Wiseco Yamaha pistons for 2.5/2.7 race CIH

[Hiro]

Hi to all,
Some pics of the Wiseco Yamaha piston I've received:
Wiseco # 4797M09700
OD = 97mm
CD = 28mm
pin = 22mm (offset mount)
crown thickness = ca. 8mm
almost flat top (very slight dish)
Looks like this one will be usefull to build my next 2.7
Or maybe I can build a 2.4/2.5 with a better rod ratio (ca. 1.62/1.69)
One question for Bob:
As the pin has some offset can I use this feature to reduce the lateral load on the bore?
If yes then how should I locate this offset (plug side or valve side)?
Hiro

[RallyBob]

One question for Bob:
As the pin has some offset can I use this feature to reduce the lateral load on the bore?
If yes then how should I locate this offset (plug side or valve side)?
Hiro

Nice pistons Hiro! Let us know how they work.

For 'quiet' road use the pins should be closer to the spark plug. For high rpm use to reduce the loads on the rod bearings and the piston skirts, then put the pins closer to the inlet/exhaust manifolds. How far are they offset? I have used as much as .060" (1.5 mm) offset for racing use. Noisy at idle speeds, but better wear at racing speeds.

Bob

[Hiro]

Nice pistons Hiro! Let us know how they work.

For 'quiet' road use the pins should be closer to the spark plug. For high rpm use to reduce the loads on the rod bearings and the piston skirts, then put the pins closer to the inlet/exhaust manifolds. How far are they offset? I have used as much as .060" (1.5 mm) offset for racing use. Noisy at idle speeds, but better wear at racing speeds.

Bob

Thanks for the info Bob,
The pin offset is quite huge (3mm),
This struck me when I took the pics,
I've never seen so much offset for a race CIH piston!
Hiro

[wrench459]

Hiro have you had the time to place them on the scale?
They look light with some room around the pin to loose some more weight.

[jeff denton]

I wonder how thick the top of the piston is. Especially after putting the valve relief notches in.

[RallyBob]

I wonder how thick the top of the piston is. Especially after putting the valve relief notches in.

Per Hiro's first post:

crown thickness = ca. 8mm

So about .315" thick. Which is fine until you put in valve reliefs. Luckily a long-stroke engine is more tolerant of big cams and big valves thanks to the higher piston acceleration away from TDC, so the reliefs won't need to be as large as a 1.9's. But it will be close just the same.

IIRC, the general rule of thumb was a minimum of .100" material at the thinnest section of the piston top (forged piston only!). Although on one set of JE's I bought years ago I measured the thickness of the piston at the lowest point in the intake valve relief at only .090".

Bob

[Hiro]

Hiro have you had the time to place them on the scale?
They look light with some room around the pin to loose some more weight.

this one is 397g,
not so heavy compared to my Wossner 2.5 (440g) or JE 2.7 (417g).
Hiro

[Hiro]

I wonder how thick the top of the piston is. Especially after putting the valve relief notches in.

about 8mm thick,
I need to carve the notches about 5mm deep,
I'm using wide LSA race cams so the valve crossover @ TDC is not very big.
Hiro

[Hiro]

Per Hiro's first post:



So about .315" thick. Which is fine until you put in valve reliefs. Luckily a long-stroke engine is more tolerant of big cams and big valves thanks to the higher piston acceleration away from TDC, so the reliefs won't need to be as large as a 1.9's. But it will be close just the same.

IIRC, the general rule of thumb was a minimum of .100" material at the thinnest section of the piston top (forged piston only!). Although on one set of JE's I bought years ago I measured the thickness of the piston at the lowest point in the intake valve relief at only .090".

Bob

I'm planning to carve the notches about 5mm deep,
this should be enough with Dave's custom cam grinds & a 1.5mm thick headgasket.
Hiro

[wrench459]

Call me stupid but where did the .059 thick headgasket come from?
I need to start a notebook for all this info.
<400 grams per piston that aint bad ..with some nice rods.. the reciprocating mass could look sweet.

[Hiro]

Call me stupid but where did the .059 thick headgasket come from?

Risse Motorsport in Germany,
98mm bore & 1.2/1.5/1.8mm choice for thickness.
Hiro

[lamchop77]

Hiro, Vagos and anyone else that has info,

Thinking of building a 2.7 at some time in the future. Can you guys give me any info on the best route to go witht the build. I have a spare 2.4 motor that i can use, but would go on the hunt for a 2.3 diesel setup if its the best route (thanks for the info on that Hiro!!).

Notice that the XT 600 pistons have an offset, big one at that, on the pin. Shouldn't the pin be central for max power applications? Looking to have pistons custom manufactured with longer skirts, higher pin location so will be able to specify comp ratios and mods to piston crowns (will solve the Wossner crown profile problem). Might get these at a good price if guys out there are interested in sets of pistons and a group buy. Only a possibility at the moment but i do want to look in to this.

Thanks in advance guys

Chris

[Vagos]

well Hiro is my teaher too on this subject but what i can tell you from my experiance is that with the 2,4 crank i think is a bit too risky to go up to 90mm stroke due to the fact that the 2,4 crank cannot be grind down off-center to 90mm and still have enough meterial for strength.When i grind down my 2,4 crank i made it 89mm stroke and for the journals to be clean and round again it took two rod journal bearings down(still one left).With 90mm stroke will you have to use the M20 rods with 48mm big end to make the journal round.So you can guess you already chop a lot off the top of the crank journal and then thin it even more to make the bearings fit.To little meterial left IMHO.But with the 2,3 diesel no issues you can go up to 90mm no problem.As for wiseco pistons they are very light and can valve pockets can be made up to 4-5mm deapth but since it has no full skirt vs wossner piston they dont last long and begin to crank on their skirts.here is a pic of mine 98mm wiseco piston

[Hiro]

for now I only have tested the 23D crank route with 48mm rod journal,
stroke up to 89.4mm is OK with piston cd 28.3mm,
keep us posted about the custom pistons you plan to order.
Hiro

[Motor Mouth]

I know a guy in the UK that has a 2.7 set up (offset ground crank and rods) and is selling it as he's now building a 2.4 with a cut down 24v head.

