does anybody know if these pistons are correct for the 1800cc SOHC Bellett engine, not Gemini ?

eBay Item number: 280667719480 (April 2012) They are 84mm +0.75mm (30thou)

My understanding is that is correct bore size (overbored), but is there any difference in the pin height and that sort of thing?

Also, I think a Bellett SOHC is standard CR of 8.7 : 1
Anybody can confirm this ?

Overall, if these pistons will fit, what is resultant CR assuming standard head (not shaved)

Finally, a part number or source or whatever for VRS set for the engine ??

Glenn

These pistons will fit but the crown of the piston is like the gemini. You will loose some compression. The piston pin is also different; not with the fastening clips but a pressure fit; so you need to adapt your pistonarm (little) bearing or machine the pistons for the rings.

Thanks for that info, Dick.

Sounds like the proper pistons have a dome on them. Since they CR is relatively low already (compared to modern engines) it would lose even more unless drastic amounts possibly removed from the head.

Re the rods, it might be possible to use Gemini rods instead of the Bellett ones.

glenn

Rods are most likely the same length, pretty sure most measurements between g series of the same capacity are the same.

I suspect you are right on the rods

I'm contemplating buying a car with this engine but engine is down a bit so need to know if i can get the right parts to do a rebuild if needed.
Using the wrong pistons would result in very low CR. The engines already are only about 8.7 : 1

Would be nice to see a picture from a parts book or better still inside an engine !

glenn

There are enough companies doing custom pistons, rods, wrist pins, and valves, that those are not a problem to have reproductions made.

Bearings, gaskets, water pumps, oil pumps, cranks, and blocks tend to be more of a problem.

I am sure one could get parts made but for a one-off and limited budget and limited use of the car also, that option would be expensive.
WE know that some Gemini/Rodeo parts, pistons, rods etc will fit but the need to maintain or slightly improve the CR, not lose a few points or worse, not know at all, is on my mind here.
The pistons are the missing link in the rebuild i think. I think that some rebuild shops can resize pistons slightly also if they in good condition generally, and then hone the bore to suit is one way, but if the engine condition is not that good then new parts are needed.

I don't have an engine (yet) I am contempalting importing a car from Japan and need to do some homework! Most cars available have the SOHC engine in them.....

glenn

Glenn.

If your looking for engine parts, I've found eBay referring to "chevy luv" will give you a good guide on what is available. With 1,260 odd parts,workshop & parts manuals listed. There are quite a few Haynes & genuine GM workshop manuals as well as genuine GM parts manuals. GM in the States ran 12 different series of models. Series 1 to 4 were the g180 single cam with 2 drive chains [layshaft where camshaft is on G150/160 ]. Series 5 to 12 were the G180z and with a option in 11 & 12 a diesel.[C223]. I bought a parts manual and photocopied the pages in the Haynes manual, that I also bought, on the engine only. It all goes down to how much you want to spend to get information.

Their series 1 had a 2 piece sump similar to the G150/160 and had a rope rear main seal. Series 2 to 4 had a 1 piece sump and neoprene seal. If your contact that you are negotiating with can advise you of which type of sump is on the engine of the car you are looking at buying, you then would be able to determine what gaskets , pistons, timing chain etc. to start looking for. This is a guide only. We can only assume that Isuzu did the same in Japan for their local cars and did not change them for their export models. I do know that the polution laws were different n the States to other countries, and there were changes in the cylinder head design to comply. The engine in my GT has a 2 piece, and at this stage I'm assuming that it has rope seals. I'm yet to find out when I start my resto on it.

There is a vrs listed on eBay, as well as a waterpump and a timing kit. Vintage Imports had the pump & MIKE1091 the vrs. Check them both out, as I have bought gaskets & timing kit from them for the GT and engine mounts for my strip taillight PR20. The gasket set you will recognize easily in comparison to a G180z as it has a 1 piece manifold gasket, no flat tappett cover gasket as such [a "o" ring for under the cam housing], and no oval hole at the front for the timing chain.

Dave.

Thanks for the info, Dave. Very helpfull.

In anticipation I bought a Luv manual.

Still a bit of a mystery though for the pistons. But Dick says dished is incorrect.

Most vendors pictures show a dished piston for the Luv. Appears the Shuttle is also dished. BUT, is the GT version dished also?

Yesterday I went to see the place who machined my GT engine.... alas, new owners and not really interested in doing anything but V8's etc. (a guy arrived with a Chev engine in parts, with big holes in the psitons ! Said it was from a drag boat, making over 1200hp)

Glenn

To make things clear I made a pic of the right piston with the cam on top.
It should look like this.

