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Discussion Starter #1
Hey guys im building a 283 chevy .060 overbore. it will be my first build. i have a blown 383 in my car now that was build buy a local machine shop, who will be doing the machining for me but i want to package the motor as much myself plus assemble the things i can at home.

i have had a hard time finding forged pistons for the small bore and enough dome for good compression, im also looking into smaller chamber heads and see what is available. compression will need to be around 11.5-1 for 91 pump and a mechanical flat tappet with 260 @ .050 duration(going to find one with .6 lift)

as far as i could guess they would be almost the exact same as any other sbc piston except for the od, and dome for whatever heads i end up using, compression height would change depending on the rod length either 5.7 or 6, i havent decided yet.

thanks.
 

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One thing to keep in mind is that with the cam a big cam for say a 350 is going to be outright flipping HUGE for a small 283 and likely too much. Also I doubt you could use heads with 2.02 valves and might have issues with 1.94 intake valves which come factory for most 350s. Forged pistons for a 283 might be a custom job nowadays so might call J&E and ask them. They will be pricey, possibly $700 if not more. A company called Eggy Machine might have pistons.
 

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283 is the same bore as a 307, find a 307 crank or 327 crank and cheat a little bit, lol.

You'll need a 13cc dome/.005 below the deck/62cc combustion chamber/.022 head gasket for around 11.5 to 1
 

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One thing to keep in mind is that with the cam a big cam for say a 350 is going to be outright flipping HUGE for a small 283 and likely too much. Also I doubt you could use heads with 2.02 valves and might have issues with 1.94 intake valves which come factory for most 350s. Forged pistons for a 283 might be a custom job nowadays so might call J&E and ask them. They will be pricey, possibly $700 if not more. A company called Eggy Machine might have pistons.
You can run a 2.05 valve with a 3.935 bore without trouble. 2.02 is fine with a 30 over 3.875 bore.
 

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Discussion Starter #5
I have the crank already. Its a prepped factory forged 283 with cut and knife edged counterweights and the end drilled.

I want to spin it up to 8500 which i believe is the max for standard style valvetrain hence the big cam.

Talking to the local shop who has built some high rpm 283s in the past he was confident a 2.02 valve head will fit. And was the one who recomended that size of cam. I would go down there to talk with him more but with our social distancing i wont be leaving the house for a while.
 

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Hey guys im building a 283 chevy .060 overbore. it will be my first build. i have a blown 383 in my car now that was build buy a local machine shop, who will be doing the machining for me but i want to package the motor as much myself plus assemble the things i can at home.

i have had a hard time finding forged pistons for the small bore and enough dome for good compression, im also looking into smaller chamber heads and see what is available. compression will need to be around 11.5-1 for 91 pump and a mechanical flat tappet with 260 @ .050 duration(going to find one with .6 lift)

as far as i could guess they would be almost the exact same as any other sbc piston except for the od, and dome for whatever heads i end up using, compression height would change depending on the rod length either 5.7 or 6, i havent decided yet.

thanks.
Bill Miller will do the pistons. No problem. Go with his dome design, and an 0.043 ring package. And if you are running a 23 degree head, stick with a 200 cc intake runner, and a 64 cc chamber, and angle mill it as much as possible.
 

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I have the crank already. Its a prepped factory forged 283 with cut and knife edged counterweights and the end drilled.

I want to spin it up to 8500 which i believe is the max for standard style valvetrain hence the big cam.

Talking to the local shop who has built some high rpm 283s in the past he was confident a 2.02 valve head will fit. And was the one who recomended that size of cam. I would go down there to talk with him more but with our social distancing i wont be leaving the house for a while.
You’ll be fine. And again, if running a 23 degree head, run the long rod. 8,500 rpm in that thing won’t be a problem. And the good stud mount rockers will handle that fine. You won’t need over 240#’s on the seat for pressure, and rockers made today handle that fine. Run 7/16 studs, and a girdle. Run lash caps.
 

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Just kidding about the crank, talk with Randy Wilson in the above post, he's a small cuin SBC guru.
 

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Thanks for clearing that up Randy. I must have done some math wrong somewhere.
Well, in a way, you’re right. With a 2.05, there is some shrouding, but it still works. Some cut the eyebrow in the block for the intake side, and I’ve done that, then not done it, and seen no real advantage.
 

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Roughed into pipemax.

