Im haveing a 331 stroker built, and I have a question. The motor will be driven on the street and maybe raced for fun 3 times a year, with spray. So what is best Dished or flat top? The heads should have 60 cc cumbustion chambers. Or maybe 70cc Roller cam for sure.
IDK which would be best for you but my 347 has flat tops and 58cc chambers and its right at 11:1 comp.Runs fine with 32 deg timing and autolite 23's on 91 oct.It's got aluminum heads so that helps,but next year it's get'n switched to E85 and after that its get'n a bump in comp.
If you're going to do what you posted, go with the dished pistons. My 331 has flat tops, 57 cc chambers and the comp ratio is 10.5 to 1. It pings slightly with 91 octane fuel, not at all on 93. 87 Octane ? FORGETABOUTIT !!!!
I'd like to know where everyone gets the idea that E85 somehow has a higher octane rating. I haul fuel and the E85 offered at the loading racks we deal with still has the same octane ratings as conventional gasoline. It may have been higher at first, but the refineries have switched to mixing it with a lower octane gasoline, resulting in the same octane ratings as what's been offered over the years (86, 87, 89, 91, 93)
93 octane? Never heard of that. I put 4 Gl. of 91 in my harley and top it of with a gallon of 100 at loves to make it run right and I dont spray it. All I heard is that corn fuel has more water and is more corrosive. All the guys who run to Canada (ON Harleys) complain about pinging when useing the gas up there. Ill just forget about it.
E85 has an octane rating of 105,but its more than just octane that makes it work.We've got guys here running e85 with BBC 13:1 comp and a 250hp shot of nitrous and many more fast cars doing it. Here's some good reading on e85 http://www.txideafarm.com/ethanol_fuel_properties_and_data.pdf
We don't get 93 in the south west and to top it off we get like 10% ethanol mixed it! Going with iron or aluminum heads?
Spray ? Never. If it won't do it on the motor alone, it's not worth doing it. Cam is a Z303 with 1.7 rockers.
Good stuff, but it's not 100% true. The final octane rating depends on the gasoline the ethanol is blended with. At first, it was blended with 87 octane gasoline, this is no longer the case at many loading racks/refineries. Second, that artical stated that vapor lock was no longer possible with fuel injection. I know from first hand experience that's not true. Given the right conditions, it will happen (110*F day, 10mph climbing out of Boulder Canyon in a 95 E150 van with the clutch fan inoperable towing a popup camper) You'd better check to see what the octane rating is of the fuel you plan on using before building an engine based on the assumption that the octane rating is 104. The E85 available at the loading rack we use comes in 87, 89 and 93 and is stated as such on the manifest, which is a legal document.
The crank, connecting rods, pistons, head gasket, and head (combustion chamber) you use will determine the compression ratio of the engine your building. So build the engine to tolerate the fuel you will use. The higher the comp-ratio, the higher the octane level you will need. There is a reason some guys run noting but racing gas in there cars. Because they have to. If using flat top pistons will push your compression ratio above say 10.5/1, then you have to consider the fuel you'll use. Also with flat top pistons, make sure you don't have piston to valve contact. Most guys buy the pistons with valve reliefs cut into the piston, this is to avoid that mess. Be honest with your self, is the cost of the pistons and higher priced fuel worth the chance you mite race it three times a year? If you want to just drive it, a 331 with dished pistons is perfect. Trust me, it will fry the street tires off! Glad to see you are keeping a ford in a ford! Good luck!
I guess it depends on how much compression you want to have. I had to go with the dished pistons with my 393 Cleveland to shed some of the compression. I believe it would have been around 12 to 1 without them. It now come in at 10 to 1 using the Boss closed chamber heads.
I hope I don't go off the deep end here, but did you ask these questions to "engine builder" you have? If he couldn't or wouldn't answer these questions I would have found another "engine builder"! So, from your intended use of the motor are you just going to "spray" on the strip????????????????? Is this a daily driver or just something you take out of the garage on nice days? How much HP do you want to make?? If this is just strictly a street motor (98% of the time) I would go with dish pistons. Just remember one thing, compression makes HP, and the lack of it...................well, you need sometype of "power builder" like NO2, blower, etc. If you are talking about a 70cc chamber in the head you had better use flat tops, if it's 60cc then a dished piston is the way to go.............for a daily driver that is, and if it's just a nice weather only car I would try for 10.5 or a little better and run some unleaded race gas in the 91. My 97 Mustang Cobra (naturally aspirated w/no internal mods) can barely run on 91 and I have to use 2 to 1 of 91 and 104 unleaded to get it run just right. As for 93, California and Oregon have not had 93 since 1999/2000. I am with BADDAD457, "If it ain't all motor, it ain't enough"......IMHO
Your right it depends on where you get it fro,here its mixed at the warehouse that has it you can get the stright e98 or they mix it with 89 for a good e85,e85 is really big here in oklahoma and has been for years.we've got guys make 2k+ hp on e85 with no problems,when looking at e85 its better to look at it as alky with gas mixed in for lube.
