Stroker power expectations

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JT68
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Re: Stroker power expectations

Post by JT68 »

Sorry Pat, you can’t build a stroker without modifying the nose of the U20 crank. It should to be modified to drive the 1600 timing sprockets. I guess you didn’t realize this? You also have to cut off the extra length of crank and tap it- or- machine a spacer to hold on the crank pulley. The mod needs to be professionally done since it affects cam timing directly and keeps the crank pulley on the engine, which is fairly important.

The easier option is an H20 crank, so you might want to get one from BrianZ and not mess up a good 2L crank.

The U20 rods are fine, they are just heavy, which won’t matter for the engine you are proposing.

We already said in numerous places that the increase in stroke will provide an increase in torque over a 1600. The head and rotating mass will provide the power and rpm limitations.


Oh yes, and stay with the stock (metric) cam if you want to optimize torque and don’t care about performance over 5k.
Last edited by JT68 on Tue Sep 14, 2021 7:17 am, edited 1 time in total.
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Re: Stroker power expectations

Post by Daryl Smith »

Greg, and others, thanks for the vote of confidence, but, I am far from an engine expert....Jim's built a lot more engines than I have...even tho we disagree on some points....

I will put my $0.02 in...take it for what it's worth...
Given the parameters of only stock parts, this is what I would do:
1) Cam - Lift the valves as high as the stock springs will handle .425" - .450" (?) , Duration in the 265* to 270* (advertised) range [215 -220* @ .050"] This duration cam should still give you a decent idle.
2) Good three angle valve grind and open the throats to ~89-90% of the valve diameter (should be minimal cost). [For a few more ponies, investigate the cost of a 33 or 34mm exhaust valve - Jim might have something priced reasonably.]
3) IF you have the equipment/ability to do yourselves rough up the intake ports and intake manifold with 60 or 80 grit sanding rolls, removing any casting flash/lumps etc. Stay away from the valve seats. The idea is to just have a rough-ish surface, not to shape the port, and to remove as little material as possible while doing it.
4) Deck the block to zero deck the pistons - assuming dished pistons....only if using dished pistons. With flat top pistons the compression will be around 10:1 which is a bit high, best to shoot for a max near 9.5:1 for a long lived street build. The stock setup the pistons sit down in the cylinder a bit, not ideal, but, can stay there if you already have the flat top pistons.
5) 1 1/2" ceramic coated header. Nothing more is needed. Dean's own testing showed this header is good to 180 hp. I personally wouldn't use the stock manifold except for a show car.

As Jim said you will likely be in the 110 - 125 hp range (crank not wheels), and peak around 5000 rpm (my opinion 32mm exhaust valve is the plug here).
Displacement alone will be 24 - 25% increase, and that should translate almost directly to a similar increase in torque across the rpm range. If well built this figure can increase slightly.

Lighter parts as mentioned - pistons, rods, crank, flywheel - don't help power much, but, make a significant difference in the RATE of acceleration - very noticeable with pistons and flywheel. The R16 rod/VG30(?) piston combo is worth a look, especially if you are already replacing the pistons.

Mike (23yrRebuild) gave good advice also and is very happy with his engine with mostly stock parts....no reason it won't work for you....

Lots of ways to build a stroker R engine, as can be seen from the opinions here and in the stroker poll (which would be good reading before you build). I honestly think 150 hp would be within reach with just the larger exhaust valve and cam/carbs/header/exhaust to support that power level. No porting nescessary. The stock intake flows ~165 cfm......
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Re: Stroker power expectations

Post by JT68 »

Thanks for chiming in Daryl, many of your points are well taken, and originally I was thinking like you about how to get the max performance for the money. (ie approaching U20 power) The op says "assume a perfect head", but then Pat clarified no significant headwork and power over 5k doesn't matter, so it's all about low end torque and low budget.

That changes the formula a lot:

no custom rods or custom pistons or custom work to make them fit
no larger valves
no port work
no webers/solexes etc.
they probably will re-use the 50 year old valve springs and I'd bet spend the least possible on valve work
no serious cam work(no degree'ing or dialing in a cam)
probably running a stock flywheel
no light components or lightening of anything

Soooo, if its all about low cost and low end torque, the answer is big cheap pistons, short duration cam and more compression. H20 pistons will be the cheapest, or you could use cheap flat tops. I think Carl at New-Datsun-Parts has the cheapest flat-tops you can buy. I would think under 5k almost anything will work ok.