291.871 Cubic Inches @ 8500 RPM with 110.00 % Volumetric Efficiency PerCent

Required Intake Flow between 255.4 CFM and 269.9 CFM at 28 Inches
Required Exhaust Flow between 175.0 CFM and 197.4 CFM at 28 Inches

600 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 553.7 576.4 587.8 599.2
Peak Torque Lbs-Ft 374.3 389.7 397.4 405.1

HorsePower per CID 1.897 1.975 2.014 2.053
Torque per Cubic Inch 1.283 1.335 1.362 1.388

BMEP in psi 193.4 201.4 205.3 209.3
Carb CFM at 1.5 in Hg. 790 879 923 967

Target EGT= 1255 degrees F at end of 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 105.9 to 106.7 Octane required range
Air Standard Efficiency = 63.49250 % for 11.964:1 Compression Ratio

Peak HorsePower calculated from Cylinder Head Flow CFM only
600 RPM/Sec Dyno Test Lowest Average Best Potential
Head Flow Peak HP = 541.6 597.6 653.7
 

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283 is the same bore as a 307, find a 307 crank or 327 crank and cheat a little bit, lol.

You'll need a 13cc dome/.005 below the deck/62cc combustion chamber/.022 head gasket for around 11.5 to 1
I’ve actually got one kinda like that in a friends car, now deceased, that is a 307, 30 over, with a large journal 327 crank, off cut, to a 2” journal with a 3.16 stroke, with Dart 200 cc heads, and a Torque Link intake that runs well. About a half tenth quicker then I thought it would, and we are running 2.02 valves in it. We twist it to a shade over 9,000. And I just did a 60 over 307 for my son-in-law. Will be on the road later this week.
 

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Roughed into pipemax.

291.871 Cubic Inches @ 8500 RPM with 110.00 % Volumetric Efficiency PerCent

Required Intake Flow between 255.4 CFM and 269.9 CFM at 28 Inches
Required Exhaust Flow between 175.0 CFM and 197.4 CFM at 28 Inches

600 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 553.7 576.4 587.8 599.2
Peak Torque Lbs-Ft 374.3 389.7 397.4 405.1

HorsePower per CID 1.897 1.975 2.014 2.053
Torque per Cubic Inch 1.283 1.335 1.362 1.388

BMEP in psi 193.4 201.4 205.3 209.3
Carb CFM at 1.5 in Hg. 790 879 923 967

Target EGT= 1255 degrees F at end of 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 105.9 to 106.7 Octane required range
Air Standard Efficiency = 63.49250 % for 11.964:1 Compression Ratio

Peak HorsePower calculated from Cylinder Head Flow CFM only
600 RPM/Sec Dyno Test Lowest Average Best Potential
Head Flow Peak HP = 541.6 597.6 653.7
That’s interesting.
 

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And don’t be afraid to give that thing some timing. 44 will be the least it wants with a dome. And depending on aluminum or iron head, it may want anywhere between 44 and 53 degrees of lead. 23 degree, by the way.
 

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Discussion Starter #17
Thanka for the info. I will send bill miller and email.

I have tried to guess at the heads but really i think the bottom end needs to be built first then i can pick the heads out.

I am looking at the best pricing option that will get me around where the flow looks like it needs to be. Maybe ported eq heads or something that can be milled down enough. The only small chamber heads i could find were darts that come 49cc in an angle plug.

I have emailed some head porters from this forum and just waiting to hear back.
That’s interesting.
Ya it does i wouldnt have guessed those numbers.

I was getting my headflow recomendation from the calculators on wallace racing websight and figures about 255cfm up to 315(for max output 127.5%ve)And i just picked an off the shelf cam that i could find online and did the math for dynamic compression to allow me to run pump gas.

I imagen that pipemax programme is picking the optimal compression thats why the numbers are high and the recomended octane is 106?
 

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I’ve actually got one kinda like that in a friends car, now deceased, that is a 307, 30 over, with a large journal 327 crank, off cut, to a 2” journal with a 3.16 stroke, with Dart 200 cc heads, and a Torque Link intake that runs well. About a half tenth quicker then I thought it would, and we are running 2.02 valves in it. We twist it to a shade over 9,000. And I just did a 60 over 307 for my son-in-law. Will be on the road later this week.

My brother had a 69 Z-28 and he kept blowing up the 302 so when he ran out of money he pulled a 307 out of a nova and installed the good stuff from the 302 and ran just as fast as he did before, that was in the late 70's.
 

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Thanka for the info. I will send bill miller and email.

I have tried to guess at the heads but really i think the bottom end needs to be built first then i can pick the heads out.

I am looking at the best pricing option that will get me around where the flow looks like it needs to be. Maybe ported eq heads or something that can be milled down enough. The only small chamber heads i could find were darts that come 49cc in an angle plug.

I have emailed some head porters from this forum and just waiting to hear back.

Ya it does i wouldnt have guessed those numbers.

I was getting my headflow recomendation from the calculators on wallace racing websight and figures about 255cfm up to 315(for max output 127.5%ve)And i just picked an off the shelf cam that i could find online and did the math for dynamic compression to allow me to run pump gas.

I imagen that pipemax programme is picking the optimal compression thats why the numbers are high and the recomended octane is 106?
I roughed in 11.9 CR because I did not allow for the valve reliefs.
 
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