The Chevy Luv has a flat top and compr ratio of 8,2 :1
The Gt has the cam on top and a compr ratio of 9,7 : 1

So you loose some HP fitting the flat tops, but with 1800 cc it will be enough HP left.
These original sohc pistons will not be possible to find I think (by the way, it is a 1600 - standard size - piston for a sohc engine in this pic ). The flat tops are available, I have them on the shelf my self too.
Fitting can be done with later type rods without modification.

groetjes Dick

That is excellent info Dick. Many thanks.

Could i trouble you to measure the height from the pin to the top edge of the piston of both types, since you have both there?

When you say flat tops you have also, do you mean with the dished top like in my initial picture? Or a true flat top?

Glenn

mmm decompressed engine that can be fixed

take some off the head.... i did this on my GT to get compression back but its quite a bit.

This also adds to machining costs as they have to cc the head etc to calc the CR and what to take off the head.

glenn

Taking some off the head can also change your valve timing.Another problem.
KB

Glenn if your not going to race the car why don't you get jp pistons in south Australia to machine up a set of pistons I get all of my run of the mill pistons done there all you need to do is send them a drawing of what you want with all the diamentions and a sample would be good as well and you need to speek to peter from the workshop hope this helps regards Peter.

Sounds ok. But i guess expensive too??

There is (or was?) a place in Dandenong "special piston services' that claimed to do the same.

It seems that runof the mill pistons G180z etc are about $150 set. That would be hard to come close to i imagine for a one off set. I assume also that they usually do this based on some standard castings they can alter.

This is mostly preparation for what might need to be, I won't know for sure until i actually have one of the engines and a Car !

Glenn

Hi Peter, didn't realise who it was until i saw your profile, Rover, HK etc.

Hope you are doing well.

I will also look up JP Pistons.
I checked and see special piston services are still going. It appears they CNC machine pistons but mainly for racing use.

glenn

If you get pistons done by collin at special pistons they will cost you about $2200.00 and they will be forged not cast where as jp will be around the $800 mark I know there are cheep pistons out there but by the time you get everything elles to fit by machining the cost may still be the same . A piston company by the name of rightway had 1800 piston which were flat tops and had circlip grooves in them and they were cheap I've fitted these to push rod motors and 1800 over head cams motors Peter Mckills 1800 had these pistons fitted and when bored to 85mm and about .75mm surfaced from the head you still end up with 9.3 to 1 and by the way the lump on top of the piston is 7cc regards Peter.

Thanks Peter for info and costs. $2200 is out of my league !

Are those 'cheap' pistons still available ?

glenn

I tried to find the check stub for how much I paid for the last engine rebuild for one of my 90's engines. It looks like it was about $1,000 USD for the labor. Stock. Not a race engine. I usually hand the guy a couple boxes of OEM parts, he looks at me funny for wasting money on dealer parts, gets a little angry because he is not going to make anything on the markup selling me parts. But the engine comes back, dynos as much as other people's home built bored-milled-multi-angle-high-lift monsters, and they last decades and 125,000 miles of street and weekend races, while others are blowing holes in things regularly.

Normal reason for an Isuzu engine going bad:
Failed thermostat overheats the engine and warps the head before the needle on the dash goes into the red.
The crank bearings wear out and the oil pressure drops to zero.
The piston rings open up the cylinder until there is no compression left.
Rod bolt breaks and throws the rod through the front of the block.

Turbo pistons from the dealership were $75 each when they were available. They aren't anymore. Piston rings were $30 per piston (four sets to do an engine).
Some expletive-deleted Lotus-expert seller in Europe is getting $2,000 USD for a set of OEM reproduction pistons.
Aftermarket pistons, forged, duplicate of the originals or made to any specification you want, were $800 per set in the US. But they usually come with the manufacturer's favorite rings, which do not match the originals.
NPR piston rings are still available, $44 per set (all 12 rings, OEM spec from the original manufacturer).

So I'm looking at this, running the numbers, and I come up with $420 for the OEM pistons and rings which I can not buy because they are discontinued, or $844 for custom reproductions, tell the maker to keep his fancy rings, make the grooves to match the originals, and use the OEM rings from the original manufacturer. To me, that's a really good alternative to not having any pistons at all, or paying some expletive-deleted Lotus-expert seller in Europe $2,000 for something that they know less about than I do.

The other alternative would be to have the block sleeved and reuse the original pistons.