M60B40 Heads on M62B44 Block

[Jean]

Alright, lets discuss this in great detail.

Has anybody done the math on what happens to the compression numbers?

The B44 has 92 mm bore and 82.7 mm stroke

The B40 has bore of 89 mm (3.50 in) and a stroke of 80 mm (3.15 in).

What about the difference in the bore size at the hg?

Does anybody see any issues with this?

I will post close up pictures of B40 and B44 combustion chambers in this thread as I have both on hand, and headgaskets as well.

[CoreyZ]

The only concern I could think of would be if there would be a sharp edge left due to the difference in bore size that could cause hotspots.

Pretty sure Garey said there was no interference issues, which is great.

[Jean]

Yes, no interference is one part, the other part is what you just mentioned above and why I made this thread :)

[JGood]

Well, the m50 and s50 head castings are the same, so they have the same combustion chamber, right? But the m50 has an 84mm bore while the s50 has an 86mm bore. Sounds like the same situation here. Aren't the combustion chambers kind of a rounded rectangular shape, just like the 24v engines?

EDIT:

Yes, they are...










Is the chamber in the head of the m60b40 actually the same diameter as the bore in the m60b40? And same with the m62b44?

[Jean]

I'll lay the two side by side and take pics / measure ? I think you have a very good point with the I6 example above.

I didn't see a thread on this discussion so want to get this topic covered :)

[CoreyZ]

Side by side pics would be great.

I'd imagine the compression difference would be very small.

No difference in the pistons other than size, right? Same shape?

[Jean]

Yeah both are flat top, i'll get some good pics.

[The Dark Side of Will]

If both engines have flat top pistons at the same piston deck, then the 10% bigger engine will give you 10% higher compression.

If the M60B40 has 10:1, then the B44 shortblock with the same heads will have ~11:1.

[Jean]

So here we go... b44 head gasket is on both heads .

B40 head combustion chamber, notice the area around the valve.

B40 head










B40 head with b44 gasket on it





'



b44nv head to compare against. I have both heads in the car, i'll bring to a friend of mine to get his 'virgin' opinion. He gets close/over 300whp out of h22 engines he builds
for his drag car, so I am curious what he has to say about these.

[Jean]

If both engines have flat top pistons at the same piston deck, then the 10% bigger engine will give you 10% higher compression.

If the M60B40 has 10:1, then the B44 shortblock with the same heads will have ~11:1.

What math / formulas did you use?

[CoreyZ]

Actually, he's right. Rough numbers put it at 10.94:1. That's a huge bump. Formula being [(pi/4)(bore^2)*stroke + clearance volume] / clearance volume.

Without knowing the clearance volume to begin with, you can solve for it - The M60b40 has an 89mm bore and an 80mm stroke. The B44 has a 92mm bore and an 82.7mm stroke respectively. Both have 10:1 comp ratios.

[Jean]

Any thoughts on how that may affect it's combustion temps / emissions running on 91/92 octane?

[CoreyZ]

Tune for it and you should be fine I'd imagine. S2000s have an 11:1 cr.

[CoreyZ]

I feel like an idiot for not looking at the math earlier. Now I have a boner.

[g3n0cid3]

Correct me if I am wrong but, at that compression ratio would a smog pump be needed to pass emissions?