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Opel Rallier since 1977
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Discussion Starter #1
So has anyone actually had a 1.9L crank ground for the Acura/Honda rods? Just looking for any lesson-learned in the actual offset grinding process to this 1.771" journal... I'm planning to stroke out to right to 3.00".

I see a thread from about 10 years ago started by Hiro, who was struggling with narrow rods widths and rod bearings, but the Eagle CRS5394A3D rods are much wide than those shown and there are wider bearings available. This rod has a big end width that is about .040-.045 narrower than the stock Opel rod, and there are bearings to fit that are only .040" narrow than the stock Opel rods bearings, so I don't think Hiro's concerns apply here.

Thanks in advance!
 

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Stroke & Poke a 1.9

So has anyone actually had a 1.9L crank ground for the Acura/Honda rods? Just looking for any lesson-learned in the actual offset grinding process to this 1.771" journal... I'm planning to stroke out to right to 3.00".

I see a thread from about 10 years ago started by Hiro, who was struggling with narrow rods widths and rod bearings, but the Eagle CRS5394A3D rods are much wide than those shown and there are wider bearings available. This rod has a big end width that is about .040-.045 narrower than the stock Opel rod, and there are bearings to fit that are only .040" narrow than the stock Opel rods bearings, so I don't think Hiro's concerns apply here.

Thanks in advance!
I don't know why you are looking for exotic combo when the best fix is right under your nose. The first stroker we built was welding up the 1.9 rod journals and offset grinding the crank to a three inch stroke. Use the forged pre 74 1.9 rods (forged) get a set of low compression pistons (72 to 75) and cut .125 off the tops which will give you a flat top piston with valve reliefs and you have a cheap well made stroker kit.
 

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Discussion Starter #3 (Edited)
Thanks for your input, Nut10.

Just curious: What is 'more exotic' about offset grinding a crank, versus welding and offset grinding it? Both cranks need to be re-balanced, hardened, etc.

And I agree that the forged stock rods are quite good.... based on personally beating on them a lot! I have no doubt that the old style design pistons have plenty of meat to mill off, but have not looked to see how high the top ring would end up with that. And it would be hard or impossible to match the at-least 250 grams weight saving of the Acura or Neon rod and a short forged piston, all out-of-the-box, versus using the old design tall pistons, etc. And, without lowering the rod ratio, with the potential detrimental effect on higher RPM operation that is common with stokers that use the same rod length.

I'm still seeking input on the Acura rod situation that anyone can share.
 

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Opel Rallier since 1977
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Discussion Starter #5
Thanks Commodaren... never knew about those rods. The price is good for a strong rod like that.

I started this train of thought with simply the idea if the 2.0L pistons.. out of stock right now!, which then turned to the idea of a long rod 1.9L just for fun. It carried me through a lot of variations, and where I am heading today LOL, after running through a lot of threads and at least 10 combinations on a big spreadsheet:

- The Honda Acura rods with the 1.9L crank offset ground like indicated for a 3.00" stroke
- Use of modern forged pistons from the GM LS family from the 5.3L family (Vortec), which has some options and variations and which I think will be available for quite a while. This is a 3.78" bore. (Which is why I have been investigating the cylinder wall thicknesses so intensely.)
- With the particular parts that I have in mind, the piston-to-deck height works out to .004" + or - above deck with no piston work.
- Static CR with a stock 1.9L chamber is around a true 9.4 (nice for pump gas), and with a .040" thick head gasket, there is a very nice quench gap, around .035" (which of course may vary with the actual block's deck height).
- Displacement is something like 2204 cc.
- Rod-to-stroke ratio is 1.80 vs the stock 1.82

The process to do this will be to:
- bore block, taking care in the non-thrust wall thickness in each cylinder
- offset grind crank, re-balance and re-harden
- remove bushing for the Eagle rods and hone out the small end bore about .040" to either float or press in a .927" pin
- I'll know if I need to massage the piston eyebrows any if this all goes down

Other matters:
- Total weight off of the piston and rod assemblies is over 250 grams for each assembly, out of the box, versus standard 1.9L parts. And another 106 grams comes off of the rod journals.
- Strong rods and pistons
- 1.5/1.5/3.0 mm ring sets for a bit less rings drag than the stock rings.
- Keeps standard main bearings.
- Modern parts sourced out of Summit and the like
- Not as cheap as a plain 2.0L piston upgrade by any means. Buying 8 pistons and rings is around $600, and 4 rods are around $340. (I just cheated and got a used set off of eBay for $170 shipped...)