1) .060 over pistons will give more power at all rpms, so that's a no brainer. At .060, the block can still be bored again if it's ever necessary. Basically free HP&Torque. Most importantly, this will get the CR into a more useful range.

2)Actually spend the money to cc the engine and accurately set the static CR at 9.8-10:1. Surface the head as needed to accomplish this. Deck the block to help if necessary. Compression is basically free HP and torque for all rpms-just stay at or slightly under 10:1.

3)H20 crank is by far the easiest path for a crank. The U20 crank offers little if any benefit under 5k and requires much more work to make it fit.
(H20 costs less and drops in w/no mod's)

4) The stock cam is the best low budget answer. (it's dialed in correctly already and it's short duration=minimal overlap=good low end)
Maximizing cam/valve lift is also the wrong direction for reliability-especially on a low budget valve train- and for improving low end.
High lift just introduces a host of problems. We have a nice "stage 1 cam" if they want a slight increase, but I'd really just stay stock if low cost is the
main objective.

We are actually building another stroker very similar to this right now: 5main H20 crank,H20 pistons and rods, very mild cam, slightly higher CR, no serious headwork, 1600 carbs. Like Pat's scenario, the owner is also ok with just moderate power improvements, but is using the billet light FW. With the lighter crank,FW and rods and higher CR, it will accelerate and pull very well on a low budget.
Last edited by JT68 on Tue Sep 14, 2021 7:19 am, edited 1 time in total.
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Re: Stroker power expectations

Post by unklpat »

Daryl, thanks for the concise reply, and unbiased advice. All of your points are what I was originally thinking when I made the original post.
Jim, as far as modifying the keyway, I'm researching that, but you most certainly don't need to shorten the crank. If you read my original post, I never said I wanted to get U20 power, or rpm's, but yet you keep going there. What is wrong with a perfect stock head with a good valve job, new valves/guides as necessary, and new/ checked valve springs? What is wrong with a slightly larger cam, to go with the increased displacement/ stroke? What is wrong with using SU carbs, with larger needles, or even larger carbs? You even said that you "test" R16 carbs on U20's all the time. Do you have a dyno? Show some results from your testing. If I am not going Solex, I'm low budget? I am most certainly not going "low budget", as the I've spent over $1000 on my U20 block just for boring, decking, crank checking, etc. I'll also have over $1000 into my U20 head, that has all new parts. The R16 head in question will also be checked by a competent machinist, as to what needs to be done. On my U20 head, I chose to replace everything, as I dropped a valve seat. There have been multiple people that have done what I'm proposing, with good results. Let's price your billet rods, lightweight pistons, and H20 crank. compare that to $1k for u20 parts. Oh, we also need lightweight flywheel and z-car clutch, because. I don't appreciate being talked down to, especially since you can't seem to grasp the message in my initial post. You've got a good reputation on this forum, but on this thread, that I started, you are hurting yourself. I would suggest you step back, and let those who have reasonable advice participate. Insulting your potential customers is never good form. Pat
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Re: Stroker power expectations

Post by Pjackb »

Hey Pat not sure how you interpret Jim response as talking down to you when he clearly answered your question in his first post, maybe missed something?
JT68 wrote: Mon Sep 06, 2021 8:58 pm If you build with stock components, most 5-main versions will fall in the 115-125hp range. Probably 25-35% torque increase over R16. Maybe 110 with a scrappy R16 head/no improvements. Here is why:
After that what I saw was him telling you the U20 crank needs to be modified in a stroker configuration an that the H20 crank is a drop in and much lighter rotating assembly this is a very well documented requirement and procedure and I believe it’s even in the tech wiki

Personally as the owner of an R16 with lighter aftermarket .30 overbored pistons with LW flywheel and mild cam my engine is probably in the 90-100hp range but it pulls strongly to ~5700 rpm , it’s obviously not even close to my modified U20 in the other car but it’s a really fun engine so I would highly recommend the lighter components for your stroker unless you already have the U20 parts (then it’s a no brainer).
If I were to build a stroker and wanted most bang for the buck without touching the head that would be my formula
H20 rods and crank, good quality light pistons at .40, stock or U20 SUs, a set of headers
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Re: Stroker power expectations

