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  #31 (permalink)  
Old 10-17-2012, 03:46 PM
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Originally Posted by mustang 671 View Post
just looked at weiand boost chart and for my 0.8 underdriven it shows around 12 psi for a 350 but i have a 351 with a 30thou over bore. so i think around 11psi approx
Sounds about right. A lot of boost for the street, you should consider lowering it.

Please tell us what the tubes from the carb are connected to (I think you said to the intake below blower), and where the vacuum ports are located on the carb itself. A carb w/an added on boost referenced power valve port looks like the one shown below:


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  #32 (permalink)  
Old 10-17-2012, 03:48 PM
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The first thing you need do is replace carbs or get ur fuel injection that u spoke of before you continue im telling u with cast piston and what u have going on not going last long before you shatter a piston and have alot more exspensive problems I wouldnt drive it as is if it was mine not at all
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  #33 (permalink)  
Old 10-17-2012, 04:24 PM
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Quote:
Originally Posted by cobalt327 View Post
Sounds about right. A lot of boost for the street, you should consider lowering it.

Please tell us what the tubes from the carb are connected to (I think you said to the intake below blower), and where the vacuum ports are located on the carb itself. A carb w/an added on boost referenced power valve port looks like the one shown below:

as t bird pointed out the tubes come out of the sides of the vac sec bodies and should be plumbed together to balance them . so i will change to that

i do not have what you have pictured . under the primary float bowls i have take offs with tubes on them coming out from the base of the carbs. currently these a stopped up with a small bolt .

from what i understood these carbs need a tube to read vacum ? i may be missing the point on that as some also use the take offs for the dizzy and other parts that i dont have on the engine .

this set up was working on a chevy when i bought it from the guy . i agree the carbs do need to be tuned and boost referneced and i have read alot about it and can be achieved. i havnt the money yet to buy fuel inj .

what do you think is a safe psi figure for the street ?

hi have keith black hyperutectic psitons. have reserached them and as long as detonation is kept at bay they are fine .
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Old 10-17-2012, 04:43 PM
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Yea they are fine if u have none but I can assure u with what u are saying u are not keeping detonation at bay with kb cast piston a little is to much they will shatter dont know wby anyone would put that kind of money into a engine place a blower on it and not use forged piston they are not that much more but yea if u get carbs replaced or figured out and lower boost psi they will live for a little while wouldnt run but bout 6 maybe 8 psi and if set up worked when u got it why mess with it what was the problem
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  #35 (permalink)  
Old 10-17-2012, 10:26 PM
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Originally Posted by mustang 671 View Post
as t bird pointed out the tubes come out of the sides of the vac sec bodies and should be plumbed together to balance them . so i will change to that

i do not have what you have pictured . under the primary float bowls i have take offs with tubes on them coming out from the base of the carbs. currently these a stopped up with a small bolt .

from what i understood these carbs need a tube to read vacum ? i may be missing the point on that as some also use the take offs for the dizzy and other parts that i dont have on the engine .

this set up was working on a chevy when i bought it from the guy . i agree the carbs do need to be tuned and boost referneced and i have read alot about it and can be achieved. i havnt the money yet to buy fuel inj .

what do you think is a safe psi figure for the street ?

hi have keith black hyperutectic psitons. have reserached them and as long as detonation is kept at bay they are fine .
I would start out w/about half or a little more boost than it's capable of making now. Somewhere around 5-7 psi max would be a good starting place to get things dialed in. That much boost will give you around 40% more hp than naturally aspirated.

That might not sound like much, but the ability of the rest of the vehicle to put that much hp to the ground needs to be considered as well. A lot of power is great- what's not so great is if all it does is make the rear tires spin. Or worse, break driveline parts.

The main thing now is keeping the engine from detonating from too much timing vs. boost. Spending on a boost referenced timing retard like the MSD boost timing master will be cheaper in the long run than cracking pistons or pinching the rings. It will also allow the engine to be tuned to run better than locking the timing. The MSD 8762 needs an ignition box like the MSD 6 series. You should be able to use the crank trigger you have.

