Disadvantages of a long stroke
Originally Posted by XLR8NSS
I believe Steve @ Race-Eng talked about the possibility of making a deck spacer and sleeves to accomodate the extra height in another thread. He seems to think it is definately possible. Darton/Steve are also coming out with a 4.2" bore capable sleeve. 4.25" stroke and 4.2" bore would be 471ci. 
. i dont think he's done a prototype LSX deck plate yet.
Originally Posted by stone4779
4.2"! aww no! not another possible combo 
But what about clearance? I never really paid attention, but can you comfortably take off the valve covers if they were 1/2" higher?
But what about clearance? I never really paid attention, but can you comfortably take off the valve covers if they were 1/2" higher?
I didnt even think of that..
lol you'd need custom headers or you could bent the crap out of whatever ones you have.... Hey I never paid any attention, but does anything mount on the driver side head?? I know on mine, theres the air pump on the pass side, but I dont remember if the driver side has any brackets with a mounting point on the head....
lol you'd need custom headers or you could bent the crap out of whatever ones you have.... Hey I never paid any attention, but does anything mount on the driver side head?? I know on mine, theres the air pump on the pass side, but I dont remember if the driver side has any brackets with a mounting point on the head....
Rod/Stroke Ratio
Originally Posted by Bo White
Take the rod length and divide it by the stroke, like the short (stock)rod 400 SBC r/s ratio was 1.48 
. The problem about strokers is the more stroke you run on a given block the lower the ratio will be because the block is only so tall.
. The problem about strokers is the more stroke you run on a given block the lower the ratio will be because the block is only so tall. So what would wear faster. A 8000 rpm 408 or a 7000rpm 422 (4" stroke verses 4.125" stroke respectively). Something to think about for sure as you would not have to wind the large stroke motor out very far given both combonations have optimal heads and valve timing events.
What does the piston look like with a stock sized 6.098" rod or 6" rod for a 4.125" stroke in an ls1. Just curious as I may try to convince APE to build something like this for me. The idea is the piston will not stay around top dead center very long which is good for warding off detonation in a high compression motor.
What does the piston look like with a stock sized 6.098" rod or 6" rod for a 4.125" stroke in an ls1. Just curious as I may try to convince APE to build something like this for me. The idea is the piston will not stay around top dead center very long which is good for warding off detonation in a high compression motor.
Originally Posted by GoatChs
I'm a bit confused by the formula here...using this formula, even the stock rod length of 6.098" does not meet a 1.55 ratio with the 4.00" crank (1.524). Is there more to the formula (bore affected), or is the 1.55 a little high for the LSx engine?
Good stuff...did you happen to see the Bore vs Stroke article in the 6/05 Hotrod magazine? Although they skewed the results of the comparo with differing rod lengths/piston configs, it was interesting to see that the big bore and big stroke variations were VERY similar in power production results.
TECH Junkie
Joined: Aug 2002
Posts: 3,726
Likes: 0
From: Fort Collins, CO
Originally Posted by Bo White
I know this is a little old but was snoopin around on some old posts of mine and ...well here it goes. The formula is right and you figured correctly. The 1.55 is actually low in some terms but you have to understand that the longer the stroke gets the lower the ratio will be with a fixed deck height, 9.24x. The stock R/S ratio is 1.68 which is pretty good were the old SBC 350 was 1.63(5.7/3.48), this is the reason alot of performance build ups had 6.00 rods used for a better R/S ratio of 1.72. IMO, 1.7 or greater is ideal for a high rpm engine(6500 or more). The longer the rod, the longer the piston stays at TDC, this allows more use of the cylinder pressure. The shorter the stroke, the faster the piston speed at peak cam lift but limits rpm- in general.
Giving up cubic inches is stupid. If I had my way I'd have the biggest bore and the biggest stroke I could possibly get. More CID = more HP. If you have to get cubic inches by using a bigger stroke, don't be afraid to do it.
Let's say that we want to build a 6.0L engine, and we've decided the max bore size we feel comfortable with is 4.03". Now most people would throw a 4" crank in it and call it a day. Why not throw a 4.100" crank in it? You get more CID and you turn less RPM (Assuming you use the same induction system as the 4" stroke engine). And don't forget what RPM stands for: Ruins People's Motors.
