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H22 build-up – part 7: the bottom-end.

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  • H22 build-up – part 7: the bottom-end.

    If you missed them, here are parts one, two, three, four, five, and
    six of the series.

    On a naturally aspirated engine, there are 3 basic methods to increase it’s output. The first lies in making more power at higher rpms (with complimentary improvements in gearing), the second is improving efficiency (inertial, thermal, and volumetric), and the third is displacement. Building up the bottom-end can improve all 3 of those areas . . . By strengthening and lightening the bottom end (crank, rods, pistons), higher rpms become possible since the stronger components can withstand higher forces - and the lower weight of forged components reduces said forces as well. By increasing the compression ratio via pistons, thermal efficiency can be improved. By reducing weight & inertia, less power is lost turning the engine. And of course, with an increased bore or stroke, we get more displacement which allows the engine to ingest a larger amount of air/fuel.

    Make no mistake, reworking the bottom-end is very intensive from a labor, equipment, and cost perspective. But if you're really looking to make some power, building up your bottom end correctly pays huge dividends - both on the dyno as well as reliability a few thousand miles down the road.

    Forged aftermarket pistons offer several advantages over the stock pistons – namely durability, lower weight, and the ability to tweak compression ratio. Durability is pretty self-explanatory, forged pistons can just plain take more abuse. Weight is a big deal as well, since any weight lost off the pistons is weight that your engine doesn’t have to sling around. Towards the stock redline, pistons are moving at average speeds of up to 25 meters per second and changing directions more than 200 times a second, so a few grams can really make a difference in the amount of force that your rods and crank have to bear. And lastly, the ability to change your compression ratio can have a huge impact on power. As I discussed in the headwork article, once you start using big cams with lots of duration & overlap, dynamic compression ratio begins to plummet. So in order to keep thermal efficiency up, you need to increase the static compression ratio. Just be sure to triple-check all your clearances before you finish reassembling the motor – you’ll want to clay your engine to find out just how much space you’ve got to spare between your pistons and valves, and how much room for camshaft advance & retard you’ve got. Not doing so can have disastrous results down the road when you attempt to tune the cam gears.

    Now, using forged pistons in the H22 has another little wrinkle – the stock sleeve liner material. Honda uses a material called “FRM”, which stands for fiber-reinforced metal, and it’s been heavily debated whether or not it’s possible to run forged pistons in the FRM sleeves. Along with a type of carbon fiber, FRM uses standard aluminum alloy as a major component. Since forged pistons are also aluminum . . . . any contact between the two is going to result in severely scarred cylinder walls, and an expensive rebuild. Now, there are companies that claim their pistons will work perfectly with an FRM sleeved engine (like JUN & Wiseco). However, I have yet to find any proof that this is the case (like an engine torn down & inspected after 30,000 miles or so of use). Bottom line, the number of engines that have been ruined by attempting it vastly outnumber the people that claim it works. So if you want to run forged pistons, plan on resleeving with some iron ductile sleeves – more on that topic in the section on increasing the bore.

    My own personal conjecture is that it is possible to run forged slugs in the FRM sleeves, but it requires a combination of factors that I don’t believe anyone has worked out yet. With a piston of the proper (read: high) silicon content to limit expansion, correct clearances, modified sideskirt design, and probably some sort of coating on the piston, I think a forged set of pistons in the stock sleeves could have no interference or scraping issues whatsoever. But I really don’t believe anyone has found that right combination yet. However, both the NSX & S2000 use FRM sleeves & come stock with forged pistons (extremely high silicon, iron-coated), so it’s obviously not impossible.

    If you're not interested in going with a full resleeve, a very viable option is to get a set of OEM Type S pistons. These aren't forged, but are attractive for a mild to moderate N/A build as they bump compression on a stock engine up to 11:1, and can be found for around $300 (including rings). And depending on the condition of your cylinders, you may not even need to rehone - but plan on one anyways.

    Connecting rods:
    Assuming you don’t need a custom length because of a moved wrist pin or lengthened stroke, there are several inexpensive (<$400) off the shelf options available. For a n/a build, you want to find as light-weight a rod as possible that has the strength you need – although most any aftermarket forged rod you can find will be plenty strong to handle the stresses a non forced induction H22 can place on it (assuming a reasonable redline, of course). Plus the more weight you can lose off the rods, the more inertia you’re going to free up. And if you’ve disabled your balance shafts, lighter connecting rods will reduce those secondary vibrations as well . . . .

