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Old 06-06-2010, 03:58 PM
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School me in high performance SBC's.

So here is the deal everyone. I am not new to building an engine,although I know very little about building a high performance one.
What I am leading up to is a lesson in what makes one head/rod/piston/cam better suited for an engine than another.
For my build I want to have the most RELIABLE power I can make with my 327
I have read alot about different combo's of internals but never seen a description of why THAT combo. A few things I am curious about:
why are longer rods beneficial to an engine.
How to I choose "my" optimal camshaft.
what is the necessary equation to find piston hight,and compression.
What do the terms:static compression,squish,and dwell among others mean ?
How to decide on heads,what does the size of the runners have to do with the performance of an engine ?
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Old 06-06-2010, 06:32 PM
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Quote:
Originally Posted by itsmecord
So here is the deal everyone. I am not new to building an engine,although I know very little about building a high performance one.
What I am leading up to is a lesson in what makes one head/rod/piston/cam better suited for an engine than another.
For my build I want to have the most RELIABLE power I can make with my 327
I have read alot about different combo's of internals but never seen a description of why THAT combo. A few things I am curious about:
why are longer rods beneficial to an engine.
How to I choose "my" optimal camshaft.
what is the necessary equation to find piston hight,and compression.
What do the terms:static compression,squish,and dwell among others mean ?
How to decide on heads,what does the size of the runners have to do with the performance of an engine ?

man you are asking a books worth of information!

well you are starting off with a good engine, larger bore, shorter stroke. this means you want to work mroe with higher rpms for more hp and lower amounts of tq, best suited for a lighter car (IMO). there is next to no benifit from using a larger rod until you get into racing applications, for a normal high performance street engine it will not make anymore power, so a 5.7 rod will do just fine, now if you go with a standard size rod (5.7) then you can use a standard size compression height piston (1.678), and if you keep the 3.25 cank then take 3.25/2=1.625+1.678=3.303+5.7=9.003 this would be your stack height. a standard SBC has a deck height of 9.025" so take 9.025-9.003=.022" that your pistons would be below the deck at TDC, now you want to get your quench/squish which is the area between the piston crown at TDC and the cylinder head. you want the quench to be inbetween .039-.046 for optimal performance, so you already know that you have .022" below the deck no you need to find a head gasket to make up the difference above the deck. so you would pick a head gasket with a compressed thickness of between .017-.024" but if you have the block decked then you would need to make up for that with extra thickness in the gasket ex: .022" in the hole then you have it decked .010" so now you are only .012" in the hole and you will need a gasket between .027-.034", this would be the route i would take to keep from using a shim style gasket. dont just slap a .041" gasket on there and call it a day like many people do cause this could put you quench well in the .060's which is still accepltable but will promote detenation easier than a .040" quench will. next you have the size of the runners in the heads, many believe that a larger runner is better, this is the "bigger is better" idiot way of thinking. the goal is acutally to keep the runner as small as possible maintaining good air velocity at all lifts of the valve but with getting the most CFM you can at the same time. think about it like blowing throught a meduim size straw and a large straw, for the medium straw you dont have to blow that hard in order to get a decent velocity of air out the other side, this equats to not having to have the motor high in the RPM's in order to make decent velocity of air in the runner ports going to the cylinders. no take the larger straw and blow the same as you did with the medium straw, you dont get as much velocity, you will have to blow harder in order to get the same velocity of air out the other side. this equates to having to have the motor at higher rpms in order to make good velocity in the runner and into the cylinder. now the larger diameter straw will flow more air but it will take a lot more effort to do it, and this equates to how much air do you reall need for you engine to make the kind of power you want (RPM). so do you get the idea of the smallest runners with the best air flow. for a 327 turing less than 6500 rpm i wouldn't go with more than a 180cc intake runner head, for less than 6000rpm go with 170cc intake runner head, for more than 7000rpm i would look into 200-210cc intake runner heads.

now as far a camshaft goes, all cam manufactures list their cams rpm ranges based on the 350, and since the 327 has less cubic inches than the 350 the same cam will act more aggressive in a 327 than it would in a 350, ex: a cam rated for 3000-6200 would actually have a power band more like 3300-6500 in a 327, just so you can understand this further i would use the example of a 383 to a 350, same cam 3000-6200 would acutually have a power band more like 2700-5900 in a 383. get it. i can't recomend a cam to you cause you haven't listed what you have and what you want to do, you have to remember that the more aggressive cam you get the higher compression you will need and this is due to overlap of the more aggresive cam leaking out compression as the intake valve stayes open longer on the compression stroke. you will also need lower gears because now the power band is higher and you will need a set of gear to get you within that powerband faster than a set of taller gears would. and then you also have the stall will have to be changed as well and typically you want your stall speed to be about 500rpm higher than the begining of you cams power band ex: 3000-6200 cam in a 327 is more like 3300-6500 so you would want a stall speed around 3800rpm.