I did consider it myself, but for now am still enjoying the 2.5

Let me know if your interested.

[lamchop77]

Motor mouth

Yeah would be interested, price is of course a factor but i do have 2 2.4 motors stripped down at the moment so if he's after crank, etc we could come to an agreement if thats possible. Please keep me informed and thanks for replying.

Hiro

Nice to hear from you. Will keep you informed if i go that route. Was looking to possibly offset grind a 2.4 crank to around 88mm stroke then get custom rods / pistons to suit. Need to sort out measurements yet to sort what capacity will be and rod ratio. Think guy at Autosprint deals with R&R Racing product who do custom lengths, pins, journals at no extra cost. Last rods cost me £375 delivered. Then would look at JE Pistons or possibly Wossner to do a set of pistons, maybe source from the US. Will try and get prices.

Don't know whether its best to design pistons with the pin central or offset slightly. Know you had concerns with the Wiseco XT600 pistons. What was the best solution?

Tried to get info on the DBilas cams and prices through Regal Autosport but they are ?#$%. Won't even ring me back. Settled on CAT CAMs to supply who have got roller rockers as well. Not the same as Bob L's but CAT CAMs rate them and there cams are designed around them.

Got a supplier for a steel flywheel in this country as well. £180 for a flywheel designed to mount your spec of clutch, but they have 5 variations in their drawing archive. Just need to send my cover plat to them to guarentee perfect fit. Thought that was a good price.

Any way thats plenty to keep me busy for a while, just need some money now!!!!!!

Keep in touch, any info or advice is always welcome

Thanks

Chris

[Motor Mouth]

Chris.....I've only just relised you're in the UK!!!!!!!

Come on spill the beans, where are you, what have you got.....more info needed!!!!

As for the 2.7 stuff, sad news i'm afraid as the friend i have has actually only recently sold it to a guy in Scotland whose just bought a 400....I wonder if he's thinking of a 2.7 16v...that could be interesting!

[lamchop77]

Mark

I'm in lancashire, Leyland near Preston. Got a Manta GTE coupe in need of resto really and a Kadett coupe Class 3 autograsser. Thats what the engines are for.

Rebuilding a 2.2 at the mo blydenstein head (2.0), 244 cam, gonna switch to 45's on that motor and keep the 48's for the 2.5 i'm building. Nice to know there are still fans of the CIH motors, everyone else seems to favour Pintos,16v Vauxhalls and Volvo motors. Definately need to give em a spanking with a serious CIH.

Looks like you've got a nice little collection there

Cheers

Chris

[Motor Mouth]

Hi Chris,

I'm sure from memory there used to be a guy up your way who ran an A series with a blower on it, used to go by the name of Aziz (I think).

Anyway back to tuning, well i agree whilst it's easier to extract easier power with a XE or LET conversion i much prefer the challenge of tweaking a CIH. Although my car is a road car and never really used in anger i do hope to drop the injection set up (i've used a chopped down 3litre plenum) and hope in the future to go onto throttle bodies. It should smooth out the running, i appear to have some pulsing going on at the moment and as i'm running an Emerald ECU at least i know i can Dave Walker to sort a remap when the time arises.....til then i'll be happy with the 184bhp and 177lb/ft (160lb/ft from 2600rpm)

[lamchop77]

Mark

My 2.2 was running 180 bhp when i had it roaded at Minisport, thats got std pistons, std dizzy, but Rob reckoned it was the best head he'd seen, power wise from a CIH so thats where the big increase must have come from, plus it ran on 48's which helped. Thats in rebuild at the moment and i might look to getting custom pistons manufactured for it or go Hiros route with 2.4 pistons and toyota rods(maybe custom lenth rods!!??!!)

The 2.5 i'm trying to build (with plenty of help from this site THANKS ALL!!) will be running Wossner pistons 12.1 comp, forged rods with ARP's, 2.2 race spec ported head, Cam, roller rockers, springs etc from CAT CAMS with a kent vernier pulley, steel flywheel (which i hope will be v/light), Manta 400 paddle clutch, 48 Dellortos and if money permits emerald ecu, otherwise its a tweaked dizzy set up for now.

Chatting with the bloke from CAT CAMS (who has just finished building a 2.2CIH for someone) he did some theorectical power figures for the engine from what i had told him. Bear in mind that one of the owners has run some seriously quick mantas in Belgium. He came up with figures of 266Bhp @8000 for the 2.5 and 288Bhp @8000 for a 2.7. Don' t think there a B******t set up so i'm inclined to believe them.

If i could get near those figures i would be one happy guy. Lets hope my building skills have not deserted me!!!!!

Just finished making a boring plate for the block so hopefully in the next couple of months some progress should be made. Still need to source a decent manifold, Hiro has put me on to a few sources but i might just get Tony Law to sort it

Got loads on my plate , not enough time and money and space and the weather is poo. typically English eh!!!!

Keep in touch mate

Chris