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Thread: F54 L28 bottom end rev limit?

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    another classic car guy EricB's Avatar
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    Default F54 L28 bottom end rev limit?

    So I'm slowly building up a nice cylinder head with some good bits from Japan (Kameari Titanium retainers & 8000rpm safe valve springs) but when wondering about picking out a cam I got to thinking about the bottom end's rev limit.

    Mine is an 81 F54 which I had cleaned up (hot tank, hone, check for straightness, etc) a year ago and to which I fitted new bearings and rings. Having only the seen addition of a deeper and baffled sump & a higher flowing oil pump it is basically stock.

    I know the L28 revs less than the L24 but does anyone have a specific number I should keep in mind?

    For example if the bottom end can only handle say a max of 6500rpm it doesn't make much sense to pick out a cam that only comes on between 6000 and 8000 rpm. Know what I mean?

    So with that said? Anyone know what's safe on an F54 bottom end?

    -e

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    Send a PM to Phred this is his area . He builds Z engines
    I'd rather die while I am living than live while I am dieing. CZC 1887 IZCC 12602 Member of NorthWest Z Car Club

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    i would guess that the bottom end could rev to at least 8... are you planning on doing any work on the bottom end? (i.e. balancing, different pistons, etc.)
    Jason King
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    Quote Originally Posted by xray View Post
    As unfortunate as it may be, if you want to vintage race, go Euro....If you want to race for real, stick with the Z!

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    Jason,

    Can you tell us what you are basing that estimate on? Not trying to have a go, just want more information. I've heard stories of harmonics popping the ends of cranks (both ends) at 7500+ but thats not really pertinent to this conversation as I don't KNOW anything.

    Keen to learn.

    Dave
    Dave Andrews

    Daily: 1973 240Z, L28ET, Autronic, GT35R.
    Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild.

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    Registered User Phred's Avatar
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    Default Safe Rev Limit

    A safe rev limit is like safe sex, there's still plenty of risk involved. Its also a very open ended question. I'll try to explain the variables that effect and change rev limits. First, the part everyone is aware of, displacement/stroke. An L-24 has less mass and stroke than an L-28, so its physically easier to throw a smaller pist/rod/stroke back and forth. So generally it can handle higher revs before it flies apart. You can quickly see why lightweight components are important for high revs. Less weight means less stress on everything that goes around or up and down. Balance, the higher the revs the more important balance is. If you have a balanced crank, and an unbalanced rod/pist. assembly, it can literally rip the crank out of the main caps at high revs. (see pics for proof). Note: to help prevent this, main caps are reradiused, and shotpeened. Then attatched with an ARP stud kit. Balance moocho important. Ok, so its perfectly balanced. Everything needs oil to continue going around. All a deep sump does is ensure a larger supply to draw from. Volume, for continually suppling fresh lube to the bearings. Pressure, ( rule of thumb here) ten pounds for every thousand revs used when hot. Z cranks have another limiter. The supply of oil to the rod bearings. The Z crank delivers oil to the rod bearings through the main bearings. But its not an equal system. the center main feeds two rods, while the rear main dosen't feed any. It works ok to 7000rpm, but if you want extended high rpm, the crank must be cross drilled, and heat treated ( another subject). Yes, I know drag racers can turn 8000+ on a stock crank. But an entire season lasts about as long as one SCCA practice session. I know the difference, I have built L-cranks that can last a full season in a GT-2 9000rpm engine. Point being, high revs? how long? how often? and how long do you expect your engine to last? I could go on, but I think you're getting the idea. Other considerations, everything else in the engine that will allow it to turn higher revs effectively. In the mid eighty's I had a customer with two L-28 GT-2 engines. One had steel valves, retainers, and a cam which gave max power at 8200/8500rpm, depending on cam timing. The lowest rpm it would run at was about 4000rpm. It wouldn't rev any higher because there was too much weight in the valve train, and it would float the valves. So the other engine had Titainium valves and retainers, and a cam that was designed for higher revs. This one would rev reliably past 9000rpm with less valve spring pressure, and of coarse it made more HP, alittle over 300. But it also didn't want to run under 4500rpm. While on this subject, I have to say that Titainium retainers are a waste of money unless the engine will see very high revs. There's much more to consider than high revs. Budget, intended use, expected life, and the ability to transform all those high revs into usefull energy. Remember to look at the engine as a whole puzzle, not just one component.
    Phred
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    Biafra for President e_racer1999's Avatar
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    Quote Originally Posted by thehelix112
    Jason,

