I"m going to rebuild my 93 efi 302 in my bronco. I have heard of using 289 rods with custom pistons in a 302. The stroke and displacement stays the same but the rod to cylinder wall angle is less seviere reducing sidewall pressure. Advantages are more low end power. Anyone that has used this combonation or has info on where to get the specs for the pistons help is greatly appretiated.

 

I appreciate what you are trying to do but that alone won't make enough difference to feel in the SOTP dyno. FWIW the 302 I just put in my truck makes 100hp more than stock and has nothing but a cam and full exhaust system.

 

the long rod issue has been beat worse than a dead horse, the theory like what you said is that it has less lateral pull on the pin, meaning less friction on the cylinder wall. also, a longer rod causes the piston to have longer "dwell" (pause) at the top of the bore, allowing more time for combustion to take place before the piston is forced down.

like wise the notice is minimal, but I dont think that long rods have ever been properly re-engineered into place, it would take rethinking cam and timing specs, and that it could be something that would be great to try.

in my searching i found that the boss 302, which needed to be revved to get air to flow through the cleaveland heads, used 289-lenght 5.155 rods

also, if you want to try it i would run 5.4 inch rods. (kit w/ forged pistons can be had for about 800 bucks- probably not much different that a set of custom, or a set of pistons that say boss)

engine----rod------ratio
302-------5.09-----1.69(351w is very close, 1.7)
289------5.155-----1.79
b302-----5.155-----1.71
302/5.4rod--5.4-----1.8
200i6-----5.88------1.88
240i6-----6.2-------1.95
300i6-----6.2-------1.56
390-------6.48------1.71(427s the same)
460-------6.6-------1.72

all modulars are in the mid 1.5 low 1.6's

I myself find it interesting that the 200,000+ mile 360 (slightly lower stroke/ higher ratio than 390) thats in my 73 will go down the road floating the valves at ~5400 rpm without complaining, but i will only run my 88 up to "touch" 5grand to get a good shift into another gear.

also, I have always heard about how much better 240's did than 300's on gas(in general for all you devil advocates) but there is also a big cubic inch difference there.

you could always use 97 2.0 ZETEC 5.48 inch rods, a short piston, and grind down your crank to fit (which would decrease your stroke= aroung 295 cubes as a rough estimate, unless you put the pin up into the oil ring on the piston) which is similar to what nascar does cause the smaller bearings create less friction, and get the best of both worlds- less friction and a 1.83 stroke/rod ratio

ok... i will step down....

 

Thankyou for the very informative post muscletruck7379, this is exactly the information i was looking for.

 

hey look what i found with the search tool

https://www.ford-trucks.com/forums/5...od-stroke.html

lots of good tech talk in this thread i started about rod vs stroke

i suggest anyone who is keen on learning about rod length to read it. Nothing was ever really settled but theres a bunch of usefull info in there.