If you are reasonably competent (which I'm betting you are) you can boost reference the carbs yourself. If they're 4150 series carbs I would use them, at least for now. Using a pair of 750 cfm blower carbs would be something else to consider if you end up buying different carbs in the future- especially if you go back up in boost.

Above, I missed where you mentioned the carb's secondary vacuum housings were what had the vacuum lines to them, sorry about that.
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  #36 (permalink)  
Old 10-18-2012, 12:06 PM
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Originally Posted by cobalt327 View Post
I would start out w/about half or a little more boost than it's capable of making now. Somewhere around 5-7 psi max would be a good starting place to get things dialed in. That much boost will give you around 40% more hp than naturally aspirated.

That might not sound like much, but the ability of the rest of the vehicle to put that much hp to the ground needs to be considered as well. A lot of power is great- what's not so great is if all it does is make the rear tires spin. Or worse, break driveline parts.

The main thing now is keeping the engine from detonating from too much timing vs. boost. Spending on a boost referenced timing retard like the MSD boost timing master will be cheaper in the long run than cracking pistons or pinching the rings. It will also allow the engine to be tuned to run better than locking the timing. The MSD 8762 needs an ignition box like the MSD 6 series. You should be able to use the crank trigger you have.

If you are reasonably competent (which I'm betting you are) you can boost reference the carbs yourself. If they're 4150 series carbs I would use them, at least for now. Using a pair of 750 cfm blower carbs would be something else to consider if you end up buying different carbs in the future- especially if you go back up in boost.

Above, I missed where you mentioned the carb's secondary vacuum housings were what had the vacuum lines to them, sorry about that.
thanks cobalt . thats very helpful . i have a good book on "supercharging for street machines " and it covers the holleys . so will go down that route and will also contact the company i purchaced the ecu from to enquire about detonation problems and a system that will work in line with theirs , i do have 2x knock sensors anywhay which retard the ign if a knock is sensed by them , i can aldo change the paramiters to make them retard the ign more and more . i think it is set to retard 3 d and hold until i change it again , i will also introduce my water injectionand onceits tuned and when i start to drive it harder i should cool the intake charge somewhat.

yep im able to boost ref the carbs. trust me that will be easy compared to what i have done to the car of the last 8 or so yrs . will read the book and also take what the posts on here have suggested, but i really want it to have the lambar sensors pluged in so i know where i am wrong . ie too rich - to lean etc.

these carbs where being use on a big block chevy ( i thought it was a 350 but wasnt ) so it would work for my cid engine anyway. each engine is always different, regardless if they are exactly the same .

am not too worried about the kb pistons , i chose them for my own reasons, i had a set of trw forged pistons and choosed against them. am happy with the set up and dont feel it will be weak. i understand the problem with this type of piston ( not a standard cast though being hyperutectic ) but any detonation in any engine isnt good regardles off what your running.

will get a pulley to give me up to 7 psi to begin with.

cheers cobalt
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  #37 (permalink)  
Old 10-18-2012, 12:38 PM
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U r right detonation is not good in any engine seen a many kb pistons in pieces and alot of other brands but with forced induction thats like beating on a piston with a hammer I would.love.hear ur reason why kb hyper were better than forged if u all ready had them the only reason ive ever heard of someone wanting go with any cast piston hyper or not was they didnt want spend the extra money ive seen it to many times in engines the hyper wont last with much boost not for long
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  #38 (permalink)  
Old 10-18-2012, 12:57 PM
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U r right detonation is not good in any engine seen a many kb pistons in pieces and alot of other brands but with forced induction thats like beating on a piston with a hammer I would.love.hear ur reason why kb hyper were better than forged if u all ready had them the only reason ive ever heard of someone wanting go with any cast piston hyper or not was they didnt want spend the extra money ive seen it to many times in engines the hyper wont last with much boost not for long
not sure if you have got the wrong end of the stick there , i choose against them not for costs as i had them already . look at what a forged piston does to a block when it cracks compared to a cast one. the chances of either cracking etc in my engine and from what i have seen and discussed with many engine builders are pretty much the same. yes forged are harder and will take a more hammering, but not the hammering "i " am talking about . with no detonation and 12 psi a kb hyperutectic piston is more than capable of handling 800 bhp . i have seen it for my own eyes and over here @ santa pod they are doing it every weekend . yes there will also be others running forged, thats up to them . i am happy with 500 - 600 bhp with what i have,

the main thing ( reason for the post ) is to work out what problems i am having @ my carbs, do you have any advise for that ? and also in ignition ?
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  #39 (permalink)  
Old 10-18-2012, 01:33 PM
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fyi -idontdrivericeieatit-

interesting read on Hypereutectic -vs- Forged Pistons


Hypereutectic pistons are used in some original equipment engines. They are favored because of reduced scuffing, improved power, fuel economy and emissions.

