Big bore, short stroke, long rod LS1
04-19-2003, 07:07 PM
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Big bore, short stroke, long rod LS1 Has anybody ever put the 4.8 crank and rods into a big bore block? You should get the same displacement, but the bigger bore would allow bigger valves (duh), and the shorter stroke and longer rods do short stroke and long rod things.
Anyone?
<small>[ April 20, 2003, 05:07 PM: Message edited by: Will's Fiero ]</small>
Anyone?
<small>[ April 20, 2003, 05:07 PM: Message edited by: Will's Fiero ]</small>
04-19-2003, 07:32 PM
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Re: Big bore, short stroke, long rod LS1 I don't think anyone has done this but, I have thought about it.
I wouldn't be surprised if this setup cracked the 500rwhp mark with 345ci(4.1" bore * 3.27" stroke).
With a 6.5" rod you could get the rod/stroke ratio to almost 2:1 and average piston speed at 8000rpm would be about the same as a stock stroke motor at 7200rpm.
A solid roller cam would be the perfect candidate for this setup.
I think you should do this and report your findings. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
If someone asked you could even say it was a "stock discplacement" motor without lying. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
John
I wouldn't be surprised if this setup cracked the 500rwhp mark with 345ci(4.1" bore * 3.27" stroke).
With a 6.5" rod you could get the rod/stroke ratio to almost 2:1 and average piston speed at 8000rpm would be about the same as a stock stroke motor at 7200rpm.
A solid roller cam would be the perfect candidate for this setup.
I think you should do this and report your findings. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
If someone asked you could even say it was a "stock discplacement" motor without lying. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
John
04-19-2003, 07:49 PM
#3
Re: Big bore, short stroke, long rod LS1 A buddy of mine and I were talking about this last night.I've been thinking about a max bore Darton (Lingenfelter) block then destroked to 346 or less. Solid roller, sheetmetal intake and C5R heads to do it right. Screaming High RPM motor. It would be fun.... but then we started looking at cost, HP/CI etc.Something to think <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> about
04-20-2003, 01:37 PM
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Re: Big bore, short stroke, long rod LS1 Yeah, the costs add up pretty quick on such an engine.
The resleeve is expensive. A racing block is way more expensive.
The radical heads would be expensive.
Solid roller cam, crazy valvetrain.
The only place you'd save over a stroker would be the crank.
How much could the stock 4.8 rods take? Polished and shot peened?
What's the deck height of an LS1 and what's the min compression height some of these strokers use?
With the high rod ratio and "smaller" displacement, I might be inclined to go with a milder cam and add a few psi of manifold pressure to make it more streetable.
The resleeve is expensive. A racing block is way more expensive.
The radical heads would be expensive.
Solid roller cam, crazy valvetrain.
The only place you'd save over a stroker would be the crank.
How much could the stock 4.8 rods take? Polished and shot peened?
What's the deck height of an LS1 and what's the min compression height some of these strokers use?
With the high rod ratio and "smaller" displacement, I might be inclined to go with a milder cam and add a few psi of manifold pressure to make it more streetable.
04-20-2003, 05:14 PM
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Re: Big bore, short stroke, long rod LS1 No, but that would be cool. My Fiero's already got a Northstar (I went back and added my sig).
There's a guy on the Fiero Forum ( www.fieroforum.com ) who has an LS1.
For the big bore/short stroke LS1 I was thinking along the lines of a 3rd gen RX7. Think Z06 handling, just 400 lbs lighter. You don't gain any weight going from rotary to LS1, either.
There's a guy on the Fiero Forum ( www.fieroforum.com ) who has an LS1.
For the big bore/short stroke LS1 I was thinking along the lines of a 3rd gen RX7. Think Z06 handling, just 400 lbs lighter. You don't gain any weight going from rotary to LS1, either.
04-21-2003, 10:42 AM
#7
Re: Big bore, short stroke, long rod LS1 I have been tossing this around my brain for about a year now. 4.125" bore and a 3.25" crank = 347 inches and you can get the 6.5" rod for a "perfect" 2:1 Rod/Stroke ratio. If I had the money I would have already done this. I'd also be interested to see what a set of professional Stage III or IV LS6 heads with monster valves could do on a motor like this instead of the mucho-expensive C5R heads.
I would think it would spin to 8,500+ without much fanfare <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" /> .
I would think it would spin to 8,500+ without much fanfare <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" /> .
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04-21-2003, 11:53 AM
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Re: Big bore, short stroke, long rod LS1 I thought about it...
I picked up a low mile 4.8 crankshaft.
I'll sell it if anyone is interested. I was looking at running a 6.200 rod.
