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Old 01-20-2007, 10:27 PM
Burnt rubber and Raceing gas
 
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Heads

I am searching for the best heads for my SB.What r better the 202 or the 194's? 64cc or the 75. Is it better to buy them from like jegs or summit or can I get some worked heads cheaper.Lots of questions.

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Old 01-20-2007, 11:37 PM
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Quote:
Originally Posted by fullthrottle
I am searching for the best heads for my SB.What r better the 202 or the 194's? 64cc or the 75. Is it better to buy them from like jegs or summit or can I get some worked heads cheaper.Lots of questions.

http://www.chevyhiperformance.com/te.../photo_14.html

http://www.eqcylinderheads.com/flow.html
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Old 01-20-2007, 11:40 PM
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I just kind of have a personal rule of thumb 1.94 and smaller heads are ok for a 350 or smaller, anything over a 350, or anything seeing over 6000 rpm use 2.02-2.08 heads.

As far as combustion chamber size, use what size you need to get the desired compression ratio. But generally go with the smallest combustion chamber you can to run flat tops or dished pistons. Don't go too big of a chamber and have to run domes though, domes kill ignition, flame and efficiency.

As far as best heads go, AFR is tough to beat, they are far Superior to 95% of other heads. They do come with a price tag though, BEWARE!

Hope this helps

- Cody
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Old 01-21-2007, 12:33 AM
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Heads

Lots of options out there where ever you buy them but they must match your other components such as cam grind, intake type, exhaust type, and cubic inches.
A good set of SBC heads can run as high as $1500 and as low as $500 a pair.
Valve size is proportional to flow rates and some 194/150 heads flow the same as a 202/160.
The CC volume will dictate the CR for a specific application such as 72CC will give a lower CR than a 64CC on the same motor.
The max valve lift for a specific head will restrict the size of cam you can use.
On a 350 SBC with a mild cam to .480 lift you could look at the GM Performance Vortec cast iron heads that have 194/150 valves BUT have 170CC intake runners and 64CC combustion chambers.
They are the lower priced heads but you have to buy a Vortec intake and self aligning rockers that my defeat the savings on the heads themselves.
In the $1000+ price range for a mild 350 look at 202/160 valves, 64-76cc chambers (depending on desired CR), .500"+ max valve lift, 170/60 intake/exhaust runner, screw in studs, and push rod guides. Also check if they call for longer push rods (More$$)
Buying fully assembled heads turn out to be cheaper in the long run than trying to have a machine shop build you a set unless you want stock.
WORLD, Summit, and Jegs sells good iron heads in the 6-$800 range and will back up the sale if you have problems.
Like I said, match the heads to your motor parts. I've seen matched systems sold by name brand manufacturers that take all the guesswork out of the equation. See what they put together in the way of parts.
Good Luck
Arlo
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Old 01-21-2007, 10:29 AM
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a machinist told me that taking a 1.94 1.50 valve head and cutting it to 2.02 1.60 and blending it with a die grinder flows pretty good because of the open chamber. but by the time i spend the money on machine work i could get a set of aftermarket vortec heads.
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Old 01-21-2007, 11:48 AM
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Quote:
Originally Posted by fullthrottle
I am searching for the best heads for my SB.What r better the 202 or the 194's? 64cc or the 75. Is it better to buy them from like jegs or summit or can I get some worked heads cheaper.Lots of questions.
There you have it......
non-specific answers to a non-specific question.

It would help us a lot if you gave us some clue at to what you are trying to acheive for what amount of money. Even then you are going to get a myriad of opinions.

