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Old 06-15-2010, 11:37 PM
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What size CC head should I pick for my build?

Hello Hotrodders members! I'm very excited to be building my first engine. I've been searching a lot of my questions online, and google seems to keep directing me to your forum. So I decided to join!

I have a question. I'm currently building a 350, bored .030 over with flat top pistons. I've got the bottom end assembled and ready to go, but I'm having trouble deciding on what heads to pick.

I'm building this engine for daily use. So first and foremost, I need it to run on regular 87 octane. I'm keeping the highway gears in the rear end. So low end torque and economy are a must.

I've already got an Edelbrock 2102 cam, with a list of specs to be found here. http://www.summitracing.com/parts/edl-2102/

So, working with what I've already bought, what should I be looking for in a set of heads to give me the result I hope to achieve?

Thanks!

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Old 06-16-2010, 12:49 AM
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What kind of horsepower goals do you have in mind?
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Old 06-16-2010, 01:05 AM
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Vortec heads are hard to beat when it comes to the balance of fuel economy and power. The cam you chose is great for daily drivers and with it`s under .460 lift, you wouldn`t have to have the guides clearanced on Vortec heads which will save you some cash. Whatever heads you go with, make sure you get the springs that match the cam. Since this is your first build I have to ask as I do many on this board. Did you scrub the bores before you assembled the engine? Take a paper towel, spray WD40 on it, wipe the bore, if you see gray, the bore is impregnated with hone grit. If it`s left in the bores it will come loose after the engine is started, get into the oil, damage the bearings and kill over half the life of the rings. If the bore isn`t clean, I suggest disassembling the engine completely and scrubbing the bores clean with a toilet brush and a heavy duty cleaner. Also, what`s the part number of the pistons you used? Some flat top pistons are "rebuilder" pistons and have .020 off the compression height, this kills compression, quench, and power.
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Old 06-16-2010, 04:31 PM
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Quote:
Originally Posted by 355Nova
What kind of horsepower goals do you have in mind?
Well, as much as I can while still maintaining reasonable gas mileage.

Quote:
Originally Posted by DoubleVision
Vortec heads are hard to beat when it comes to the balance of fuel economy and power. The cam you chose is great for daily drivers and with it`s under .460 lift, you wouldn`t have to have the guides clearanced on Vortec heads which will save you some cash. Whatever heads you go with, make sure you get the springs that match the cam. Since this is your first build I have to ask as I do many on this board. Did you scrub the bores before you assembled the engine? Take a paper towel, spray WD40 on it, wipe the bore, if you see gray, the bore is impregnated with hone grit. If it`s left in the bores it will come loose after the engine is started, get into the oil, damage the bearings and kill over half the life of the rings. If the bore isn`t clean, I suggest disassembling the engine completely and scrubbing the bores clean with a toilet brush and a heavy duty cleaner. Also, what`s the part number of the pistons you used? Some flat top pistons are "rebuilder" pistons and have .020 off the compression height, this kills compression, quench, and power.
I've heard a lot about those Vortec heads. How can I tell a set of Votrtecs at a wreckers? I hadn't considered the possibility, but it appears you can actually buy a spreadbore vortec intake manifold.

Great to hear the cam is a good one. I'll definitely pick up a set of matching springs for it.

When I started building the engine I cleaned everything I could with brake cleaner, hosed it down, brake cleaner again, and a coat of WD-40. But just to make double sure, I'll definitely be taking a clean towel to the bores to see if there's any hone grit left.

As for the part number, that I'm not 100% sure. I can look inside the skirt for one, and I'll try and measure the distance to the deck at TDC.
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Old 06-16-2010, 05:56 PM
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The cam you have chosen will work with a static compression ratio of between 8.0:1 and 9.5:1. Assuming 6.5 cc's of eyebrows in the piston crowns and a compression height of 1.560", you will need heads with a 75/76 cc combustion chamber to arrive at a 9.0:1 static compression ratio. If the pistons you chose have a shorter than stock compression height, you may have to disassemble the motor and cut the block decks or change pistons. Stock compression height is 1.560". Many "rebuilder" type pistons have a compression height of 1.540", leaving way too much piston deck height above the piston and making it impossible to arrive at a tight squish that will quell detonation and make a good running motor on junk pump gas.

You have made the same mistake that almost every inexperienced hot rodder makes. You started buying parts before you sat down and pencilled the whole combination out.

Post the part number of the pistons so we can proceed with our suggestions for you.
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Old 06-16-2010, 08:09 PM
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Sure thing. The only markings on these pistons are the words "Made in Canada" and the part number Z8222 A4.

I bought a dial indicator and a magnetic base to try and measure the piston height to the deck height. I'm not sure if it's the best way to do it, but my measurments were showing .030 to .035. So it looks like these have quite a bit off the top.