    Can you tell us what you are basing that estimate on? Not trying to have a go, just want more information. I've heard stories of harmonics popping the ends of cranks (both ends) at 7500+ but thats not really pertinent to this conversation as I don't KNOW anything.

    Keen to learn.

    Dave
    depending on the tune of the engine......

    there's really nothing i can say that phred hasn't already covered..... besides, he said more than i could've anyway!
    Jason King
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    1996 Infiniti I30 *I finally have all Nissans again!*
    1971 510 4door (wife's car)
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    Quote Originally Posted by xray View Post
    As unfortunate as it may be, if you want to vintage race, go Euro....If you want to race for real, stick with the Z!

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    another classic car guy EricB's Avatar
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    Thank you Phred

    -e

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    Crank harmonic balancer?

    Seen plenty of problems with the stock item literally falling apart, a lot of this may well be due to the age of the component concerned. But the ultimate solution seems to be to use a different type, Stewart Wilkins in Sydney for one supplies a special, based I believe on a BMW item.

    I'd assume that something similar would be available in the US.

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    ATI make a twin-dampener for the L28 too:
    http://www.atiperformanceproducts.co.../damnissan.htm

    And Chris Wood (of Speed Technologies Melbourne) makes a very similar unit, also based on a BMW I6 dampener.

    Phred, nice post, people like you are the reason internet forums work as well as they go. Much obliged. I'm going to get laughed at, and I'm sorry for hi-jacking the thread, but while we're on the topic of high revs, say I was interested in getting my L28 to spin to 9000-9500 safely, you are saying this would obviously require titanium retainers, valve springs approximately how stiff? This magical (expensive) engine would be running custom forged billet crank, rods and pistons, dry-sumped obviously. What are the limits of standard nissan main-caps with ARP studs in terms of torque, assuming a precision balanced setup? Have you ever experimented with girdles?

    I fully expect to be laughed off as an internet-dreamer, so feel free to ignore that in its entireity.

    Dave
    Dave Andrews

    Daily: 1973 240Z, L28ET, Autronic, GT35R.
    Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild.

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    Dave,
    You can't do what you don't dream of first. Your questions are valid, but you must understand that high rpm is NOT the goal, but the results of trying to build the most HP out of a regulated size of engine. Thats why F-1 engines rev so high. They are regulated to a certain displacement, and the only way to make more HP is to up the revs. While the opposite is now found in some drag racing classes. With no (or very high) displacement limits, they are using large displacement engines with relatively low rev limits. So the old saying "there's no replacement for displacement" has merit. First, make it as big as you can, then work on the details. In the attempt to build the most HP out of a L-6 engine, we first maximize the displacement. For SCCA roadracing, that is an L-28 bored +.040. Then we deal with the details such as the questions you ask. Knowing it would take 9000+ rpm to achieve Max HP, titainium valves, and retainers are mandatory. Consider, a Ti 1.425 in. exh. valve, weighs about 48 grams. A steel 1.383 in. exh. valve weighs about 75 grams. Thats a 35% weight savings! And its the most important kind of weight. The type that has to get pushed open against the valve spring pressure, stop, and get pulled back down with the valve spring. At 9000rpm, a valve/spring assembly ossilates 75 times per second!!! With that kind of weight savings, a Ti valve engine can use a lighter spring and rev higher than a steel valve engine with heavier springs. Lighter pressure springs also have other HP increasing properties. They create less heat, and produce less internal friction. This is known as mechanical efficiency, where developed HP gets to go out the back of the crank, rather than lost turning over an engine with stiffer valve springs. So, one of the tricks is to use the lowest spring pressure you can without valve float. The range for a full Ti valve L-28 engine (depending on max rpm) is from 100/120 lbs. on the seat, and 265/300 lbs. open. I have built steel main caps, but its a real job. I found that by re-radiusing the area whrere the bolt head spot face cuts into the main cap, then shotpeening, they would hold up to high revs without cracking. The ARP studs are best for clamping the main caps on. Their specs are 60lbs. with ARP moly lube. I never built a girdle simply because of the work involved. But I have installed, and used them on other types of engines.
    Dream on, I do. It doesn't cost anything.
    Phred
    Last edited by Phred; 06-05-2005 at 08:53 PM.

