406 comp ratio decision.
Thread Starter
Safety Car
Joined: Jan 2009
Posts: 3,873
Likes: 25
406 comp ratio decision.
I have a 406 block (.030) ready for pistons.
My thinking was to use speedpro dished pistons. With a 64cc heads.
What comp ratio would this make?
I still have to smog this motor here in calif.,,,,,,,
My thinking was to use speedpro dished pistons. With a 64cc heads.
What comp ratio would this make?
I still have to smog this motor here in calif.,,,,,,,
Thread Starter
Safety Car
Joined: Jan 2009
Posts: 3,873
Likes: 25
I just looked up one of those comp ratio calculators. (those are so cool).
looks like 10.3 cr.
Cool.
So my goal is to make torque, and max spin at 5500rpm or less.
Can't use any kind of duration/lift cam unless I spend big bucks.
And I don't want to tip off the smog guy (20 years old) that this isn't the 305 block.................
What's a good head at 64cc.? Remember even 5000rpm is cool.
Going to go in our 85 z.28.
looks like 10.3 cr.
Cool.
So my goal is to make torque, and max spin at 5500rpm or less.
Can't use any kind of duration/lift cam unless I spend big bucks.
And I don't want to tip off the smog guy (20 years old) that this isn't the 305 block.................
What's a good head at 64cc.? Remember even 5000rpm is cool.
Going to go in our 85 z.28.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
With 10.3 c.r.you want aluminum heads Bryan. The better quality heads for bolt on and go are AFR, Edelbrock, Trick Flow, GMPP, Brodix and maybe Dart, World Products. The lower priced heads seem to have quality control issues and I would not buy them and try to put them on w/o an shop inspection. Really now I know enough local shops that I would buy heads through them - possibly even bare heads - hand have them assembled and inspected before using them. Maybe a few more bucks but you will get that back fast if you had to remove the heads again for problems. And its good to get to know your local builder/cylinder head shops - ask around and meet them. But make sure you have any details you want in writing on the work order.
Good luck.
Good luck.
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
10.5:1 iron heads
11:1 aluminum heads
smog can not check for compression..
do not leave this on the table unless you do not want to buy premium gas.
And yes, cardo0 is correct,, don't cheap out on heads.. get some AFR's Edelbrock, Trick Flow, GMPP, Brodix and maybe Dart, World Products........AFR's are the best of the bunch.. World are best in iron and budget.
11:1 aluminum heads
smog can not check for compression..
do not leave this on the table unless you do not want to buy premium gas.
And yes, cardo0 is correct,, don't cheap out on heads.. get some AFR's Edelbrock, Trick Flow, GMPP, Brodix and maybe Dart, World Products........AFR's are the best of the bunch.. World are best in iron and budget.
Melting Slicks
Joined: Mar 2008
Posts: 2,666
Likes: 289
From: Spring Park MN
You won't be able to run much duration and still pass smog. You will also want a fairly wide lobe separation also.The good thing is the better the heads, the less duration it takes to make good power. I'm talking having good flow at low, mid and high lifts. You are still going to have to run cats, so that is going to be a problem too.
Mike
Mike
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,025
From: New Braunfels Texas
10.5 to 1 is where my 406 is and it was easy to do with shelf parts. You can go 11 to 1 with todays new fast burn kidney bean chambers they offer.....(AFR,Dart)
I love my 406 at this ratio.......nice and crispy and runs on 91. I have Dart heads. But it has a lot of duration @ .050 (244).
220 will be your max and that will boost actual cylinder pressure.........possibly over 190 psi which is considered knocking on the door (pun intended).
New LS stuff runs 10.5 to 1 or better but has mega advanced engine controls........I own one of those too in my pickup. It is tuned by Blackbear for 93 octane and is BIG TIME noticable when you run 87. The point is that 11 to 1 is a nice number but maybe too high for standard distributor and carb.......
Now go Sniper FI and IGN and 11 to 1 is a safe bet......
Jebby
I love my 406 at this ratio.......nice and crispy and runs on 91. I have Dart heads. But it has a lot of duration @ .050 (244).
220 will be your max and that will boost actual cylinder pressure.........possibly over 190 psi which is considered knocking on the door (pun intended).
New LS stuff runs 10.5 to 1 or better but has mega advanced engine controls........I own one of those too in my pickup. It is tuned by Blackbear for 93 octane and is BIG TIME noticable when you run 87. The point is that 11 to 1 is a nice number but maybe too high for standard distributor and carb.......
