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anyone here have experence with 671 at 9lb boost on 347 with 10.2 compresion,can with 306 duration 612 lift. sportsman block, my christmas present. any one know what i can expect....... the old trucker
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I dont know, but it sounds like you have one hell of a set up now. That truck sounds narly. I take it that its not a street truck?

actually i bought it from the drag strip, wired up the lights, put a 6000 rev limiter on it. i have sons that drive, five of them.bought a tag and went on the street. was told 600 hp before the blower. blower drive service said blower will add 200 hp. blower on but plumbing not finished yet. and waiting for dist. takes low profile with flat cap to clear blower snout. its like having a birthday present and can't open it up.

Would love to see some pic's of it. Im getting a chuby just thinking of what that thing will look like with that 671 . That would be sweet!!!!!

one thing i can tell you with the blower there is no room left for the radiator. have to move it to the bed roll cage. a lot of plumbing to do yet i just do car shows and night cruse

With that much compression and that much boost, what are you runing for fuel? Alky maybe?

Thats one badass small block ford you got there. I would love to see some pictures of that truck to...

After reading through your signature w/ the description of the truck, I cant imagine anything but good things w/ that setup. The only thing that I would be concerned about is your compression w/ the blower. Unless your running race fuel or something similar, than you are going to be risking pre-detonation.

A friend of mine with a 67 Chevelle blew up a 496 that was topped with an 871 blower because of his compression. I dont know exactly what his compression ratio was but it was obviously abit to high for 93 octane pump gas. He over-revved it a little and a piston grenaded itself and wrecked the entire motor, including the blower. You would definitely want to look into that a little more unless you already run race fuel.


I have Desktop Dyno on my computer, if you want I could put the engine into it and see what it says for horsepower, message me if you want and I'll tell you all the numbers I need.

i have actually seen guys with rails run alky and no radiator but wont be good for street just track

Yeah I was wondering the same thing, 10.2 compression with 9lbs of boost. I'd love to see pics.

ok try to get some pictures on but have figure it out i have a friend who can do it i hope.blower drive service said i should be ok with 93 ot at 6000 rev limit. but then again they wanted to sell a blower too. they are hurting like everyone. nobody buying, no money. greg at bds said 15% under at 8000 rev 10% under at 6000 rev. i got 10% under driven. does anyone know what 1 can expect.

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few pictures for you guys...will add pictures of the blower added on as soon as my son takes the pictures and uploads them...

thanks

E85 would probably work if you can find a gas station in your area that sells it. E85 is mostly ethanol alcohol but not quite as resilient to boost and high compression as methanol alcohol is.

But they bring up a very good point. High boost engines are usually low compression engines. Purpose built track engines designed to handle ~25PSI of boost often only have a 7:1 or even 6:1 compression ratio. They aren't generally well behaved or acceptable gas mileage getters on the street. With pump gas and a 10:1 engine, I would expect 3-4PSI to ping like crazy and 5-6PSI to start blowing head gaskets. Boosted applications are why head makers sell heads with big combustion chambers that measure in the high 60s and mid 70s cc range. Naturally aspirated engines are the ones that make use of the higher compression and thus get the low 60s & high 50s cc heads.

BTW, a member of this site that put a 5.8L/351w in his Ranger made the mistake of putting 58cc AFR185s on his engine. I think he calculated his setup to be in the 11:1 compression range. And because of that, he had to pull LOTS of spark from the stock tune @WOT to get California premium to not ping...and that was naturally aspirated. I don't believe his engine would have a chance at running boost on pump gas.

good point there alot of true race engines are o-ringed too with copper headgaskets (a pain in the butt to seal) we used some kind of spray sealent to put the ones in we did and sealed ok for a while. runnin that much boost on an engine thats not really built for that may have bad concequences... but if you have a strong bottom end you may get lucky, ive seen people throw a ton of boost at 5.0 mustangs and **** fly everywhere

i was told compresion will go 13/1 at 6000 rev. i did the carb cfm [rev cu in boost] it came to 803 cfm. i'm going to use a quick fuel 750 cfm. quick fuel said these actualy flow 830 to 835 cfm. guess i'l see if it works........the old trucker

cgrey8 wrote:But they bring up a very good point. High boost engines are usually low compression engines. Purpose built track engines designed to handle ~25PSI of boost often only have a 7:1 or even 6:1 compression ratio. They aren't generally well behaved or acceptable gas mileage getters on the street.

You sure about that? My cobra drive's like a lexus out of boost. Idle is silky smooth and it drives like a dream. I once managed a tank of gas around town mostly out of boost and I got 19 mpg.

As an FYI 03 Cobra motors are 8.5 compression ratio and people are finding with a twin screw (kenne bell) they can get around 17 to 19 PSI tops on pump gas (each person's varies a little). Over that they are running race gas.

Malcolm, that makes perfect sense. 8.5:1 compression isn't what I call high compression at all. I don't imagine your Cobra, even in modified form, hits much above 15PSI. Even at 15PSI, that's low enough you can run 8.5 compression no problem especially with an intercooler and premium gas. In fact, that's pretty typical of street driven boosted applications. 8.5 is high enough you can get decent fuel economy and behavior from it but low enough you aren't blowing the heads off when you shove a little boost down the engine's throat. Many many naturally aspirated engines were built in the 8.5:1 compression range from the factory...particularly Big Blocks which rarely left the factory over 9:1 until injection was more popular.

Getting 19PSI on an 8.5 compression engine is running the ragged edge and you got to have one hell of a good intercooler to keep the ACTs down or you wind up loosing power. It takes a lot of engine power to produce 19 PSI of boost. And if you aren't getting a return for the investment, you are wasting your tune boosting that high. People without intercoolers often find they actually loose power due to all the spark they have to pull to keep the predetonation under control at higher boost levels. But if you are looking to get into the ~25PSI boost range, 8.5 compression will be way too much compression with pump gas...at least from everything I've read. Maybe someone else can give an example of engines that are commonly built contrary to that and hold together. But this is just the extreme case of a purpose built engine that needs 7:1 and 6.5:1 compression levels to run pump gas.

However in this thread's case, you are talking a 671 which can move some air. Then the topic was discussing putting that on a 10+:1 compression engine. I was just trying to put things into prospective that if you run big compression, you limit your boost capacity sometimes to the point that you got no room left for any boost because naturally aspirated, the engine pings too much.