Xnke
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Posts posted by Xnke
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I would seriously reconsider Top End Performance, myself.
I've had dealings in both Datsun parts and Mitsubishi parts with him...neither went well or smoothly, nor did I get what I paid for.
That's all I've got to say on that front.
Anyway, I'd really reconsider on the +1 valve sizes...they're just not needed in 99% of applications and can actually HURT performance in some cases.
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One of the few things you can read from the Honsowetz book without having to glean from a photo...talking about how Devondorf was running stock rods and switched to the "currently unavailable" sports option rods to save prep time. Backed up in the other publication that was recently posted here, as well. Heck, there are L24e small-journal rods being flung around on offset ground LD cranks pushing 8000RPM out there too. (One of them is local to me, and while we've not convinced him to dyno it and see where he's at, 12.4@111mph is good enough for me.) Stock prepped rods are perfectly fine for 99% of applications with this engine.
I have been caught drooling over the investment cast alloy rods from Merchart...568 grams...138mm...NCA...
I was looking into the long rod/short piston configurations, and it just doesn't seem like good money spent when you get the pin height that short.
I'd get your headwork done, find out where your head will take you (220cfm intake flow at 28" *can* net you 300FWHP) then decide on the rest of your configuration.
(I know what you mean about the 2.5" exhaust Tony, I'm slowly aquiring parts to replace mine!)
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Problem is if you get any fuel/air/N20 mix recirculated through the turbo, THEN get a backfire....Bye-Bye compressor housing!
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I think you could do well to step back and take a look at what you've got, what you want, and what you really want to spend. You've got big plans and will need an enormous wallet to do what you're talking about unless you're doing a lot of the work yourself. And I don't mean assembly...I mean rod prep, head prep, engine assembly, carb work, exhaust, "a lot of the work".
First off, 46/38 valves are HUGE, and in my opinion have no place on a street L28 unless you're running 89 or 90mm bore diameter. I'd go so far as to say that with a proper valve job and really good valve unshrouding, 45/37 is big enough even for full-race applications. I was able to obtain flow numbers good enough for a 300HP 2.8L N/A engine with the stock valve sizes, and any good L-series head-porter can do as well or better. Not all cylinder head castings are going to accept the big valves without undue stress...a little core shift one way or the other and you can run out of room for the exhaust valve. Talk to your cylinder head guy and get his opinions, get him to prep the chamber side first and make sure you can fit the big valves and not be shrouding them. A big shrouded valve is not going to flow as good as a stock size valve with good valve unshrouding done.
Second; you're planning for forged pistons and rods. Stock rods are forged, and are plenty strong enough...Don Devondorf ran prepped stock rods in his turbo L28 at 1000HP levels, switching to the Nissan sports option rods to save time and get the floating pin options with less work. Aftermarket forged rods aren't needed even for moderate race engines, good prepped stockers are just fine.
How much time are you planning to spend at 7000RPM+? If the answer is none...skip the forged pistons, good cast replacements are fine for any street engine that isn't exceeding the limits of the piston skirt/wrist pin section strength. A quality cast piston will hold up at 7000RPM, but if you are going to spin it, run with a forged piston. Any sustained engine operation above 7000RPM would benefit from forgings, but on a street car you'll need to balance that against the warm-up characteristics of forgings. Your comment about a long rod/short piston being better in any engine isn't really fully thought out...the shorter the piston, the shorter the life of the piston and the block bore. Going from a 130mm rod to a 140mm rod isn't going to mean much of anything in an engine that isn't living at 8000RPM for half it's life, and will be quite a lot of effort for little return in an engine that is street driven.
Stock crankshaft is forged. It can be lightened and balanced, high-speed balanced, ludicrous-speed balanced, to your heart's content. Knife-edging of the counterweights will save a little power above 7000RPM; but under that it's unclear if it makes a difference. Offset grinding of the crankshaft will change your rod length and compression height on your pistons...Make sure if you go that route that you are prepared for what will come.
If I was building a hot street N/A L28, then a stock stroke crank, lightened and balanced, with a lightweight steel flywheel that was balanced to the crank, doweled to the crank, and a quality damper up front would complete the crank work. Prepped and shot-peened stock rods would be next, with 9mm ARP rod bolts. Cast 87mm flat-top pistons would be acceptable for an F54 block, or 88mm flat-top forgings (can't find a casting I like available in that bore size yet) would be good for an N42 engine block. Quality rings and bearings, KA24E truck oil pump, and cleaning up of the front timing cover casting for ridges and flaws in the passages would complete the bulk of the bottom end work.
Cylinder head would be a P90 or P79 casting, skimmed a little to set the compression ratio after the chamber work to between 9 and 10 to 1. Camshaft selection would be determined by both the final port flow numbers and the compression ratio, bottom end being a 0.480" lift, 230*@0.050" profile on a 108 lobe center, up to a 0.530" lift, 270*@0.050" profile cut on a 106 lobe center. It would depend on how the ports flowed...if I need more lift to get the flow I want, bigger cam profile...if I can get it with less lift, well, that's less work to do with springs, valves, and valve seals. Bigger cams will want more RPM to make more power.
What size are your carbs? DCOE's are great...but if they're 40mm throttles, you'll be limited to around 7000RPM. 45's would make more power, and more RPM. Spend the time and money for good carb tuning, and run an air filter.
Ignition system...if you're running at 7000RPM and under, the dizzy is ok. I'd go with a crank-triggered system personally, but it isn't really needed till your engine is living between 5000 and 8000RPM, and even then some people get along fine with the distributor.