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    Phred,

    I do understand that revs aren't the goal, horsepower is, not even that, torque is the goal. However in order to get the torque I want with a usable power-band I fear the engine will be required to spin to 9000. If i can get what I require from less than so be it. Good advice re valve spring pressure, all these little things that I haven't even considered yet. On a related note, how does one determine if they are getting valve float? Or is it extremely obvious once the engine is running?

    Light-weight valve-train sounds like a must. On Ti though, I have heard/read that Ti has limited life cycles unlike steel? Ie, it will fail after a given number of cycles?

    WRT displacement, I understand that the concept behind `there is no replacement for displacement' I believe, however, I have to weigh up the benefits of reducing cylinder wall thickness (reduced block rigidity and strength), increasing the likelihood of piston-jamming, and undoubtedly a host of other things I haven't considered when the HP increase could be made up with another few hundred RPM and/or few PSI of boost. That being said, interesting that you only mentioned 0.040 overbore? Taking bore to 87mm I believe. What are your views on the guys running 0.120 overbore on L31 engines etc? I'm not seriously considering it, more fishing for your comments on block strength?

    Also while I'm dreaming and picking your brains, on SCCA engines (which I'm assuming you have worked on judging by your comments) did you have any issues with blowing head gaskets between #5 and #6? If so, what was the solution? A fellow here in Melbourne (RPMZ) has had his head drilled and uses an external water manifold to ensure correct coolant supply (I think?).

    Also, what was the HP achieved from the SCCA turbo L28s? Around the 600hp mark as noted in various books?

    Kindest Regards,

    Dave
    Dave Andrews

    Daily: 1973 240Z, L28ET, Autronic, GT35R.
    Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild.

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    Registered User Phred's Avatar
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    Default Detail$

    Dave,
    Ti valves do require special care. But they do not reach a cycle life, and die. They degrade because of the less-than-perfect conditions their subjected to. A steel valve can survive those same conditions simply because the steel alloy is more durable. A pure Ti valve needs a slightly wider seat width than steel, or it will wear abnormally. They also need a nice, straight, honed valve guide bore, or stem wear will result. And, the tips will fail quicker than steel when subjected to valve float. In the past, a hardend lash cap had to be used on the end of the stem, but now most companys offering Ti vaves have a hardend tip manufactured into the stem. There are a couple of high tech companys now offering special treatments that will extend the life of Ti valves. One buzz word used to describe these finishes, is "Diamond Like Coating" or DLC, Very trick stuff. Do a web search for "Casidium". or "Black Diamond" high performance coatings. As far as trying to find the limit where valve float occures, that has been described as being the same as cleaning your gun without unloading. Formula V, Formula Ford, and Sports 2000, are what I call non-leathal engines. They have single springs, and can RPM exceed the springs capability to follow the cam. It can be seen and heard on the dyno. An experienced "ear" can detect it on the track. There are usually no devestating effects, because they use stock cams which have very mild ramps leading onto and off the lobe. When radical lobe profiles are used its much harder for the spring to control the valve. Thats why you need stiffer springs. That's also why some cam manufactures have gone to a asymmetrical lobe profile. The on-ramp is nearly flat, and hammers the valve open. Then, the off-ramp is gradual to allow the valve/spring to follow the lobe closed, and not "float" down. If this float is allowed to continue, such as in a massive over-rev, The valve will bounce on the seat, just when the cam wants to open it again. The spring ossilates, gets confused, and all mayhem can result. I have seen (post mortum) Valve locks spit out, Broken springs, spring seats, valve locks sucked through the retainer, rocker arms broken, or dislodged, and of coarse the final insult, valve hits piston. When engine building reaches this level, its very easy for the "do it yourself builder", to get into very expensive trouble. I think I've use up my space and energy on just one of your questions. I'll try to answer the others tomorrow.
    Phred

