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588ci BBF
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Paul P
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Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Mon Oct 14, 2013 9:52 am    Post subject: Reply with quote

Wow! o-ringed and still lifting? Will the block and heads support larger diameter head bolts/studs? How else can you secure it?
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2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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Big Dave
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PostPosted: Mon Oct 14, 2013 10:23 am    Post subject: Reply with quote

Are these stock cast iron casting? Or a does it have a set of aftermarket heads (like a nice set of Kasse 9 Boss 429 hemi heads to fit on top of a standard 385 series 460 block).

I suspect cast iron stockers which have decks too thin to seal up with that much temp increase do to that much nitrous oxide. Cast iron is hard, which makes it also brittle, but it is also incredibly elastic. Great stuff to make a canon ball out of as it will deform enough under the pressure of detonation to seal to the bore of the canon barrel.

I suspect the decks are fluttering like a butterfly's wings under the full 450 horse hit of NOS. It is to combat this deformation that they cast aluminum heads with a deck three quarters of an inch thick. Four times thicker than stock cast iron heads.

Your motor has six head bolts just like the big block Chevy so it is alright there (some GM motors that will remain nameless have only four head bolts per cylinder which will hold the head on so that it doesn't fall off, but is next to useless for sealing up the chamber, but Keith knows who I'm talking about).

It does share a thin deck common to all Detroit iron where cooling and maintenance free use trumps high performance. In an effort to prevent detonation the engineers designed the heads to have a thin deck intentionally so that you could get any localized heat out as fast as possible. By localized I am referring to the Exhaust-Intake-Intake-Exhaust-Exhaust-Intake-Intake-Exhaust lay out of the head. Having two exhaust ports side by side concentrates the heat in the head making it harder to cool.

Big Dave
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William Jones
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Joined: 30 Jan 2006
Posts: 823
Location: Lake city, FL
28541.86 points


1971 Ford Mustang

PostPosted: Mon Oct 14, 2013 10:30 am    Post subject: Reply with quote

Paul P wrote:
Wow! o-ringed and still lifting? Will the block and heads support larger diameter head bolts/studs? How else can you secure it?


It has a 9/16th head stud and 160ft pounds of torque. After talking with a few people that have experience with this type of combination. The consensus is to go to a thicker gasket to add quench since its to tight the way it is now and to get a new camshaft that will bring the cylinder pressure down to help the 10 bolt head survive.

_________________
Take the horse out off the barn and let her RUN BABY RUN!!!!!

92 LX 454ci Clevor 9.24@142.53 N/A
71 Mach1 454ci Clevor 10.16@134 N/A 3850lbs race weight "Lost in fire"
03 Cobra Bone stock 12.42
68 Falcon 363ci 10.55@126 N/A
95 GT 363ci 11.08@118 N/A
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William Jones
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Joined: 30 Jan 2006
Posts: 823
Location: Lake city, FL
28541.86 points


1971 Ford Mustang

PostPosted: Mon Oct 14, 2013 10:55 am    Post subject: Reply with quote

Big Dave wrote:
Are these stock cast iron casting? Or a does it have a set of aftermarket heads (like a nice set of Kasse 9 Boss 429 hemi heads to fit on top of a standard 385 series 460 block).

I suspect cast iron stockers which have decks too thin to seal up with that much temp increase do to that much nitrous oxide. Cast iron is hard, which makes it also brittle, but it is also incredibly elastic. Great stuff to make a canon ball out of as it will deform enough under the pressure of detonation to seal to the bore of the canon barrel.

I suspect the decks are fluttering like a butterfly's wings under the full 450 horse hit of NOS. It is to combat this deformation that they cast aluminum heads with a deck three quarters of an inch thick. Four times thicker than stock cast iron heads.

Your motor has six head bolts just like the big block Chevy so it is alright there (some GM motors that will remain nameless have only four head bolts per cylinder which will hold the head on so that it doesn't fall off, but is next to useless for sealing up the chamber, but Keith knows who I'm talking about).

It does share a thin deck common to all Detroit iron where cooling and maintenance free use trumps high performance. In an effort to prevent detonation the engineers designed the heads to have a thin deck intentionally so that you could get any localized heat out as fast as possible. By localized I am referring to the Exhaust-Intake-Intake-Exhaust-Exhaust-Intake-Intake-Exhaust lay out of the head. Having two exhaust ports side by side concentrates the heat in the head making it harder to cool.

Big Dave


The heads are aluminum EX 514s and the block is aftermarket A460 and it has 6 bolts per cyl but the heads are the factory 4 bolts per cylinder which is part of the problem and always has been a problem with this engine.