    The stock H22 crankshaft is an extremely good piece. Forged steel, fully counter-weighted and balanced right from the factory, you’d be hard pressed to find a superior unit without spending an obscene amount of money. It can, however, be lightened - it’s possible to take as much as 8 or 10 pounds off without sacrificing it’s strength or balance, which equates to a significant reduction in rotating inertia. You do not, however, need to “knife-edge” the crank – anyone who suggests this procedure is not familiar with how Honda engines operate, and I would recommend going elsewhere for advice. Knife-edging typically reduces the amount of friction, frothing, and windage resulting from the crank spinning through the oil bath. On a Honda engine, however, the crankshaft does not spin through an oil bath, so there is negligible windage to begin with. Therefore, there’s nothing to be gained by knife-edging it.

    Again, the Honda bearings are extremely good. I’ve never encountered any evidence that supports the necessity of replacing them with aftermarket ones. On a full rebuild, you’ll want to check clearances to make sure they’re within spec, and replace if necessary. But as long as they’re getting proper oiling, and your engine is in a good state of tune, the bearings will take anything you can throw at them.

    Prodrive makes an upgraded oil pump gear, and while this piece isn’t cheap by any means, it can be good insurance. Combined with improved reliability, it increases oil pressure slightly. On a street motor, I think it’s probably overkill – but if your engine spends a prolonged amount of time at high-rpms (aka track time), it’d be a worthwhile investment.

    Increasing the bore:
    While it is possible to bore out the stock sleeves on the H22, it’s not possible to go very far on them . . . . at all. In fact, the factory potential for overboring the stock 87mm is just .25mm, which will garner you a whopping 12cc’s (a 0.6% increase in displacement over the stock 2,157cc’s). On a budget rebuild (i.e. Type S overbore pistons & stock sleeves), this may be worthwhile as a “why not” modification, but don’t kid yourself about the amount of power you’ll see from doing it, aside from the increase in compression. If the improvement due to the extra displacement were measurable on a dyno, I’d be surprised.

    In order to increase the bore a little more substantially, a resleeve is required. Resleeving the block needs to be done by a competent machine shop, and replaces the factory FRM (fiber-reinforced metal) sleeves with iron ductile ones. Some options available for resleeving include Golden Eagle, AEBS, Darton, and LA sleeve liners. A full-on resleeve will cost anywhere from $800 to $1,500, while replacement sleeve liners can be as little as $400 after labor. But bear in mind – stripping & shipping your block is a significant expensive just by itself.

    Once resleeved, the bore potential is now only limited by the bore spacing and the size of your balls. While I’ve read of people going out as far as 91mm on the stock block, doing so leaves a laughable amount of material separating the cylinders. Even a 90mm bore is pushing the limits of reliability, and you can have trouble with the head gasket sealing properly between cylinders. For a streetable engine, an 89mm bore is probably as far as you want to go – or possibly 89.5, if you can find pistons in that size (I’m not aware of any off the shelf). With the stock stroke, an 89mm bore represents a solid 100cc more displacement, or an almost 5% increase. Assuming your top-end is up to the task of the extra flow, this theoretically gives you another 5% more torque across the board – nothing to sneeze at.

    And if you’re boring out your cylinders, you may want to have a matching bore done on your head – a topic I touched upon briefly in the headwork portion of this series. This sort of deshrouding can take some finesse, as any material you take off the head is going to reduce your compression ratio – so I definitely recommend the advice of an experience engine builder/head porter if you plan on going this far with your engine build. Some builders don't recommend bothering at all, claiming that the gains from opening up the head bore are negligible compared to the amount of effort to do it correctly.

    Here's an few articles on sleeving courtesy of and And here are a few links to some of the more popular sleeving companies for Honda blocks: Golden Eagle, Darton, and AEBS - another way to go that seems to have a good reputation is Dan Benson, but I'm unable to find a website for him. A search on honda-tech should bring up contact information, though. Another possibly more affordable option is going with LA sleeve liners - places like use them.

    Increasing the stroke:
    The stock stroke of an H22 is 90.7mm, and there are several (relatively) inexpensive ways to go about stroking it even further using Honda crankshafts if you're so inclined.

    The F & H series blocks are all extremely closely related – so in many instances it's possible to use an F or H series crank in a different block. The only limitations lie in the change in crankshaft mains in 1998 – they went from a 50mm main to a 55mm main. The most common option for an H22 is to use the 95mm crankshaft from the H23 or F22. With the stock bore, this works out to 2,259cc’s of displacement – a 102cc increase (or 2,364cc’s and a 207cc increase if combined w/ an 89mm bore). An even more extreme crankshaft can be found in the F23 engine from some of the more recent Accords – it rings in at a 97mm stroke (2,306cc’s for the stock bore, 2,414cc’s on an 89mm bore).