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    Phred,

    Awesome. I appreciate the posts/time. There is no way I would contemplate building my planned engine myself. I think I could rebuild an L (I never have), but I don't have the experience/tools to do it to this level. I have no questions (thank god I hear you say?) about your post, all makes perfect sense to me. Looking forward to more of your posts.

    Dave
    Dave Andrews

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    Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild.

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    Default Block Stability

    Dave,
    I have a fair amount of experience with boring and honing performance L-engines, so I'll pass along my thoughts. They may be diffrerent than other peoples ideas, but that's what makes the world go round.
    With respect to L-28's, the F-54 is the only one to start with if you have a lot of cyl. pressure in mind. Before the F-54, about .060 was all the block could handle. I remember trying to go further, sometimes you could. But block/core shift causes the cly. wall thickness to to be inconsistant. You might end up with a nice thick wall on one side, and a very thin wall on the other side. No good. Finally, technical advances caught up with the need. Now, small portable ultra sonic testers have taken the guess work out of block/core shift. These testers have a small probe that you slide around the inside of the bore, and it reads the exact wall thickness on a digital readout. If you find a good block, yes you can bore well past .040. Lots of people have bored to over 3 liters with sucsess. Most of these are street racers. But, the more you bore the less strength the cyl. has to fight the pressure in a highly stressed engine. An engine which is designed to produce the max HP possible, must have a stabile bore. Even if a smaller bore is needed to assure this. The main reason you must have a ridged, straight bore, is ring seal. If the bore distorts in service, The rings will not be able seal all that mixture and compress it into that wonderfull explosion. So #1 is a straight, round, ridged bore. For optimum ring seal, I strive for a finished bore that is .0003 tighter at the top of the bore. Which with the extra heat produced at the top, expands more than the lower part of the bore, and ends up straight when hot. Also it must be within .0003 (three ten thousanths) of being round. A round ring can't seal against an out of round bore. Also a Torque plate, or deck plate is required when honing. It is torqued to the same value, and ideally with the same fasteners as will be used on the completed engine. This will distort the bore right where it counts, at the top of the ring travel. Also the main caps must be torqued similarly. Then final honed. For years, I even honed Coswoth formula atlantic, formula ford and Sports 2000 with the block pre-heated, with hot water circulating within the block, to simulate the exact distorsion conditions the bore would be under. It makes a difference if you're looking for that last little bit of power.
    More later.
    Phred

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    Phred do you have much experience with lightening rockers? I ask because we are looking to save some weight by drilling out some weight in the rocker arms and then getting them all balanced. I was just curious if you had any thoughts or comments on this process?

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    another classic car guy EricB's Avatar
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    Phred

    I've got to admit I am pretty impressed with the level of detail you're going into.
    I forget did you say you were retired from the SCCA scene or do you still build these motors on a regular basis?

    -e

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    Registered User MikeW's Avatar
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    Quote Originally Posted by Phred
    Thats why F-1 engines rev so high. They are regulated to a certain displacement, and the only way to make more HP is to up the revs.
    Speaking for F1 engines and high RPMs, here's a really cool video. Note how responsive the engine is:

    http://www.smele.com/video/
    -Mike
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    Gavin, I'm no expert but drilling the rockers to loose valve train mass sounds like premature failure to me! I understand that some engine builders will smooth, polish and balance the rockers....but drilling holes in a high stressed member seem questionable. Phred will likely add to this, based on his experience.

    P.S. If you paint the rockers RED, it will improve your HP 50%!!!