The risky areas that I see are in:
- the boring of the block..... which I have beat to death as much as I can
- and if there is anything odd in the offset grinding outcome.. which is the reason for this thread.

Thanks!
 

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Apples and Oranges

Thanks for your input, Nut10.

Just curious: What is 'more exotic' about offset grinding a crank, versus welding and offset grinding it? Both cranks need to be re-balanced, hardened, etc.

And I agree that the forged stock rods are quite good.... based on personally beating on them a lot! I have no doubt that the old style design pistons have plenty of meat to mill off, but have not looked to see how high the top ring would end up with that. And it would be hard or impossible to match the at-least 250 grams weight saving of the Acura or Neon rod and a short forged piston, all out-of-the-box, versus using the old design tall pistons, etc. And, without lowering the rod ratio, with the potential detrimental effect on higher RPM operation that is common with stokers that use the same rod length.

I'm still seeking input on the Acura rod situation that anyone can share.
Nothing exotic about grinding the crank, I was talking about Acura rods. If you are going to race this motor instead of street drive it you can always polish the rod beams which will not only make them stronger and will lighten them some, after you get the crank done when you go to balance it just turn the counter weights down and take some more weight off the rotating assembly. The top ring is still far enough down in the bore that it will be no problem. I ran one of these motors well over 50,000 miles on the street without a problem. I just don't believe in spending money when you can get the same results for less. World Rallye championships have been won with Opel Cranks, rods and pistons, so if you insist on spending money I'm sure that there is someone out there that will be more than glad to relieve you of it.
 

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Another simple route is RallyBob's 1.9 to 2.4 resapie.
All that's required is welding and grinding 1/4" more stroke to the crank. Mill 30 thou off the top off cheap Chevy 305 low compression pistons, bore your block out to fit your pistons and your done!!!!! Even better is your still using stock Opel rods!
 

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Discussion Starter #8
Thanks Vince. Been through that article in detail a few times so have that down pat. Keep in mind... I started down this road with the thought of a long rod motor for the intentions of keeping the rod-stroke ratio up.... Keeping the short stock rod length drops your rod-stroke ratio lower and lower as you stroke it more and more. That 2.4L conversion ends up with the rod-stroke ratio dropped to 1.55.... as opposed to 1.82 stock.

That is big change, particularly at the middle and higher RPM's. Strokers with fixed rod lengths tend to just not want to rev, due to the quicker pace of the piston leaving TDC versus crank angle. That situation rolls off the upper end of the torque curve more and more as the rod-stroke ratio decreases; the piston is leaving TDC too fast before the combustion process is mature.

And again no issue on the Opel rods per se....I have a set on which I nicely polished the beams 35+ years ago setting in the shop. That is just not where I am wanting to head here. My rod-stretcher was borrowed and never returned :D and so I have to look elsewhere to get longer rods. Heck, I even came up with a 5.700" Chevy rod setup with the rod-stroke ratio exceeding 2.0... but the displacement drops. The Neon rod ends up in-between but then you can't stroke as much unless you go to crank welding. Offset grinding alone seems simpler, and less expensive to me. Yes?? No????

So is the idea of using the Honda/Acura rods just a fiction? I don't seem very skilled with the search function on this site, but have not turned up anything yet. Tnx again.
 

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Ok, I get where your coming from and I can relate to your concerns of revability and bad con rod ratios....

So why not just get a 2.2 crank, and a good set of aftermarket pistons? It's super simple and gets you in the area your striving for with minimal cost and complexity..