This discussion really needs to be about piston speed. Cylinder heads don't respond to Stroke or RPM by themselves, but piston speed, which is the combination of Stroke and RPM. True engine builders can relate pistons speeds to pressure drops on the flow bench. A port and valve job that looks good at 28" H20 might not look that good at 35" H20 (Speaking of turbulent flow, not laminar). This is all propriatary information, so don't expect a true engine builder to just give you the information he's gathered from years of standing in front of his flowbench, behind the controls of his dyno, and looking at his timeslips. Your best best is to give them your money, tell them what you want, and let them work their magic.
This is all pretty basic stuff...
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
TECH Resident
Joined: Dec 2004
Posts: 845
Likes: 0
From: K-W, Ontario
I'd have to agree.
My sources say, pay more attention to bore/stroke than rod/stroke.
Rod angle doesn't change much with a longer con-rod (Do the math),
therefore piston speed can't be that different.
"Side loading" seems to be a loose concern.
N/A applications tend to favour the "extra" hang time at TDC, but
how much gain for the swap? LSx 'fast burn' chambers probably wont enjoy that.
How about during the overlap period when scavenging is tailing off...
the exhaust valve begins to close and the piston is not moving much.
Does this tend to hurt the incoming charge as the pressure remains
relatively higher?
Longer rods tend to be a touch heavier.
I don't see much to support the longer rod craze.
My sources say, pay more attention to bore/stroke than rod/stroke.
Rod angle doesn't change much with a longer con-rod (Do the math),
therefore piston speed can't be that different.
"Side loading" seems to be a loose concern.
N/A applications tend to favour the "extra" hang time at TDC, but
how much gain for the swap? LSx 'fast burn' chambers probably wont enjoy that.
How about during the overlap period when scavenging is tailing off...
the exhaust valve begins to close and the piston is not moving much.
Does this tend to hurt the incoming charge as the pressure remains
relatively higher?
Longer rods tend to be a touch heavier.
I don't see much to support the longer rod craze.
Last edited by Adrenaline_Z; Jun 23, 2005 at 10:40 PM.
TECH Junkie
Joined: Aug 2002
Posts: 3,726
Likes: 0
From: Fort Collins, CO
Originally Posted by Adrenaline_Z
I'd have to agree.
My sources say, pay more attention to bore/stroke than rod/stroke.
Rod angle doesn't change much with a longer con-rod (Do the math),
therefore piston speed can't be that different.
My sources say, pay more attention to bore/stroke than rod/stroke.
Rod angle doesn't change much with a longer con-rod (Do the math),
therefore piston speed can't be that different.
Originally Posted by Adrenaline_Z
"Side loading" seems to be a loose concern.
Originally Posted by Adrenaline_Z
N/A applications tend to favour the "extra" hang time at TDC, but how much gain for the swap? LSx 'fast burn' chambers probably wont enjoy that.
The 'fast' chambers isn't referring to anything but their effeciency. They don't need a lot of timing to make maximum power. The high-end SBC and BBC heads are the same way.
Originally Posted by Adrenaline_Z
How about during the overlap period when scavenging is tailing off...the exhaust valve begins to close and the piston is not moving much.Does this tend to hurt the incoming charge as the pressure remains
relatively higher?
relatively higher?
I agree also, my statement is really targeted toward my oppinion of a longer rod on a given engine combo. I always recommend running the longest rod that is available for any given combo, my findings is that is also makes for a less noisy running engine. Its like the 383 LS1 rotating assemblies, some have 6.125 rods and some have 6.200- I run the 6.200. I will also look at my belief on the rod/stroke, if I was going to run a SBC 383(4.00x3.75) you have 3 different popular pistons available: a 1.425(5.7 rod), a 1.125(6.00 rod), and a 1.000(6.125 rod) compression height piston. I will run the 1.000 piston/6.125 rod combo on the 3.75 stroke crank for the mechanical advantage of the better rod/stroke ratio(1.52 vs.1.60 vs. 1.63).
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
Originally Posted by LOnSLO
The main problem with larger than 4" strokes is the piston design. The compression height of the piston gets smaller as stroke length increases. A piston for a 4.250" stroke on an LS1 looks ridiculous.
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
Originally Posted by grinder11
Very interesting. I was of the opinion that it was the same at both ends. Oh well, wish it was the first time I was wrong! Hey, are you the editor of.....one of my favorite magazines? 'Fess up if true!
