My L20B build, piston cam and other questions

Engine, Transmission and related drivetrain.
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obrut
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Joined: 15 Mar 2016 18:06
Location: Lemont, IL

My L20B build, piston cam and other questions

Post by obrut » 25 Jan 2018 18:11

So I now have a L20B short block with 85mm standard bore. I just measured the cylinders and they are in great shape and do not need to be bored, just hone.

I'm trying to find new L18 pistons that are 4cc dish and 85mm so I can raise the compression. I will be using the open chambered U60 cylinder head I have and this combo should give me 9.2.1 compression. I searched and could not find an answer on L18 pistons that are 4cc. Most places list L20B and L18 piston with the same part number. If I can't find the L18 pistons then I'll probably just use the stock L20B pistons.

I'm also looking at cams, can anyone make a recommendation for a L20B, U60 head, side draft dcoe 40 or 45s and eventually a nissan comp long tube header? The goal is a fun street car and autox with a few track days here and there. The only cams I have are the cam that came on the L18 with A87 head that I had and the stock L16 cam in the 210 head.

I plan on having the machine shop recondition the rods and balance the rotating assembly. I'm going to prep the block and assemble it myself. Should I swap the rod bolts to ARP before having the rods reconditioned or not needed on a street engine?

I'm looking at cleggengine.com rebuild kits and I'm also pricing individual parts from rockauto. Both sell ITM, I'm not familiar with this company, rockauto sells clevite and sealed power both of which I used before. Any recommendations?

This will not be a daily driver and I'm not worried about gas mileage, I will drive it as much as I can and I will always run 93. I will be running a dogleg 5 speed and I would like to eventually swap to a 4.44 diff with LSD.

Thanks
1972 4 door hopefully with a L20B and side drafts before to long

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abisel
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Joined: 29 May 2014 14:30
Location: St. Charles, Missouri

Re: My L20B build, piston cam and other questions

Post by abisel » 26 Jan 2018 05:53

A couple things I did to my L20B.

My U60 head dropped an intake valve seat so I got it repaired at a local speed shop http://stiegemeier.com/.
- Increased the size of the intake valve to 43mm, new SI valves (http://sivalves.com/flipbook/2016-SI-Catalog.html#p=40)
- Installed steel valve seats for both intake and exhaust (speed shop sourced the seats)
- Installed bronze valve guides (can get from ebay https://www.ebay.com/itm/Valve-Guides-I ... Sw~G1Z2XqZ),
- new stock valve springs and retainers, new rockers (Nissan parts from Nissan Parts Source)
- Decked the head for flatness which resulted in getting shims for the cam support towers. (got shims from ebay, but the zstore has them http://www.thezstore.com/page/TZS/PROD/10-1151)
- Machine shop ported the intake and exhaust runners to match the intake/exhaust gasket.
- Installed a Webcam 91 camshaft (http://www.webcamshafts.com/), new lash pads based on wipe pattern on rockers, new cam chain, chain guides, tensioner, etc.

My L20B block is stock with stock pistons and rods. If you get ARP rod bolts, you should have them assembled on the rods when you balance the rods. I replaced the stock head bolts with ARP studs and nuts. Recommend this. (http://arp-bolts.com/kits/ARPkit-detail ... ordID=1115). I used an ITM head gasket https://www.ebay.com/itm/Engine-Cylinde ... BG&vxp=mtr but first removed the silicon coating with lacquer thinner from the gasket and then applied a light coating of KM copper-coat spray to the head gasket during assembly. No leaks.

Then worked with the jetting in the dual Weber 40DCOE on a Cannon intake manifold. Back and forth with different jets and a test drive.
- go here: viewtopic.php?f=30&t=28635

All the above was with a stock exhaust header with a previous owner installed 2.5" exhaust system. I have on order a header from Ermish Racing and a 2.25" exhaust system. https://www.ermish-racing.com/exhaust-s ... rs-headers

I have no idea of the resulting horsepower of the above, but the car does get up and scoot with a 280Z 5-speed. I will be replacing the transmission with a close-ratio 280ZX 5-speed this spring. I plan to get it on the dyno at the speed shop that did the head work and find out just how much HP the L20B does produce.

Other things I plan:
- Ermish Stage-2 coil over kit in 280ZX spindles.
- poly and/or solid bushings for the differential mustaches bar and rear cross member
- adjustable camber/toe for the rear suspension (http://www.datsport.com/adustable-rearxmember-kit.html
- eventually will upgrade to Wilwood brake system with 15x6 Panasport in the front and 15x7 in the rear
- larger anti-sway bar for the front.

I hear that Clevite is a good source of crank/rod bearing for the Porsche 911, so they may be good for Datsun too.
For pistons, maybe ITM has the answer too.

