Z24 l20B Timing Chain Links

[rdhull]

I was hoping someone who has been down this road can help. I,m finishing up my Z24 with SS l20B head and 44 sided drafts but I know it need to add four links to a L20B timing chain but how many links between cam sprocket mark and the crank sprocket mark at top dead center, same as L20? Also, how are people measuring the number of links on a chain, I get more than the books say.

Roger

[Farmer Joe]

How to put an L-series head on a Z block

To use the NAPS-Z block with an L series head, you need to use all the parts foreward of the block from an L20B. Use the front timing cover to match the L series head pattern as the NAPS-Z is slightly different shape where it seals to head around the timing chain. You also need the longer L20B timing chain and matching gears, guides, tensioner and longer L series distributrer drive spindle. The NAPS-Z blocks lack a chain oiler peg. You could drill the block and add a chain oiler peg but this is probably unnecessary since L series front cam tower and the chain tensioner both oil the chain. Im told the L28 6 cylinders didn't even use a oiler peg. Drill a dipstick hole on appropriate boss on right side of block and plug the left side dipstick hole since it will now be covered by exhust manifold. Use an L series dipstick and tube in the new hole, the NAPS-Z dipstick wrong length. Use an original 510 L16 oil pan and oil pickup, NAPS-Z or L20B oil pan wont clear the 510 crossmemember and steering. You will need a headgasket with larger bore if cylinders are over 86mm. The cheap but difficult solution is to use a NAPS-Z headgasket. The shape of the timing cover to cylinder head gasket surface is different between L series and NAPS-Z, headgasket modifications are necessary to seal front cover section if using the larger bore NAPS-Z head gasket (use an entire NAPS-Z gasket and seal the front cover with silicon or cut and splice the front segment of a L series gasket onto a cut NAPS-Z gasket.) The NAPS-Z gasket lacks the valve "eyebrows" so the gasket bore is a true circle, this would prohibit beneficial grinding of the head chamber and block to unshroud the valves, probably best to use the 89mm Z24 gasket even if on a 87mm Z22 block since it will allow the most unshrouding within cirular bore. The NAPS-Z block has all the water passages of the L series (plus a few extra) however the NAPS-Z gasket covers some of these coolant passages that should be open for an L series head, drill holes in the NAPS-Z gasket to match an L series gasket for correct coolant circulation. Even easier to assemble, buy the expensive Nissan Motorsports 88mm big bore L-series gasket. The opening of the cylinder head oil passage at the headgasket should be elongated to better match to the oil passage of NAPS-Z block.

The NAPS-Z20E block that I checked had headbolt threads same as L20B block but I have heard that some NAPS-Z blocks have the headbolts threads deeper in the block hole, you can obtain more clamping force for headbolt by using all long length headbolts (turbo 280zx headbolts part #11059-P7600). Countersink or mill down the upper face of cam tower by 0.5" where headbolt contacts camtower so the headbolt sits 0.5" lower into block. For headbolts that do not thread through camtowers, use .350" thick washers below the longer headbolts to keep them from bottoming out in hole.

For the taller NAPS-Z 2.4 block, do all the above modifications, lengthen the L20B timing chain by adding 4 extra links of datsun chain using 2 master links from a Mercedes-Benz timing chain (#000997-0598), lengthen the L20B timing cover to seal the extra 3/4" block height (welding and machining involved), and modify motor mounts/oil pan so engine sits low enough to close hood. (or use hood scoop!) Another method I have heard of is to space the entire front x-member downward from the chassie and then relocate the controll arm pick-up points upward. Ground clearance to oil pan will be minimal. Most used NAPS-Z 24 blocks will be cracked around at the headbolts, finding a good used core can be difficult.

[Farmer Joe]

post #5 from the thread above yours...

[Sealik]

I was hoping someone who has been down this road can help. I,m finishing up my Z24 with SS l20B head and 44 sided drafts but I know it need to add four links to a L20B timing chain but how many links between cam sprocket mark and the crank sprocket mark at top dead center, same as L20? Also, how are people measuring the number of links on a chain, I get more than the books say.

Roger

 At TDC just set the cam sprocket notch with the groove on the thrust plate.

 No 1 cam lobes at 10 and 2

 

 

Take a pic after it is set.

[hang_510]

if you haven't welded the timing cover where it doesnt mate with the head, i suggest you do.

then no HG mods are required, maybe a few coolant passages.

 

i sold all my spares...

 

also, if you dont lower the motor and have a nice hood, ill trade my hood with the cover bump :D

[rdhull]

I'm not a newb to Jason Grey's info, been into Datsun's for 20years, in fact my 72 510 has a long rod 2.1L that I built from his write up.  Just that I never came across anything that told me exactly how many links between cam sprocket mark and crankshaft mark at top dead center on this conversion since block is 3/4 " taller than L20B and cam sets at a different height also with this head.  I want a number so I can double check my setup, you know one link off and you have retarded it or advanced it. I used the Z24 front cover, very small amount of aluminum welding needed. I used ARP head bolts from L20B, ground off the engine ID projection to clear header, by the way IWIS W0133-1641757 is a good substitute for the MB timing chain link. Bad Doctor Doug, does that blue page you posted have a link? I think the cracked bolt hole think has been oversold on Z24 blocks, lots of them still running over on 720 site and my 720 Z24 with cam and supercharger ( yes, supercharger) is still strong after 66K  from a rebuild.  I suspect overtorquing the headbolts, 55-60 ft lbs isn't much.  Anyway anyone know how many links exactly?

 

71 Z L3.0

74 720 4X4

72 full on rally car 2.1 long rod L20B

71 510 2dr Buick V8 project

garage full of shit

[DanielC]

I may be off base on this, but it seems to me that if the crankshaft is at TDC, and the camshaft sprocket "V" is somewhere in the thrust plate groove, you have the correct number of links in the timing chain.

[Sealik]

I may be off base on this, but it seems to me that if the crankshaft is at TDC, and the camshaft sprocket "V" is somewhere in the thrust plate groove, you have the correct number of links in the timing chain.

 

Correct.

 

Well...since the L20B TC has 44 links between the "light sections" 

The Z24 is 3/4" taller.

2 links...<....1 section......<......3/4" 

 

You are adding 4 links...soooo.....divide that by 2 and add 44

 

Should be 46 links for the LZ24

[rdhull]

Doug, where did you find that "blue " page above?  I think your right about 46, just want to hear it from someone who has done it before for a double check.