Long stroke L28 using LD28?

[ezzzzzzz]

Just looking for openminded discussion on the subject. I've got lots of spare parts including a LD28 block. My thoughts were to use a L28 crank along with the LD28 rods in this block. Either a N47 (44cc) or P79 (53cc) head would be drilled to accept the 12mm head bolts of the LD28. I've also got the needed L20B timing cover on hand. The block would be bored to accept a custom 86mm piston (1.5mm oversized).

39.5mm (L28 crank) + 140mm (LD28 rod) = 179.5mm. LD28 block height of 227.45mm - 179.5mm = 47.95mm. That would be the piston compression height. Would that be reasonable or too tall causing excessive side loads on the piston and cylinder walls? As a side note, I know the block is taller than the L28 by 19.5mm. The motor mounts could be sliced vertically and rewelded dropping the front of the block to a manageable height.

I will be pulling a rod from the LD28 to compare it side by side with a 240Z rod this evening. I'll even weigh them to provide accurate comparison. I am of the opinion that these are very usable in a petrol engine for most applications. Lastly, I do believe the LD28 rods use full-floating pins vs the pressed pin of the 240Z rod...this will be confirmed too.

[OlderThanMe]

For a gas engine you do't want to use the LD28 rods. They are WAY too heavy. Why not use the LD crank, LD block, L24 rods, and whatever head you want? You can also go WAY higher bore than that (like another 3-4mm).

 

Rods: The LD rods are aprox. 145mm and the L24 rods are aprox. 133mm so you would want to get a piston with a taller pin height to make up for the extra gap in the engine.

 

 

Also remember that lowering the engine raises the output shaft on the tranny and inducing more wear on the tiny driveshaft U-joints.

Just some of my thoughts...

[Kennysgreen280zt]

DAW is (or was) running a gas converted LD28, if you search by his user name im sure you will find info on it. IIRC he was using all LD internals (pistons, rods, crank) and a N42 head I believe.

[kj280z]

I'll be curious to see how this works out... I have heard about some successful projects using the LD28 block, but have never "actually" seen one.

 

Good luck!

[mario_82_ZXT]

He is a member here

 

Sounds vicious.

Mario

[Mack]

tons of misinformation going around already, and this thread is only a few posts long.

 

first of all, the LD28 rod is only 140mm long, and only weighs 80 grams more than an L28 rod. EDIT: might have been L24 rods we weighed it against, cant remember. 80 grams aint crap tho.

 

IF you were goign to do it, and go all the way and get FORGED, CUSTOM pistons. Use the LD28 crank and block and get uyourself some longer L20B rods, or maybe even Z20E or Z20S rods. as long as you are using the 19+mm higher deck of the LD28 and you are going complete custom, may as well go all out. You can find some of those older 4 cyl rods on 510 sites for DIRT cheap.

 

for the sake of arguement, the LD28 piston has a 46mm (me thinks) pin height, while a regular L28 has a 38.1mm pin height. If you went with an LD28 block and crank, then got some Z20E roids, a custom piston with a 33.5mm pin height, you would have a motor with a rod/stroke ratio of about 1.83:1.

[ezzzzzzz]

I haven't discounted actually using the LD28 block and crank for my new engine. This post was more in the line of separating fact from fiction. I have a set of the 240Z (9mm) rods ready to go. I am going to make a comparison of these against the LD28 rods tonight. Mack, if you're correct then there's only 2.85 ounce difference between the two rods. That isn't enough to be of concern with for all but the most demanding applications. A set of ARP bolts would certainly lower the risk of failure. Of all the rod failures I've seen in many engine makes nearly all were related to the bolts giving way. Oil pressure failure has also played heavily into rod bearing/rod bolt/rod failure. I'm not even talking about 7500+ sustained rpm or high boost failures. Wrist pin/piston failures must be taken into account for rod damages too. Enough of that rant though. Olderthanme, I understand the drive angle and u-joint issues. I'd have to work it out on paper but I don't believe dropping the front of the engine 15mm to 19mm would have any detrimental affect on the u-joints. I have the following to work with (excluding the L24 engine presently in the Z) and haven't made my mind up yet as to what configuration(s) I might choose.

 

LD28 complete engine

N42/N47 complete engine

F54/P90A complete engine with dished pistons (280ZXT)

F54 block

L28 crankshaft

P79 head

L28 rods and flattop pistons

L20B timing cover

Lots of ancillaries to choose from...

 

I'm leaning towards a 2.9 liter using the F54/P90A combo with the LD28 crank, 240Z rods and custom forged pistons in the 8:1 cr range for an Eaton supercharger project. This would also use either a Clifford 4 bbl intake modded for injectors or the L28 intake sliced (for the injector bungs) and tig'd to the LD28 intake (modified for a throttle body) for a unique hi-flow manifold. The manifold and head would be port matched to minimize restrictions. I'm off subject again.

The LD28 could be converted to petrol using the L28 crank, LD28 rods and custom pistons with either the N47 (N/A version) or P79 (turbo'd or SC'd version). Using the LD crank and rods along with custom pistons is very interesting but I'm reluctant to drill the P90A head for 12mm bolts. I suppose bushings could be installed to use on a standard block later if need be. I'll have to look into the L20B rods too.

