MAGK944

Interesting, Darton don't list those sleeves for the 2.5 just the 3.0, so that's an option for bore. If I did stick with my 951 rods I would clearance the block. Custom hg and JE's should make it all right. I really haven't thought about the cam as I have an NA cam in my 951 and it controls the power well. I am thinking about bigger intake valves, possibly the SS 48's.

rlm328

The blocks between the 2.5 and the 3.0 are basically the same. The 3.0s do have windage ports between 1/2 and 3/4 cylinders. You may want to look at them also.

blade7

Supercharge it then .

MAGK944

No thanks I have turbos to play with so why increase complication and go backwards.

I understand that they are basically the same, just curious why Darton specifically separates the two with different max bore specs. They list:

800-400 for the 3.0L blocks max bore 106mm
800-420 for the 2.5L blocks max bore 104mm

Assuming I can go to 106 then my options are:
Stock crank 106 for 3.10
Hybrid crank 106 for 3.35

KSira

The 3.0 block has a much taller deck. I remember measuring it to be substantial, but cannot remember the exact numbers. It is clearly visible with the naked eye. Anyway, this might affect the fitting of the Darton sleeves for 3.0 on a 2.5 engine block?

V2Rocket

if you want to go seriously bonkers, you can offset grind the 3.0 crank to use toyota 4age rod bearings (which ACL makes as well) on a custom rod by carillo (150mm long, 40mm bearing, and whatever piston pin size you want, $1500/set) giving you 100mm stroke.

maxing out the block at 108mm bore and 100mm stroke (if there is room in the 3.0 girdle for that much) gives you 3.66L.

rlm328

The Darton mids totally remove the old cylinder. They form a new seat at the bottom of the old cylinder. They install the mid and machine the top flat with the deck.

I have used the 3 liter crank with 2.5 l and 3 l blocks with the same rods. No problem.

The largest you can bore a 2.5 l alusil cylinder is 104 mm. The the largest standard head gasket you can get for a 2.5 is 104. That is the reason for Darton sizing.

I required a custom head gasket.

Taller deck? Er?

MAGK944

That's good news, thanks for confirming.

So here's where I'm at:
Darton 800-400 bored out to 106
Stock 3.0L crank
Stock forged rods
Custom JE pistons

Reasoning:
I don't want to mess with a good 3L crank plus I don't know anyone nearby who I am confident could offset grind the crank.
The stock 951 rods should be sufficient as power should be in the range of a stock 951. If Glyco bearings are good enough for M-Mount they are fine by me. I will clearance the 2.5 block for the rods.
Pistons are relatively cheap, I would probably try for non-interference.
Stock NA cam simply because it works well in my 951.
Mildly ported & flowed head with 48mm intakes as suggested.

Any comments on the above or on what I can expect?
Compression ratios on premium, what should I be looking at?
Don't forget I'm running all this with some decent engine management.

rlm328

Stock 2.5 l 951 rods are too long. The 3.0 l crank has a longer stroke.

MAGK944

iirc 3.0L rods are the same size are 2.5L rods. Isn't it all corrected at the pin?

V2Rocket

You might be able to do 106 on a dry sleeve. Blown944 iirc is at 105.5 on dry sleeves in a 2.5 block.

The thing with darton is they are sort of expensive at about $1500 installed for sleeves (quoted 2 years ago) and will only go to 104 because they say the block gets too thin at the bottom of their cylinder.. dry sleeves should be closer to $500.

If you really have a preference for stock rods that's OK but they are very heavy and huge where they don't need to be. Not to mention the newest set in the US is 25+ years old. I'd get forged after market rods for weight savings and super strength, even if you don't buy mine :-(

MAGK944

Thank you V2 and yes I've read blown944's thread with the 105.5 dry sleeves, that is a much cheaper option.

My rods are perfect, they were tested (x-ray??) and end-to-end balanced a few years ago for another project. Yes I know they are heavy, but I'm not concerned about squeezing every ounce of power from this build and strength should not be a concern with 951 rods on this non-boosted engine. Focus is a reliable, low maintenance engine for everyday street use only with good low down torque and hp in the stock turbo range.

rlm328

You maybe able to correct with the wrist pins. You will need to do the math.

KSira

What I meant is if you compare the 2.5 and 3.0 engine blocks, the bottom of the water channels are at different levels.

blade7

Original 2.5/2.7/3.0 rods are all the same length. Dry sleeves fitted here are over $1500 . What are your goals for power/torque and at what revs ?