Buddy of mine is "look'in-to-buy"..a Chevy with the old 396/375HP engine. He said it is "factory" with a hotter cam than the standard 325HP engine AND.....wait for it ...11:1 compression. He plans on driving this beauty as well as showing it but is concerned about the need for high(er) octane fuel. What all would need to be done to make it run on E-85! It's more available than av gas or pump racing fuel. I know the E-85 is hard-on(no pun) on rubber fuel lines and gaskets but what else would need to be changed to make the E-85 an option? Don't really like the idea of turning back the ignition timing or thicker head gaskets. Certainly don't want to "neuter" this thang with flat top pistons or such. Thanx 6sally6
Jetting will change of course. I don't know how hard it is on valve seats. Will be a little harder to start a fire so ignition improvement would be necessary. Pete
I think it’s basicaly going to need a carb that’s friendly to it or a rebuild of the current one, rubber lines that are friendly to the corn, different plugs and tune. Though plenty of guys seems to get away with 11:1 on the street. Most are running aluminum heads and cams that will bleed some compression off though. I know of a couple guys that just buy the bottles of octane booster by the case and call it a day as wel
I'm thinking that a swap to lower compression heads will let it work on Today's premium gas along with the carb redo and rubber change to E-85 compatible rubber pieces in the fuel system. That would kill the 375 horse thing though. I think that after doing the carb and hose thing I'd see what it did on the best gas I could buy locally and go from there. I remember that back when gas went to crap a lot of high performance big block guys around here swapped heads to drop the compression and get hardened valve seats. Not the cheap way out but he could stick the closed chamber heads on the shelf and save them as part of the 375 horse package. Maybe someone will offer up a combination that will work and not be that hard to put together.
I have a 396/325 that is next up to be built. CR is 10.25:1, closed chamber heads, oval port. I'm sticking with the heads, the part number is one of the desirables. Aside from a bore and stroke, the CR should remain close to stock. The factory carb was a Q-Jet spread bore, I have a Holley equivalent that pulled strong. I'm hoping a re-jet should be all it needs. For the 11:1 engine in question, I'd be more inclined to use 93 octane and boost it to a 101 octane over using E85. I use an octane booster on my 355 that is 10:1, more conservatively to around 97 octane. No ping, no detonation.
I owned a number of 396 Chevelles but the best performer was a 69 with the 375. A great running engine but that was years ago when the octane ratings were a bit higher. My advice would be to drive it first before solving a problem that may not exist. My avatar car has a well built 427 with Dart pro heads (which is a bit different from the iron heads of the 375 of course) but I have mini pop ups with a bit less than 11:1 compression but it runs fine on 92 Premium. When I race the car I do pop for some $7 a gallon race gas but that is only because I feel I need some additional magic, that is probably not necessary. My other 62 Vette has a 327/365 that runs 11:1 compression with original iron heads and I have had guys tell me I could not run it on 92 premium, which I have proved is nonsense. A few years ago I broke a ring and tore it down to replace it and when I did everything looked great after running it for years with the available premium. I have no spark knock or run on or any other such issues. Give it a shot first and then see where you stand. If and when the issue does arise then you or your buddy can attack the problem then.
Holley offers e85 change over kits e85 fuel pump and hoses and go. It takes about 20% more fuel than gasoline.
E-85 will work with 13-1 plus. You do need a good e-85 carb and a fuel system to handle more flow..A lot cheaper than race gas and runs cooler. Also.I have ran it in the race car for 5 years.
the e85 thing is all the rage right now and sounds good until you talk to some guys running it. every gas station that sells it has a little different formula, there is no consistency from station to station. not to mention the guy delivering the fuel when the regular tanks are full and he empties the rest of the load in the e85 tank. the only way to run e85 with consistency is to buy it by the drum from vp or sunnoco. you get what you pay for.
I currently have a 69 SS/RS with a 375 hp 396. I did add aluminum heads and an air gap manifold but it too runs 11:1 CR, and solid lifter cam. I run 91 octane, clear if I can find it, no octane booster, runs very nice.
