new 3.9 block

**Grumndriva** · 15th December 2010, 05:39 AM

Originally Posted by milld

Hi all,

I just got a quote from TRS, and to top hat line my block alone is $1700.
With high comp pistons, crank grind etc. I've been told $3500 for the complete short motor. I'm thinking this is a good option, as then I have a block that will be strong. Sure I could go with a new 4.6 short for a bit more but then I would always have that nigly idea that the motor could fail at any time. Peoples thoughts?

Hi Milld,

My original 4.0 engine lasted 163,000 km and failed due to a "slipped liner": actually a cracked block behind the liner on two cylinders .

The first replacement was a new 4.6 short motor. It lasted 7000 km before it had to be replaced under warranty due to it having been improperly drilled for the crankshaft, leading to rapid wear and excessive crankshaft end float.

The second replacement was a factory new 4.6 short motor. It lasted 53,000 km before it too failed due to "slipped liner" on cylinder no 6.

The third replacement engine is a top hatted rebuilt 4.6 from TRS. I am due to get it back today.

My thoughts: don't even consider a factory new 4.6 unless you also have it stripped and fitted with top hat liners.

**milld** · 15th December 2010, 02:48 PM

thanks for that info, MR automotive said the same thing, the funny thing is that TRS are reluctant to tophat line my block saying that they don't like to do the job on the pre 94 block. I've asked if they could do this job on a 3.5 thickweb but they haven't gotten back to me. It seems they are more interested in A: selling their second hand motors and B: Selling their new short motors. They seem to avade the question when you mention the need for top hat lining.

but anyways, I'm getting my block done anyway. It wont be a 4.6 but the combo of unichip, extractors, and high comp pistons should see it slightly past the 200hp mark.

Cheers

**Traco** · 15th December 2010, 05:37 PM

That should be a nice motor. The 3.9 is the smoothest of the Rover V8s due to its bore / stroke combination.

Yes, undoubtedly the moral of the story is don't fit another big bore RV8 unless it has had flanged liners fitted. Not even a new LR/Coscat unit. Not all bigger motors fail due to cracking but a significant percentage of them do after a while - some estimates have put this as high as 70%.

The 3.5s rarely if ever have this problem, so don't really need top hatting.

TRS I suspect are wanting to clear NOS blocks. The profit margin on getting blocks machined for fitting top hat liners is not that great - they farm the work out to a local engine shop. They will do the job for you for about $1300 if you front up with your own block.

Incidentally TRS are selling the new US cast TA Rover heads, based on a V6 Buick design and reportedly able to unleash 600hp from a race prepared 5 litre RV8, for a cool $8,000! So much for the promise of a poor man's alternative to the Wildcats!

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