This topic has been covered 4-5 times in the last 3 weeks.
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Old 01-21-2007, 11:54 AM
Burnt rubber and Raceing gas
 
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heads

I have heard of the vortech heads from several people but get mixxed opinions some say they r ok some say they suck and would not use them for a boat anchor. I am building a 350,I am trying to decied if I want to spend the money for a stroked crank and machine work on the block or go with a stock crank. I have been givin a great combo for a stroker motor but the money to stroke it is alot. Right now I have a stock block that looks to be rebuilt,it has a 4 inch bore looks like stock pistons very clean motor.I do not feel any ridge in the tops of the cylinders besides a little carbon that cleans up easy.It was in a 57 chevy belair show car.It was never really ran on the open road just started to pull on and off the trailer and around the show grounds.They installed a large towwing cam just for a little thump in the exhaust and they lost oil pressure shortly after (it ran around 20 lbs) I bought the engine for very cheap pulled it apart and found the cam and bearings wiped out but every thing else looks good. I am trying to build a engine on a budget.I understand that speed is money.Down here we say for every second you want to drop in time will cost you a 1,000 dollars. Seems about right. So see I want to pull as much tourqe and power as possible for the 1/8 as cheap as I can without building junk. I have had my hands in a few circle track motors 600-800 horses but that knowledge I have found does not apply for the 1/8 mile. The guys I race at the track are just throwwing things together and trying to run top. The guys who really run good times either will not tell you anything or they r running blown big blocks which does nothing for me since I am a SB lover. I can imagine what I want my car to do but getting it there is a diffrent story. I will have to do this a little at a time but I don't want to do one thing a then have to back up the build to apply somrthing else.I am hoping to get everything together then send my block to the shop so when it returns I can put it together and break it in.I do not want it to set half together for any period of time. I have rambeled enough.Looking forward to your comments.
Shut up, Buckle up and hang on!
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Old 01-21-2007, 04:05 PM
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Anyone who says that Vortec L31 heads are only good for boat anchors, doesnt know much about teh smallblock Chev engine. theyare the highest flowing Gen 1 head that GM ever put into a production vehicle. They outflow the 1993-97 LT1 head on the intake side. they even outflow the Phase 2 Bowtie race head(not as durable however).

the Vortecs do require a specific 8 bolt intake manifold withraised intake runners. These bolts are located in pairs at the corners of the intakes. They have a 170cc intake port and 64cc chamber.

GMPP now makes the 207cc intake port Largeport Bowtie Vortec head along withteh Smallport Bowtie Voretc head with 175cc intake port.
These heads flow close top what teh aluminum 210cc intake port head flows.
Then there are the 180 and 200cc Edelbrock ETEC heads which are also aluminum.

theVoretc L31 heads have a lift limit of .475" stock. But with retainers and springs much more is attainable.
The Vortecs have a high flow intake port, but teh exhaust side isnt as good when compared to teh intake. This is why you should run cams with at LEAST 10 more exhaust duration than intake.
I suggest full porting of the exhaust ports.

Vortec heads as boat anchors lol, give them to me if you dont want them.

peace
Hog
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Old 01-21-2007, 04:44 PM
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Quote:
Originally Posted by Hogg


The Vortecs have a high flow intake port, but teh exhaust side isnt as good when compared to teh intake. This is why you should run cams with at LEAST 10 more exhaust duration than intake.
I suggest full porting of the exhaust ports.


peace
Hog

That depends on the valve/bore ratio and the required LSA lobe separation angle of the cam. They are designed for 350s.

When you do that, you are blowing the exhaust out sooner and crutching the overlap with a too wide LSA.
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Old 01-21-2007, 06:54 PM
Burnt rubber and Raceing gas
 
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What?

PLease explain what you said--you are blowing the exhaust out sooner and crutching the overlap with a too wide LSA-- blowing out exhoust to soon is bad? LSA? Never seen anyone work a flow bench so I don't understand.
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Old 01-21-2007, 07:33 PM
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As far as bang for the buck goes, I beleive that there are two ways to go, vortecs or AFR's. For the price they are both great heads. I have had cars wtih both of them and have been very impressed with each. Just a few questions...

How much can you spend on a set of heads?
how much does your car weigh?
Do you want to run pump gas?
What is the max stall you want to run?
how much hp are you after?
What gear are you running?
What tranny are you running?
What kind of cam are you going to be using?
Is there an RPM range you want to stick to?