Back in the day, when octane levels declined, water injection was a common trick to get the engines to live with lower octane. Water injection goes back to WWII at least, used in piston aircraft to reduce detonation under heavy load. Ex-servicemen brought the technology home with them and used it on their hot rods. I recall a Hot Rod or Car Craft mag article on using the windshield wiper system routed to a nozzle in the air cleaner lid, and using a vacuum sensor to trigger the system when vacuum reached a preset point, which would be different for each car.
Try it as is. If it pings adjust the timing. It's a pay to play ordeal. If you dont want to buy good gas or drop the compression ratio there is always a Prius to drive.
I remember reading about systems like that when I was a kid. I just couldn’t remember how they were triggered, thanks Blues4U! Once again you have taught me something! Sent from my iPhone using The H.A.M.B. mobile app
Your compression ratio will actually be a bit low at 11:1 to run E85 if you're trying to retain full power. I think a lot of guys get confused about octane ratings. When the feds required octane ratings to be posted at the pumps, they didn't go with the used-up-till-then RON (research octane number) numbers, they decided on the current R+M/2 numbers which can't be directly compared. By averaging it between research octane and motor octane (with the latter being a lot lower), the 'new' numbers came out much lower. Add in the dark days during the roll-out of unleaded fuel when super-premium disappeared and even premium fuel became hard to find (many stations only had two pumps so converted to 'unleaded regular' and 'leaded regular', no premium available) and hi-compression motors became albatrosses. It became 'common knowledge' that you 'couldn't get fuel for these anymore', so wholesale detuning was done to these, not always with good results. Basically, if you didn't drop compression, they wouldn't run right. 9.5:1 became the 'new' high compression, which had been the upper limit for regular gas. 'Back in the day', typical RON numbers for leaded gas were 91 for regular, 96 for premium, and 101 for super-premium (give or take by brands). Most of the motors that needed super-premium could be detuned to run on 'regular' premium without a big power hit. Now I do think that the refiners struggled with octane in unleaded fuel for a while, but got better at blending it over time. Fast-forward to today, and the 85 R+M/2 regular works fine in any vintage regular-fuel motor I've ever tried it in. And in case you haven't noticed, high compression is back; my OT daily has 11.25:1 compression and runs great on 92 premium. Sure, it uses all sorts of electronic trickery to make the power it does (420 HP from 5 liters!), but the trickery will only carry you so far; you still need octane. I'm with Dillon; run 92 premium in it, and tune it to work.
Been runnning a 365 hp, 327 with 11 to 1 for 35 years, most of which has been on junk gas, with no issues, no detonation. Sent from my Chromebook 11 Model 3180 using The H.A.M.B. mobile app
Same here on a 69 350hp 350 with stock 11 to 1 pistons and 2.02 heads Runs fine on the current 92 stuff. Also, if you read in most any of the engine rebuilding trade magazines, the general consensus is that standard valve seats will survive with unleaded gas.