Hypereutectic 390 refers to a unique aluminum piston alloy that contains dissolved and free silicon. The material can be T6 heat treated to high strength and stiffness. Non-heat treated 390 hypereutectic alloy aluminum has slightly less strength than conventionally cast F-132 aluminum.

With this in mind, we caution the reader about the use of non-T6 heat treated O.E. design hypereutectic pistons for high performance. Silvolite and others do make replacement-type hypereutectic pistons that are worthwhile for stock replacement applications. Original equipment design is almost never suitable for performance applications.

The KB line of hypereutectic pistons were designed around the 390 alloy. The result is a high performance part intended to give the performance engine builder access to the latest in piston technology.

Forgings have long been the mainstay of the performance business and did well in the big cubic inch engines of the 60’s. Now, with focus on peak cylinder pressure timing, ring sealing dynamics, cylinder air tumble and swirl, combustion chamber science, and extended RPM ranges, we need to consider some new piston options.

The KB T6 hypereutectics are considerably different than the forgings. The KB pistons have shown improvement in power, fuel economy, cylinder sealing, service life, and cost effectiveness. The reduced thermal expansion rate allows the piston to be run with reduced clearance. A tight piston is less likely to rock, make noise, and burn oil. A rocking piston wears rings and increases blow-bye. The close fit of the KB piston allows the piston rings to truly seal, minimizing blow-by.

The design flexibility enjoyed by the KB series of pistons has an advantage over present day forging practices. The die for a forged piston must be designed so it can be easily removed. This limitation makes it difficult to make a light weight piston without sacrificing strength.

The KB pistons' utilization of the permanent mold with multiple die parts allows undercut areas above the pin hole and material distribution in the skirt area that stiffen the entire piston unit. The forged piston requires thick skirts to achieve comparable piston rigidity. A rigid piston rocks less in the cylinder and improves ring seal.

The forged pistons' thick skirts add weight. The design of KB pistons gives us the option to build the lightest pistons on the market.

Some current KB pistons are not super light for several reasons. If the piston is to be used as a stock replacement, more than a 10% weight reduction will mandate that the engine be re-balanced.

Common sense suggests that the introduction of a new product be extra strong at the initial release. As the product becomes accepted, weight reductions are scheduled as regular product upgrades, as justified with actual race testing.

There will always be a market for custom forged pistons. Small runs of forgings are more economical than small runs of permanent mold pistons because of the complexity of permanent mold tooling. Where quantities justify, expect to see future KB pistons developed that are lighter and stronger than anything else on the market. Machined head profiles are easily changed with our CNC equipment so we will stay current with new cylinder head developments. Volume production is expected to keep the price reasonable.

Our pricing policy has given the impression to some that we are building an economy, or in between, piston. The truth is, we are striving to build the "State of the Art" piston that is best, regardless of price. Reasonable pricing is just an added benefit.


- if the instaltion instruction are followed exactly these pistons i feel are very good. ( i am not comparing them to forged ones - i dont want forged ones ) but if people are suffering from kb hyperutectic pistons cracking braking rings and shattering then clearly there is another problem with either the instalation and or the tuning of the engine. maybe detonation maybe timing. who knows. but it is always difficult to listen to people saying they brake they arent any good but clearly they work and clearly kb wouldnt invest millions in creating this, etc if there principal idea was floored. its not . it depends on what you want from your piston and how you intend to drive. i made the decision not for a money saving ( it was only a 100 odd quid ) i didnt want to put some old age old trusted piston that hadent had any new tooling or desing in it since the dinorsaur age when there was fantasastic new designed material that wanst like stone and actually absorbed slight problems and can give a bit. which on a blown engine is a good idea and especially where i live as from day to day the humidity and temperature change withinn 24 hrs.