[Mack]

oh sorry!! misread your post. yeah you could use the LD28 rods and an L28 crank and custom pistons. I beleive the LD has 1" wrist pins. you could get them bushed for smaller pins and custom pistons and you would have the perfect 1.75:1 rod:stoke ratio.

 

there have been rumors of people using L20B rods in L28 blocks with LD28 and L28 cranks. thats one SHORT compression height!

[Guest Aguyandaredhead]

If you need them I have a set of L20b rods for you..

 

Jeff

[kj280z]

Your supercharger idea sounds very similar to what I did for mine... It's posted on other threads if ya search some... or email me if you'd like more info

[ezzzzzzz]

The rods are virtually identical at the big end. The small end is obviously larger by all dimensions to accomodate the big floating pin. The diesel rod shanks are identical from the side and slightly larger across the girth. I'll have to find a means to weigh them as my triple-beam only goes up to 2610 grams. I'm guessing the small end could be narrowed and bushed for a smaller pin if desired. With a set of custom pistons a larger pin bore could be used. The full floating feature is very nice for durability and performance too. I would definiately install ARP 8mm rod bolts if I used these.

Now as for the block height, the LD28 is approximately 20mm taller than the L28 block when a petrol head is installed. I took a quick look around the engine bay of my 240Z. Using a plug of modeling clay I checked for hood clearances at the valve cover, front SU dashpot and the air cleaner vane lever. In all cases a minimum of 1" was available. The block could be lowered about 8mm before the the oil pan lip interfered with the upper saddle of the passenger side steering rack. That saddle could be slightly modded to allow 10mm to 12mm of total drop. The next problem would be the front anti-sway bar to oil pump bolt. That bar could be lowered using .25" shims on both bar brackets. Lowering the block even 8mm still provides 13mm or .5" clearance from the hood using the diesel block. While that is tight it isn't a critical issue.

I'm going to talk with Aguyandaredhead about those L20B rods. I'd also like to get hold of a set of L13 rods to make comparison between all. If anyone knows a source for the L13's please let me know. Also, if anyone knows of another make of vehicle that uses a rod of like dimensions I'm very interested. There has to be something out there that is still in production that could be used with little or no machining.

[ezzzzzzz]

I took a 240Z rod (9mm bolt) and a LD28 rod into the quality control/calibration labs at work this morning. Using a digital scale I came up with the following overall and small end weights.

240Z 710gm 200gm

LD28 784gm 260gm

The small end was weighed placing a pencil through the big end and trying to keep it level while the small end rested on the scale. It wasn't scientific but should be reasonably close for comparison purposes.

There is only a difference of 74 grams in overall weight and 60 grams difference between small ends. Considering everything that is not a lot to be concerned with in my humble opinion. I have a set of L20B rods coming and hopefully a set of Z22E rods too (both have a length of 145.9mm) that I can also compare. My decision will rest on those parts. Right now I'm heavily leaing towards the LD28 block/crank, the L20B/Z22E rods and custom pistons (40.05mm compression height). If I use a 21mm pressed pin then I have 29.55mm for the rings/lands. If I have custom rods made then I'll go to a bigger full floating pin which will reduce the room for rings and decent lands but should still be doable. I'm heading over to Abacus Racing to talk to the owner as he has raced Datsuns/Nissans for a number of years and should be able to provide viable input to my idea.

[Kennysgreen280zt]

Is there enough room to fit the KA24 rods in there? IIRC they are 167mm long.

[ezzzzzzz]

Even with the 227.45 deck height of the LD28 block and a L28 crank's 79mm you're left with only 21mm of compression height using a 167mm rod. That's only 10mm (<.5") of usable space if you keep the wrist pin out of the oil control ring land. I don't see how it could possibly be done and last anytime.

[Kennysgreen280zt]

yeah, I didnt check the math, I just was thinking while typing

[ezzzzzzz]

I'm backkkk... I am acquiring L20B rods bit by bit. Yesterday I bought a L20B from a mid 70's truck headed for the crusher! It was a total rust bucket and had actually collapsed upon itself. I could see the oil pan and stopped the frontloader operator just in time. The engine was pulled down last night. The whole engine was in great shape just worn out. I pressed out a wrist pin today to allow comparsion of all three rod types. The L20B rod look just like the 240Z rod only 12.9mm longer. I'll post pictures of the three rods side by side tonight. I hope to get two complete sets so someone else can opt in for building one of these. There is already a spare timing cover from this engine. A fellow in AZ(?) is going to ship me another set of four this coming week. Some folks over on the Datsun 510 and 1200 sites are trying to help me get the extra rods. Now to look into custom forged pistons.

[Sven]

Ezzzzzzz, I may be interested in your extra set.

[ezzzzzzz]

I hope I can acquire enough. The old trucks are out there. Scrap metal pulls in so much cash now that all of the local yards are crushing much of their old inventory. I'll keep looking and asking until I can get it all together.

[TABrinn]

I realize this is an old thread but has there been any progress made on the LD hybrid? Really cool idea!

[ezzzzzzz]

All of the pieces are in the machine shop (Abacus Racing) in Virginia Beach, Va. The LD crank has been completed and work on the LD block and P90A head are in progress. I'm still waiting for the intake flange to get completed (from Justin) so the porting can be completed on the head.