Kakimoto And Os Spaced Blocks?

[GTRNUR]

Hi All,

Just thinking about the longevity of these spacer/liner kits and lack of cooling around the top of the sleave with a closed deck engine. The Kakimoto is only about 20mm thick which wouldnt leave much material to make it thick enough and allow for material to be removed to make it an open deck extension.

I have no idea about the thickness of the OS kits. There seems to have been 2 versions with diferent thicknesses.

Are these spacers really designed as more of a race only item?

[Adriano]

SK posted a pic of the thinner OS spacer not too long ago.

[GTRNUR]

SK posted a pic of the thinner OS spacer not too long ago.

Yep saw it and it wasnt possible to tell if it was open deck or not as it was pictured the same way up as it is instaled on the engine.

...

[bigmikespec]

For those of us who do not know, what is "open deck" or "closed deck"...?

Mike

PS: anyone actually used a Kakimoto spacer block in Australia?

[GTRNUR]

If you were to get an engine block and cut it in 1/2 down the center of the cylinders you would see the cylinders are about 4-5mm thick, and coolant is able to flow around the entire cylinder. Only at the top of the block does it become a seemingly solid piece.

Around each cylinder are 4 slots that water passes through from the block to the head, then it flows through the head over the combustion chamber and out the water outlet that is mounted on the plenum.

When sleaves are inserted into the block the normal cylinders that are cast into the shape of the block are bored out to allow the sleave to be fitted to the block. The sleaves can be pressed in, or shrunk fit and slipped in. The result is that the sleave material is considerably stronger than the standard cylinder material. This is for 2 reasons. Cylinders liners/sleaves are spun cast or in some cases machined from billet steel, which means no porosity. When boring out a standard block there is no guarantee the wall thickness is 100% even the full length of the cylinder, and also there risk if finding porosity increases the thinner the walls get. Even if you cant see it, it could blow through to the water chambers the first time the engine is started if its over-bored too much.... ala cracked block.

The whole point of a spaced block is to allow a better rod ratio to be maintained when running larger stroke crankshafts. What it does it make the block taller, but so the pistons and rings dont catch on the join between the block and the spacer, liners are inserted through the spacer into the block. I think the Kakimoto spacers are more suited to the RB28 strokers. An RB28 with SR20 rods would be possible with a 16-18mm spacer and would produce a 1.75:1 rod ratio. Larger is possible though and I suspect that the RPMGTR RB29 is a Kakimoto spaced block.

Now with a closed deck spacer, if you consider that the thickness of a spacer is 20mm, add the top of the block thickness to that and you end up with an area that the sleave is not exposed to coolant, especially where it needs it the most... at the top where combustion temps and pressures are their highest.

An open deck spacer looks the same as a closed deck from the top. Its the under side where you will see its hollowed out around the sleaves so that coolant can flow around them and joins up with the 4 water galleries that surround each liner. This means the cylinder liner is getting better cooling at the top.

Thats as much as ive been able to learn about them. It seems to me that it is still a good way to go instead of the RB30DET/AWD conversion option for the a GTR. There wont be a lot of diference in cost (a few K perhaps), and it makes fitting a lot easier too.

The taller the block the more need for cooling. I figure a thin spacer might survive on the street (this is what I really want to find out about), and if it was alloy it might conduct enough the heat away from the cylinder liners.

[godzl1975]

saw this spacer kit on RHD website, 1.5k for the kit....using this method to achieve 2.8L would it be a more cost effective way or to the incressing of the bore size etc to get 2.8L.

be interesting to know as havent seen many people take this path, maybe not as good??

What would you require parts wise to make it a 2.8L??

http://www.rhdjapan.com/images/product/270...rmal/Image1.jpg

was looking at the pic from RHD, looks like open deck if my understanding of it is correct.

Edited September 17, 2008 by godzl1975

[GTRNUR]

That looks closed to me. The water galleries around the cylinder go straight through to the head. The spacer is the same thickness at its thickest part as it is around the cylinder liner, so there is no coolant contact with teh liner where it runs through the spacer plate.

Thats a much better picture than anything ive been able to find so far too.

To make it a 2.8 it would only need the tomei/gt500/hks crankshaft. Then using sr20 rods and standard compression height pistons, or even rb30 pistons, 2.8lt is achieved. Becaused its sleaved they can be bored to 88mm to for a little more displacement.

Edited September 17, 2008 by Vspec R33

[bigmikespec]

Thanks for that, very informative. I am loving your posts VspecR33 your journey to find out which path you want to take with your GTR is very interesting and it helps people like me who have no idea what they want to do just yet.

