tried searching and didnt find anything has anyone tried putting longer rods in the ln2 i was thinking about 6.0 from a sbc engine
depends on how much you can either move the pin up or cut off the top of the piston.
just out of curiosity.. how long are stock LN2 rods as is?
the stock rods are 5.59 with .80 wrist pin and 2.00 big end . sbc small journal cranks are also 2.00 the wrist pin is .927 and the rod is .940 thick i havent found the ln2 thickness and dont have my bottom end appart yet to measure them. i know i will need custom forged pistons as the motor will spend most of its time between 6500 and 8500 . just hoping i can make the rods work
has anyone tried long rods in the ln2
I have a set of rods and pistons I can send to you Mike. Still have the rods of them. Pm me if you are interested.
Sig'less since '02!
Rich Grayo Jr. wrote:What benefit would this have? Wouldn't that much more rod put the piston way above deck height?
Moving the pin and/or milling the piston dolwn would solve the deck height problem. With a longer rod you achieve better rod/stroke ratio. This means the engine can do its job easier and you loose less power through rotation. Basically there is less stress or effort on the piston pushing the crank, kind of like a bigger lever. This in turn produces more power and a higher freer revving engine.
Rich Grayo Jr. wrote:What benefit would this have? Wouldn't that much more rod put the piston way above deck height?
http://www.stahlheaders.com/Lit_Rod%20Length.htm
--a good article to explain the effect of changing the rod/stroke ratio. There are some things not covered however.
Rich,
You are correct that a longer rod would put the top of the piston above the deck. This is compensated for by moving the wrist pin position up in the piston (requiring custom made pistons). The practical limit here is how far up the pin can be moved before it gets into the space needed for the oil control ring.
The primary rod/stroke ratio issues are:
With low ratios --side loads on the pistons, and at higher RPM, acceleration of the piston and rings can cause the rings to "flutter" when the ratio is too small. There is an practical limit going up in ratio too due to the decrease in rod angularity. It takes away torque but allows higher rpm and less chance of ring flutter. Because HP is RPM x Torque, an increase in the highest rpm the engine is making useable torque is also more HP.
Ring flutter should be explained. The piston is reciprocating back and forth in its bore. This requires the piston to obviously start/stop as it reverses course. The rod/stroke ratio affects the rate of acceleration/deceleration. If the RPM reaches the point where the inertia of the piston ring's mass overcomes the pressure of the combustion taking place above it, there will be a sudden loss of the combustion pressure and the rings will "slam" up against the top of the piston ring land. The slamming up is nothing compared to the slamming down as the combustion pressure sends the ring back the other way. Granted, this is only a small distance, maybe a thousandth or two, but the fact that it is happening several thousand times a minute will quickly destroy the ring grooves in a piston. Years ago, piston rings were quite a bit thicker and heavier, but we are now seeing rings on the order of 1.5 mm or approximately .060. Thinner rings have less mass and are automatically able to endure higher RPMs. Many years ago while tuning a two stroke drag bike, this was the first issue to deal with, as it defined the maximum RPM the engine could be turned. I'll try to find the formula I used but 1978 is a long time ago.
I don't know the rod ratios being used for much else beyond our J body stuff and small block Chevys. However, there is a good reason why the 2.2 has a 5.59" length......it helps with torque....and torque is what actually moves the vehicle. A rod length of 5.7" from a small block would enable the engine to turn a bit faster and make a bit more HP before ring flutter sets in. It would require custom pistons. Milling off the top surface of a standard piston to compensate would weaken the top surface of the piston, decrease its ability to transfer heat (increasing detonation possibilities), and require the engine to be re balanced.
From what I've read in various places, the rod ratios rarely get above 1.8 or 1.9 to one, but recall seeing a 2.0 to one somewhere in the past. For the LN2 the stock ratio is 5.59" rod/ 3.46" stroke, or 1.615 to 1 ratio. The small block Chevy is 5.7" rod/ 3.48" stroke, or 1.638 to 1 ratio. This is only a 1 1/2% difference. The expense of custom pistons for the slight benefit makes it pretty impractical for a beneficial mod. However, if there were enough space in the piston from the wrist pin to oil control ring, moving to a rod/stroke ratio of 1.7 or 1.8 to 1 or so (approximately 6 to 6.25" rods) might have some high RPM benefits. Now we're talking custom piston AND rods! Why bother? (For the fun of accomplishing something no one else has!)
Related issue: Stroker cranks-- that is-- installing a crankshaft with a longer stroke than normal (isn't this how the 2.0 became the 2.2?) The fact that the top of the block, or deck, is, practically speaking, immovable, the methods of compensating for the increased piston travel are limited to-- 1. moving the wrist pin, 2. shorter rods, 3. increasing deck height (very challenging). Solution 1 has the same issues with the position of the oil control ring. Solution 2 in this case is a double penalty. First, the Rod has to be shorter; second, the stroke is longer. Both have the effect of decreasing the rod/stroke ratio. You would end up with a really torquey, quickly worn out, but lower max RPM engine. Solution 3 .....$$$.
