal exhaust gas temps are in the 1,000~1,400 deg range which is plenty to make them glow.
What diameter pipes are you using?
They could be a restriction as your moving a LOT of gas through them.
You really need to get it on a dyno with multi gas analyser, it will be much cheaper than a re-build
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Old 02-01-2012, 11:11 AM
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Quote:
Originally Posted by crazypj
Red hot headers seems pretty normal to me, zero airflow as it's not moving and takes about 30 sec.
Your using tube exhaust manifolds which are pretty thin, normal exhaust gas temps are in the 1,000~1,400 deg range which is plenty to make them glow.
What diameter pipes are you using?
They could be a restriction as your moving a LOT of gas through them.
You really need to get it on a dyno with multi gas analyser, it will be much cheaper than a re-build
It is not normal at all.
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