thinking about stroking
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
thinking about stroking
I have a rebuild coming up soon as I get the running gear all done and thinking about stroking my '81. What would be involved in the stroking part? New Crank, rods and pistons....anything else?
I should know this, but have never actually done one.
Thanks
I should know this, but have never actually done one.
Thanks
Burning Brakes
Joined: Apr 2003
Posts: 844
Likes: 0
From: Central KY
383?
You are going for 383 ci? I know about the big blocks, but you can find all sorts of articles on the internet for a 383.
In hopes that this background will help you choose what to do, for my 454 going to a 489, I would need a new crank (stroke from 4.000" to 4.250"), new pistons and maybe new rods. This is what may help you - in the BB world some folks will reuse their old rods and use new pistons that go with the increased stroke and stock rods. Other folks want to use rods that are proportionally longer to accomodate the stroke increase (0.250" in my case). Such longer rods definitely require matching pistons as the pin heights are different for the pistons depending on which rods you use. I am not sure, but when you do a web search (even of this forum for topics) you may find a similar set of opinions for the small block 350 to 383 stroke job. BTW, I am convinced by the folks who call for the longer rods and I will go that way when I rebuild my motor.
In hopes that this background will help you choose what to do, for my 454 going to a 489, I would need a new crank (stroke from 4.000" to 4.250"), new pistons and maybe new rods. This is what may help you - in the BB world some folks will reuse their old rods and use new pistons that go with the increased stroke and stock rods. Other folks want to use rods that are proportionally longer to accomodate the stroke increase (0.250" in my case). Such longer rods definitely require matching pistons as the pin heights are different for the pistons depending on which rods you use. I am not sure, but when you do a web search (even of this forum for topics) you may find a similar set of opinions for the small block 350 to 383 stroke job. BTW, I am convinced by the folks who call for the longer rods and I will go that way when I rebuild my motor.
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Hmm, interesting stuff. I currently have a SB350 so I guess I would be going for 383. Anything magick about that number?
So if your extra stroke is .25" that would be .125" at each end, so you would need pistons .125" shorter to keep them inside the bores correct? Original heads would produce higher CR?
Anyone got recomendation for head package for 383?
So if your extra stroke is .25" that would be .125" at each end, so you would need pistons .125" shorter to keep them inside the bores correct? Original heads would produce higher CR?
Anyone got recomendation for head package for 383?
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
I am in the process of building my 383 right now. I just finished clearancing the block. It took me 6 hours to do it right. I have plenty of clearance for the rods now. I went with a forged Eagle 4340 crank and forged Scat rods with 7/16 rod bolts good for 700 HP. The pistons are SRP forged that with my 68cc heads will give me 10.67 to 1 compression ratio. I am using my 190 AFR heads and a big solid flat tappet cam. Nothing magical about it just takes a little work to make sure you have proper clearance for everything rotating around inside the block. This should be a pretty bullet proof lower end. I am hoping to make around 500 HP and 500 ft/lb torque. 
Le Mans Master
Joined: Nov 2004
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St. Jude Donor '07
Originally Posted by Gordonm
If you build it right it will produce a good HP and torque
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Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
Originally Posted by Frank O'Hara
If you do a 383 - You'll most likely need an externally balanced flywheel or flexplate. I found out the hard way. SBC 400 cranks used in 383's are externally balanced
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Are those real numbers or Desk top Dyno numbers. I never had much success racing a computer. They are just numbers based on calculations. There is wayyy to much else invloved to put any facts behind those numbers. I have seen a 383 make as little as 400 ft/lbs and as much as 600 ft/lbs. Its all in the heads and cam and induction system.
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
I am looking to get a good streetable engine, is the CR of10.67 a bit high? Will it run ok on pump gas? I am planning on keeping the stock electrinics and doin a bit of work to the carb(mainly change the secondary needles)
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
Originally Posted by SIXFOOTER
I am looking to get a good streetable engine, is the CR of10.67 a bit high? Will it run ok on pump gas? I am planning on keeping the stock electrinics and doin a bit of work to the carb(mainly change the secondary needles)
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,443
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Originally Posted by Gordonm
I am in the process of building my 383 right now. I just finished clearancing the block. It took me 6 hours to do it right. I have plenty of clearance for the rods now. I went with a forged Eagle 4340 crank and forged Scat rods with 7/16 rod bolts good for 700 HP. The pistons are SRP forged that with my 68cc heads will give me 10.67 to 1 compression ratio. I am using my 190 AFR heads and a big solid flat tappet cam. Nothing magical about it just takes a little work to make sure you have proper clearance for everything rotating around inside the block. This should be a pretty bullet proof lower end. I am hoping to make around 500 HP and 500 ft/lb torque.
Racer
Joined: Sep 2004
Posts: 424
Likes: 2
Originally Posted by Gordonm
Are those real numbers or Desk top Dyno numbers. I never had much success racing a computer. They are just numbers based on calculations. There is wayyy to much else invloved to put any facts behind those numbers. I have seen a 383 make as little as 400 ft/lbs and as much as 600 ft/lbs. Its all in the heads and cam and induction system.
Race Director
Joined: Apr 2000
Posts: 17,650
Likes: 190
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Yes it is true, if all you do is increase the stroke the HP stays pretty much the same, torque goes up.
