M20B30 Stroker build in progress

[bradnic]

It was 291hp, but bought down to a safer level of what you see

Sent you PM. would LOVE to know more about the engine and that project.

[rav320uk]

Replied.:)

[AWDBOB]

I've been reading about m54 rotating assembly based strokers, as I'm getting into a 3L built on an m54b30 bottom end with the pistons shaved down to accomodate.

The 3L I'm picking up also comes with a 731 head that Rama totally worked over.

I am going to clay (obviously), but am trying to get an idea on PTV clearance because I haven't bought a cam yet and don't want to buy two.

[digger]

Logic says you are going to need to cut reliefs assuming you set piston to head clearance properly. What cam are you planning on running?

A stock piston has reliefs about 2mm below the piston compression height an aftermarket set may have around 5mm or more depending on the cam overlap . The 24v pistons will have reliefs in the wrong place

Check with stock cam and there's your reference. From that I can tell you how much you need based on the cam you use .

Mockup to get the piston to head clearance set correctly at 0.9-1.0mm or so first, then check piston to valve. Don't rely on the piston being down the hole to give you p to v

[AWDBOB]

Logic says you are going to need to cut reliefs assuming you set piston to head clearance properly. What cam are you planning on running?

A stock piston has reliefs about 2mm below the piston compression height an aftermarket set may have around 5mm or more depending on the cam overlap . The 24v pistons will have reliefs in the wrong place

Check with stock cam and there's your reference. From that I can tell you how much you need based on the cam you use .

Mockup to get the piston to head clearance set correctly at 0.9-1.0mm or so first, then check piston to valve. Don't rely on the piston being down the hole to give you p to v

Roger that. I figured I had a high chance of having to cut reliefs in.

I’m going to talk to the builder to find out more. The car runs very strong with the setup as-is with an 885 and stock cam. My plan was to fit the worked 731 and modify what I have to to put a decent cam in it. It’s already going strong as-is, just with a stock cam and an 885 head, of which I am sure neither are doing the bottom end any favors.

[digger]

Stock cam and head will be fine at bottom end but midrange and topend will not be very good for the size of the engine. If the pistons are installed you'll have to cut reliefs in situ. A modified junk head makes this pretty easy

[AWDBOB]

Stock cam and head will be fine at bottom end but midrange and topend will not be very good for the size of the engine. If the pistons are installed you'll have to cut reliefs in situ. A modified junk head makes this pretty easy

Oh yeah, the car is stout now with the stock cam and 885 with the 3L bottom end but will really wake up with the ported 731 and a nice cam.

My only problem is that I can't find a junk 731 head to use to cut valve reliefs, but have a spare 200 head I can use to do so. Wondering if the 200 head will be similar enough for it to work out the way it needs to.

[digger]

All castings should have same valve position. Haven't checked myself though

You could check using an old b25 piston, maybe or maybe not

[digger]

Oh yeah, the car is stout now with the stock cam and 885 with the 3L bottom end but will really wake up with the ported 731 and a nice cam.

Please do a power run now before you start the swap then again after

[AWDBOB]

Please do a power run now before you start the swap then again after

I should be able to make that happen! I’ll post it in my build thread when I get to that point.

And good to know re: valve placement. Perhaps Mr Forcedfirebird has tested this theory and knows for sure?

[jeffnhiscars]

I wouldn't know an M54 if it ran me over but I am about to finally install my built 731 on an eta bottom end. What I do know is that the 731 preserves the CR on a 2.7 whereas the 885 would lower it. Based on this I'm imagining potential piston to head concerns on your M 54

Just thinking out loud

[digger]

. Based on this I'm imagining potential piston to head concerns on your M 54

Just thinking out loud

he said pistons have been (or going to be) shaved so you'd hope not. its fairly simple mathematics, famous last words....

[AWDBOB]

Oh yeah, I know I'll have to fly cut these pistons for valve clearance, but I don't think piston to head clearance will be of concern. But as digger mentioned above.....famous last words.

More than half of me just wants to use the head on a 2.7L with ITBs and forget about modifying the pistons on the 3L motor. Exponentially cheaper, too, and the 2.7L bottom end will likely have room for a decent cam without modification. It's the same head Rama built for that 2.7i that made 198whp on 8.5:1 compression.

We'll see.

[jeffnhiscars]

Oh yeah, I know I'll have to fly cut these pistons for valve clearance, but I don't think piston to head clearance will be of concern. But as digger mentioned above.....famous last words.

More than half of me just wants to use the head on a 2.7L with ITBs and forget about modifying the pistons on the 3L motor. Exponentially cheaper, too, and the 2.7L bottom end will likely have room for a decent cam without modification. It's the same head Rama built for that 2.7i that made 198whp on 8.5:1 compression.

We'll see.

Rama was kind enough to provide detailed guidance for our head work and we do have a 272 ready. I'm actually assembling the head in the next few days.

I wasn't actually thinking of piston to valve clearance which I know can be mitigated with cutting pockets. The 731 preserves CR due to a flatter combustion chamber than an 885 which is mated to higher profile pistons. Flatter CC with higher pistons sounds like a concern to me...unless I'm missing something.