Bam

_________________
Take the horse out off the barn and let her RUN BABY RUN!!!!!

92 LX 454ci Clevor 9.24@142.53 N/A
71 Mach1 454ci Clevor 10.16@134 N/A 3850lbs race weight "Lost in fire"
03 Cobra Bone stock 12.42
68 Falcon 363ci 10.55@126 N/A
95 GT 363ci 11.08@118 N/A
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Paul P
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Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Mon Oct 14, 2013 12:19 pm    Post subject: Reply with quote

Is it possible to put the holes in it for the extra head bolts? Even if it is something you have to plug at the top just to get a short bolt down at the deck level.
_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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William Jones
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Joined: 30 Jan 2006
Posts: 823
Location: Lake city, FL
28541.86 points


1971 Ford Mustang

PostPosted: Mon Oct 14, 2013 1:41 pm    Post subject: Reply with quote

It would require welding ears on to the head on the outside.
_________________
Take the horse out off the barn and let her RUN BABY RUN!!!!!

92 LX 454ci Clevor 9.24@142.53 N/A
71 Mach1 454ci Clevor 10.16@134 N/A 3850lbs race weight "Lost in fire"
03 Cobra Bone stock 12.42
68 Falcon 363ci 10.55@126 N/A
95 GT 363ci 11.08@118 N/A
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Paul P
Member


Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Mon Oct 14, 2013 4:13 pm    Post subject: Reply with quote

Hope that quench change does the trick. 9/16'' studs are huge for heads! Has it been decked with those studs in place with a torque plate?
_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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William Jones
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Joined: 30 Jan 2006
Posts: 823
Location: Lake city, FL
28541.86 points


1971 Ford Mustang

PostPosted: Mon Oct 14, 2013 5:18 pm    Post subject: Reply with quote

I've never seen a block decked with head studs and torque plate in place but it was bored and honed with them and decked with the main studs. My thinking that the .040 to .050 extra quench and the right cam might do the trick if not we will look into new heads.

Bam

_________________
Take the horse out off the barn and let her RUN BABY RUN!!!!!

92 LX 454ci Clevor 9.24@142.53 N/A
71 Mach1 454ci Clevor 10.16@134 N/A 3850lbs race weight "Lost in fire"
03 Cobra Bone stock 12.42
68 Falcon 363ci 10.55@126 N/A
95 GT 363ci 11.08@118 N/A
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Paul P
Member


Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Mon Oct 14, 2013 5:30 pm    Post subject: Reply with quote

smoking Sorry you can't do that can you. My extreme bad on that one. decked with plates in place.... That is a good one isn't it.

You have the knowledge base and it is likely a quench change that will solve it. I'm not worthy

_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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clay
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Joined: 24 Nov 2002
Posts: 3209
Location: South Carolina
318129.23 points


1972 Chevrolet Nova

PostPosted: Tue Oct 15, 2013 7:27 pm    Post subject: Reply with quote

O.k. I need some education. I've never used nitrous past street car levels so what is the theory on what is the problem. From what I know (or think I know) nitrous revolves around being able to control burn rate as it can get too fast and out of control with nitrous being an accelerant. I'm thinking the larger quench should slow down brun rate. Did you ever consider water injection? It can help turbo's and superchargers drastically and I know some nitrous guys are running it also. I'm curious to learn on this one. Clay
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Big Dave
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Location: Tampa Florida
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PostPosted: Wed Oct 16, 2013 8:54 am    Post subject: Reply with quote

Quench is used to mix the fuel for a fast even burn. It is the principle reason that the a small block makes more horse power per cube than a big block (a big block was designed to be a modified hemi, or as it is known a semi-hemi since only half of a full dome was stuffed up into the chamber). If the quench area is too tight you risk detonation caused by super heating the quench volume above the auto-ignition temp. Dumping in an oxidizer aggravates the problem by adding in heat faster than the coolant can withdraw it through the head. Dieseling the engine can not only bend or break a crank or connecting rod, but it can also lift a head off the block.

Increasing the quench reduces the mixing and thus reduces the power as it slows down the rate of combustion. This is why Smog engines from the mid-seventies through the nineties are so down on power, but can be brought back from the dead with a new set of heads.

The reason a multi-spark ignition box was developed was to fire off a lean burning smog motor with no quench due to increased head chamber volume. Without the multi-spark ignition the flame front actually would go out resulting in increased hydro-carbon emissions rather than the goal of reducing emissions.