I picked up a low mile 4.8 crankshaft.
I'll sell it if anyone is interested. I was looking at running a 6.200 rod.
04-21-2003, 11:59 AM
#9
Re: Big bore, short stroke, long rod LS1 </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong>I picked up a low mile 4.8 crankshaft.
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">What is the stroke on it?
<strong>I picked up a low mile 4.8 crankshaft.
</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">What is the stroke on it?
04-21-2003, 01:42 PM
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Re: Big bore, short stroke, long rod LS1 Not to pick nits, but it's 83 mm (3.267).
Everybody's talking about 8K-8500 with custom rods, which would be really cool, but I'm still curious about how the stock 4.8 rods would do. At 159.65mm (6.285"), they'e already 4.5 mm longer than LS1 rods. I would guess that they would take rod stres similar to that of the LS1 rod, so the extra RPM they allow would only be a function of the decrease in stroke, not of rod strength.
How much are custom rods? Since building this engine already implies spending $2500 on a resleeved block, and buying custom pistons, and a lot of head work to make the most of it, maybe I shouldn't be so concerned about the cost of custom rods. <img border="0" alt="[burn out]" title="" src="graemlins/gr_burnout.gif" />
Everybody's talking about 8K-8500 with custom rods, which would be really cool, but I'm still curious about how the stock 4.8 rods would do. At 159.65mm (6.285"), they'e already 4.5 mm longer than LS1 rods. I would guess that they would take rod stres similar to that of the LS1 rod, so the extra RPM they allow would only be a function of the decrease in stroke, not of rod strength.
How much are custom rods? Since building this engine already implies spending $2500 on a resleeved block, and buying custom pistons, and a lot of head work to make the most of it, maybe I shouldn't be so concerned about the cost of custom rods. <img border="0" alt="[burn out]" title="" src="graemlins/gr_burnout.gif" />
04-21-2003, 05:54 PM
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Re: Big bore, short stroke, long rod LS1 Yes. I contacted Goodwrench about it. The 5.3, 5.7, and 6.0 rods are 155.15 mm long. The 4.8 rods are 159.65 mm long. The 4.8 has 9 mm less stroke than the others, which is 4.5 mm less crank throw. The 4.8 uses the same pistons as the 5.3, but when they shortened the stroke, they lengthened the rod to make up the difference.
They did the same thing with the LT1. The L99 4.3 litre v8 that was used as the base engine in Caprices has a 3.000" stroke and 5.940" rods, while the LT1 has a 3.480" stroke and 5.700" rods. They used the same compression height as the LT1 pistons, although the 4.3 has the same bore as a 305.
They did the same thing with the LT1. The L99 4.3 litre v8 that was used as the base engine in Caprices has a 3.000" stroke and 5.940" rods, while the LT1 has a 3.480" stroke and 5.700" rods. They used the same compression height as the LT1 pistons, although the 4.3 has the same bore as a 305.
04-22-2003, 01:02 PM
#16
Re: Big bore, short stroke, long rod LS1 Yes, I would think that custom length forged rods would be a given. A cam that would allow this motor to make power that high (8,000+ rpm) would have to be pretty damn big. Thus meaning no low end torque.............
Guess I'd have to fix taht with the best low end torque maker around..... A TURBO KIT!!!! <img border="0" alt="[burn out]" title="" src="graemlins/gr_burnout.gif" /> . <img border="0" alt="[worship]" title="" src="graemlins/gr_hail.gif" />
Yeah, that's it. Big Heads, Big Cam, Big RPM potential and a Turbo. <img border="0" alt="[evil]" title="" src="graemlins/gr_devil.gif" />
I think I need therapy................
Guess I'd have to fix taht with the best low end torque maker around..... A TURBO KIT!!!! <img border="0" alt="[burn out]" title="" src="graemlins/gr_burnout.gif" /> . <img border="0" alt="[worship]" title="" src="graemlins/gr_hail.gif" />
Yeah, that's it. Big Heads, Big Cam, Big RPM potential and a Turbo. <img border="0" alt="[evil]" title="" src="graemlins/gr_devil.gif" />
I think I need therapy................
04-25-2003, 11:20 PM
#17
Re: Big bore, short stroke, long rod LS1 Yeah, that's it. Big Heads, Big Cam, Big RPM potential and a Turbo. I think I need therapy................ It would be cheaper to build the motor! Do it and get back to us. <img src="https://ls1tech.com/threads/images/graemlins/grin.gif" alt="" /> <img src="https://ls1tech.com/threads/images/graemlins/grin.gif" alt="" />
