The V8 Owners Forum -

Hey,

Been offered a short motor with a rather unusual combination of bits:

1988 3.5 stiff block
4.2 crank
Rover low comp pistons machined down
Standard rods (I believe)

gives about 3800cc or just above.

The guy was running an Eaton M112 with water injection, at 13:1 compression ratio with LPG

Was in a Rangey, he reckoned about 300bhp.

Now, question is, would this run on petrol, and if so, with 36cc stage 3 heads, what would the comp ratio be? Also, how much is the short block worth?

Was thinking it might be a good spare engine for the MG before I get the 4.6 built.

cheers

Presumably the heads it did have were 36cc too?, if so the compression ratio will be unchanged.

13:1 would not be great for petrol I would say!

Chris.

Jesus, how did he get that compression ratio with low comp Rover pistons with a bit of milling? I thought milling would reduce the comp ratio even more?

cheers

That sounds like allans old engine.

chodjinn wrote:Jesus, how did he get that compression ratio with low comp Rover pistons with a bit of milling? I thought milling would reduce the comp ratio even more?

cheers

Its a 4.2 crank which has the same bore as a 3.9 but longer stroke and shorter pistons. The 3.5 pistons are longer (same as 3.9) so they need shortened, also because of the longer stroke the CR naturally goes up (more volume compressed into same space) so low comp pistons have to be used.

No good for me then! I was hoping it had forged pistons, but not to be unfortunately!

How much did he want for it?

he asked me to make him an offer . . . I've jsut sent him an email saying thanks but no good for my set up! I can pass you on his email if you would like?