I understand I should either have the block decked, or buy new pistons. But lets assume I keep what I have now. What is my best course of action to get a decent running motor?

Last edited by ACA; 06-16-2010 at 09:20 PM.
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Old 06-16-2010, 09:18 PM
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You can get a thin head gasket of around .018 thickness and still land on your feet quench wise. .040 is said to be the safe point for quench but anything over .060 will cost power. So lets say the piston is .030 down which is about normal, with a .018 head gasket you would have .048, which works out fine. You can run up to 9.5:1 compression and higher with a tight quench, but you`ll have to use premium fuel. But as tech said, you could also step up to a larger cam to help bleed off some of the low speed cylinder pressure. A comp cams High Energy 268 cam works well, and like most flat tappet sbc cams, it`s cheap. It has .218 duration @.050 and has a slight lope at idle, but it still has excellant low end torque qualities. You can also keep a stock torque converter.
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Old 06-16-2010, 10:02 PM
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Quote:
Originally Posted by DoubleVision
You can get a thin head gasket of around .018 thickness and still land on your feet quench wise. .040 is said to be the safe point for quench but anything over .060 will cost power. So lets say the piston is .030 down which is about normal, with a .018 head gasket you would have .048, which works out fine. You can run up to 9.5:1 compression and higher with a tight quench, but you`ll have to use premium fuel. But as tech said, you could also step up to a larger cam to help bleed off some of the low speed cylinder pressure. A comp cams High Energy 268 cam works well, and like most flat tappet sbc cams, it`s cheap. It has .218 duration @.050 and has a slight lope at idle, but it still has excellant low end torque qualities. You can also keep a stock torque converter.
I'm relieved to hear that. There's so much to learn, and I respect the hell out of all you guys for what you know.

Are you saying I should run that cam with this setup? Or is it for an engine running a tighter quench and thus, more prone to detonation?

Either way, I have no idea how a cam with even a slight lope would run in our 30 below Canadian winters.

Is this something I should be looking for in a head gasket? Or would you have one type in mind I could ask my local shop to ship in?
http://www.usedwinnipeg.com/classifi...BORE-_12176039
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Old 06-16-2010, 11:22 PM
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Let me explain. Lets say you have a engine with 9.5:1 compression, but, it has no quench. It`ll detonate on a regular basis, even on 93 octane fuel. Then lets say you have another engine with 10:1 compression and has a tight .040 Quench distance. It`ll run fine on 93 octane and not detonate at all. tight Quench lowers the octane requirement, it`s fast sweep action cools the combustion chamber. What tech was trying to say is the cam you picked is designed to work in a pacific compression ratio, going over it may result in detonation problems which will destroy a engine. Larger cams need more compression, because the valve overlap bleeds off cylinder pressure at low RPM. That`s why I recommended the cam I did. However, if you use Vortec heads, they have a heart shaped combustion chamber which is far superior to the older heads and they require less spark timing to make power, which will work in your favor. IMO, you won`t have any problem using the cam you have and Vortec heads if you use a thin .018 head gasket so the quench action is good. One thing you will have to make sure of is the block`s deck is flat and so are the heads. Thin gaskets don`t like warped surfaces.
Vortec heads are easy to identify. They use a 8 bolt intake pattern. The bolts are straight up. Older SBC heads use 12 bolt patterns at a slant. So if someone is trying to push heads on you saying there vortecs but have 12 bolt pattern pass on the deal. If you get a pair out of the wrecking yard make sure they are either 906 or 062 castings. Also make sure you can return them if they are cracked. First thing to have checked when they reach the machine shop is have them magnafluxed to check for cracks.
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Old 06-17-2010, 02:11 AM
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Quote:
Originally Posted by ACA
What is my best course of action to get a decent running motor?
Keeping what you have now, what would I do? I'd locate a set of heads with 74/75/76cc chambers and bolt 'em on with this shim gasket.....
http://www.summitracing.com/parts/FPP-1094/
Of course, you'll want to use a 24" machinists straightedge to check the head and block surfaces for flat and straight. Any deviation over about 0.002" would call for a skim in the mill if it were mine. This is from a ricer site, but it shows the use of a straightedge and 0.002" feeler gauge blade....
http://www.importtuner.com/tech/impp...eck/index.html
This operation is not normally necessary with a composition gasket because of the additional thickness and multiple plies of material, but with a steel shim gasket, there ain't much "give"....

If I wanted to go with a new head, I might use these.....
World #042770-1 SR Torquer 170cc assembled head, 76cc chambers, 1.250" single springs, Hydraulic Flat Tappet, Spring Specs 1.250": 100 lbs. @ 1.810", 300 lbs. @ 1.250", coil bind @ 1.200", max lift @ .560" 1987 & up intake

If I wanted to take my chances with a used production head, I might use one of the following numbers....

