OK folks,
Just to be different, I am putting a 300-6 into my 81 FS Bronco to race short course bajas, 100 yd. sand drags, tough trucks, mudbogs, etc. I know it is tough to build one engine that will do all of these well, but we have classes that I can work in. Major rules I have to deal with are: no porting in the bowls, behind the valves, or more than 1/2" in on the ports; no roller cams (mechanical lifter cams ok); single carb.; no nitrous; I can have any clutch I want.
The specs on the rig are 4200lbs race ready, 4.88 gears, 35" MTs, 4" lift with extended arms and center drop brackets, 4spd tranny.
I would like input on available hotrod parts, and theories on 240 head vs. 300 head.
I have an 89 injected engine for the build up and a rebuilt 81 engine for now. I also have an Offenhauser 4bbl intake, Clifford headers, and a bare 240 casting with screw in studs.
I would like to put hardened seats in the 240 head to fit larger valves (any ideas?) port match the head, header, and intake, roller rockers, and a healthy cam.
Did the injected engines have any advantages/disadvantages over my current 81 engine? Maybe better compression, oiling, etc? It would be nice not to have to buy new pistons if I can get the compression up over 10:1 without them.
Any ideas, theories, etc. welcome.
Thanks,
Blair
Please respond to b_howze(No Email Addresses In Posts!) also. Thanks!

 

I also want to do some port work on the 240 head - see my post below. I'm also seeing a little bit (with no real details) in other forums that Ch*** small-block valves (1.94" intake, 1.5 or 1.6" exhaust) is a mod that some guys make. I hope we can get some guidance here. I am also asking around at local shops, and I will report what I find. We should be able to pick up another 10-15% more power with porting, right?

Clifford does a port and polish for $450 - I would rather do it myself. I can get scrapyard 240/300 heads for $25, so I can afford a mistake or two, but not three.

 

Porting and polishing on my engine has to be limited to portmatching, unfortunately. Our race members set up that rule to keep the costs down on engines. Just about anybody can portmatch their own heads on the cheap, but a really good flow job can get expensive really quickly. Another source for ported heads is PowerHeads out of California. www.powerheads.com
They seem to have a handle on CNC porting and they have a program for the 300-6. I think they wanted about $650 for a completely rebuilt head including valves and springs with their porting combo. For someone not under rules restrictions, this might be the way to go. You would certainly have to make more compression to make use of this porting, and probably a bigger cam. That would move your RPM range up considerably.
Blair

 

Oh, and I forgot to add that my machinist said that the 240 head actually flows quite well. He was under the impression that for street use that very minimal porting should be done. Portmatch, clean up the runners with as little impact as possible, and basically debur and gently slope the areas behind the valves, with bigger valves installed (size depends on your desired rpm range). I would be suprised to get much more than 10% gain if this is all true. I think the tuning and combination of the parts is going to be the real trick. I have an established RPM range I want to get to, based on not having to shift in short course tough truck racing, of approx. 6200 rpm. That will make some fairly extreme mods necessary. Crower makes a cam in the range I want, but getting the valves not to hit the pistons and still have compression might be a problem, especially if I zero deck the block. A lot of measuring will have to be done.
I hope that my existing 600 Holley (worked over pretty well for flow and blueprinting) works on this engine. I'd hate to have to do another one of those.
Any ideas on ignition systems? Preferably on the cheap. I forgot to mention that this is hobby budget racing!
Blair

 

I say dump the stock crank. Go to a junkyard and find yourself a heavy duty engine out of a truck. They are forged steel cranks and handle the RPMS better. Someone fill me in on how to find the engines....PLEASE

 

They came in the HD 300/6s and the only machine i know of that has them in it, obv there in more machines then this, but i know they are in the bombardiar sidewalk plows. My uncle had one to groom snowmobile trails, thing had all the power in the world.


Primary rig is:
95' F-150 EB 300/6 5 spd with 4" Superlift, MSD, Ram Air, Gibson Exhaust, and coming are some BFG MEATS

Then theres:
88' F-250 Superduty 351 + c6
92' Thunderbird 3.8L V-6 FOR SALE!
95' Mercury Cougar 4.6L V-8
80' E-350 300/6 and a
3 spd column shifter baby.

The newest addition to the Ford family is a 99' Mustang GT 4.6L