"that awful log head" still stands, I know the limitations you guys have with the heads, we're lucky with crossflows. As to stock stuff for under 15psi, that is my experience, I run more than that with all stock pistons etc, and old ones at that, I've done 5000km with mine, and although I dont race it, so far its held up. You can't give it full noise for long periods because of traffic conditions, this is probably the saving grace, unless our local stuff is better than yours.
There has been many twin turbo small six started and none finished that I know of, there has been many singles finished.
Well, being a fan of positive displacement blowers I would not advocate for one to wo turbos in any event. Trbos IMO are great for Diesels when there is heat available to drive the turbine or when they are fully integrated into the engine like the ecoboost engines. However for everyday driving and amatuers like us a blower, either Rootes Lysholm or others will give much better overall performance on the road. There are disadvantes to live with too. Ive had the whole gammit of go fast stuff, big carbs cams etc, turbos etc, now I have a blower, thats is much preffered power delivery and instant torque available just by putting the foot down. As to difficulty of install, id say its 50-50 either way. And just one more thing, LPG Ive been using for years, compared to petrol propane is easier to deal with. Just my two bobs worth. If your interested read my two write ups on this matter, or ask away on my current rig.
As far as blowers go how much do you think I'd pay for a scrapped one?
I cant really give an answer to that for you in USA, and I would be a bit warry of buying a scrapped one. a rootes or Lysholm type of blower can be easily wrecked by eating something. The smaller rootes types like the eatons or weiand would be where Id look. Lysholm types are technicall superior but a bit more expensive. I got an Australian made Sprintex here for $500 with all the drives etc, I was lucky and got a good one. Others on the forum might be more help to you.
90ci per revolution, maximum rpm shown as 14000rpm. So theory for a 250 application to give 12psi is 27/14.7x125ci=230ci per rev. Supercharger would need to rev to 230/90=2.55 times crankshaft speed, which in the case of a log 250 would be no more than 5000, so that gives 12750rpm blower speed, all is good. This take NO account of any efficiencys. Rough calcs would show a 27/14.7 increase in stock torque, so around 380 lbsft. IMO this would be OK with mostly stock parts, would need an 8 rib poly belt drive it. It should work on the better available petrol. LPG would allow for higher compression.
Basically.
But why go with blow through or petrol at all? LPG is a terrific fuel for boost, higher octane, cheaper (here anyway) can work draw through. Ignition is easy. Ive put up piccies of what Ive done before, but here it is again. I know you guys dont get the crossflow six, and the GRA stuff is a bit hard to get for you, but IMPCO stuff should been OK. This is a sprintex blower on 3.3litres, it runs up to 18psi on stock bottom end thats done 100000 km. I run NO advance or retard curve on a factory Bosch electronic dizzzy. I dont see why something similar could not be done on the 300 or log six. this has plenty of torque and is easy to get along with.
Fuel use is OF course down to owners opinion, I chose LPG for the reasons I spoke of above. I do understand that its not widely used in USA, which is a puzzle to me, could you give me some rundowns on its availability and cost for you guys. The price here is a bout 95cents per litre ($4 gallon) and its easily available here in Victoria, for instance, there are 5 outlets just in my town in Gippsland. Ive worked with gas fuels over many years and although I would prefer CNG, its NOT available for auto use. A draw through petrol setup could be done with a single point EFI. I run 9:1 cr in mine and timing is fixed at 25degrees BTDC, i get no knock, ping or any other ignition problems. because I have had such a good experience with this I want everybody to know about it. Setting up the drive was relativey easy, it has an idler on the back of the belt, but its fixed.
Do I have to use a 4bbl carb?
The Eaton M90 flows 520 cfm with 10 lbs of boost at 12,000 rpm which would be around 5,000 engine rpm.
No, any carburetor upstream of the blower can be whatever you like, a sidedraft Weber DCOE or Delorto equivilent will work. The size is slightly less important than NA because of the suction that a blower can provide. I run a "carby" rated at only 400cfm and I get lotsa manifold pressure even at part throttle. Sidedraft may fit more easily. The other common sidedraft carb is the SU or Stromberg CD, these have been commonly used and run well, you would need the 2inch SU to get the power. Ive run A weber 45dcoe on a turbo engine years ago, its was plenty big enough for a 3.3litre engine. Down here sidedraft carbys are used quite a bit, webers are very tunable, everything can be altered to get best performance, main jets idle jets pump jets, air correctors, emulsion tubes venturis secondary venturis, ram tubes. And there is several different throat sizes, 38-48mm. In this reagrd they are superior to most of the other aftermarket carbys. If you want to run EFI Im sure you could find a throttle body to use.
