horsepower L20b

[sdsurf]

What is a good set up, crank to carb, for an L20b. I am looking at full rebuild - carb, header, cam, etc

[banzai510(hainz)]

save about 1500$

then well talk.

 

the fastes bolt on improvement is the install of a 38DGES Weber.Simple carb

 

The twin SU carbs might be the same but most I have seen are old junk.

if I heard a running pair on a rig I might pay 150$.

[sdsurf]

save about 1500$

then well talk.

 

QUOTE]

 

Ok That I can do... Then we'll talk

[e_racer1999]

i'm planning a bore to 87mm for flattop 280Z pistons, twin SUs, P&P closed chamber head. not TOO familiar w/ 4cyl l-series specs, but my Z set up ought to have close to a 12:1 CR, so driveability won't be optimal. maybe some dished pistons w/ an open chambered head?

 

oh yeah, add to that a .500 lift .300 duration ground stock cam (for durability), resurfaced rockers, schnieder springs and Ti retainers, big valves, Ford viton seals, nice tubular header (maybe 1 1/4" primaries?), to a 2.5" exhaust.

[datzenmike]

For an L20B with 0.040" oversize flattop Z pistons I get:

 

With open chamber head... 10.27 c/r.

With Pnut chamber head... 11.03 c/r.

 

As a rule of thumb, for every 10 degrees of cam duration the peak power point rises by about 500 RPMs. A 300 degree cam is over 50 degrees more than stock. This places peak power in the 8,000 RPM Range. Twin SUs may be a little light for this. Bottom end drive ability will be marginal at best. With the right rear gear and tranny ratios, fine for racing, forget the street.

[ssfwgn]

My brother's L20b got 148 hp at the wheels. He went with .040 over flat tops U67 head with larger ports, ferrera valves. I forgot what cam but its in the 480-500 lift range. It also had 44mm mikunis. He first built this motor over ten years ago, so I really wouldnt know how much all that would run now.

[makya]

we have a sticky for this, with all the Jason Grey info.

[banzai510(hainz)]

L20b got 148 hp at the wheels????

You sure???????

Thats very impressive. I talked to a guy who had a a Rebello motor and had only 142 to the wheels

was a LZ22 hybrid. with crank fire ignition and coil packs with Fuel Injection.

 

Like to know the cam and ignition setup?

 

 

eracer,

87mm needs a bigger head gasket on a L20block as the standard ones will hit into the bore ,NIsmo Gasket if still avail ????????

 

I have HEARD alot of headgasket proplems using flattops in L20s(280zx non turbo). Where you get these pistons from? I have NEVER actually seen somebody purchase a set before.

 

Detonation proplem unless ruunning really good gas.

I believe datsunfreak on here has L18 piston with a open chamber head and runs 94 in Texas and has detonation issues. Better ck that out. If a race car then it doesnt matter and Ill shut up.

 

let us know

[Bleach]

Hainz, the 148hp engine says overbored flat tops in an L20b. Probably 11:1 compression using race gas. ;)

that might have something to do with it. 148hp is impressive. What rpm did he take it to in order to run those numbers? 7K??

[Jason]

Personally, I think that the 38mm SU's wouldn't be able to support the AFM at 6500rpm or above on a larger displacement performance engine, even with re jetting. You;d need a modified set of Roadster or 240Z SU's to do this with. In this case you might be better off looking for Webers or Mikuni's to optimize the high end....

[ssfwgn]

the dyno said 148hp, when we put this motor back together we had alot of timing and fuel issues. the first time the motor blew was because it starved out blew holes in two of the pistons. We fixed the fuel problem with 3/8 fuel line and a holley blue pump.

Its running a standard black box distributor. we recurved the timing, I don't know what the advance curve is it was all trial and error.

we used a felpro head gasket. I dont think we had problems with it hitting.

 

we did have detonation problems, that car wasnt really a daily driver so we ran a 91 110 or 112 mix.

 

The head had alot of port work done to it. I dont know much about the cam, he has them reground by a friend. That L20 out produce my LZ23.

 

[datzenmike]

Something is wac here. 148 hp at the engine would be difficult to swallow. Doing it at 5,900 RPMs at the rear wheels!!!!... choke. Dyno must be reading the RPMs wrong, should be 1,500 RPMs higher maybe? Maybe the graph paper is numbered wrong, should be 1,000 RPM per division?

[ssfwgn]

you can usually run the scale how ever you want on dynos. The car wouldn't go any higher cause it would still starve for fuel. I dont no maybe it is off. I drove the car and the car just has a weird power band. It dosn't have any bottom it has alot of top end though. We dynod it two different places, other than the improvments from tunning the power curve is real similar. I going off what the dyno sheet said, people tell me you cant trust those number, maybe there right.

[datzenmike]

Dynos measure torque not hp. If you know the torque and at what RPM you can calculate the hp. Hp is torque X RPM divided by 5252. Notice that at 5,252rpms the lines cross? They always will, if a dyno sheet says otherwise it's wrong. A flat torque curve indicates that the hp is doubling with every doubling of the RPMs.

[banzai510(hainz)]

SSFWGN

 

well I have a rebuilt L20 in my garage with new pistons and its just a .5mm(.020) overbore and it almost hitting the gasket(Nissan or Felpro),right on the edge. I had ordered some 87 mm gaskets from Baz at Datsport. these go up to 87mm for sure as the Nismo 87mm are all GONE.

 

YOu said you have 87mm pistons in there. I guess I have to believe you.

But I have caught alot of people lying to me and bust that head open and find out there dished pistons in there.