Post by unklpat »

Thanks for your response, I don't appreciate someone telling me I'm going "low budget" when the head will be rebuilt to specs. I also don't appreciate somone telling me in one sentence that the R16 carbs are fine, but then in another sentence, I'm not doing solex's, so low budget. If no head work, or larger valves, then low budget? If no lightweight crank/pistons/rods/flywheel, then low budget? What budget would you put on a stroker R16? Do you just rebuild the motor as is, or get a bit more torque? This brings me back to my original post. Pat
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Re: Stroker power expectations

Post by Pjackb »

Well I have a few projects on the go right now so the pushrod stroker build is on hold but I’m definitely going big budget
2.2l displacement, forged pistons, beehive springs, big valves, mild street cam , HSR42s, billet FW ,225mm clutch, 123 ignition .
It will probably cost around 8-10K but should be an interesting machine
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Re: Stroker power expectations

Post by unklpat »

Thank you for your interest, it helps all of us. Pat
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Re: Stroker power expectations

Post by JT68 »

unklpat wrote: Tue Sep 07, 2021 8:39 pm
Jim, as far as modifying the keyway, I'm researching that, but you most certainly don't need to shorten the crank. If you read my original post, I never said I wanted to get U20 power, or rpm's, but yet you keep going there. What is wrong with a perfect stock head with a good valve job, new valves/guides as necessary, and new/ checked valve springs? What is wrong with a slightly larger cam, to go with the increased displacement/ stroke? What is wrong with using SU carbs, with larger needles, or even larger carbs?

"but you most certainly don't need to shorten the crank" I said "or machine a spacer to hold on the crank pulley". A spacer takes up the space where the long U20 crank gear was. You need one or the other method, neither is free.

Yes, you MUST cut a keyway in the U20 crank to locate the shorter 1600 crank sprocket. What is there to research?, it's pretty much job 1 (unless you use the H20 crank). It needs to be done on a mill by a competent machinist because 1degree of accuracy is needed. (otherwise your cam timing is dorked). The h20 crank is a direct fit, so much less trouble and for under 5k rpm, it's totally fine.

Pat, You asked for advice and lots of people gave similar advice for head modifications, carbs etc. I think it is because you said "get the most bang for the buck" many of us thought you wanted to make significant power. Then you later clarified that over 5k didn't matter and you just wanted lower rpm torque.

You also said "so expect a perfect head". A stock 1600 head will be far from perfect for 99.9% of 2L strokers. The other posts explain why, but you clearly don't want the advice there. That is cool, its your project.

I'm sorry if you feel I was talking down to you, but 3 or 4 people have told you similar things in different ways and you didn't seem to like the answer.

My last post gave you a recipe without any significant head work, with very inexpensive parts, just like you asked. - The recommendation was even for other vendors, so I'm only trying to help. Not trying to sell you anything

3 or 4 people have also suggested a lighter rotating assembly is a big plus-yes that costs money and you don't seem interested in those very significant performance gains. - that's ok too, use the heavy parts if you choose.

Yes, a roadster clutch would be fine, but you mentioned a novice driver....they tend to tear up stock clutches...that is the rational for that. It doesn't matter to me at all what clutch you use, but Dad won't be too happy if junior tears up a clutch in a year and they have to pull the engine again.

Comparing modern CNC billet/forged engine components to 60's tech cast pistons is like comparing a Hyundai to a NissanGTR. Both will get you down the road, but there is a huge quality and cost difference-you get what you pay for. Most folks get that, and I never suggested any of our high end parts for your build. - except possibly the billet FW since it is very high bang for the buck--you'd have to spend 2 or 3 times as much on other engine components to make the same improvement in drivability. Ask anyone who has one

Since you asked the questions:
What is wrong with a perfect stock head with a good valve job, new valves/guides as necessary, and new/ checked valve springs?
--nothing, just far from optimal for MOST stroker builds. For what you are doing it will be fine.
What is wrong with a slightly larger cam, to go with the increased displacement/ stroke?
--nothing, a slight increase is fine. A big cam won't help your objective though, that's a step backwards. Specifically, it will hurt low end power.
What is wrong with using SU carbs, with larger needles, or even larger carbs?
--nothing, I think I was the first to say stay with the stock SU's, they will be fine if you can tune them properly.
--2L carbs will work fine too if you can tune them properly.