Good luck mate!

Mike

[JFKGTR]

"I suspect that the RPMGTR RB29 is a Kakimoto spaced block"

I've seen Ben's engine and it is definitely open deck.

cheers

Edited September 18, 2008 by JFKGTR

[NXTIME]

That looks closed to me. The water galleries around the cylinder go straight through to the head. The spacer is the same thickness at its thickest part as it is around the cylinder liner, so there is no coolant contact with teh liner where it runs through the spacer plate.

Thats a much better picture than anything ive been able to find so far too.

To make it a 2.8 it would only need the tomei/gt500/hks crankshaft. Then using sr20 rods and standard compression height pistons, or even rb30 pistons, 2.8lt is achieved. Becaused its sleaved they can be bored to 88mm to for a little more displacement.

The rare HKS 2.8L "High-Deck" bottom ends use a spacer and longer rods (possibly SR20).

[GTRNUR]

The rare HKS 2.8L "High-Deck" bottom ends use a spacer and longer rods (possibly SR20).

It would make sense to use Sr20 rods. Common size, good rod ratio (1.75) with the 77.7mm crank. Im going to have a go at building one of these engines in about 6 months once other projects are out of the way. Custom sleaves and an open deck spacer plate fitted to a standard RB26 block for starters.

Im not chasing huge power with the project. I want response and drivability so I figure an RB30 crank/Sr20rod combination for starters. 9:1 compression and a limit of 8000 RPM will be fine. Probably GTRS's and a 1.5 bar tune. If it works well im contemplating making a cheap kit to allow someone with a blown RB26 to turn it into a 3lt relitavely cheaply.

[NXTIME]

I am sure that Ben from Race Pace has alerady developed a local "hi deck" 2.9L RB26 engine. See his RB29 thread. Very impressive.

[GTRNUR]

Yes ive seen that thread and it is very impressive, although out of most people's price range I suspect as well.

[NXTIME]

Compare it to the expensive Jap stroker kits and it would be relatively cheap. Also, I guess if the local kit was made in significant numbers, I would imagine that the cost would be significantly lower.

Custom crank, SR20 rods, custom pistons, sleeves, spacer plate, block mods to suit. Better RS ratio than an RB30 and would rev to 9K+Also, I have heard of a Sydney workshop that has used a modified RB30 (or was it an RD28?) crank in an RB26. Also, Risking have an "RB29" kit usng the RD28 crank with 87.5 pistons.

[GTRNUR]

I totally agree with you that the race pace method would be the best approach for ultimate performance. The problem is that all that custom work and parts puts the price tag up so much.

There is no middle ground with RB26/gtr modifications, and there needs to be. Its either keep it stock stroke and go to an 87mm bore, or throw three times+ more money at an engine rebuild project and step up to a 2.8. RB30 bottom ends have their issues as well. Mounting external accessories and that welding and re-drilling of the gearbox bell housing to acomodate the spaced sump adapter. Plus the height issues of the RB30 block, vs an RB26 spaced to use SR20 rods. Spaced/sleaved blocks would be used by everyone if they were just a cheaper.

[MBS206]

How high do you plan for the spacer to be?

[GTRNUR]

The options work out to be as follows:

2.8lt high deck, 1.75:1 ratio, sr20 rods, 28mm rb26 pistons, 77.7mm crank = 14.7mm spacer

2.8lt high deck, 1.75:1 ratio, sr20 rods, stock rb26 pistons, 77.7mm crank = 16.7mm spacer

3lt high deck, 1.75:1 ratio, sr20 rods, 28mm rb26 pistons, RB30 crank = 18.35mm spacer

3lt high deck, 1.75:1 ratio, sr20 rods, stock rb26 pistons, RB30 crank = 20.35mm spacer

Im also considering using the chevy 5.4, 5.5 or 5.6 inch rod sizes as this provides more options with the rod ratio's. 1.61 - 1.67 is possible. Plus Chevy rods come in sets of 8 and are cheap as chips, were as you would have to buy two sets of SR20 rods otherwise. Chevy rods also support a larger gudgen pin bush so you could then use VG30 87.5mm pistons with 22mm gudgens and get a little more displacement.

All this is just calculations on paper and a few autocad drawings so far. Im a long way off making a prototype at this stage and am too busy with the rebuild of my other car and work in general.

[FRParts]

Nissan rods & billet steel crankshafts

furiousracingparts

[Blitz]

Nissan rods & billet steel crankshafts

furiousracingparts

Great way to get banned, goodbye.