static compression is basically the ratio of area contained in side the cylinders with the heads on at BDC and the area contained inside the cylinders with the heads on at TDC. in laymens terms how much squeeze do the motor make in the cyldinders. then you have dynamic compression ratio which is a calculation of the static compression ratio with the intake closure of the cam +15 and this will give you, your cranking pressure inside the cylinders with the correction of the overlap on the cam, typically 8.1-8.6:1 is the DCR you are looking for if you plan to run pump gas. for a steel head you can only get away with about a max of 155-160psi inside the cylinders under pump gas, and that is with a very good tune. but for aluminum heads you can get away with more like 175-180psi for pump gas, and there for you can run a higher compression ratio with alum heads which will help to make more power. but in my opinion if the car is going to see more street time then i am in favor of iron heads, but if it will see more track time i am in favor of aluminum heads

i tried to answer all your questions without writing a book, if you have some others or you just want me to help steer you in the right direct for building this motor then feel free to ask some more
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Old 06-06-2010, 08:05 PM
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Sorry......Thanx for the helpful,and kind reply. I was a little worried I would get frowned on for being a dumb@$$. Now for me to give you a little info on what I am working with: 1936' chevy 2-door sedan,camaro 5-speed trans,zoom aluminum flywheel,4:11 rear gear,unsure on tire size as I am just gunna have to see how big I can fit once the car is ready.I will be running a 65,000 volt dizzy,and will build long tube headers to fit the car once finished.
The car will be a cruiser for the most part,but it will see some 1/4 mile blasts(I'm all about acceleration).
I am wondering if I should go 3.73's instead to maintain a little less RPM while cruisin' ?
As far as heads go,I am unsure hence all the questions.
I was looking at these heads in the 190cc version http://www.skipwhiteperformance.com/...?Item=3303-CYL
They are available in either angle or straight plug design so i'm curious as to how much difference there is between the 2 For a real world app. ?
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Old 06-06-2010, 09:01 PM
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Quote:
Originally Posted by itsmecord
I was a little worried I would get frowned on for being a dumb@$$.
Only way you're gonna get frowned on is if you try to bluster your way through a subject not knowing what you are talking about. All of us began this hobby knowing NOTHING, so ignorance is ok here.

Quote:
Originally Posted by itsmecord
1936' chevy 2-door sedan,(I'm all about acceleration).
This car will be no lightweight and you're starting your project with a rather small motor. I think most fellows would start something like this with a 383 or larger in mind. Any motor you bolt into the car is just an air pump. The more air that is pumped through the motor, the more power the motor makes. You can change the amount of air going through the motor by running the rpm's up, but then you have to use a cam that takes the whole mess out of the realm of daily driveability and into a racing mode only. A naturally aspirated 327 that makes 450 ft/lbs of torque at 6000 won't be near as much fun (after about 10 minutes) as a 383 that makes 450 ft/lbs at 4000.

Quote:
Originally Posted by itsmecord
I am wondering if I should go 3.73's instead to maintain a little less RPM while cruisin' ?
I might use a 3.73 rear gear depending on the ratio of 5th in your manual box. I would want to end up with somewhere around 2.80:1 in 5th. Any taller than that and the motor is down so far in rpm's that is is really lugging and not making enough power to pull in my opinion.

Quote:
Originally Posted by itsmecord
As far as heads go,I am unsure hence all the questions.
I was looking at these heads in the 190cc version http://www.skipwhiteperformance.com/...?Item=3303-CYL
They are available in either angle or straight plug design so i'm curious as to how much difference there is between the 2 For a real world app. ?
In my opinion, these heads are too big for a 327. You would have to rev the motor to the moon to take advantage of their capability and that is not what you're saying you're building this rig for. Build a 383 (use your block, Scat 3.750" stroke cast steel crank and Scat forged 5.7 rods). Straight plug heads are much easier to fit headers. The angle plug heads might show a little more hp, but not enough to have to put up with the hassle of fitting headers to them.