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    Quote Originally Posted by Phred
    Dave,
    You can't do what you don't dream of first. Your questions are valid, but you must understand that high rpm is NOT the goal, but the results of trying to build the most HP out of a regulated size of engine. Thats why F-1 engines rev so high.
    I'll just jump in here with a counterpoint. Although I have never read or heard this view, from my own experience, I suspect that high RPM's may actually be part of the car control puzzle.

    Have you ever notice that it is much easier to drive at the limit in corners in a lower gear at high RPM's than a higher gear at low RPM's? I have.
    --John B
    '73 FP 240Z

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    gramercyjam: Wouldn't that simply be because you have more power 'on tap' so to speak, in the higher gear, than in the lower gear? If you had an engine with double the capacity, making the same power at half the revs (everything else being equal) it'd behave much the same around the corner at that lower rev point.
    RS30-000756

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    Biafra for President e_racer1999's Avatar
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    ^^that sounds right
    Jason King
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    Quote Originally Posted by xray View Post
    As unfortunate as it may be, if you want to vintage race, go Euro....If you want to race for real, stick with the Z!

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    Quote Originally Posted by Datto-Zed
    gramercyjam: Wouldn't that simply be because you have more power 'on tap' so to speak, in the higher gear, than in the lower gear? If you had an engine with double the capacity, making the same power at half the revs (everything else being equal) it'd behave much the same around the corner at that lower rev point.
    Thats not what I'm talking about. I'm talking about control of power. This is due to gear ratios. input RPM/output RPM. fine thread VS coarse thread. 100:1 VS 1:1.
    --John B
    '73 FP 240Z

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    ?

    Wouldn't it be the same thing really? At higher revs you have more power at WOT and more engine braking off the throttle = better control over the cars attitude with the right foot? Also, a smaller change in throttle position will have a larger change in power output than at lower revs = better responsivness. Is that what you mean?
    RS30-000756

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    Exactly the opposite. Larger change in throttle is a smaller change at the rear tires. Less responsive. It's real easy to mash down the pedal. Resonsivleness is something amatuers worry about. That is _easy_ to achieve. The key is control. How closely can you walk the line between a crash and a win?
    --John B
    '73 FP 240Z

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    Seems to me you can have both response and control depending on your definitions. Reponsiveness to me is a measure of the time between an input and a response from the engine/car, while control is a measure of how well/finitely you can adjust something.

    It would appear hard to have control without response however as good response means you are less likely to overshoot an input adjustment.

    But anyway John, WRT to your point, perhaps you are implying that at higher rpms the air is moving much faster and hence the response is that much faster simply because everything is happening faster? Better response leading to better control.

    I think control can be achieved at any RPM given adequate response and throttle travel. Given the choice between a slightly more difficult to control engine and one which requires rebuilding twice as often, I know which I'll be going with.

    Dave
    Dave Andrews

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    Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild.

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    Quote Originally Posted by 240ZX
    Gavin, I'm no expert but drilling the rockers to loose valve train mass sounds like premature failure to me! I understand that some engine builders will smooth, polish and balance the rockers....but drilling holes in a high stressed member seem questionable. Phred will likely add to this, based on his experience.

    P.S. If you paint the rockers RED, it will improve your HP 50%!!!
    I havd had a bit of experience in 'lightening' Datsun rockers. I think there are some pics in the Datsun "How to Hot Rod..." book. You want the weight as light as possible without creating a weak link. Stress relieving the rockers by lightening, polishing and shot peening is the way to go. I have never heard of anyone 'drilling' a rocker arm assembly. Sounds like creating a weak point to me!
    Z Saint, the vintage racer! I've traveled a long way and some of the roads weren't paved.

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    Gawd... I remember when Phred was just learning about L6 engines. I built the first torque plate for the L6 in 1977 and it is still at Hatch's Engine Service!! He built a couple for me and they were pretty good. We had a limit of 7600-7800 in those days because of the harmonics in the L28 crankshaft. The large diameter dampner was the answer. Prior to Datsun Comp providing that baby, 7200 was the max before the flywheel fell off! Ol' Phred has learned a lot over the years, yes he has!! I think I paid for most of his education, however!
    Z Saint, the vintage racer! I've traveled a long way and some of the roads weren't paved.

