408 stroker 8-71 blower e85...teach me

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68 blufish

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Tried searching for a thread related to this topic but could not find one so I hope I am not creating another similar thread.

My question and the knowledge I am looking for is what should my static compression ratio be to run a roots blower on e85? How much boost can I run safely etc.
The build on the car and other info. I live in Colorado so high altitude.
The car is a 68 barracuda notch back. I will be stroking a 360 LA block to a 408. I have cage installed already and did inner fender delete and have glass fenders, hood and trunk lid. I am planning on running trick flow heads that are 190cc intake and the only options I see with these heads are 60cc chambers. Looks like ordering a scat forged rotating assembly with dished pistons at -20.5 cc I will be ranging a high compression ratio still. Looks like I made need to consider ordering custom dished pistons? At looking at some compression calculators running this scat kit with 62cc chambers that puts the compression ratio around 10.2:1. Obviously the 60cc chambers will be a higher compression ratio.
Has anyone done a build similar to this that the car is ran on e85 and is forced induction? With e85 being a higher octane rating than 91 octane. Is higher compression ok or is there still risk of too much compression and detonation?
I have tried reading up on this and find conflicting info. I have read in some other forums of people running higher compression with e85 and up to 35° in timing and others running lower compression with less timing. I just don't want to blow up the engine.
My dreams may be too much for reality. I'm not trying to make a pure race car. I am trying for best of both worlds. A cruiser that can fly on the street and a few trips to the track a year.
Still have to put in sub frame connectors and need to order magnum force front suspension w/ manual rack. Rear end planning on ordering moser fabricated rear end and running cal trac mono leaf and moving rear perches in.
 
Well I didn’t think you should be left hanging here so I’ll jump in with what I’ve learned. There are more than a few threads with valuable information in them here, but I’ll mention Subcom’s first build thread and Walker434’s thread since he’s also supercharged. Both threads are informative and have great participation from other members that will help catch you up on boosted small blocks. Other builds(off site) of significant note are Dizuster and Duner.
Dizuster has threads all over, but his posts on yellowbullet are especially informative. Duner has made big power as well, and more info can be found on DakotaRT and theturboforums. Both those builds are turbocharged, but they still highlight our engine weaknesses and strengths.

Back to your original question on compression. It’s my understanding that higher compression is mostly valuable to turbo cars to assist with off boost power and spool. Your roots build isn’t going to need help there. My personal preference is low compression for detonation resistance, and compensation via boost and timing. Regardless, a zero deck piston further improves detonation resistance. For pistons check out DSS pistons. They have stuff built for boost and, I believe, -29cc dishes for stroked sb mopar. Also consider Chevy 350 pistons which give you a .927 pin, shorter compression height, and a huge rod selection(speed master race I beams(6.2 and 6.25 lengths)) which can get you a more desirable rod/stroke ratio.

lastly: Tune Slow. Slower. Keep your timing stupid low under boost until you know your fuel curve is solid.
 
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Why not call the folks who build the blowers?

I built my 354 with a 671 and 8-1 Arias 2618 pistons.

I wouldn't put Speedmaster rods in my lawnmower.
 
My turbo build has 10.5:1 shelf pistons and E85. Tune is important as was mentioned before. Lean AFR and intake temps can lead to detonation.
 
With a roots blower the intake temps will be higher than a turbo. I wouldn’t go stroker IMO. Do one or the other but not both. You said it yourself, you’re not purely racing it.
 
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May I ask why you recommend not stroking it?
 
I am running a 408, 6-71, I have 28cc inverted pistons, I am also using a thicker cosmetic head gasket to help with lowering compression. I have never had a problem using 93 octane fuel and 10psi boost, But if I had it to do again and I new I was going forced induction I wouldn't stroke.
 
To the OP, nowhere have you mentioned a power goal for this combo yet and imo it is valuable info. At 10:1 on e85 with a roots at 10 lbs you’ll be fine but the desire to add boost comes very soon. Roots blowers have a very sharp point of diminishing returns when cranked up. You’ll get to the point when they just turn in to big heat pumps and you’ll run into problems. They are also difficult to add some kind of charge cooling to. So if you can keep the boost down to reasonable street levels, and can keep a conservative tune up in it, then I see no reason why the detonation resistance of e85 can’t keep you safe. For what it’s worth the v6 Honda in my falcon is 10-1/2:1 comp on e85 and it’s seen 26 pounds of boost without a peep from the knock sensors.
 
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You need to pick up a few good books on supercharging and running alcohol. Asking people to "teach you" on a forum is pretty dangerous.
 
RustyRatRod said:
You need to pick up a few good books on supercharging and running alcohol. Asking people to "teach you" on a forum is pretty dangerous.
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While I agree with the advise to get a couple of good books on supercharging, I don’t think asking for help on this forum is a bad idea. There are plenty of people here with all levels of experience and some really good knowledge and advise has been passed around.
 
TT5.9mag said:
While I agree with the advise to get a couple of good books on supercharging, I don’t think asking for help on this forum is a bad idea. There are plenty of people here with all levels of experience and some really good knowledge and advise has been passed around.
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Of course it's a good idea....what I meant was, just like everything else, you're gonna get answers and opinions from A to Z.

