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V4 convert from alloy cast bore to wet liner !?

V4 convert from alloy cast bore to wet liner !?

V4 convert from alloy cast bore to wet liner !?

Hi All,

Just read this thread whilst trying to find some info for a project I'm working on.
Big Overbore Limitations

Same scenario, but with an 800cc V4 motorcycle engine rather than the 400 in the original. Open deck cylinders.

I've already concluded that wet liners with a flange are the way to go & can source these from other models along with pistons etc, so thew only mods I would need to make would be custom modified head gaskets.

There are two questions I need answers too.
1. What is a safe minimum horizontal distance for a water tight seal with an MLS head gasket between the bore edge & the water cooling holes ?

2. What is the best way to seal the wet liner into the alloy crankcase to avoid water ingress to the crankcase ?

Thanks for any assistance with these questions.



RE: V4 convert from alloy cast bore to wet liner !?

Don't know the answer to the first question but the only wet liner engines I've worked on used o-rings to seal the liner to the crankcase.


The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: V4 convert from alloy cast bore to wet liner !?

Thanks dgallup, I know that's an option & is how it is on some engines I have worked on, just looking for the alternatives if there are any.

RE: V4 convert from alloy cast bore to wet liner !?

FWIW, While it may exist, I've not seen a wet open-deck iron sleeve sealed to an aluminum crankcase; all were iron crankcases.

How do you propose to retain the sleeve at the bottom? An O-ring certainly won't do it; will there be a solid step for the sleeve to seat against?

jack vines

RE: V4 convert from alloy cast bore to wet liner !?

Hi Jack, Honda did this with the VF1000R motor & the plan would be to copy that method.

Bore out the old MMC liner, machine the base such that a stepped press fit to seat the bottom of the new wet liner with one or two O-rings to seal the crankcase from coolant contamination. The flange on the liner top will be skimmed to level everything & that will be the sealing face to the head. The liner will be supported over 2/3rds of it length in the crankcase, with only the top third as an open deck.

The liners I have in mind have 75mm bore (stock is 72) & may get bored to 76mm. That will leave 3mm wall thickness for a total diameter of 82mm. Current alloy cylinders are 88mm diameter OD, so the coolant capacity of the block will increase a bit which will be a small benefit & should help compensate for the reduced thermal conductivity of the iron wet liners.


RE: V4 convert from alloy cast bore to wet liner !?

Is there enough material that you could bore the liner completely out and Nikasil the remaining aluminum?

RE: V4 convert from alloy cast bore to wet liner !?

Well yes, no & no.

The wall thickness is 8mm as stock, but the MMC liner is castleated & 2.5mm wall thickness & due to casting movement from a block I cut up, it needs to be bored out to 78mm to clear the MMC fully. That would leave 5mm wall thickness, so possibly enough, possibly not.

A friend in New Zealand has taken my research & bored the MMC to 74mm for 825cc & added 20hp !

The wall can't be nikasil coated in the traditional manner as no company I've contacted can do a crankcase with 4 integrated bores.
I did find a very helpful Austrian company that do plasma deposition work for F1 etc & they could do the boring, plasma coating & final honing, but for 2000 euro ! so no :(

I have a local (ish) machine shop that is willing to under take the work to fit wet liners. They just did a wet liner replacement for a big bore twin cylinder for me.

RE: V4 convert from alloy cast bore to wet liner !?

Millennium Technologies seems to specialize in exactly what you are doing. Give their website a browse. They did a 5mm over GSXR, there can't be much cylinder left. One of these outfits Millennium, Powerseal, or US Chrome advertised in the past that they did monoblock engines.

RE: V4 convert from alloy cast bore to wet liner !?

Thanks Tugboateng, I believe that is where TTS in the UK used to send the VFR blocks to have a big bore fitted. The results of those upgrades were not always successful. Hence I'd rather keep it local if possible. The plasma deposition coating would be ideal, but I can't afford that much for the coating process alone !

RE: V4 convert from alloy cast bore to wet liner !?

If you're looking for horsepower, a 750cc four cylinder motorcycle should be able to easily make 120-130 wheel horsepower reliably and rideabely. Perhaps you should look into why the inline-4 bikes make those numbers so easily. Cam profiles, compression ratio, intake port flow, and throttle bodies. If you can push your peak power to over 12,000 RPM you'll easily add 20 horsepower to the bike.

RE: V4 convert from alloy cast bore to wet liner !?

Thanks Tugboat, I already have 120hp at the wheel ! Working more on the fact that Honda have not produced a 900-1000cc V4, but I'm convinced that this engine can accommodate the upgrade. It is basically an RC45 engine that in endurance trim made 150hp, in WSB trim made 180-190hp ! so the bottom end can take the load. Their was a super charger kit a few years ago that lifted the stock 95hp to 160-180hp depending on trim, they have been running for a few years with no issues, so again the bottom end can stand the load. Largest I could make it would be 916cc (current is 782), a 2mm overbore version in New Zealand has made 140hp. The valves are the same size as current 1000cc+ bikes, so good for 200hp of flow !

RE: V4 convert from alloy cast bore to wet liner !?

This may be heresy, but have you considered fitting Aprilia's V4 engine? Considerably more power from a stock engine.

RE: V4 convert from alloy cast bore to wet liner !?

"open-deck iron sleeve sealed to an aluminum crankcase" How about the LT5 Corvette V8 and those old aluminum block Cadillacs.

You'll need a good support flange at the bottom. Suggest you load the flange to perhaps 50% of the compressive strength of the aluminum at maximum based on the bolt loads. Make the liners stand about .002"/.003" taller than the deck to start.

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