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I want bigger valves for this setup, right?


sneax

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Pulled the engine and preparing for the L20B! 

 

4al8mp.jpg

ClryxR.jpg

 

J trans - no.

 

Have Rebello get you one and bundle the shipment. You can probably mock it up with the trans you have and make adjustments when you get the new bellhousing.

 

Why not a 5 speed from a J engine?

because it would fit on the engine ... and into my prepared tunel!  :angel:

but the rear part of the Z transmission look way more beefy! 

Is the Z transtronger?

what about the ratios? 

how do I identify the trans?

GaqwQP.jpg

 

4cGXLH.jpg

 

Spray bar & cam towers from a 260Z. No external lines/fittings to deal with.

 

 

Simple & works great.

Just don't use the early one with die cast junction blocks.

Late ones are stamped steel, and fully oven brazed together.

 

Ok - thanks

Rebello takecare of my spraybar!

 

:thumbup:

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There is a 5 speed for the J series??? News to me.

 

GaqwQP.jpg

 

Left is an FS5W71B L series (pretty sure) 5 speed from an '80 or newer zx/810/Maxima or 1980 720. This would be much stronger that the J transmission. They were made for six cylinder cars and were also used in the trucks.

 

Right is an FS5W71C probably from a Hardbody with Z24i or KA engine. Not from a 240sx. The 71C would be stronger than the 71B

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There is a 5 speed for the J series??? News to me.

 

 

 

Maybe just here in Mexico... they build J engines here for a long time and had them as well in the mexican 510 etc... with 5 speed! 

(I think..)

 

 

 

 

Left is an FS5W71B L series (pretty sure) 5 speed from an '80 or newer zx/810/Maxima or 1980 720. This would be much stronger that the J transmission. They were made for six cylinder cars and were also used in the trucks.

 

Right is an FS5W71C probably from a Hardbody with Z24i or KA engine. Not from a 240sx. The 71C would be stronger than the 71B

 

the left one is my old "J engine 5 speed"!!! 

if that one is a strong one - great!!! 

i had only vibration problems with it before the last Panamericana ... up to a point where the neck had to be replaced because the bushing at the end got loose and fucked it up!

turned out it was the output-shaft that was bend! 

had it straightened for about 7 bucks!! ... including check on a lathe! hehe

 

the right one is stronger? ... looks bigger....  B)

 

Or both are strong?

 

what about the ratios? I remember 2nd to 3rd was a big jump and I had to rev second a lot uphill  to get into 3rd!

 

thank again! :thumbup:

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Why not a J engine trans? I guess I just assumed it had a different bellhousing bolt pattern. If it's the same, go ahead and try it. Datsun/Nissan did go through a growth period where they were continually upgrading the transmissions and the early stuff was not as strong. The pinnacle of strength for the 71B transmission was arguably the ZX turbo trans, with better bearings and synchros than the earlier generation.

 

If you want to get into ratios, they are flexible and you can build your own ratios using parts from a couple different transmissions, but it sounds like getting them may be the hard part for you. If you find the one you want, then no need to get into it.

 

What gear do you think you'll spend the most time racing with? Third gear?

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Why not just swap that early bellhousing onto the 71C? I wonder what the difference are (my knowledge of later transmissions is not great). Is the rear output spline the same or bigger? Are the bearings inside larger/thicker? It's a whole lot newer than the J trans so logic dictates it will be in better shape.

 

I don't know if that larger shifter base would be a blessing or a curse though. On the one hand, it would be a lot easier to work on, and probably be less likely to leak. On the other hand, it's very bulky and may not fit very easily under the car.

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The right one is J series 5 speed??? We didn't get them as the J13 was last used in the '69 L521. Well if so it is a 71C which is stronger even than the L series to the left.

 

What you can do is swap the front L series case from the left transmissio onto the right J 5 speed. This would allow you to run an L20B on the J 5 speed. There is more to this but it is doable.

 

 

Why not a J engine trans? I guess I just assumed it had a different bellhousing bolt pattern. If it's the same, go ahead and try it. Datsun/Nissan did go through a growth period where they were continually upgrading the transmissions and the early stuff was not as strong. The pinnacle of strength for the 71B transmission was arguably the ZX turbo trans, with better bearings and synchros than the earlier generation.

 

If you want to get into ratios, they are flexible and you can build your own ratios using parts from a couple different transmissions, but it sounds like getting them may be the hard part for you. If you find the one you want, then no need to get into it.

 

What gear do you think you'll spend the most time racing with? Third gear?

 

The 71B was never used with the L28ET engine, only the normally aspirated L28E. All early L28ET only came with automatics. In Jan '82 a T-5 BW 5 speed was offered on the turbo engine.