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    Read my first post. It did not go through the first time, at first!
    Last edited by ZSaint; 06-08-2005 at 09:28 PM. Reason: double post
    Z Saint, the vintage racer! I've traveled a long way and some of the roads weren't paved.

  29. #29
    Registered User Phred's Avatar
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    Eric,
    Unfortunately, I'm a long way from retired, just tired. Yes, I still build SCCA engines. So far this year, a T-2 350Z, GT-4 L-16, and an odd rally Z-22 w/L-18 head. Also a Baja 1000 302 Ford, a couple of Gaerte Midget engines, and a full 360 V-8 Gaerte sprint engine. For about eight years I did Cosworth, F-F, & S-2000. Now, its nice to have lots of different things to do.
    Gav240Z,
    I'm with ZSaint, polish and shot peen, (not the contact pad) Lightening the pivot end is a waist of time, concentrate on the valve end. No drilling. I will also be trying one of the new hi-tech cam/rocker coatings on my own 3 liter later this year. So I won't know how, or if, it effects the L-engines for a while.
    Phred

  30. #30
    somewhat twisted thehelix112's Avatar
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    Hey Phred,

    I realise you're a busy man and probably sick of this but I still have some questions.

    Do you have any issues with blowing head gaskets between #5 and #6? If so, what was the solution? A fellow here in Melbourne (RPMZ) has had his head drilled and uses an external water manifold to ensure correct coolant supply (I think?).

    Also, what was the HP achieved from the SCCA turbo L28s and at what rpm/boost? Around the 600hp mark as noted in various books?

    Many thanks,

    Dave
    Dave Andrews

    Daily: 1973 240Z, L28ET, Autronic, GT35R.
    Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild.

  31. #31
    Registered User Phred's Avatar
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    Hi Dave,
    There is no more of a risk of blowing a gasket between 5&6 than there is in any other cyl. Just make sure the basics are covered. Perfectly flat deck surfaces, and quality fasteners, properly installed. As far as external water lines, it should not be nessesary. At least we havn't found it is needed on NA 300hp L-6's. Having said that, I have seen other engines that were modified in this way to help coolant flow around the back cylinders of hot engines. Many USAC midget engines have external lines to ensure an even distribution of coolant. These engines run over 15:1 compression on alcohol. Bottom line, if you think you have a problem with uneven cooling, modifications may be in order. Also, Redline has a product called "water wetter", which really works. It allows the water to flow easily around tight restricted areas inside the engine, eliminating air pockets, and thereby reducing coolant temp.
    The most common way of sealing high compression/turbo/supercharged head gaskets is "o" ringing. It is most effective when used with a solid copper gasket, but can be used with standard gaskets if the wire is located properly. The "o" ring in this case is a .041 stainless wire. A .028/.030 deep groove is cut in the block around the cylinder bore. Then the wire is installed, which protrudes about .012. This protruding wire creates a sealing groove in the fire ring of the head gasket. (the metal edge of the head gasket around the cyl. bore,) When used with a solid copper gasket, a reciever groove must be cut in the head where the wire will push the displaced gasket into. This creates a stepped edge seal, and will hold mega pressure. For instance, this method is used to seal many blown alcolhol drag race engines. I use this this method on L-6, and L-4, high compression road race engines (around 13.8:1) as well as other types.
    I don't know how much HP the old L-28 turbo engines put out, but 600 sounds reasonable. I was involved in the development of a twin turbo 302 chev for road racing in the early eighties, and it was easy to make 850 HP. The killer was heat. controling both the compressed air temp, and the EGT were the keys to sucsess. Enough for now.
    Phred

  32. #32
    somewhat twisted thehelix112's Avatar
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    Phred,

    Thanks mate. The engine runs with redline water wetter as is, and race 40w oil and will definitely be o-ringed when it comes apart.

    Thanks for all your help, will keep you informed of how things go.

    Dave
    Dave Andrews

    Daily: 1973 240Z, L28ET, Autronic, GT35R.
    Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild.

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