Again hope this helps you Pat, based on your objectives the last formula I posted is the most bang for the buck:

big bore using low cost pistons on whatever crank you choose
compression at 9.75-10:1
mild or stock cam
lighter FW
stock or 2000SU's
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Re: Stroker power expectations

Post by unklpat »

Jim, nobody said I was shooting in the dark, except you. I asked for what can be done with a good stock head, U20 crank, rods and pistons. You immediately went elsewhere. I will make sure this motor is correct, and the best it can be, as to the owners requirements. You once told me that a U20 crank had no value if turned to .020, is that true? What is the thickness of the nitride coating? Have you had it tested by a lab? Maybe I should throw this crank away. Nobody should use a .020 turned crank, because it will wear quicker. Why did nissan sell up to .040 bearings for the U20? I'm not interested in your recomendations, as they all seem to steer towards products you sell. And in the end, there is nothing wrong with my suggestions, how curious. Pat
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Re: Stroker power expectations

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unklpat wrote: Tue Sep 07, 2021 11:17 pm Jim, nobody said I was shooting in the dark, except you. I asked for what can be done with a good stock head, U20 crank, rods and pistons. You immediately went elsewhere. I will make sure this motor is correct, and the best it can be, as to the owners requirements. You once told me that a U20 crank had no value if turned to .020, is that true? What is the thickness of the nitride coating? Have you had it tested by a lab? Maybe I should throw this crank away. Nobody should use a .020 turned crank, because it will wear quicker. Why did nissan sell up to .040 bearings for the U20? I'm not interested in your recomendations, as they all seem to steer towards products you sell. And in the end, there is nothing wrong with my suggestions, how curious. Pat
That’s fine Pat, whatever you choose to believe is fine.

The information on the crank is certainly factual, and again I’m not trying to sell you anything at all, so I don’t know what you are talking about there??? I even suggested 2 other vendors for low cost parts for your build.

Regarding the crank, the Nissan factory nitriding is still present at .010, pretty much gone at .020. What I told you is WE don’t build engines with cranks at .020, UNLESS THEY ARE NITRIDED AGAIN. Any good crank grinder or anyone who has cross drilled a Nissan crank knows the hardened surface is thin, once you cut through it the crank is quite soft (and easy to drill). A soft crank surface will wear rapidly. You might look into the metallurgy if you don’t believe me. The lab work was done decades ago and hasn’t changed.

Yes you can run .02,.03,.04 bearings, but they won’t last nearly as long as .STD or .010 UNLESS you have the crank nitrided again! A GOOD crank shop is aware of this, if they don’t know it, you are in the wrong shop or they just don’t care how long your old Datsun crank lasts.

.03 and .04 bearings are very rarely used, but they will work perfectly IF you nitride the crank.


Like Jacques said, I answered your question immediately and factually with no motive to sell you anything at all! Not sure how you came away with anything different: "If you build with stock components, most 5-main versions will fall in the 115-125hp range. Probably 25-35% torque increase over R16. Maybe 110 with a scrappy R16 head/no improvements."

Regarding your budget, if you are trying to build a stroker for 2-4K, that is relatively low budget by almost any measure. Some guys spend more, significantly more than that just on carbs. That is just stroker reality. You might ask the guys what their Rebello engine cost including carbs, FW, intake etc.

I’m very sorry if I offended you. My apology.

Lots of guys start on a stroker project and then find out it’s WAY more involved than they expected. Best of luck with your rebuild.
Last edited by JT68 on Wed Sep 08, 2021 9:24 am, edited 1 time in total.
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Re: Stroker power expectations

Post by 70MTRoadster »

Pat, you might want to read my stroker article under the tech wiki, engine, Scott Lindley's stroker. Kinda what you have in mind of doing. Dynoed on a dynojet at 83 hp to the wheels, so maybe 115 at the crank. I have since got lucky and was given a stock 69 SU U20 and it is noticeably more powerfull than my stroker. Like so many say the power is in the head and my stock aluminum one would have needed at least the 34mm exhaust valve mod, maybe a port and polish and an even bigger cam than my reground one.
After reading JT's deal on the .020 regrind I might consider disassembling my stroker some day and having the crank renitrided.