    But however much fun it is to dream about the vast amounts of displacement available via stroke, there are some serious considerations to make beforehand. By changing the stroke, you’re messing with some fairly vital engine geometries – namely bore/stroke & rod/stroke ratios.

    Without delving too deeply into the physics of engine geometry, basically the length of an engine’s stroke (and the resultant rod length) is directly proportional to it’s ability to rev. Longer stroke = faster piston speeds. Shorter rod = faster piston acceleration, more side-loading, and less dwell time at TDC. As a result, the engine’s torque curve will want to move lower in the powerband (which can make any kind of aggressive final drive you’d like to use quite frustrating). Because of the increased piston speeds, do NOT expect to be able to rev to the stock redline w/out some seriously strong connecting rods & rod bolts. And even if your bottom end is physically capable of taking the abuse of the forces resultant of uber-high piston speeds, chances aren’t good of you making any power up there to begin with – at least, not without some hardcore headwork & massive camshafts. The longer your stroke gets, the harder it is to fill those cylinders efficiently. The shorter the rods, the more power you'll lose due to friction against the sides of the cylinder walls. At it’s extremes, the pistons will actually begin to move as fast (or faster) than the combustion’s flame front. There’s obviously not much power to be found in that scenario.

    Another concern is that on the 95 & 97mm crankshafts, less care is taken from the factory in getting them balanced for higher rpm operation - although they're still very nice forged steel units, they're simply not designed to be spun at the kind of speeds the H22 was. So if you decide to use one of these cranks, some extra work balancing, polishing, and even cryo-treating for more strength would be in order.

    One final reliability consideration is the oil squirters . . . The H22 comes stock with oil squirters aimed up at the bottom of the pistons. This helps cool the pistons and ensures proper oiling in the cylinder. However, when the move is made to a larger crankshaft, they may not fit anymore . . . which would hardly be desirable for sustained high-rpm operation.

    As far as actual stroker kits that are available for the H22, there's some options available, but only a few of which are at all realistic. Supposedly JUN makes one, but I wouldn't know where to start to find it for sale. And knowing JUN, it's no doubt obscenely expensive. Another option I'm semi-aware of is via Top Fuel. The page is all in Japanese, but it appears to be a kit w/ crank, rods, & pistons, costing 168k yen (~$1,500). This seems to be too affordable to be true, though - and again, I wouldn't begin to know where to purchase it.

    Or you could go the Crower route - custom Crower crankshafts start at about $2,600. Pair it up with custom rods & whatever pistons you like, and there's your kit. The last possibility that I know of would be R&D Dyno - they advertise 2.4 liter shortblocks assembled starting at $4,500 - or unassembled kits starting at 3 grand.

    For putting your bulletproof bottom end together, unless you've got an incredibly comprehensive home garage, you'll want to have it done by someplace familiar with Honda/import engine assembly with access to a machine shop. Checking clearances during assembly requires some pretty expensive measurement tools, most of which aren't likely to be kicking around an average toolbox. And of course, there's a good chance you'll need machine work done of some kind - at the very least, a fresh hone on the cylinder walls, and often a fresh deck is necessary.

    If you're getting a full resleeve, often places like Golden Eagle offer short-block assembly services while it's in their possesion - this is an excellent option in my mind. Simply ship your internals along with the block, and after they get the new sleeves in, they put it all together for a reasonable cost. Then once you get the block back, it's ready to rock - no fuss. The peace of mind (and usually some sort of assembly guarantee) of having this done is a very nice luxury.
    Last edited by Daemione; 03-28-2005, 02:46 PM.

  • #2
    You rock

    I couldn't have done it better myself (nor would I be inclined to) You covered all the relevant points accurately and succinctly.

    I would recommend to anyone who is really interested in building Honda engines to check out the Endyn "Old One" site. There is a lot of controversy surrounding Larry (which I won't re-hash here) but the information he provides is top flight.