Unless you did this yourself I dont believe alot of people Esp if the previous owner said he did it before he sells it to you.

 

148hp is impressive and you have a Dyno chart to show it which is good so the next guy who comes along and says he has a L16 with 200hp natural asp .I can really say hes full of it.

I remember Dave Carol showing me a nasty L18 with SUs saying it had 180 HP.

I was LIKE WHAT???????

 

 

But remember what gear is this dyno pull and the rear diff ratio?

 

Byron 510 had a LZ22 hybrid/sidedrafts and said he got 133/138RWhp out of his motor. But he said he has a 4.44 rear diff so this cheats the sytem a little.I believe 3rd gear is a dyno pull? Correct me if Im wrong.

 

I believe your Dyno pull as you documented it. Iam leary of the head gasket bore size as Felpro on sell one head gasket and just on a stock bore L18/20 its near the bore and could cause proplems.

 

148hp out of a L20b is so impressive that there is no need to do LZ hybrids as the L20 is counter balance better the then Napz 22.

So all Jeffs spare L20 blocks are now worth 100$ apc instead of becomming one with the earth

 

I would like to know who built this Motor/cam specs/head work as they could put REBELLO out of Bussiness(with just a recurved matchbox ignition).

I could only dream of having 148RWHP out of a L motor.

[nismopu]

i'm planning a bore to 87mm for flattop 280Z pistons, twin SUs, P&P closed chamber head. not TOO familiar w/ 4cyl l-series specs, but my Z set up ought to have close to a 12:1 CR, so driveability won't be optimal. maybe some dished pistons w/ an open chambered head?

 

oh yeah, add to that a .500 lift .300 duration ground stock cam (for durability), resurfaced rockers, schnieder springs and Ti retainers, big valves, Ford viton seals, nice tubular header (maybe 1 1/4" primaries?), to a 2.5" exhaust.

 

the 87mm flat tops arent just specific to the l28, they came in the n/a vg's as well. peace.

[datsunaholic]

Except that L28s are 86mm, not 87.

 

Also, VG30 pistons have a far different pin height than an L-series piston. All L-series pistons have a 38.1mm pin height (center of pin to top of piston) and VG30 are 31.75mm. So you'd end up with a 6.80mm understroke (L20Bs are 0.45mm understroke stock)... not good, you'd end up with something like 5:1 compression. Plus the pin diameter is different (not a big issue). The pin height problem can be fixed if you use a VG30 piston with a Z20E rod (which is 6.6mm longer), and bushings to equalize the pin size.

[banzai510(hainz)]

Datsunaholic they do list 87mm flattops in my Nismo book.

as for VG pistons I do not know.

 

nismopu,

He hypethetically wants a 500 lift 300 degree cam. Yeah by which maker??Lobe center#? reground. Why not new? Or reground is chosen to get cam in the cam towers?

I would like to know. So this is all suspect.

 

sswgn.

clames and has documented 148 HP at the wheel.for a L20.

I would like to know this combonation if possible or just some of it as I am truely impressed.

 

read this DYNO ratings of L motors Tech Dept then find DYNO

http://www.datsuns.com/Index.htm

[ssfwgn]

heres a couple of pictures of the piston and rod. pistons are 86mm .040 is 1mm overbore stock L20b pistons are 85mm. the motor is disasembled right now it needs to be line honed. If I was to go .080 over like the next motor I would just run NapZ22 head gasket. I run a NapZ24 gasket on my lz23.

 

 

 

I think you can do a pull in what ever gear you want as long as the rpm on the car and the computer match up. The car has bad gears its a truck short tail trans and a R180 out of a 240 (3.30s or .50s?). I blew up his good r180 when I was 17.

 

I've noticed that felpros are usually a bit over sized.

 

I got alot of help from dave rebello on my LZ23 with timming curves and carburation we just used what we learned and used it on the L20. I have be for and after dyno charts of theLZ23

maybe if I have some time on the weekend I take more pictures.:)

[banzai510(hainz)]

sswgn

 

well the Dyno pulls does mattwr what gear its in. I just dont know if its 3rd or 4th gear. or maybe 5th cause if you do 1st that is cheating!!!!!!Of coarse its going to read a higher #

 

anyway I believe you,

Yellowcar (TIM)had a LZ24 and got like 152 RW hp out of his motor . So looks like Nobody needs a LZ hybrid with all these cheap L20 blocks lying around.

 

Be nice to know Parts and secrets here even if I could get 112-120 true RW hp at the rear on my beater I would be impressed.

 

did you look at the Dynos on those Long rod L motors and LZ Hybrids? they are not even close to yours. Your in at KA/NON turbo SR range for HP ratings

[ssfwgn]

No one remembers if it pulled in 3rd or 4th. The guy at the shop said he usually does them in 4th because because its 1:1.

 

The first dyno we went to we had to a 3rd gear pull because it would load the car too hard and slip the clutch in 4th, that was on with no wheels just the dyno on the hubs. these last numbers was at a mustang dyno. there no way for me to know what gear its in cause there is no mph.

 

I actually still like the LZ hybrids, I got 127hp with stock w53 valves mild port work and a stock exaughst manifold. This cam I do know about, 470 lift 284 duration. Dave Rebello said they where good numbers but I should be able to get 150 at the wheels.

 

my brother dosnt tell me much about some parts like cam. If I need one he'll have one made or he will open up a bin in the garage and pull out the cam I need.

 

 

 

may be some some one should start a thread for dyno sheet and numbers:)