I have been running a 350 horse 396 since 1971, and went through that period when people were having problems with gas that wasn't much better than warmed over dog piss. I made my own water injection system, and it enabled me to run the truck without having to adjust the timing or make any other changes. There were water injection kits available, and I am guessing that a little searching will result in finding a manufacturer that still produces these kits. Another thing that can help on the street in the summer, is to use octane booster. It costs a little more to drive the car, but the octane boost really can make a difference in a high compression engine. I am also running a 335 hp 390 Ford FE, that was really cranky on E85, and the adding octane boost was enough to solve the problem. You will have to rebuild the carb to update to the ethenol resistant components. That should be a Holley carb, and it is not as difficult to do at home as it would be to convert a Quadrajet. BTW, there are a lot of differences between the 325 and the 375 hp engine. The 375 hp engine has a forged crank, 4 bolt mains, larger square port heads, and a much hotter cam. They are an awesome engine. I attempted to do a search for a water injection kit, but after doing an update last night, my search engine has gone TU. Bob
This is just an example of what is available. This is more complex that most users would need. My system was basically a Ford windshield washer bag, which has a pump at the base, some tubing, an adjustable jet ( that I found in an aquarium pump), and a vacuum switch to trigger the pump. I found that triggering the system at 5 inches worked well to eliminate pinging. I used mixture of water and methyl alcohol in the winter, and straight water in the summer. I ran it for over 20 years, and when I pulled the heads to do the seals, the upper portion of the engine looked like it had been steam cleaned. The link is at the bottom. It worked great Bob https://www.aemelectronics.com/prod...injection-kit-for-high-compression-na-engines
This is REALLY kind of funny, in MY own personal respect anyways. I built my first Pro Bracket, 1956 Chevrolet, 150 Utility Sedan (AKA Business Coupe), based on a 360 HP 396. OK, a LOT more than 360 HP after I was done with it. But, this was done WITHOUT the factory rectangular port heads, factory aluminum intake manifold, and factory Holley carburetor; and it was't any kind of slouch either, especially for a "little" 396 BBC. Loved that car, engine, trans. rear end, ETC, ETC, ETC; it was't until my "new partner", BLEW it all too HELL, that I HAD to RECONSIDER what I needed to do. That's when I stepped up to the FED I had waiting in the wings. Wish I'd kept that 1956 Chevrolet car; I just did't have a place to store it, and I was going to college at the same time; decisions, decisions, decisions. I even let a good friend race the dragster, while I was in school (and THAT was a really hard thing to do!!!). Anyway, there is NO replacement for displacement!!! Built the biggest, 454 based, BBC you/he can.; TORQUE, is the ruler of all things automotive; build on that!!!!!! I am Butch/.56sedandelivery.
Butch, I kept my 350 hp 396 bone stock, so as to preserve it for a future restoration. It had the Holley manifold, and I have a continuing emotional attachment to it. I have since built up and installed a fairly wild 2 bolt 454 to replace it. I am using the square port heads, GM 425 hp manifold, and a comp 280 magnum cam, including roller rockers, as the heart of the replacement. It was a good choice, because I am free to make whatever changes I wish to make without worrying about affecting the value of the 396. I must admit, that I was conflicted about using the square port heads, and I still may go back to the hi performance oval port heads to get an improvement in the torque curve at the bottom end. I am looking at putting on oval port aluminum heads, and will probably go ahead with the change when I am feeling a little better. I love those big blocks, and have been running them since 71. Bob
With the fuel and pinging problem, I forgot to add that I live in an area where the gas was so bad in the mid 70s, that even the premium 94 octane gas that was being sold, was still crap. That was why I was forced to use water injection. I found that with the water injection, I was able to run regular gas with absolutely no problem. Even while hauling a fully loaded 8 ft camper, I was actually able to run the engine with the stock advance using regular gas. There were no performance or pinging issues. In regard to the 350, 360, and 375 hp 396s, I forgot to mention that these engines had a high volume oil pump that was not offered with the 325 hp 396 engines. Bob
find some second design L-88 heads for it, they're aluminum, open chamber, and will drop the compression some. And look bitchin. and cost a boatload of money for a decent pair
I am going to try to forget about the money issue, and concentrate on the amount of weight I am going to save. The problem with the aluminum heads I have seen, is that they don't seem to have the crossover to warm the carb. In the high humidity here on the coast in the fall, winter, and early spring, the closeness of the temperature to the dew point causes carb icing, unless the carb is warmed. The swearing I do when the engine suddenly dies, is enough to warm things up, but it is traumatic to the family. Bob
My 396 is sort of buried in my shop, but I have to dig it out when it gets warmer. I recall the steel heads being a desirable casting number. It ran well with the L88 cam and I fed it aviation gas since it was in a stock car. I can live with a 10.25 or 10.5 CR. I definitely want to go .030 over and stroke it a bit. It should make good reliable power. I may keep the factory intake if the number is good, believe it is a medium high rise.
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