 

 

For road racing a 4 speed is most useful. Five speeds are used only for cruising along at the highway speed limit. A car will accelerate faster in 4th than 5th with a stock rear end gearing. You could maybe use 5th if you had 4.875 but then first and second would be  so low they wouldn't be useful.

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Sorry, I meant 280ZX, not turbo.

 

You're right about the 4 speed, but he seems to have trouble finding parts down there in Mexico, so if he can use what he has...

 

And I wouldn't call this road racing, per se. Yes, it's on the road, and it is racing, but I bet a lot of the time, he's probably at 6/10ths traveling from place to place. A 5 spd may help him in the long ruin by allowing the car to relax during these transit stages.

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I always thought a lot of this race was on rough and sometimes gravel roads - hauling ass.  Lots of 3rd to 4th gear shifting.  Lots of time at 80 mph+ cruising where 5th gear comes in handy. Then slow through small towns where they punch a clock and take breaks overnight.  With a car as light as an MGA, the L20b will pull like a train in 5th even at a .81 ratio - not far off from the original MGA 4 speed with electric overdrive.  Once you hit 90 hp at the wheels, it'll pull in 5th almost as well as 4th.  

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Why not a J engine trans? I guess I just assumed it had a different bellhousing bolt pattern. If it's the same, go ahead and try it. Datsun/Nissan did go through a growth period where they were continually upgrading the transmissions and the early stuff was not as strong. The pinnacle of strength for the 71B transmission was arguably the ZX turbo trans, with better bearings and synchros than the earlier generation.

 

If you want to get into ratios, they are flexible and you can build your own ratios using parts from a couple different transmissions, but it sounds like getting them may be the hard part for you. If you find the one you want, then no need to get into it.

 

What gear do you think you'll spend the most time racing with? Third gear?

yes - 2nd 3rd and 4th most of the time in the race stages!!!

 

La Carrera Panamericana goes over 3300km - only on pavement!  there are each day about 8 to 15 race stages .... and equal transfer stages in between!

in race stages - crazy curvy public roads with good pavement and fully blocked traffic!

(for example = "mill cumbres" in Morellia... google it - its a rollercoaster! yeah!)

in transfer stages - a lot of cruising at 5th gear ... 70 - 80 mph ... sometimes with cops front and back, making room for us at over 100mph - They love it as much as we do! haha 

 

 

Why not just swap that early bellhousing onto the 71C? I wonder what the difference are (my knowledge of later transmissions is not great). Is the rear output spline the same or bigger? Are the bearings inside larger/thicker? It's a whole lot newer than the J trans so logic dictates it will be in better shape.

 

I don't know if that larger shifter base would be a blessing or a curse though. On the one hand, it would be a lot easier to work on, and probably be less likely to leak. On the other hand, it's very bulky and may not fit very easily under the car.

Yes - that sound like the best option!!! will check today if the bulky shifter part fits in my tunnel!

 

The right one is J series 5 speed??? We didn't get them as the J13 was last used in the '69 L521. Well if so it is a 71C which is stronger even than the L series to the left.

 

What you can do is swap the front L series case from the left transmissio onto the right J 5 speed. This would allow you to run an L20B on the J 5 speed. There is more to this but it is doable.

 

 

 

The 71B was never used with the L28ET engine, only the normally aspirated L28E. All early L28ET only came with automatics. In Jan '82 a T-5 BW 5 speed was offered on the turbo engine.

 

 

For road racing a 4 speed is most useful. Five speeds are used only for cruising along at the highway speed limit. A car will accelerate faster in 4th than 5th with a stock rear end gearing. You could maybe use 5th if you had 4.875 but then first and second would be  so low they wouldn't be useful.

the left one is my old J trans!!!

 

Last year I raced with a weak J 1800cc and that trans! in race stages i only reached ~ once a day full speed, what was about 110mph! could have gone faster but the gearing was at 5th at maybe 6500 rpm (guessing)!

 

so the 5 speed is definitive useful! 

 

Sorry, I meant 280ZX, not turbo.

 

You're right about the 4 speed, but he seems to have trouble finding parts down there in Mexico, so if he can use what he has...

 

And I wouldn't call this road racing, per se. Yes, it's on the road, and it is racing, but I bet a lot of the time, he's probably at 6/10ths traveling from place to place. A 5 spd may help him in the long ruin by allowing the car to relax during these transit stages.

Yes exactly!!!

see description above...

 

 

thanks guys!

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What size tires and what differential ratio on the MG????

 

If going 6,500 RPM using a 4.3 differential, a usual 0.759 5th gear on a 71C and on very small 24" diameter tires you would be going 142 MPH. Guessing isn't the same as a tach.

 

The above with a 5.5 differential would be 111 MPH.