    I am in the process of sourcing the components for a full H22 rebuild. I have the head and i'm looking for a cheap, re-buildable block. I plan to take the bore up to 89mm amd use the stock crank. Golden Eagle will be doing the re-sleeve. DPR will be doing the head (and de-shrouding the combustion chamber as you mentioned) I will be using Arias pistons at 11/1 CR and Eagle rods. I won't be lightening the crankshaft as I believe you gain the same effect by lightening the flywheel and I don't want to spend any more $$$

    I expect to get about 270 HP from that combination which is plenty for a car like the attack. Should I ever want more I can easily swap the pistons for slightly lower compression ones (around 9.5 or 10 to 1) and supercharge that bad boy.

    Yes, I know about the issues with the JR Prelude charger and the Attack chassis but chew on this idea Use a Whipple charger mated to the lower half of the stock intake manifold (Just as JR does it) Since the Wipple spins the opposite direction than the Eaton use a transfer shaft across the header side of the block, a' la' the vortec design for the B series, and do an end run around the shock tower. The whipple input shaft would be on the side of the engine where the intake usually resides. You could use a Ford throttle body and stock castings from Whipple or Keane Bell. the intake can be fab's up out of 3" tube stock routed to the drivers side air inlet. Yes, theres a boat load of fabrication issues but nothing fundementally un-solvable.

    But I digress I'm going to stick to the NA route for now and see how sucessfull that is.



    • #3
      Hey Daemione,
      Great job as usual.

      One question. Will windage screens and crank scrapers provide any benefits for these Honda engines? I know they can reduce crank drag on SBCs, but is there really anything to be gained in this Honda engine design?


      • #4
        Originally posted by ozarkbw
        Hey Daemione,
        Great job as usual.

        One question. Will windage screens and crank scrapers provide any benefits for these Honda engines? I know they can reduce crank drag on SBCs, but is there really anything to be gained in this Honda engine design?
        The block/main cap girdle basically acts as a windage tray. Nothing else is needed although some people do open up the oil pick up for better flow.


        • #5
          No, not really - windage as you'd experience on a SBC or the like is practically non-existent. If the crank were already out of the engine, the farthest I would go might be some kind of coating on the crank to help what little residual oil there is slide off it's surface. Piston coating companies like Swain Tech & Polydyn offer services in that department.

          Dreamer - sounds like some solid plans on your NA build. 270hp . . . (at the flywheel) sounds like a good aggressive goal.

          As for the whipple setup, I'd love to see it done. But the amount of custom fabrication necessary is pretty intimidating. Would you attempt to incorporate any kind of intercooling?


          • #6
            An intercooler is certainly possible. The twin screw design is so efficient though that It may not be necessary at lower boost levels (in the 10 PSI range) but a fully built H22 can take a lot more pressure than that.

            I have done a fair ammount of research on this and there are a couple of companies/individuals who make 'universal' Laminova type interecoolers designed as a plate to be inserted between the supercharger outlet and the manifold. There is one in particular designed by a guy who is into old Volvos that would be perfect.
            It would basically form the interface between the supercharger and the bottom half of the Prelude intake manifold. I need to calculate what the entire height of the blower/intercooler package would be to see if it would fit in the space of the stock manifold.

            I spent some time this past weekend thinking about the drive shaft idea. I am certain that a bracket could be made that would mount to the head in the place where the PS pump normally resides. A six rib pulley could be mounted to the end of the shaft and use the same drive belt as the alternator. The alternator istelf could be used to tension the belt (which it is designed for)

            The other end of the shaft could be supported by an aluminum plate bolted to the transmission bell housing (like on the Vortech Civic kit) The shaft would have to extend out far enough to clear the distributor but that shouldn't be an issue. The big unknown at that end is how a tensioning idler pulley would work. I'll have to mock something up. Idler pulleys are available from Jackson Racing.

            My biggest concern is the blower bypass valve. It needs to be placed between the blower intet and and throttle body and has to connect to the manifold. There isn't a great deal of room to work with, particularly if I flip the blower orientation around from the usual Jackson Racing/Eaton design. I'm running into the old shock tower issue again. I need to find out if there is a stock casting for any of the domestic kits that might work.

            If not, I have information on a couple of alumining casting companies that do one-off prototype work based on customer supplied models (but they aint cheap
            BTW, the design of the intercooler sandwiched between the blower and the manifold could provide the perfect solution to the bypass valve problem.

            The more I think of this the more convinced I become that it is definitely possible. I spent a lot of time on the McMaster Carr webside last night looking at needle bearings, shafts, bronze bushings, aluminum bar stock, etc. It can be done.

            Unfortunately, while I am long on ideas I am always short on cash. Architects don't get paid jack S%!#. Its a source of endless frustration.