"487" 3973487, OR 3973487X. The regular casting was found on the 1971-1972 350
LT-1 engines, had 1.94/1.50" valves, 76CC combustion chambers, DO have accessory
holes, intake port volume should be 161CC's, exhaust port volume should be 65CC's.
The 487X had 2.02/1.60" valves. Here's a set from a respected seller....
http://cgi.ebay.com/ebaymotors/Chevy...Q5fAccessories

"441" 3932441. This head was found on the 1969-1970 350 engines (255hp 350), it
was a decent flowing large chamber head. It had 1.94/1.50" valves, 76CC combustion
chambers, DO have accessory holes, intake port volume should be 161CC's, exhaust
port volume should be 61CC's. Not to be confused with 3923441, which was a
1.72/1.50" valve, 327 truck head. Virgin heads will need hard seats. Here's a set that needs the full monty....
http://cgi.ebay.com/ebaymotors/1969-...Q5fAccessories

Last edited by techinspector1; 06-17-2010 at 02:51 AM.
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Old 06-17-2010, 04:56 PM
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To DoubleVision:

I found a pair with the 906 castings. There was also a set of 062s but with 400,000k and milky oil. I'll have a shop look them over for cracks, and deck them if necessary. The block has already been decked, as the shop recommended it when I brought it in.

Just so I don't run into any surprises, what else is needed when doing a Vortec swap? A Vortec intake for sure. I'll probably just use the stock Vortec rockers. Are the accessory holes in the same place?

How big are those Vortec heads' combustion chambers? Looking online I found someone saying 64cc. I plugged the numbers into a compression ratio calculator online, and it's coming up with 10:1. Is this right?

To techinspector1:
As I said to DoubleVision, I'll be sending my heads in to have them checked. I did have the block decked, so in theory it should be good. I'm liking the idea of Vortec heads more though. Plus, it gives me an excuse to ditch the stock intake!

Last edited by ACA; 06-18-2010 at 03:44 PM.
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Old 06-18-2010, 07:16 PM
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Lets say I ran my setup with Vortec heads, and a really thick gasket. Say .060. This isn't in the ideal range for quench, but results in a ratio of 9:1, which I think should be low enough to not worry about detonation on 87 octane.

I'm still confused as to why you reccomended a setup that nets a 10:1 compression ratio. Wouldn't this detonate with the regular gas I plan to run?

Last edited by ACA; 06-18-2010 at 10:01 PM.
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Old 06-20-2010, 01:24 AM
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Quote:
Originally Posted by ACA
Lets say I ran my setup with Vortec heads, and a really thick gasket. Say .060. This isn't in the ideal range for quench, but results in a ratio of 9:1, which I think should be low enough to not worry about detonation on 87 octane.

I'm still confused as to why you reccomended a setup that nets a 10:1 compression ratio. Wouldn't this detonate with the regular gas I plan to run?
Using a 0.060" gasket with the piston deck height of 0.035" and a 64cc head will yield 9.08:1 static compression ratio. Ford Motor Company tried this "no squish" open chamber experiment on their 1972 big blocks and found that they had to reduce static compression ratio down into the 7's to prevent detonation on pump gas.

Proceed at your own risk. A workable solution has been laid out for you.
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Old 06-20-2010, 09:36 AM
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I guess I won't be trying that.

Techinspector1: Your solution yields me roughly an 8.8:1 ratio I've found. I've already got a couple sets of 76cc heads, so that's something I'm considering.

Wth DoubleVision's solution I'm runninng close to 10:1. But you yourself said my existing cam is good from 8.0:1 up to 9.5:1. So am I to understand that running Vortec heads with my current setup is just not possible?

If that's the case, I'll stick with Technispector1's plan, and save the Vortec idea for my next build. When I do it properly instead of ordering parts first and thinking afterwards.
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Old 06-20-2010, 10:12 AM
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Do you have the ability to do a little clearance grinding with a die grinder and a carbide burr?? If you can it would allow you to deshroud and clearance the combustion chamber of the Vortec heads around the intake valve chamber side, and to remove the big bump near the sparkplug boss. This should enable you to get the 64cc Vortec chamber enlarged to about 68-70cc to hit a 9.5-1 compression ratio number. The deshrouding can also slightly increase intake valve flow improving power.

That's the way I would do it with the pistons you have, nobody says just because a chamber is 64cc out-of-the-box that it has to stay 64cc forever. Modify it to what you need, it's how the race engine builders do it, they either modify the piston dome or the chamber to hit a target compression ratio if they can't get what they want with out-of-the-box parts.
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