250 build up

[cameljockey]

Hi every one,

I am in the research/budget phase of my build for the summer a 250 ci ford six for my daily driver '66 stang (assuming the fspp aluminum head comes out as scheduled) I found these h-beam rods on e-bay that are for ford 2.3 hsc engines they are bushed for floating pins I haven't talked to the guy yet but I don't think getting my hands on a set of six shouldn't be a problem. My question are:
Will these fit and will they clear the cam shaft?
are these worth it for a daily driver w/ occasinal drag strip action?
What Pistons hsould I use to avoid valve clearance issues?( I need a reasonable compression ratio in order to run the pump stuff right?)

Here is the ebay link to those rods;
click

Keep sixn' guys

Dan Hanna


asa67_stang was here

 

[CZLN6]

Howdy Dan:

Here's a piece I wrote up some time ago. The goal is to reduce the deck height, or the distance from the top of the piston to the deck of the block. The goal is zero deck height. The 250 usually have way too much deck height to achieve good quench and combustion efficiency. My 250 had .150". When we rebuilt it I was not aware of the swapability of the 2.5 Tempo rods, or the taller pin height of the 255 V8 pistons, so just deck the block about .070". The next block will be much more refined. However, finding a source for 2.5 Tempo HSC rods may not be as easy as it seems. The 2.3 rods are not long enough to work in a 250. I don't have their length.


************************
"Use a longer Tempo 2.5 HSC rod with the flattop HSC piston. This has the advantage of reducing the deck height .110" and giving a slightly better rod/stroke ratio.
Rod Length & weight;
250 =5.88" 592 grams
2.5 HSC =5.99" ??? grams
Difference = .110" grams

Rod Length to Stroke ratio;
250 = 5.88" : 3.91"= 1.5:1
2.5 HSC = 5.99" : 3.91"= 1.5319:1
The difference in rod to stroke ratio is probably too little to matter.

Deck the top of the block to achieve zero deck height. Use a FoMoCo composite head gasket with a compressed thickness of .037".

Use with an HSC flattop piston, with plans to mill a "D" shaped dish into the top. The goals will be to create a higher quench to bore ratio then the round dissh stock piston, lower CR, lighten the piston, reduce knock tendency, and maximize combustion efficiency.

Mill the head only enough to ensure it's flat. At this point it is critical to measure all volumes to assess CR. Reshaping the combustion chambers to reduce CR, unshroud the intake valves and match chamber volumes is critical.

The advantages of using the 4-cyl rods are- longer, for a slightly improved rod to stroke ratio, tougher than I6 gear. The four cylinders vibrate much more, rev to a much higher RPM, produce more power per cylinder, carry more load per cylinder than a six, and suffer more detonation than a I6 was ever designed for.

This combination will have a more ideal deck clearance, likely have a lighter reciprocating weight, and be able to tolerate CR in the 9.5:1 range, at sea level, with 91 octane gas.

Additionally, plans are to use ARP rod bolts, polish the rod beams, balance the whole rotating assembly, and polish the piston tops and the chambers.
*******************

Just more to think about.

Adios, David

 

[cameljockey]

these rods are 5.7 in long so with the right piston you could, theoretically, build a smokin' torbo motor no? with the lower static CR your could run a torbo on on pump gas I think. bummer though I don't want a turbo at least not for now. I'll check w/ the guy who sells them to see if he can make them in longer lengths

thanks again,

Keep six'

Dan Hanna