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The most common MG gear ratios are 4.3 for the MGA, 3.909 for the MGB (drops in like a Ford 9") or a 4.55 from the Magnette and others.  There is also a 4.1 , and a 3.3 which are both much harder to acquire.  I'd say with a good motor the 3.9 would be most useful, having had that setup in an MGB with the 280Z 5 speed.  5th gear was a little weak but I was under 100 hp.  With an L20b it would be a great combination in that car!!!

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Ah ok... I had no idea! You guys seem to know more about my car than me!   :thumbup:

 

not sure about the diff ratio.... yet!
need to take it out to check it anyways... then I will count! 

 

from your calculations... 111mph sounds about right!

 

==============================================

 

Different question>>

 

Can I support the engine at some points at the front, other than the original engine supports?!?! 

 

on the right there would be the lower bracket for the alternator and on the left there are 6 hole in the front! 
...not sure if they are deep and strong enough...?!?!

 

1ygNW9.jpg

 

FB9TLa.jpg

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from your calculations... 111mph sounds about right!

 

 

 

Read my post again. To be going 111 MPH you would need a 5.5 ratio differential... this is next to impossible that you would have this. The estimated 4.3 ratio would give you over 140 MPH @6,500 RPMs.. What I'm saying is you can't really know your RPM without a tach. It always sounds higher than it really is. Then there is the speedometer drive gear... it's also unlikely to be the correct one for the differential in the MG.

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those threads on the drivers side were for AC and possibly some smog things, they are pretty deep. I don't think I would use it as a main mount, but as a supplement, sure I see no issues with that.

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Interesting find on the rods.

 

I wonder if theres someone out there that makes this rod in a non-ebay rod (carrillo). Im using stockish rods in my lz23 with a 100 shot of nitrous. They are strong. Rpm is what breaks them.

 

With 45 mil intake valves i wonder if it clears the edge of the bore with an 85.5,86mm bore. Also stuff as much exhaut valve in it you can, maybe get some 38mm ones made. If your ported to 1.5 or so on the intake you'll be good, but the exhaust ports need help bad.

 

The ferrea valves are shorter than stock u67 valves by about .100 i dont know if the other l motors have shorter valves or whats with this.

 

So its a bit of fucking around with your seat height and lash pad height. My valves are set a little deeper with a lil chamber reshape. With the big cam i have (530 lift) i ended up with a .260 lash pad AND a .080 this manley valve tip button under the lash pad.

Its been working for 3 years and turning it to 7500 fairly often.

 

The 71c's have a better gear ratio spread than any of the other trannys.

 

Because race car, id put either the isky z196 grind or the .590 lift cam. Yeah its not gonna be a stump puller, but itll wail 4-8000 which is good. It a car that light it wont be that sluggish on the bottom end, even cammed out that hard.

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Stock valves have some 'overhang' of the valve face. A stock U67 intake valve is about 43.5mm total width but is considered a 42mm valve. The exhaust is almost exactly 35mm. The valve spacing is 43.24mm so the distance across both valves side to side is 81.75mm or call it 82mm. This will easily fit an 85mm bore. You could run a 46mm intake and still have 1.6mm space between it and the exhaust. Over all the total width would be 83.5mm and still loads of room on an 85

 

The combustion chamber would shroud the valves. The tops of the cylinders can be ground away but not to the top of the ring travel. 

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The mounts follow ribs on the interior of the block.  If you utilize the bolt holes at the old mount and span the front bolt holes at the 1st main bearing with a large plate, you'll be plenty strong.  The very front holes in the block could also do a fine job of carrying the load, but its a longer cantilever to the trans mount, so additional support would be good.  The more holes you use the better.  

 

You can either use a GPS speedo or buy the adapter gear from these guys:  http://rivergate5speed.com/

No affiliation but I've used their products.  

 

I've built a few MGs, and ran one for a LONG time with the 280Z trans.  Tried 3.9 and 4.1 and 4.3 gears.  3.9 was the most useful when driving over 70 mph by far.  By far.  100 mph in an MG Magnette sedan with the AC blasting - for most of the length of Nebraska.  

 

A hybrid rear axle utilizing the center section of the Banjo MGA axle, and the outer ends of an MGB Salisbury axle  will give you stronger axles, better bearings, and more durability overall.  Then you can run the fine spline MGB axles (26?) rather than the 10 or 11 spline MGA.  Plus you can run wire wheel axles (shorter) with blt-on hubs to make more room for tires.  Add Corvette wheel studs so you can shim the wheels to perfection in the center of the well.  

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The mounts follow ribs on the interior of the block.  If you utilize the bolt holes at the old mount and span the front bolt holes at the 1st main bearing with a large plate, you'll be plenty strong.  The very front holes in the block could also do a fine job of carrying the load, but its a longer cantilever to the trans mount, so additional support would be good.  The more holes you use the better.  