You will want a 3" exhaust with a good header. Primary size, 38mm is good up to 250-275HP, 42mm for anything higher. Secondary size 2.5". Set the throat diameter of your final merge at about 2.25", then cone up to 3" and out the back.
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It does matter, and they are not easy nor cheap to find right now.
Call SI valve, Ferrea, or find a machinist who can shorten up valve stems.
E31, E88, N42, N47 heads all take valves that are 2mm longer than P79 and P90 valves.
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Most of your suspension hardware would have to change. Look at your strut tube diameter, length, and gland nut fittings, your suspension height, and then look at your wallet.
Anything can change if you've got the cash.
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I'd say you could pull some timing around 3000RPM, add a little more fuel, and it will change for the better.
Bet 30PSI felt GREAT till it quit...
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Rod bearings fail for two reasons, both of them oil-film related. RPM's cause the suface speed of the bearing to shear the oil film, and high specific impulse on the rods causes the rod to literally push the oil film aside and make contact. The latter isn't such an issue on the VG because the oil pressure is higher, most L's are only pushing 20-25PSI at 2000RPM. This latter effect is how detonation kills rod bearings.
I assumed you were turning a turbo L28, my bad. 2000RPM is definitely in the lugging range there; even though most don't consider it so.
So, the worst of the problem is right about the time you get into "full" boost? Does it correlate with temperature at all, on a cold day is it worse than a hot day, IAT's, ect?
If you run a smaller gap, say your 0.035" instead of 0.044", does it get better or stay the same? Are you running projected tip spark plugs? They are harder to foul in my experience; but they are essentially the same as adding in 4* of timing. I am waiting on a set of non-projected tip plugs to try in my car under boost. (BPR6ES is a projected tip NGK, BR6ES would be non-projected NGK)
Maybe pull a little timing right around 3000RPM; does peak torque occur near that range? Might be pre-ignition more than spark blowout; even if you're not getting any detonation. If you're hitting full boost right near the torque peak you could need some more fuel and less timing in that area. You can get a good idea of your torque peak by looking at your fuel maps; generally maximum fuel consumption lines up with peak torque.
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Any throttle spacer for the stock manifold/throttle body, the KA24DE manifold/throttle body, or the Weber throttle body could work. It's not like it's a difficult part to make, nor would it be expensive to have machined. Check the bottom side of your throttle body for an unused port/boss and see what you can find. Looks like there is some material there to work with.
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Set your valve lash.
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So you're not used to the normal stuff that occurs when really lugging the engine hard?
That's the individual firing pulses smashing your rod bearings to bits when you load the cylinders with lots of fuel and lots of air and the oil pump is just barely keeping oil on the journals. It's a really excellent way to ruin your rod bearings.
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If you apply the Maximum Boost principles, then yes, a stock cam is fine.
There are plenty of things to do before you change the cam; and if you plan to run more than 10lbs of stock turbo boost you really need to think about engine management before cams/boost/turbo/etc.
In the state you live in, you will most likely run into a LOT of problems trying to drive with an open pipe. I'd venture a guess that you'd get a ticket within a month of driving an open pipe; out here in semi-rural Kentucky as long as you aren't bothering someone else they'll leave you alone.
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An open downpipe on a stockish L28ET with a stock cam and turbo isn't godawful. It is pretty damn loud, though.
Add a moderate cam and it's HELLISHLY loud...Just ask RedZedTurbo here.
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Might have skipped off a valve stem seal; Cylinder 4 is oiling up a plug but has perfect compression. Causing a misfire, but running that plug in #5 cleans it up in 50-60 miles. In that same 50-60 miles, it'll oil-foul the plug I replace it with...black, oily, but not sooty.
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I would be looking at the oil pump as the main culprit for spinning that gear...takes a lot more to turn that pump than it does the dizzy, under normal conditions
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Then get a stock crank and measure it out!
Crank design is less intuitive than it appears at first glance...but if you're only giving the specs, then it *is* as easy as it sounds.
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Measure from the spring seat to the spring retainer with a spring height caliper
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They're normally pretty audible.
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He's got spring height goofed with lash pad thickness.
1.75" installed height = 110lbs seat pressure.
1.70" installed height = 125lbs seat pressure.
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Remember there are TWO oiling holes for the head. One near the front of the block, and one near the middle of the block. They don't need to be opened up much unless you're running molasses for motor oil. I have PLENTY of oil flow at idle, 18psi oil pressure, using both a drilled cam and a spraybar.
I also turn my engine 7000-7200 multiple times every time it's out, usually every stoplight if I get the chance....
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Yeah, your spraybar is totally broken. I run both the spraybar, and the drilled cam, and right now both the restrictors in my block have only been opened up 0.010" diameter over stock. I have oil streaming out of my spraybar at idle, at 15PSI of oil pressure.
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Ment to say plumbing supply...especially near a brewery
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Try your local electrical supply house for a sweep 90.
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Check for a sticking valve. That will chuck rockers every time.
All I can say about running tall lash pads in stock retainers is that it is only a matter of time and revs. I did it for two years before I lost the first one.
building a hot street car
in Nissan L6 Forum
Posted
Bryan Blake would be my first choice, since he's local and has extracted very good power from the L, both N/A and boosted. I would call Slover's Porting Service and see if I could convince them to do an L-head, Or call Dave Rebello...his port work is quite reasonably priced for the return. (Quite!)