Adam
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Old 01-21-2007, 07:58 PM
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...

I will answer those for you adam,
#1-as little as I can get away with
#2- Its a stock 85 S-10 blazer right now maybe 3500 lbs
#3-sure if I can get away with it but I dought it
#4-Something around 3500 I think I want to drive it on the road
#5-As much as I can get of course
#6-Have not decided
#7-as of now a 350 turbo , I would like a 2 speed power glide
#8-undecided
#9-Well I am learning that high rpm's are more for the circle track
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Old 01-21-2007, 08:09 PM
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fullthrottle, your #'s 1 and 5 are contradicting. Spending as little as you can on heads isn't going to get you as much power as possible.

3500 stall is a little much for street use.

Stick with a T350, don't bother with the Powerglide. You'll thank yourself for keeping the additional gear in a street vehicle.

You'd be surprised what you can do with pump gas. You can still build a substantial amount of power using 92 octane. Of course, using cheap heads with poorly designed or old fashioned combustion chambers will make that harder to accomplish. Spending a bit of money on a set of efficient, well designed heads will go a long way.
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Old 01-21-2007, 08:26 PM
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Vortecs would be the cheapest performance heads you could buy.I would replace the pressed in studs,with screw in studs and guides,Port the exaust side,Bowl blend,Install bigger springs,and better locks and retainers.Although some places sell Vortecs already done.For around $625 a set.Split duration cams are better for vortecs.One I like is the new Thumper cams
http://www.compperformancegroupstore...ry_Code=Thumpr
But there's nothing wrong with using flat tappet cams.The XE comp cams and lunati Voodoo cams are fairly good.I also like an Isky.But Lazer cams can also recomend the right cam.
www.lazercams.com
And so can comp cams
http://www.compcams.com/
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Old 01-21-2007, 08:29 PM
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Quote:
Originally Posted by fullthrottle
PLease explain what you said--you are blowing the exhaust out sooner and crutching the overlap with a too wide LSA-- blowing out exhoust to soon is bad? LSA? Never seen anyone work a flow bench so I don't understand.

LSA is determined by the valve/bore ratio. Not by duration or flow benches. Only one LSA is right for each situation. You chose duration to put the torque peak where you want it rpm wise by duration. Get all the lift you can.

A 2" valve feeding a 302 is better than a 2" feeding a 502. In fact, you can't put a big enough valve in a 502 to flow the amount proportionately equal to a 302/ 2". So bigger cubes need different LSA and longer duration. That is why a 240 cam in a 302 is radical..... but the same specs in a 502 idles like grandma's car.

In order to get the power people desire they up the duration and then spread the LSA to preserve pressure and idle. A wider LSA kills the low-mid and adds some up higher.

When you open an exhaust valve sooner in the power stroke, the expanding gasses are blowing out the exhaust valve instead of pushing down on the piston. You start losing torque. As rpm increases..... the inertia of the air is such that a longer cam can be beneficial..... since hp is a function of torque x rpm.... so a long cam kills the low and mid range(less dynamic compression)..... but ups high rpm hp since TIME for the airflow is increased. Remember at 6000 rpm there is only about 14 milliseconds to fill a cylinder,,,,, whether it be on a 302 or a 502.

Here's some good basic stuff..... if you search around on the site you can get a decent understanding of cams.

http://www.popularhotrodding.com/sea...+cams&x=14&y=9

http://www.popularhotrodding.com/eng...ecs/index.html

Edited= I guess I should add, that contrary to popular belief, the exhaust valve is more sensitive to duration changes than lift, because the gasses are being pushed out and they are expanding at the same time and often exceed the speed of sound velocity out the ports.

This really isn't something that can be handled in a couple paragraphs. Study Vizard's articles on the cam and the charts. He regularly makes more hp with less cam than most everybody.

Last edited by xntrik; 01-21-2007 at 08:38 PM.
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