DeWolf

Hi All,

Is it possible to bore the 97mm block to 100mm and use the 5.0 pistons?

Cheers
Scott

Speedtoys

In as many words, no.


Needs a LOT more words...

Rob Edwards

If the question is to _only_ use 5.0 pistons, then the answer is no. The question is whether the compression height (top of piston to the centerline of the wrist pin bore) of 5.0 pistons is the same as that for 4.7 pistons. The block dimensions are the same, the crank stroke is the same, but 4.7 rods are a different part number from 5.0 rods, so I'm guessing they're different lengths to accommodate different compression heights of the pistons.

If the question is can you take a 4.7 block (and girdle) and bore it out to 100 mm and fit everything else from a 5 liter motor, yes, you could do that.

Speedtoys

And recoating..

Rob Edwards

The pistons or the block?

GregBBRD

The 4.7 liter block gets a bit "thin" at 100mm bore.

I generally use a 5.0 block when I want to go to a 100mm bore.

DeWolf

What I want to do is bore the block to 5.0 and use S4 pistons on the 4.7 rods. I have 5.0 rods as well. The other thing I want to do is use the 16V 4.5 heads if bore the block as well. Opinions please.

Cheers
Scott

DeWolf

Thanks Greg. I don't plan on revving the snot out of it. More interested in just the occasional blip up to 5,000rpm or so. Would it be ok do you think. 5.0 blocks here are hard to find and extremely expensive.

Cheers
Scott

GregBBRD

Probably maybe.

Another way to look at it....
If you have a set of 5.0 pistons without a home, what do you have to loose?

slate blue

Well I have run my 4.7 liter with 100 mm pistons, the wall thickness is 5.5 mm and the deck is not reinforced but despite no problems I am thinking about the reinforcement


About 16 mm thick.

hacker-pschorr

Why go through all the trouble with the plan of never going above 5,000rpm? This isn't a big block chevy or a diesel.

My 79 is at 3,000rpm going down the highway.

Survival at high(er) RPMS is a function of the lower end's strength which we know is rather strong on these cars if tuned correctly. If the thin cylinder walls are going to fail, it's going to be at peak torque which is much lower in the RPM range.
If you don't tune it correctly and detonate the snot out of it, all bets are off no matter what RPM you seek.

Strosek Ultra

4, 7L 97mm bored to 100mm same cylinder wall thickness as 5,0 L 100mm bored to 105mm.
Åke

GregBBRD

In my opinion, it is tough to make a "universal" statement about wall thickness....it's going to depend on the specific block.

There's quite a bit of "core shift" from block to block and the "85/'86 5.0 engines have thicker cylinder walls, to start with, which makes them more suitable for the offset pistons which are upside down on the 5-8 side of the engine.

rexpontius

I have a spare 5.0 S3 motor which will be for sale soon.

Let me know if you are seriously interested and if it is worthwile with the long shipping distance

IcemanG17

Probably the best option is to get a S3 (85-86) shortblock and have the pistons fly cut for valve clearance. You'll get a bump in displacement and a slight bump in compression with Euro heads. You don't have to fly cut the pistons, but compression might be a bit high for street fuel if you don't with the euro heads...american heads are a few CC bigger, so it might work...I want to say Euro S heads are around 50-52cc and USA are more like 57cc