P.S. Btw, I always wanted to go this route for all the reasons you ve mentioned.....
 

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Thanks Vince. Been through that article in detail a few times so have that down pat. Keep in mind... I started down this road with the thought of a long rod motor for the intentions of keeping the rod-stroke ratio up.... Keeping the short stock rod length drops your rod-stroke ratio lower and lower as you stroke it more and more. That 2.4L conversion ends up with the rod-stroke ratio dropped to 1.55.... as opposed to 1.82 stock.
Mark, I’m well aware of the shortcomings of the stock 128 mm rods. But where the 2.4 conversion shines is in torque anyway. Most guys only need to rev theirs to 5500 or so. Even a pretty built up 2.4 stroker I did with a .504” lift/257 degree @ .050” camshaft, 45 DCOE’s, and 185 hp/180 ft lbs of torque had no reason to rev past 6200.

I’m building another 2.4 stroker for one of my street cars, and it will have a much nastier camshaft, 48 mm Dellorto carbs, and 11:1 compression. I am using 5.4” aftermarket rods (137 mm) and shorter 305 Chevy pistons. Rod ratio falls in at 1.66:1.
 

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So is the idea of using the Honda/Acura rods just a fiction? I don't seem very skilled with the search function on this site, but have not turned up anything yet. Tnx again.
Actually, Gary (who started this site) has a used Acura rod/piston setup from Ernie Bello in Florida who not only ran it, but raced it.
 
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Opel Rallier since 1977
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Discussion Starter #12
Thanks all. Bob, If can I ask: Where do you get your crank work done, and how much do you estimate this one will cost in today's $$? And tnx for the note on the Acrua rod thing existing. I was kinda thinking this crank is plenty strong to take the pin diameter down 1/4" or so, and that seems to confirm it. It is a bit of a 'tank crank' to start with LOL

Hey Vince, one reason to use the 1.9L crank is that I have 6 1.9L short blocks here... they're taking over the place LOL. And also, for 1.9L owner, this is another way to use what they have if they wish, with modern, off-the-shelf parts that are readily bought on-line, get to a true mid 9's Static CR with a few steps for easy tuning on pump fuel with a moderate cam, all with much lighter parts. The one concern I have over these 3.78" diameter pistons is the cylinder non-thrust walls are getting thinner and thinner. The overbore for 2.0L pistons in a 1.9L block is getting down to .100-.110" thin non-thrust walls. The proposed .120" overbore here is getting those same walls down in the .080-.090" thick range. May be fine with the rest of the walls being so stout....???

If I want to do a small weld on the crank before offset grinding , then KB153 pistons and Acura rods (for stroking an SBC 305) will get to the same place with mid 9's SCR, and zero decked pistons. Or, offset hone the pin holes upwards in the rods (I'll know when I get the rods if this is reasonable) and deck the block about .012", with no crank welding to get to zero deck. The KB153's are hypers, which would be nice as the fit in the bores will be much snugger when cold than forged units.

Thanks again.
 

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one reason to use the 1.9L crank is that I have 6 1.9L short blocks here... they're taking over the place LOL. And also, for 1.9L owner, this is another way to use what they have if they wish, with modern, off-the-shelf parts that are readily bought on-line, get to a true mid 9's Static CR with a few steps for easy tuning on pump fuel with a moderate cam, all with much lighter parts.

If I want to do a small weld on the crank before offset grinding , then KB153 pistons and Acura rods (for stroking an SBC 305) will get to the same place with mid 9's SCR, and zero decked pistons. Or, offset hone the pin holes upwards in the rods (I'll know when I get the rods if this is reasonable) and deck the block about .012", with no crank welding to get to zero deck. The KB153's are hypers, which would be nice as the fit in the bores will be much snugger when cold than forged units.
All the advantages you speak of are there but, bear in mind, you are talking about a ton of machining to get to that point. Done correctly, it is very expensive where I come from.
 