Last edited by techinspector1; 06-06-2010 at 09:12 PM.
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Old 06-06-2010, 09:06 PM
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stay way from these heads, they are made by ProComp and are very questionable, they have had major quality issues in the past and have the flow numbers of other aftermarket 170cc heads. if you do get them then buy them bare not assembled and have them checked out by a machinest, then have them assembled with the parts your machinest recomends, these heads are also in serious need for some port work to be done to them to make them perform anywhere near what most 190cc heads do. my advice is to just stay away from them.

here are some good heads but you will pay for them, but for anything decent you are going to pay for them.

http://www.competitionproducts.com/A...tinfo/AFR0916/

http://www.competitionproducts.com/B...fo/BRO1021003/

http://www.competitionproducts.com/D...tinfo/D1864SA/

http://www.competitionproducts.com/R...fo/RHS12317K1/

even these would be a really goo fit if you dont plan on turing it up much past 6000rpm, and unless you plan on going with a solid cam or a hyd roller cam these are the heads that i would recomend the most

http://www.competitionproducts.com/R...fo/RHS12410K1/


Tech1 is 100% correct about the angle plug heads, and all i have ever seen them do is burn up plug wires left and right. the 383 idea is right on the money if you have the loot, but if you build the 383 i would still stay away from the ProComp 190 or just about anything that says ProComp, why not just start with a set of heads that you know will preform well from a company that has not had near the amount of issues, and by-pass all that extra machine work. if you were to go with the 383 i would recomend the AFR 195's, DART iron eagle Platinum 200's or the RHS pro action 200's, maybe even the Pro-filer 195's

Last edited by my87Z; 06-06-2010 at 09:13 PM.
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Old 06-06-2010, 09:31 PM
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My 36' would be considered heavy ? I would not have thought that as it is a "skin" only car that came with wood. I am at the stage of building a body structure rite now. I am not arguing though,just surprised.
My choice of engine is because I have the engine,I like them because around here they are the "under dog" and considered a waist. They have been Compared to the 305. I would really like to stay away from a stroker,because it is such a "cookie cutter" engine. keep the info coming guys I really appreciate it

What about this package ? http://sdparts.com/details/scoggin-d...ter/sd8060arpm
What about Brodix heads ? do they offer anything that might fit the bill ? They are only 45 minutes from me.
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Old 06-06-2010, 09:48 PM
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Quote:
Originally Posted by itsmecord
I would really like to stay away from a stroker,because it is such a "cookie cutter" engine.
And a small block Chevy isn't? I don't understand this kind of thinking. You're gonna put together a small motor with limited hp and torque just so you can say "Naw, It ain't very fast, but at least I didn't build a cookie cutter motor."
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Old 06-07-2010, 02:43 PM
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Quote:
Originally Posted by techinspector1
And a small block Chevy isn't? I don't understand this kind of thinking. You're gonna put together a small motor with limited hp and torque just so you can say "Naw, It ain't very fast, but at least I didn't build a cookie cutter motor."

i have to disagree Tech1, i respect the whole idea. i dont think he is looking for crazy power. and although it is a small motor i like the 327. but i will say that this would not be the project i would be putting a 327 in. i would choose something very light weight, like a late 70's early 80's malibu, vega, monza, or maybe even an old datzun teamed with a 4-5sped and running the 327 up to say 7500rpm that would be a fun screamer.

anyway i wouldn't consider the 327 a cookie cutter engine, but opinions are opinions. about the vortec kit from scoggin' dicky, that is a bit over priced at 1109.00

here look at these;

http://www.summitracing.com/parts/SUM-151124/

619.00 for the pair

http://www.summitracing.com/parts/EDL-7116/

now you're at 806.95, and you could find head gaskets, intake gaskets, and bolts for less than another 300.00
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Old 06-07-2010, 06:31 PM
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To me selecting a combination begins with a bunch of questions about a project. What is reliable power for a bracket racer is different than reliable power for a daily driver.

How much is the car going to weigh ? Do you have any E.T. goals ? If you have an E.T. goal that will lead you to how much power you need to make and an rpm range based on the displacement of the engine used. This will help with choosing the proper sized heads, gearing etc.
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Old 06-07-2010, 07:44 PM
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what do you guys think my car will weigh in at ? I really thought it would be considered a mid weight car. As far as how much hp/tq. ? I have no true goals.
I'm after a quick revving engine,that can take being daily driven.
I'm after the " wow,a 327 you hardly see them anymore "....."damn thing runs pretty good to ! " kinda thing. Not a drag car,and I'm not out to beat the corvettes out there running around.
And yea, a SBC might be considered cookie cutter,but not so much a 327 as a 350,383. And BBC is not an option at all.
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Old 06-08-2010, 07:06 AM
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Well kinda splittin hairs now...a SBC is a SBC is a SBC