DS
I know custom pistons would be needed and i want them this is an all out circle track engine that will be running from 6500 to 8500 rpms maybe more if i can make 6.0 chevy rods work i can buy them with honda journals for about what eagles are for the ln2 and i get 8 rods
Mike Golding wrote:I know custom pistons would be needed and i want them this is an all out circle track engine that will be running from 6500 to 8500 rpms maybe more if i can make 6.0 chevy rods work i can buy them with honda journals for about what eagles are for the ln2 and i get 8 rods
If you can get the crank turned down to the proper bearing clearance, they could conceivably work. The remaining issue is custom pistons. What diameter is the big end of these rods?
DS
chevy rods are .927 small end i was thinking of having them bushed and using floating pins im going to a 90mm bore crank only needs to be turned .12 im just not sure if 6.0 length is to long
I'd be really interested to follow your success with this. I'm in the planning stages of an LN2 max street/some strip NA engine. I'm interested in turning it about 8k or so. I'd like to have forged pistons and H beam rods, but if I can get regular 6.0 rods to work with forged pistons, I think it will save a few $ and get better geometry inside the engine.
So far I can think of 3 issues. The piston ring/wrist pin interference issue is first. The second is whether the big end will fit as it rotates. Third, with cutting down the crank pins by 1/8 inch, you are sacrificing crank strength.
Let me know how it turns out.
Dennis
Mike Golding wrote:I know custom pistons would be needed and i want them this is an all out circle track engine that will be running from 6500 to 8500 rpms maybe more if i can make 6.0 chevy rods work i can buy them with honda journals for about what eagles are for the ln2 and i get 8 rods
I've been searching around a bit for "custom" pistons that are essentially replacement pistons for other engines. UEM, the makers of KB Silvolite pistons has a forged turbo piston for the Toyota 22R engine that might work. They use a similar Compression Height (1.167) but is about 91mm bore and has a larger piston pin diameter.
http://www.uempistons.com/assets/icon_catalog.pdf \
The PN is IC987 on page 66.
I'm going to ask them about moving the pin up a bit more and making it the right size to fit SBC 6.0 rods. As it is a forged piece for turbo applications, maybe they can also trim the top of the piston to help set the deck height. While they're at it, maybe they have enough left in the top to mill a small dish for the proper compression ratio (similar to using the 2200 piston with the 95-98 head. My expectation is "NO, we can't" but if it is "YES" my expectation is I can't afford it.
They have a special supporting ring that goes under the oil control ring to allow the piston pin to actually go through the same space the oil ring needs when the piston, pin and rod are assembled.
Anyway, let me know what you find too.
Dennis
IIRC, some of the LN 2 gurus talked about this before. One of them--Slowolej, I think-- mentioned the possibility of using the 6"-rods from a Chevy "Stovebolt" I-6. Search that out!
Go beyond the "bolt-on".
Nickelin Dimer wrote:IIRC, some of the LN 2 gurus talked about this before. One of them--Slowolej, I think-- mentioned the possibility of using the 6"-rods from a Chevy "Stovebolt" I-6. Search that out!
Yep, I'd noticed that and was looking at Scat H beam rods for the Inline 6's today. About 71 each plus the usual shipping, etc. For 4 it would be cheaper to get these in 6" than the Eagle H beams in standard length. Gotta head out in the shop and start measuring!
Dennis
OK, to all interested.
I just pulled apart the long block from my 95 cavalier 2.2. I took a few pics so if I can figure out how to move them from my new Droid X2, I'll post them here.
Here's what I observe. The 6" rod will be a major challenge, possibly requiring additional height to be added to the top of the block. The standard piston pin on the standard rod already comes within 1/16" of the oil ring. To get the pin up enough in the piston to make room for the long rod would put the pin easily up into the compression rings. 5.7" rods are more likely to be useable with the right piston, but not much is gained in rod/stroke ratio.
I think we'd need to add about 1/2 to 3/4 inch to the top of the block by creating a plate with the proper cut outs for the cylinder bores, bolt holes, and water passages. It could be sealed by using head gaskets on either side, but studs would probably be mandatory to assure proper clamping. It would probably be best to use sleeves for the cylinders. Special length pushrods would be required.
Sounds like fun. Anybody got access to a scanner and laser cutting tools? Wait a minute, I used to sell that stuff....maybe I should call..........
Dennis
i have also been measuring the chevy rod is to thin on the big end maybe 2.3 quad rods will work the are .002 thicker on big end 5.81 long 1.88 pin diameter it might just work
Mike Golding wrote:i have also been measuring the chevy rod is to thin on the big end maybe 2.3 quad rods will work the are .002 thicker on big end 5.81 long 1.88 pin diameter it might just work
Hmmmm.
I measured the LN2 rods as slightly over 1" wide at the big end. The Scat 6" rods are spec'd as 1.050" wide at the big end.
http://www.summitracing.com/parts/SCA-66000206SGL
some of their big block rods are less than 1" wide, but these are for the Inline 6.