i also have a brand new electric power steering pump instead of a clunky old one and a brilliant ecu that can have anything changed to it, thats what i like to use. new types of techynologies . good luck to forged
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Old 10-18-2012, 02:21 PM
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Never said kb hyper are bad they are not but where the problem with them are they are harder let me repeat that kb hyper are harder than forged piston thats where problems with detonation comes in a forged piston will bend and warp if it gets to bad a hyper will not it will shatter in a million pieces if u dont have any detonation yes u should be. Ok but with the carbs like they are what I saying is wouldnt run it at all if the carbs are not right. U will have problem and I dont know anybody running 800 hp with hyper piston its not the installation with pistons thats the problem u got it right its running and detonation that is the problem it dont take much for somebody get little off hit detonation and have problem some are not smart enough not to drive it not saying that you im not just saying a forged is way more forgiving that any hyper if u have a problem
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Old 10-18-2012, 02:32 PM
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As far as carbs go I would either take them to somebody that knows what they doing and have been doing it for years or buy tge right carbs for the job or save money to. Buy the fuel injection you really want no advice on ignition im one them dinosaur that dont like or want fifty million sensor or computers on my car I got gas I got spark and im drivin mine quits I dont need computers to fix it I can fix in matter of min because there can on be a couple things wrong thats how I like it mines never been down for days.OR weeks chasing a problem
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  #42 (permalink)  
Old 10-18-2012, 03:04 PM
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COBALT

do the 4150 carbs normally have a tube going from the base of the carb to the inlet manifold ? i am sure i read some where that it needs to have a vacum tube ?

i know some will need to be pugged as i dont need a take off for the dizzy for example .
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Old 10-18-2012, 04:30 PM
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I have holley 850 dp mine has two vac lines one on front left of carb for dizzy u wont need and one in center back of carb to intake
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  #44 (permalink)  
Old 10-19-2012, 10:06 AM
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COBALT

do the 4150 carbs normally have a tube going from the base of the carb to the inlet manifold ? i am sure i read some where that it needs to have a vacum tube ?

i know some will need to be pugged as i dont need a take off for the dizzy for example .
They don't usually use a tube from the carb base back into the intake. All the vacuum the carb needs comes from the throttle plate and/or the throttle bores of the carb, making them basically 'internal'.

You are correct- just plug any unneeded ports.

The carb's ported vacuum port is on the side of the metering block. As you know, ported vacuum is not present at idle, it comes on as the primary throttle plates start to open. BTW, the instructions will often say to use ported vacuum for the vacuum advance but in many cases manifold (full time) vacuum works better. You have no need for a vacuum advance port anyway so this is a moot point.

The small vacuum port(s) down on the baseplate will usually be manifold vacuum sources. The larger ports on the baseplate are used for the PCV system (usually the front port) and for the power brake booster vacuum (usually the rear port). The power brakes could use an intake manifold mounted port instead of the carb port.

Hope this helps, but if I've misunderstood you or missed the point, just let me know.
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  #45 (permalink)  
Old 10-19-2012, 12:02 PM
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cheers guys .

yep that has put my mind at rest . i will plug all vacum lines and agree i will not use the vacum off the primary metering block as intake vacum is always better .

i am going to get another top pulley to reduce the psi down to 8 and then build up at a latter stage ( if needed ) also my power brakes are off the intake .

i have spoke with the guys at the dyno shop that i am going to see a week wednesday and they stock all the bits in need for the holley .

so this weekend im going to tidy up . gap my plugs ( what do you recommend for my application ? or will stock factory set do ? they are champion )

i am going to stip the carbs down and give them a good clean out and make sure they are flowing correct etc . also i still think i have a fuel leakage . possibly fronm the power valve ? being a 6.5. will this oen and over fuel or would i need to be putting the enginbe under load for it to open ?

it is really lupmy and will not repsond to mix srcew adjustment , i am going to un hook the billet linkage and double check they are not holding open the butterflys just slightly etc .

any things to look for when im cleaning out the carbs ?

cheers guys
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