That being said I have seen a few articles about 383's claiming over 500HP with AFR 190 heads, one of them with 9.5:1 CR. Kinda makes me wonder why I had to go to 11:1CR with 219cc racing heads and a big solid roller cam to make over 500HP when you can do it with less cubes, less cam, less .....you get the idea.
I am rather skeptical of some the claims I see as if 500/500 was nothing special anymore and you just order up some street heads and cam from Jegs and your there. I would love to see a dyno printout for that motor you are building Gordonm, or put it on an chassis dyno, anything over 400 at the rear wheels gets you 500 at the crank, I hope you make it, that is going to be a wicked motor
That being said I have seen a few articles about 383's claiming over 500HP with AFR 190 heads, one of them with 9.5:1 CR. Kinda makes me wonder why I had to go to 11:1CR with 219cc racing heads and a big solid roller cam to make over 500HP when you can do it with less cubes, less cam, less .....you get the idea.
I am rather skeptical of some the claims I see as if 500/500 was nothing special anymore and you just order up some street heads and cam from Jegs and your there. I would love to see a dyno printout for that motor you are building Gordonm, or put it on an chassis dyno, anything over 400 at the rear wheels gets you 500 at the crank, I hope you make it, that is going to be a wicked motor
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
Originally Posted by MotorHead
Yes it is true, if all you do is increase the stroke the HP stays pretty much the same, torque goes up.
That being said I have seen a few articles about 383's claiming over 500HP with AFR 190 heads, one of them with 9.5:1 CR. Kinda makes me wonder why I had to go to 11:1CR with 219cc racing heads and a big solid roller cam to make over 500HP when you can do it with less cubes, less cam, less .....you get the idea.
I am rather skeptical of some the claims I see as if 500/500 was nothing special anymore and you just order up some street heads and cam from Jegs and your there. I would love to see a dyno printout for that motor you are building Gordonm, or put it on an chassis dyno, anything over 400 at the rear wheels gets you 500 at the crank, I hope you make it, that is going to be a wicked motor
That being said I have seen a few articles about 383's claiming over 500HP with AFR 190 heads, one of them with 9.5:1 CR. Kinda makes me wonder why I had to go to 11:1CR with 219cc racing heads and a big solid roller cam to make over 500HP when you can do it with less cubes, less cam, less .....you get the idea.
I am rather skeptical of some the claims I see as if 500/500 was nothing special anymore and you just order up some street heads and cam from Jegs and your there. I would love to see a dyno printout for that motor you are building Gordonm, or put it on an chassis dyno, anything over 400 at the rear wheels gets you 500 at the crank, I hope you make it, that is going to be a wicked motor
Last edited by Gordonm; Feb 18, 2006 at 06:53 AM.
Pro
Joined: Jan 2006
Posts: 548
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the increase in torque alone is only true if you ONLY stroke the engine, and do no supporting modifications such as heads and cam. this is because the existing heads, cam, intake, carb, etc will run out of flow at a lower RPM thanks to the 30 extra cubes. this is why you see a much steeper dropoff of the torque curve in the dyno sheets posted above. while it is true that you could *just* throw in a stroker crank and pistons and have an increase in torque, such a modification isnt really worth it without things to let it breathe at higher RPM. increasing breath up top increases high-rpm torque, and we all know that means more hp.
so no, swapping to a 383 does not only produce an increase in peak torque with minimal change in peak hp, unless you ONLY stroke the engine and leave the rest alone.
so no, swapping to a 383 does not only produce an increase in peak torque with minimal change in peak hp, unless you ONLY stroke the engine and leave the rest alone.
Pro
Joined: Jan 2006
Posts: 548
Likes: 0
Originally Posted by MotorHead
Yes it is true, if all you do is increase the stroke the HP stays pretty much the same, torque goes up.
That being said I have seen a few articles about 383's claiming over 500HP with AFR 190 heads, one of them with 9.5:1 CR. Kinda makes me wonder why I had to go to 11:1CR with 219cc racing heads and a big solid roller cam to make over 500HP when you can do it with less cubes, less cam, less .....you get the idea.
I am rather skeptical of some the claims I see as if 500/500 was nothing special anymore and you just order up some street heads and cam from Jegs and your there. I would love to see a dyno printout for that motor you are building Gordonm, or put it on an chassis dyno, anything over 400 at the rear wheels gets you 500 at the crank, I hope you make it, that is going to be a wicked motor
That being said I have seen a few articles about 383's claiming over 500HP with AFR 190 heads, one of them with 9.5:1 CR. Kinda makes me wonder why I had to go to 11:1CR with 219cc racing heads and a big solid roller cam to make over 500HP when you can do it with less cubes, less cam, less .....you get the idea.
I am rather skeptical of some the claims I see as if 500/500 was nothing special anymore and you just order up some street heads and cam from Jegs and your there. I would love to see a dyno printout for that motor you are building Gordonm, or put it on an chassis dyno, anything over 400 at the rear wheels gets you 500 at the crank, I hope you make it, that is going to be a wicked motor
i've been seriously wondering about that setup as well...seems like nobody else is cracking 420 with 9.5:1....afr heads are good but i'm not sure they're that good.