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Discussion Starter #14
All the advantages you speak of are there but, bear in mind, you are talking about a ton of machining to get to that point. Done correctly, it is very expensive where I come from.
That's always a good question..... but a 'ton' of machining?
- Boring is not any real difference here IMHO, just more.
- Welding is a lot of labor and thus cost, and why I was leaning to avoid it. (But the lower cost of KB153's may offset that.)
- Offset grinding is a cost above normal crank turning. But what is the cost (and availability) of a 2.2 crank, versus having a 1.9L crank in-hand already for $0?
- Pin honing .040" or so in rods is normally not all that much.
- Eyebrow cutting can be a pricey thing if a new set-up has to be done. But if not much to take off, you can manage it at home. And that is TBD anyway with the 5.3L pistons and very unlikely needed with the KB's with their large eyebrows.
- Piston milling is typically not a home job. (Though I have been setting up to try to manage simple stuff here.) So another cost that I would like to get out of the equation.
- Rod reconditioning has been cut out... if you bother with that.

So, IMHO, the real costs are in the parts. But, coming from Mopar-land.... honestly, this is truly cheap-to-typical cost stuff here for stroking and quality rods, forged pistons, etc. And a set of 2.0L cast pistons plus rings is $425....

This is always a discussion in these matters.... there are trade-offs, and folks will place different values on different matters. And yes, machine work cost varies all over the map. I am lucky that it is a lot more affordable locally, and can interact directly with a very experienced machinist.
 

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You are quite right about the valve reliefs in KB pistons. Although we only turned .025" off the tops. I opted for the 2.0L, 143mm h-beam rods from CX Racing. Stock stroke though, so doesn't really apply to this thread. I looked at the Eagle/Honda stuff but I thought they would be too narrow. All good discussions.:biggthump
 

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Manta Rallier,

may I ask why you are using the 2L (42mm) Opel intake valves , and not the larger, better flowing, 45mm Opel valves ?


PS. My apologies, I should have asked this on your other thread.....
 

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Discussion Starter #18
Vince, I just started the head re-work to replace a cracked one on a 1.9L so just did the 2L valves as a modest upgrade. The whole bore/stroke thing came up after the head was in the shop, so there's no real relationship between the 2 projects. And the nice Serdi cuts below the valve seats, in the throat, and the avoidance of excessively sinking the valves, hopefully helps the 2L valves work a bit better than standard valve work. I attached a pix below in case anyone is wondering what a Serdi cutter can do. Look at the smooth cut in the throat below the 3 angle valve job. A Serdi bit is like a router bit for iron/aluminum.

Next head project, whenever that may be, will be using something other than Opel valves. 9 mm valve stuff is obsolete; setting spring heights with new springs is proving to be tedious as suitable retainers are being found by experiment; I'm ending up with Mopar small block retainers on the intakes LOL. No off-the-shelf lash caps or keepers that are readily available here.

And yes on the rod side clearance, Commodaren. It is the normal thing these days to buy rods for American V8 engines from SCAT and Eagle and others, that have the big ends .025-.030" narrower than the stock rods. With 2 such rods on a V-engine journal, you are increasing rod side clearance by .050" + or -. My son and I have a nice 375 HP Mopar 340 running with SCAT rods just like that... No harm comes from that, and no need to do any rod centering at the piston with such a small increase in side clearance. And the bearing width for these Acrua rods is plenty good for stability, and carrying the load.

Sounds like this particular crank cut is going to be an 'almost' new thing; sounds like it has been done but maybe once or twice only? I really started this thread to find about that, and see if anyone could shoot holes in this setup (that I have not already shot in it myself....). It is easy to miss a fine point in these great plans and schemes !
 

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Actually, Gary (who started this site) has a used Acura rod/piston setup from Ernie Bello in Florida who not only ran it, but raced it.
Yup. I do have that setup. I had a block bored out for the custom pistons and have the rings and bearings. Brings it out to ~2.1.

Just waiting for the time to assemble it. I'll try to get some pics later.
 

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Discussion Starter #20
Gary! The man....the myth. LOL

I look forward to seeing pix. If you have any further info and/or lessons learned on this rod/crank setup, I'd love to hear them. Tnx.
 
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