The chamber volume was increased as a cheap means of dropping static compression so that the factory could reduce oxides of nitrogen from forming as a result of high combustion temperatures. When Chevy got around to addressing this issue they changed the shape of the combustion chamber from a wedge to a heart shape to induce increased fuel mixing by increasing the head area involved with quench. The new fast burn combustion chamber was designed from scratch to better mix gas and air in the chamber by increasing turbulence in the chamber.

Honda engineers had looked into adapting (or we could call it reverse engineering) a Mercedes Benz diesel head to include a pre-combustion area in the head to promote flame front propagation. They abandoned the project eventually as being too expensive, but retained the name CIVIC which was supposed to reflect that pre-combustion chamber design that mixed the fuel and air before ignition using piston quench called CVCC (or Controlled Vortex Combustion Chamber) to reduce emission.

Quench like high compression is free horsepower. It uses the dynamics of the engine to move the goal posts from what the results would be predicted by the Ideal Gas Law and Thermodynamics because both engineering principles depend upon adiabatic (you can not change pressure or temperature allowing only the volume to vary) gasses in equilibrium (a steady state condition not found in a running engine). By looking at what goes on inside a running engine (initially by creating a viewport made out of polycarbonate, and using high speed photography; but later using super computers to model the conditions inside the chamber) engineers have been modifying the small block, and gas burning engines in general, continuously in an effort to meet reduce emission requirements and increased CAFE mileage numbers as motivation.

Big Dave
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Paul P
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Joined: 15 Aug 2002
Posts: 2404
Location: Townsend, Mass.
81616.60 points


1971 Chevrolet Chevelle

PostPosted: Wed Oct 16, 2013 10:35 am    Post subject: Reply with quote

Wow and he didn't mention the BMEP and got it done.
_________________
2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.86@102.5 MPH 1/8mi
10.78@122 MPH 1/4mi
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View user's profile Send private message
William Jones
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Joined: 30 Jan 2006
Posts: 823
Location: Lake city, FL
28541.86 points


1971 Ford Mustang

PostPosted: Wed Oct 16, 2013 6:46 pm    Post subject: Reply with quote

Im learning on this deal also but my understanding of the issue is to fold one issue being that a big block needs more quench than a small block in general due to expansion from heat of the rods and pistons. Then the other problem is cylinder pressure is to high for the 10 bolt head to handle which is a byproduct of the amount of nitrous and the camshaft profile.

Bam

_________________
Take the horse out off the barn and let her RUN BABY RUN!!!!!

92 LX 454ci Clevor 9.24@142.53 N/A
71 Mach1 454ci Clevor 10.16@134 N/A 3850lbs race weight "Lost in fire"
03 Cobra Bone stock 12.42
68 Falcon 363ci 10.55@126 N/A
95 GT 363ci 11.08@118 N/A
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clay
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Joined: 24 Nov 2002
Posts: 3209
Location: South Carolina
318129.23 points


1972 Chevrolet Nova

PostPosted: Wed Oct 16, 2013 10:10 pm    Post subject: Reply with quote

Dave - I agree with you and think that computer modeling must have been a huge help in especially the direct injection setups. I'm sure they probably adapted some diesel technology but had to adapt it for spark ignition and lower compression ratios.

William - I'm wondering if it's not too much cylinder pressure but pressure at the wrong time. I'm trying to remember from some books and it's sorta fuzzy but since nitrous accelerates the burn rate you wind up with more pressure around tdc and it tends to decay faster. N/A, turbo, and supercharger don't develope as much pressure but they maintain it longer so you wind up with more pressure past tdc which is very beneficial since the connecting rod has a much more favorable angle for mechanical advantage. I'm going to try to dig through some books this weekend. Theoretically all the pressure in the world at tdc would never turn the crank - it would just eventually break stuff. I'm wondering if the quench change and the cam change are changing the timing of cylinder and not actually how much. To me cylinder pressure is power so trying to reduce it seems counterproductive - unless you can't control it. Really curious how it turns out. Keep us posted. Clay

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Knarley Darley
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PostPosted: Thu Oct 17, 2013 11:43 pm    Post subject: Reply with quote

Sorry to hear that he wrecked it. Water under the tires is indefensible. I was under the impression that you were using the block with a head bolt pattern similar to a GM block. You definitely need to have the block checked, and probably re decked, and don't over torque the head bolts. What is actually happening, is the deck is being pulled up by the bolts so the heads are sitting on raised little mounds around each head bolt hole. Over torquing them is actually worse than under torquing because the tighter you go the more you are lifting the heads mechanically by distorting (raising) the block. The block may even have hair line cracks around the bolt holes, and you may only be able to make several passes at a time, and then have to take it apart and re deck. I have seen the surfacer take .010 off the bolt hole area of a block before it started to contact the rest of the deck. Hope it works out.
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