Now go Sniper FI and IGN and 11 to 1 is a safe bet......
Jebby
Last edited by Jebbysan; Dec 2, 2018 at 02:21 PM.
Thread Starter
Safety Car
Joined: Jan 2009
Posts: 3,873
Likes: 25
Good comments guys. .....
I'm afraid aftermarket heads would catch the eye of the smog guy.
I'm thinking that going from 305 cu in to 406 cu in is going to be enough.
Can you imagine the torque curve..............
That said, I could use a recommendation on a factory cast iron head I can port.
Still keeping torque at lower rpm range. Not likely going to use headers.
Still use the CCC system as well.
Operators are standing by............
I'm afraid aftermarket heads would catch the eye of the smog guy.
I'm thinking that going from 305 cu in to 406 cu in is going to be enough.
Can you imagine the torque curve..............
That said, I could use a recommendation on a factory cast iron head I can port.
Still keeping torque at lower rpm range. Not likely going to use headers.
Still use the CCC system as well.
Operators are standing by............
Dr. Detroit
Joined: Mar 2012
Posts: 10,095
Likes: 4,025
From: New Braunfels Texas
Good comments guys. .....
I'm afraid aftermarket heads would catch the eye of the smog guy.
I'm thinking that going from 305 cu in to 406 cu in is going to be enough.
Can you imagine the torque curve..............
That said, I could use a recommendation on a factory cast iron head I can port.
Still keeping torque at lower rpm range. Not likely going to use headers.
Still use the CCC system as well.
Operators are standing by............
I'm afraid aftermarket heads would catch the eye of the smog guy.
I'm thinking that going from 305 cu in to 406 cu in is going to be enough.
Can you imagine the torque curve..............
That said, I could use a recommendation on a factory cast iron head I can port.
Still keeping torque at lower rpm range. Not likely going to use headers.
Still use the CCC system as well.
Operators are standing by............
You will be surprised how a well tuned HP engine is on the smog meter.......they do very well if everything is happy.
Jebby
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Race Director
Joined: May 2003
Posts: 10,956
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From: California
Thread Starter
Safety Car
Joined: Jan 2009
Posts: 3,873
Likes: 25
Awesome company.
I can afford exactly 1 bare head. $440 bucks. ............
So let's look at chevy cast iron heads that actuality came on a 400.
I remember my buddys dad had a caprice (72 I think) that would smoke the rear right tire up the block, turn and all the way back without letting up.
He's dad found out ...and he is still grounded to this day,.....
What casting number do I look for ?
I can afford exactly 1 bare head. $440 bucks. ............
So let's look at chevy cast iron heads that actuality came on a 400.
I remember my buddys dad had a caprice (72 I think) that would smoke the rear right tire up the block, turn and all the way back without letting up.
He's dad found out ...and he is still grounded to this day,.....
What casting number do I look for ?
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
Awesome company.
I can afford exactly 1 bare head. $440 bucks. ............
So let's look at chevy cast iron heads that actuality came on a 400.
I remember my buddys dad had a caprice (72 I think) that would smoke the rear right tire up the block, turn and all the way back without letting up.
He's dad found out ...and he is still grounded to this day,.....
What casting number do I look for ?
I can afford exactly 1 bare head. $440 bucks. ............
So let's look at chevy cast iron heads that actuality came on a 400.
I remember my buddys dad had a caprice (72 I think) that would smoke the rear right tire up the block, turn and all the way back without letting up.
He's dad found out ...and he is still grounded to this day,.....
What casting number do I look for ?
as even compared to a sportsman head.. those 400's are junk..dont wast your money... save a little while for something worth doing the work for..
what you saw was tq... not hp, hp comes in at the higher rpm's...
compression ratio and ci gets you tq..
And to add to that it was 1 skinny hard rubber tire.. looks cool as a teenager maybe..
Last edited by pauldana; Dec 2, 2018 at 11:18 PM.
Thread Starter
Safety Car
Joined: Jan 2009
Posts: 3,873
Likes: 25
Yep, your correct.
In fact.....I wrote that wrong. I intended to write '' what 64cc OEM head number would I look for
If I stumbled upon a pile.
The original heads I think had 111cc chambers. making 7.8comp ratio with those dished pistons.
Keep thinking torque and low RPM. We'll get this.
In fact.....I wrote that wrong. I intended to write '' what 64cc OEM head number would I look for
If I stumbled upon a pile.
The original heads I think had 111cc chambers. making 7.8comp ratio with those dished pistons.
Keep thinking torque and low RPM. We'll get this.