I think the only time you wouldn't get crap for a SBC being "cookie cutter" is if it was a real 302...and its STILL a SBC
Nothing wrong with them I love em and i love my 307 but to say a 327 is "rarer" and only better for that purpose is kinda ridiculous. especially when it(383) would probably work better for you in almost every way in terms of driveability.
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Old 06-08-2010, 10:12 AM
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Quote:
Originally Posted by DeathRattle
Well kinda splittin hairs now...a SBC is a SBC is a SBC

I think the only time you wouldn't get crap for a SBC being "cookie cutter" is if it was a real 302...and its STILL a SBC
Nothing wrong with them I love em and i love my 307 but to say a 327 is "rarer" and only better for that purpose is kinda ridiculous. especially when it(383) would probably work better for you in almost every way in terms of driveability.

i wouldn't say that a SBC is a SBC, i still am a little shocked when i see a 283,327 and especially a 302. and that is shocked in a good way. i do agree with the idea that the 383 would be a far more fun ride and would do it while being more street friendly in being able to keep lower rpms but still make good power, likely better than you will make out of the 327. but i can understand the thought behind the 327. but i dont think in the OP's case that he should go after too much power if he still want to stay with the 327 in the car he has picked
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Old 06-08-2010, 12:08 PM
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Quote:
Originally Posted by my87Z
i have to disagree Tech1, i respect the whole idea. i dont think he is looking for crazy power. and although it is a small motor i like the 327. but i will say that this would not be the project i would be putting a 327 in. i would choose something very light weight, like a late 70's early 80's malibu, vega, monza, or maybe even an old datzun teamed with a 4-5sped and running the 327 up to say 7500rpm that would be a fun screamer.

anyway i wouldn't consider the 327 a cookie cutter engine, but opinions are opinions. about the vortec kit from scoggin' dicky, that is a bit over priced at 1109.00

here look at these;

http://www.summitracing.com/parts/SUM-151124/

619.00 for the pair

http://www.summitracing.com/parts/EDL-7116/

now you're at 806.95, and you could find head gaskets, intake gaskets, and bolts for less than another 300.00
Don't forget to match that kit you'll need...

GM self aligning rocker arms - $61.95
http://www.summitracing.com/parts/NAL-12495490/

Head bolts - $25.95
http://www.summitracing.com/parts/NAL-12367959/

Vortec Intake bolts - $19.95
http://www.summitracing.com/parts/ARP-134-2002/

Head gaskets - $30-$60 for a pair depending on the set.

Vortec Intake gaskets - $21.95
http://www.summitracing.com/parts/FPP-1255/

AND some sort of valve spring upgrade. $60


That puts you at least in the $1026.75 range. Only about $75 savings. Even still, you'll only be able to get .450 lift with only a spring change, a little more with a seal change I've heard, unless you go with beehive springs and matching retainers. That would be another $325 at least.

I think it's not that bad of a deal AND you can get up to a .525" lift.
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Old 06-08-2010, 02:54 PM
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super beatle if you actually look at the heads i posted they are rated for a lift up to .520" and the scoggin' dicky heads are rated for a lift of .525" i would say the difference is litterly splitting hairs, so you can take that 60.00 off that price that you came up with. then if you look a the scoggin dicky kit it doesn't come with self-aligning rockers either so you take the 61.95 off the price that you came up with too, that will leave you with about 900-940.00 and that from 1109.00 is a solid 150-200 savings and that is worth it so now do you see why i say the price from scoggin dicky is a bit steep, you and i just priced all the parts in their kit from other sources and came up with 900-940 bucks, so why is their's 1109.00
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Old 06-08-2010, 03:07 PM
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Quote:
Originally Posted by my87Z
super beatle if you actually look at the heads i posted they are rated for a lift up to .520" and the scoggin' dicky heads are rated for a lift of .525" i would say the difference is litterly splitting hairs, so you can take that 60.00 off that price that you came up with. then if you look a the scoggin dicky kit it doesn't come with self-aligning rockers either so you take the 61.95 off the price that you came up with too, that will leave you with about 900-940.00 and that from 1109.00 is a solid 150-200 savings and that is worth it so now do you see why i say the price from scoggin dicky is a bit steep, you and i just priced all the parts in their kit from other sources and came up with 900-940 bucks, so why is their's 1109.00
Ahh...you're right. Good call. I looked at the link, but was thinking they're 060 GM heads with the .450 lift limit cause I just glanced at them.

The dickey kit does come with "GM stamped rockers" like the ones I posted a link to. Either way, you could save some $$$ buying the parts individually through Summit and spend the savings on other needed parts. That and Summit has great service and cheap, fast shipping.
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