MasterFlight wrote:OK, to all interested.
I just pulled apart the long block from my 95 cavalier 2.2. I took a few pics so if I can figure out how to move them from my new Droid X2, I'll post them here.
Here's what I observe. The 6" rod will be a major challenge, possibly requiring additional height to be added to the top of the block. The standard piston pin on the standard rod already comes within 1/16" of the oil ring. To get the pin up enough in the piston to make room for the long rod would put the pin easily up into the compression rings. 5.7" rods are more likely to be useable with the right piston, but not much is gained in rod/stroke ratio.
I think we'd need to add about 1/2 to 3/4 inch to the top of the block by creating a plate with the proper cut outs for the cylinder bores, bolt holes, and water passages. It could be sealed by using head gaskets on either side, but studs would probably be mandatory to assure proper clamping. It would probably be best to use sleeves for the cylinders. Special length pushrods would be required.
Sounds like fun. Anybody got access to a scanner and laser cutting tools? Wait a minute, I used to sell that stuff....maybe I should call..........
Dennis
Hmmmm, a tall-deck LN2...
Here's a thought: What about trying this with the earlier OHV cranks? Namely, the one used in the 1.8L. I don't know what kind of rear-main seal it uses, but if one of those bolt-on 6+1 trigger-wheels could easily make it adaptable to later management systems. It may not be a torquey as the LN2, but it'd be a screamer. Just imagine putting a properly sized turbo on that... With the longest rods possible fitted in it would come very close to a 2:1 rod/stroke-ratio, which--from what I read once elsewhere--would be ideal for a turbo engine. Imagine that... A OHV that makes a twin-cam look wheezy!
Go beyond the "bolt-on".
Nickelin Dimer wrote:MasterFlight wrote:OK, to all interested.
I just pulled apart the long block from my 95 cavalier 2.2. I took a few pics so if I can figure out how to move them from my new Droid X2, I'll post them here.
Here's what I observe. The 6" rod will be a major challenge, possibly requiring additional height to be added to the top of the block. The standard piston pin on the standard rod already comes within 1/16" of the oil ring. To get the pin up enough in the piston to make room for the long rod would put the pin easily up into the compression rings. 5.7" rods are more likely to be useable with the right piston, but not much is gained in rod/stroke ratio.
I think we'd need to add about 1/2 to 3/4 inch to the top of the block by creating a plate with the proper cut outs for the cylinder bores, bolt holes, and water passages. It could be sealed by using head gaskets on either side, but studs would probably be mandatory to assure proper clamping. It would probably be best to use sleeves for the cylinders. Special length pushrods would be required.
Sounds like fun. Anybody got access to a scanner and laser cutting tools? Wait a minute, I used to sell that stuff....maybe I should call..........
Dennis
Hmmmm, a tall-deck LN2...
Here's a thought: What about trying this with the earlier OHV cranks? Namely, the one used in the 1.8L. I don't know what kind of rear-main seal it uses, but if one of those bolt-on 6+1 trigger-wheels could easily make it adaptable to later management systems. It may not be a torquey as the LN2, but it'd be a screamer. Just imagine putting a properly sized turbo on that... With the longest rods possible fitted in it would come very close to a 2:1 rod/stroke-ratio, which--from what I read once elsewhere--would be ideal for a turbo engine. Imagine that... A OHV that makes a twin-cam look wheezy!
Maybe would work but my goal is to make 200 hp naturally aspirated without breaking the bank. I'd like to develop something anybody can do with a reasonable amount of tools and experience.
guess i will need to pull apart one of my sbc short blocks the rod i measured was .940 must have been custom made
im looking make 225 whp with a carb and dist and high rpm
Mike Golding wrote:im looking make 225 whp with a carb and dist and high rpm
Well, in theory, just spinning it faster will make a lot more HP.
(110# torque * 5600rpm) / 5252 = 117 hp (approximation of standard engine)
(110# torque * 8500rpm) / 5252 = 178 hp
create a bit more cylinder pressure with larger intake, cam, headers, and a good tune....
125# torque * 8500rpm / 5252 = 202 hp
140# torque * 8500 rpm/ 5252 = 226 hp
Yes, I realize this is the theory and dyno proof is mandatory! (for the critics reading this)
Had a cool thing happen today. I'm a certified aircraft mechanic, so I went out to the local maint shop to see if I could get some sheet steel rolled into a tube for my log intake. I met the chief of maintenance for a corporate flight department who drag races a sub 9 second Mustang (turbo & nitrous, 441 CID V8) He's got everything I need to build the intake from AL, including the Tig welder. I love it when a plan comes together!!
May have found my answer 2.0 crank 3.15 stroke 6.0 sbc rods did find they were thicker mine must have been a custom set . With the 2.0 crank 1.9 rod ratio and 1.0 compression height . Custom pistons shouldnt be a problem with these specs hum can you say 10000rpm