For instance, MY opinion would be screw E85 and go to 100% alcohol. Then you could make some serious HP. You'll almost be there anyway with E85.
 
RustyRatRod said:
Of course it's a good idea....what I meant was, just like everything else, you're gonna get answers and opinions from A to Z.

For instance, MY opinion would be screw E85 and go to 100% alcohol. Then you could make some serious HP. You'll almost be there anyway with E85.
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For a race only car 100% alcohol might make a touch more power but for a street/strip car e85 is really hard to beat. It’s readily available (here at least) at the pump and depending on the quality and percentage it can be like 116 octane. I’ve seen 1400hp from a twin turbo 6 liter LS in a street car on e85. Not many people need anywhere near that.
 
TT5.9mag said:
For a race only car 100% alcohol might make a touch more power but for a street/strip car e85 is really hard to beat. It’s readily available (here at least) at the pump and depending on the quality and percentage it can be like 116 octane. I’ve seen 1400hp from a twin turbo 6 liter LS in a street car on e85. Not many people need anywhere near that.
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Aside from the "need" there's the apparent waste of all that HP, because very few people will have a chassis that can handle it.
 
I appreciate all the input and advice. I just want a bad *** mopar. I want to be able to take it to work on a nice day and do a night cruise here and there and drive it to a car show and above all drive it to the track and when the day is over drive it home. My original build/dream and idea was to do the 408 and procharger on e85. My good friend and engine builder may have twisted my arm a little on the blower. I trust him. His pacer was featured on jay leno's garage when they ran his car against that gremlin. If you haven't seen it that episode check it out lol.
 
Speaking of higher intake temps from the roots. That is why I was going with the 8-71 and not the 6-71. It is my understanding that the 8-71 will obviously produce more boost but that isn't why I'm choosing it. I'm choosing it because the 8-71 will produce the same amount a 6-71 will but at a slower speed thus reducing intake temp. If heat was still a problem for some reason then according to my engine builder we will add water meth injection to cool intake temperature. Hp goal. Idk to be honest. My engine builder is thinking closer to1000 hp. I would have been happy with like 700 hp. He shocked me when he said 1000. Apparently he built a conservative 408 fora customer as a daily driver and the car still produced over 500 to the rear wheels. I told him I would be happy if the car ran 12's and he just looked at me and was like I it will definitely hit 12's without question
 
I like the 408/procharger combo better than the roots. Lends itself well to intercooling and the new prochargers are well above the old school blowers as far as efficiency is concerned. You will easily make enough power to question the integrity of whatever block you choose. @Walker434 has a nice combo you should check out. Maybe he’ll chime in.
 
And if you need a blower to run 12s you’re doing it wrong. An NA 408 on pump gas will go easily in to the 12s in an A body.
 
How do you plan in keeping this engine together with 700-1000 HP? A SBM will have a limited lifespan at those power levels. Maybe an R3 or aftermarket block will last...

The amount of boost is controlled by the size if the pulleys not the rotor size.

Built to last you will be well into five figures with that HP ....
 
Badass HP needs a badass transmission, torque converter, driveline, axle and gear, brakes, tires and suspension, chassis, roll cage.

What you want, you said in your own words. 12 sec 1/4 mile, Night cruise, drive to work, drive to car show. all that is obtainable with a worked over 360 and gasoline. You don’t need a blower or a stroker to get that. You may WANT it because your friend and magazines and internet have conditioned you to believe it but you really don’t need it. You’re not jay leno and don’t need a jay Leno car and engine to get what your original goal needed. Get yourself a roller 360 and make a normal car and enjoy it. Not some steroid blown alcohol small block you can’t get to meet your goal of a night cruise or simply drive it to work because it’s a ******* animal that will not be tame.

Start small and remember your original goal. Your friend is selling you product.
 
I agree that the procharger probably makes more sense than the roots style blower but if that's what you want, go for it. I have no experience with a roots style blower but I think I'll go down that road someday on a different build.

My 408 is 9.0:1 compression and I run 10 lbs of boost with my procharger. I run water/meth injection to cool the air charge. If you run too much timing you will blow holes in your pistons... ask me how I know :)

I was told by tons of people I'd be able to run 30 degrees of timing all day long with my combo. I thought I was being conservative so I started out at 27 degrees. It ran like a scalded dog but was detenating but the procharger is so loud you couldn't here it. By the time I got the timing backed down to about 21 degrees it had already blown holes in 6 of the 8 pistons.

Anyway, it's back together now and very happy. It runs 6.20s to 6.40s in the 1/8th depending on the weather. I run a max of 21 degrees timing.

All engines are different, but just be VERY careful with your tune. I personally wouldn't run that much compression with an 8/71 blower. I'm thinking you are better off getting a custom piston.

As everyone has said, making that much power isn't cheap. I've been through a lot of transmissions. My Dana 60 is holding up but transmissions have been the weak link. I'm probably around 700 Horsepower on a stock block. That I'm sure is pushing the limits so I plan to go to an aftermarket block someday. Check out my build thread.

It's very fun to go this fast in a street/strip car, but sometimes I miss my junkyard 5.9 magnum combo that went high 11s and low 12s that was bullet proof and I could and did drive anywhere. That junkyard motor still lives in my buddies 73 cuda.
 
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