fwiw, Scott
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Re: Stroker power expectations

Post by unklpat »

Jim, no harm, just that I specifically stated no custom headwork, to save $. Naturally, that includes no larger intake/carbs. This whole process started with a chance meeting with a 1600 owner who wanted more power. I have a magnafluxed 10/10 U20 crank, and U20 rods, and gently used .020 pistons. I am trying to offset the costs of my U20 rebuild. Gee, let's build a stroker! I'm sure that whatever power increase will be noticable, but not trying for U20 power. I am not an R16 expert, nor do I want to be, I'm trying to help someone acheive their goal of a "not too expensive" increase in power. Just increasing the bore size won't give him that, so stroking the motor came up. By not cutting the crank, it can still be viable later, for U20 use, and He would be replacing the pistons anyway. In my opinion, the only cost increase over a stock rebuild, is in the U20 crank and rods. That's it. Everything else stays the same, except maybe a new cam, needles for the carbs, header, and electronic dizzy, most of those would have been done anyway.
Scott, thanks for your input, I need to find out exactly what the keyway modification entails, but am encouraged by those that have not done much more than increasing the stroke and bore, and are happy with their outcome. Pat
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Re: Stroker power expectations

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unklpat wrote: Wed Sep 08, 2021 11:48 am . I am not an R16 expert, nor do I want to be, I'm trying to help someone acheive their goal of a "not too expensive" increase in power. Just increasing the bore size won't give him that, so stroking the motor came up. By not cutting the crank, it can still be viable later, for U20 use, and He would be replacing the pistons anyway. Pat

From the tech wiki
http://www.311s.org/pmwiki-311/pmwiki.p ... kerWriteUp
Next you have to make a choice as to what crank, rods, and pistons to use. I used the H20 crank and pistons which is a direct drop-in for the R16 with no modifications. The H20 pistons are dished which will reduce your compression ratio with an uncut head. They are perfect for an aluminum head that has been cut too much. The part number for the H20 crank is the same one NISMO uses as a stroker crank. It is 12200-E0700. I priced an H20 crank new at $516.00 which is more than a bit pricy. Several have picked the NISMO stroker crank up for around $325.00. Shop around. The 1600 fly wheel and crank pulley bolt right up. Some have reportedly used the U20 dampened front pulley. I really find no need to do this.

The U20 crank with the U20 flat top pistons is your other choice. The problem with the U20 crank is that you must have the front end of it machined. What do I mean by machined? You have to have exactly 1" removed, the crank pulley hole re-bored and tapped and a key-way put back in. I did not go that route so I have no idea what the costs may be. A lot depends on where you are located. Not cutting the crank will cause you all kinds of grief as the water pump and alternator pulleys will not line up without Mickey mousing something together. Another way you could go about this is to take the machine shop a 1600 crank and have them match the U20 crank up to it exactly.

The third option for the lower end would be to use a G-15 (1500) crank in the R16 3 main block. I am told the displacement would be right around 1900- but will not be quoted on that one.

http://www.311s.org/pmwiki-311/pmwiki.p ... eysStroker

2L crank from Florida. I had to shorten the 2L crank nose. I have a 13x40 Jet lathe and Grizzly milling machine and was able to part-off the nose to the correct length and machine a new single slot for the keyway. I was unable to drill and tap the nose though due to not having the correct centers to support the crank properly so took it to a local machinist and he charged me $50 to do this. We changed the thread to 5/8x24 and I used a hardened bolt and torqued to 140 lbs. I used the entire Motor Power timing set (cam gear, crank gear, chain, tensioner). The H20 crank gear had a .005 larger keyway slot in it than did the crank pulley from the 1600 so I had to make a double width keyway to allow for this.
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Re: Stroker power expectations

Post by unklpat »

I read all of that, I also read that someone made a 1" spacer, someone else machined down a spare R16 pulley. I am of the understanding that the U20 keyway might have to be modified/lengthened. If someone wants to chime in on the specifics, having actually done it, that would be appreciated. I have someone to cut down and tap the nose, I was trying to avoid ruining a perfectly good crank for future U20 use, and don't think a 1" extra nose on a crank would be that big of a deal. I also have the R16 crank, to match up if machining. Pat