 

You can either use a GPS speedo or buy the adapter gear from these guys:  http://rivergate5speed.com/

No affiliation but I've used their products.  

 

I've built a few MGs, and ran one for a LONG time with the 280Z trans.  Tried 3.9 and 4.1 and 4.3 gears.  3.9 was the most useful when driving over 70 mph by far.  By far.  100 mph in an MG Magnette sedan with the AC blasting - for most of the length of Nebraska.  

 

A hybrid rear axle utilizing the center section of the Banjo MGA axle, and the outer ends of an MGB Salisbury axle  will give you stronger axles, better bearings, and more durability overall.  Then you can run the fine spline MGB axles (26?) rather than the 10 or 11 spline MGA.  Plus you can run wire wheel axles (shorter) with blt-on hubs to make more room for tires.  Add Corvette wheel studs so you can shim the wheels to perfection in the center of the well.  

 

ok great info!

 

I still have to take the 3rd member out - have no idea whats in there! 

 

do you think my axle might be a weak spot with the Rebello engine if it is the 10 or 11 spline?

 

==============================

 

another question: Does the turbo oil pump from the KA engine has exactly the same dimenion like the L20B one?

this is important since i dont have it here yet but have to lower and re-shape the MGA crossmember to make room for the L20B!

thx

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I don't know about the axle shafts, but you're not doing standing starts. If you watch your step, I bet it would be fine.

 

All oil pumps that bolt to that front cover, with the exception of a few very rare Datsun Comp oil pumps, will have the exact same outer dimensions. Mock it up with whatever you have. The new one will fit.

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The mounts follow ribs on the interior of the block.  If you utilize the bolt holes at the old mount and span the front bolt holes at the 1st main bearing with a large plate, you'll be plenty strong.  The very front holes in the block could also do a fine job of carrying the load, but its a longer cantilever to the trans mount, so additional support would be good.  The more holes you use the better.  

 

You can either use a GPS speedo or buy the adapter gear from these guys:  http://rivergate5speed.com/

No affiliation but I've used their products.  

 

I've built a few MGs, and ran one for a LONG time with the 280Z trans.  Tried 3.9 and 4.1 and 4.3 gears.  3.9 was the most useful when driving over 70 mph by far.  By far.  100 mph in an MG Magnette sedan with the AC blasting - for most of the length of Nebraska.  

 

A hybrid rear axle utilizing the center section of the Banjo MGA axle, and the outer ends of an MGB Salisbury axle  will give you stronger axles, better bearings, and more durability overall.  Then you can run the fine spline MGB axles (26?) rather than the 10 or 11 spline MGA.  Plus you can run wire wheel axles (shorter) with blt-on hubs to make more room for tires.  Add Corvette wheel studs so you can shim the wheels to perfection in the center of the well.  

I've always wanted one of those Magnettes. Kind of a poor man's 3.8 MKII. And that's ironic, because I bet they cost the same to restore.

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The Magnette is smaller, lighter, more nimble to drive than the MkII.  Handles like a BMW when set up right.  Taking a car that was meant to top out at 54 mph, then going 100 mph for 3 1/2 hours straight is quite pleasing!  

 

MGAs aren't known for breaking axles like an old TR2 or Midget/Sprites.  But if you push it hard enough, you will have issues.  Quite a few vintage racers use the combo I described above because it allows them to quickly swap diffs for different tracks.  You may want to simply install an MGB diff with the 3.909 gears - they're all the same gears from 62-80.  I'm not sure when the swap was made from the banjo to the Salisbury axle.  Before 1970.  Might cost you $100 to get a complete drop-in axle assembly.  They're plentiful.  The older style like you have is not so plentiful.  Guys like Paul at Sportscar Craftsmen in CO probably have a shelf full.  

 

Jack up one rear wheel and put a mark on your driveshaft.  Turn the tire 2 revolutions and count the shaft revolutions.  You have your gear ratio.  Should be easy to tell between 3.9/4.3/4.55.  I doubt you have any other variation.  

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Hey

I just got the 2 Datsun L engine books - and for some reasons I thought the gearbox will be covered by them as well.

 

So now I have more gearbox questions - 1. the 71C is stronger right?

2. How do i identify the gearbox and gearing?

3. how complicated is it to change the bellhousing? open the screws In the bellhouse and in the middle and extract? ;)

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And for the identification I found a lot of numbers!

Right side big cast letters: TA71B#10

Right side at the shifter: C2606426

And an metal label attached to a screw on the right side in the middle: 2S700-1 AESWK 01

32010F4030~1 0062

 

???

:)

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