Thread: 4.6 in the D2

Found this on Wiki.

And what are you up to? Are you going to fiddle with your 4.6?



Parts stack height

When the various parts that make up the reciprocating assembly are selected, these parts have to fit into the SBC deck height dimension of ~9.025". When calculating the stack of parts that make up the reciprocating assembly, use the radius of the stroke, which is the same thing as 1/2 of the stroke, because only 1/2 of the crankshaft stroke swings above the crankshaft centerline. So for a stock 350 Chevy having a stroke of 3.48", use 1/2 of the stroke (3.480" times .5 = 1.74") to start putting the stack of parts together that will fit into the block.
In a running engine, the oil clearance will create a slightly longer stack- a 0.003" rod bearing oil clearance will add something slightly less than 0.003". In this article, oil clearance will NOT be added into the stack height. If desired the oil clearance may be added; easiest way to do this would be to either add the oil clearance to the rod length, or simpler yet, just add the oil clearance after the stack height is calculated. The added height from the oil clearance would only be an issue if the engine is being built with a marginal amount of quench (<0.035" for steel rods); if built with the "ideal" 0.040" quench, the oil clearance can be basically ignored.

found this-
Buick 215 Rover 3.5 Land Rover 4.0 and 4.6 differences

Soooooo-- if the 4L rod is 155.2mm and the piston compression height is 35.9mm

is that my stack length? (191.1)

Sooooo-- add the crank stroke of 82mm
and you come up with 273.1mm from the crank centre to piston crown.

Yes?

no!! its had its last fiddle!

Its seemed strange to me that all the Thor blocks are the same,, (quality aside),
you just add the bigger crank and get 4.6 yes?

well no. The 4L rods are 5.5mm longer and from what I can find out, the only difference in the pistons is the 4l has a smaller dish on top.

so do all the selected 4.6 blocks get decked 5.5mm ???

and where do the different compression ratio's come in?

AARRGGHHH! My head hurts already! I havent played with stuff like that for 30 yrs! I will need to do lots of googling I see I thought the 4 rod would be shorter and the piston pin to crown was longer? And the oppisite for the 4.6. So the main difference is in the crank throw tween the 2.
Cheers Scott

apparently they made the Thor rods longer (and pistons shorter)than the 3.9 ones to stop piston slap?

This may help? Let me know if you want the original file to play with. Note that this calculates compression ratios including the volume above the top ring of the piston. Traditionally this isn't included, so my matrix slows a very slightly lower CR than normally quoted. Dimensions are in inches (per the original design) unless otherwise identified. This is my file pulled together with whatever information I could glean from various sources (including direct-measurement of several engines) which I used to correctly design and specify my stroker engine. It may not be 100% accurate outside of the 3.9 variant, please use it as a guide.

Hi Pedro, refer your other thread on this topic for more info posted.

Mods - worth merging?

I converted my 4.0 to 4.6 myself with a crank from the UK and rods and pistons from the US.

The US 4.6 Pistons that came with the rods are identical to the AUS 4.0 Low comp. Although the compression is up 20psi on the compression tester due to the higher cylinder volume with the longer stroke.

Now I got stuffed around when I ordered my first set of crank, rod and pistons from the UK as they sent me 4.0 stuff I noticed the pistons had quite a noticeable shallower dish as I guess the UK get the 4.0 High Comp engine cause they have 95RON fuel as their standard.

So the difference in compression ratios is I think is in the dish volume of the piston.