Why the 4.44 diff?

obrut
Posts: 45
Joined: 15 Mar 2016 18:06
Location: Lemont, IL

Re: My L20B build, piston cam and other questions

Post by obrut » 26 Jan 2018 12:23

Thanks for the reply, I thought I would swap to a R180 4.44 and LSD all in one shot. The car came stock with the 3.90 and 4 speed and now with the 5 speed I think I can make the sacrifice for the improved mechanical advantage.

My U60 head looks to have steel seat already installed. I'm going to buy valves and have a valve job done. I don't see a 91 listed on webcams site are you using the 94a or 391 from webcams? Did they recommend stock springs or does it come with different springs?

I'll probably just buy ARP rod bolts, install and have the rods reconditioned and balanced.

Sounds like we have similar build plans, I would love to see dyno numbers but would really like to see and hear video ride along.
1972 4 door hopefully with a L20B and side drafts before to long

iceman510
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Joined: 27 Jul 2015 19:05
Location: Howell, MI

Re: My L20B build, piston cam and other questions

Post by iceman510 » 26 Jan 2018 12:30

Tim, it's not a huge expense, but I don't consider the ARP rod bolts all that necessary for your projected usage. The early L16 bolts were small, but the later including the L20B I believe are 9mm and were considered in the "How To" books as sufficient for most HP usage. Your choice of course.

Glad to hear the engine looks good inside.

I may have an L20B cam around if you are interested. I might be interested in your 3:90 diff when you are done with it.

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abisel
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Location: St. Charles, Missouri

Re: My L20B build, piston cam and other questions

Post by abisel » 26 Jan 2018 12:39

WebCam catalog, page 94, Dataun L-series near the bottom of the page.
.450/.450 260°/260° 238°/238° 91 15-000 15-001 15-002
Strong mid and upper end performance for street / strip. Requires Lash Caps.

I used stock valve springs from Nissan. Lash pads to get wipe pattern on rockers centered. Can't remember which lash pads I got.

Check your valve seats with a magnet. Unless you are sure they are already steel.

obrut
Posts: 45
Joined: 15 Mar 2016 18:06
Location: Lemont, IL

Re: My L20B build, piston cam and other questions

Post by obrut » 26 Jan 2018 14:59

The engine looks like its in good shape, I still need to pull the pump and check it but I did pull all the rod and one main caps and so far everything looks good. FYI the rod bearings looked worn but I didn't see anything that would have stopped it from running. I'll let you know on the diff, but thats way out in the future.

I did check the valve seats with a magnet and they are steel, even the guides look good but I may replace them anyway. The head has had some work done to it in the past.

Great post on your weber carb jetting, I'll definitely be reviewing that as soon as I get to that point. I am currently looking for carbs and an intake and I have a speedhut wideband that I'll be using for tuning.

I'm going to also run 2.25 exhaust but I'm going to make my own, I plan on just a turbo muffler.

I looked at webcams website not the catalog, I'll have to download it.
1972 4 door hopefully with a L20B and side drafts before to long

datzenmike
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Location: Van. Isle.

Re: My L20B build, piston cam and other questions

Post by datzenmike » 26 Jan 2018 19:08

As the L20B piston does not reach the top of the block anyway, why not mill 0.5mm off the deck? This removes 2.8cc from the combustion chamber.
Now mill the head 0.75mm for an additional 4.25cc removed.
Use cam tower shims to keep the chain tight.

This is 7cc or the same as running 4.36cc L18 pistons and gives you the same 9.27 compression.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

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Baz
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Location: Lonsdale South OZ

Re: My L20B build, piston cam and other questions

Post by Baz » 29 Jan 2018 02:51

Sorry guys , So busy these days I don't get much time for the forums these days.

All the engine we build these days L16 to L18 conversions & L20B we use T6 alloy flat top pistons.
Usually 86.5mm, I prefer to increase capacity & use flat top pistons to increase comp.

I never face cylinder heads to increase compression. If a head is thinner than 106.5mm I scrap it.
I also only use Nissan factory spec camshafts. the 70/72 is the biggest we recommend for street & occasional track days

For L20B engines the we use OSK jap timing chain kits and Kings competition bearings.
We never ever use cam shaft tower shims to correct loose chains. Saves time & effort sorting lash pads.
There are other ways to correct chain slack.

When the chain is fitted & set right there will be Zero extension of the tensioner.
This keeps the timing correct at high RPMs.

If we require over 11:1 comp we use an A87 peanut head. Or a W53
I have more to add on the valve seating & stem heights. This will have to be later on.

cheers for now & hope I get more free time to get back on the forum.

datzenmike
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Re: My L20B build, piston cam and other questions

Post by datzenmike » 30 Jan 2018 12:30

The original poster is using the old bore with a hone and new cast iron rings. Seems like a budget home made rebuild using stock parts. If L18 pistons are unavailable, then he will have to keep the L20B pistons. If all there is available is an open chamber head to work with then milling it and decking the block is the only way to increase the compression and it's cheap. Cam shims and a new chain will be close enough, after all, this isn't a high revving race engine. L20B cam is fine.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

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