429idi
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You'll probably finish your blower before mine, but I'm working on it.
pic of a super charged 7.3 idi that's pulling
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You'll probably finish your blower before mine, but I'm working on it.
429idi
Full Access Member
Sounds fun.. kinda lolHave you done anything to drop the compression? This is my other hidden idea about running a blower, theoretically in my mind that would allow running even lower than "lower" static compression. Say the blower is boosting 2-3lbs at idle. That would make a 17-1 engine more like 18-1 at idle... if ya get me, then again at this point im not sure that i get myself, but im havin fun. With a blower that is going to boost no matter what, you could drop the CR waaay down, fuel like crazy, and light that big ol' nasty turbo you have. Set the propane to come in with the turbo, and i dont see 40lbs as a problem. So long as you have the fuel to make it all happen.
That is a good point, it could get rid of the hard starting issues that lower compression engines have.
88 Ford
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Sounds fun.. kinda lol
I think you would still have a hard time starting it. Idk just my opinion.
hairyboxnoogle
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I never thought of that, did the 5.7s run the stanadyne pumps? I dont think id want 4400 either, but i get your point. Ive been talking to a local engine builder that does alot of race motors around here, going to have him do some lightening, balancing, knife the crank, and maybe bore it. He said he can tell me what he thinks will be safe rpm wise after tearing into it, so im going to go mostly off of that. I have heard of people running them in stock form at 4k and even 4500. So maybe after surgery 4400 will be fine. Like you said, just because it will go that high doesnt mean i have to... but i will
. Which means ill have to get a new tach
88 Ford
Full Access Member
I just have to get my truck from Idaho and that might be awhile. But hopefully I can get it sooner than later. As for the compression thing,I still think it would be too low cus when the engine is just turning over, the SC isn't making as much boost. But who knows until we try.
88 Ford
Full Access Member
I never thought of that, did the 5.7s run the stanadyne pumps? I dont think id want 4400 either, but i get your point. Ive been talking to a local engine builder that does alot of race motors around here, going to have him do some lightening, balancing, knife the crank, and maybe bore it. He said he can tell me what he thinks will be safe rpm wise after tearing into it, so im going to go mostly off of that. I have heard of people running them in stock form at 4k and even 4500. So maybe after surgery 4400 will be fine. Like you said, just because it will go that high doesnt mean i have to... but i will
I'd be careful with boring it too far cus of cavitation issues. Idk how far is safe though. You could also run a stiffer PSD spring too.
hairyboxnoogle
Full Access Member
I dont know about that, was thinking more along the lines of keeping it running once you started it. And since it is such low compression, it wouldnt be such a dog getting the turbo spooled. That is, running a blower instead of a single or even twins.
I think you would still have a hard time starting it. Idk just my opinion.
Im curious about this tho, with good GPs and a good mist injector, i dont know how hard it would be to start even at 17/18:1. Although i dont plan on running a good misting injector. My dads had the compression dropped to 20:1 iirc when they did the rebuild, and that thing fires right up when its 10* out, and not being plugged in. So even if you do have to plug it in when it gets chilly at night, i dont see a problem getting it started. If all else fails, steal an ether assist setup off a tractor and youre in the clear.
As far as i know, no one has dropped their compression low enough to cause even harder starts let alone a complete non starting issue. Dave S. is running 20-1 too i believe and last i heard didnt have any problems. Only engines i have heard of having starting issues were the Hypermax and DPS Idi's both were at or around 15:1, which would cause starting problems in any diesel, IDI or DI
429idi
Full Access Member
I never thought of that, did the 5.7s run the stanadyne pumps? I dont think id want 4400 either, but i get your point. Ive been talking to a local engine builder that does alot of race motors around here, going to have him do some lightening, balancing, knife the crank, and maybe bore it. He said he can tell me what he thinks will be safe rpm wise after tearing into it, so im going to go mostly off of that. I have heard of people running them in stock form at 4k and even 4500. So maybe after surgery 4400 will be fine. Like you said, just because it will go that high doesnt mean i have to... but i will
Ya they run the db2, there was a pump on ebay that I was watching, and the auction ended while I was at work, it sold for 5.00
Ya, the volumetric efficiency is pretty low at low rpm, but if you aren't using the idle bypass it could make some boost.
By the way, It would only take 1psi to make 17:1 static turn into 18:1.
14.7+1=15.7 /14.7=1.068 x 17 = 18.15
hairyboxnoogle
Full Access Member
Oh yes stiffer springs will be mandatory to go that high im sure, if not due to just boost alone. Not to mention i want to use a exhaust brake. Was going to use the same springs NMB2 anr Racin are using, they have good numbers installed, even have room to shim, or go with a 1.7 rocker before bind. As far as boring goes, it would be only to clean up the block and get everything aligned so .030 or .040 at most. Im going to run a pre-charged coolant filter so even if i did bore it out to a 7.3 or higher cavitation wont be an issue.
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blown84
Full Access Member
ive got a line on a 7.3 factory block and heads. plan: bore 7.3 to accommodate sleeves, actually reducin the bore from 4.11 to 4.10. get a fully balanced 4.36 inch stroker rotatin assy. with ceramic coated, low-topped pistons, with DEEP valve reliefs, makin it a non-interference motor, even with with a big, 460-torque-monster inspired hydro-roller cam, gettin .550"/.500" intake/exhaust lift, respectively. this would make it a spot-on-the-nose 460ci motor, with a compression goal of 18:1. '94 moose pump with torque screw, 4400rpm spring, and moose misters, extensive head work with studs, custom intake with water/**** injection, to perch a 6 or 8-71 (or maybe an 8-92??) blower on top of, pushin 9 psi at idle, and a set of stans headers with true dual exhaust. goal: i only want to push a measly 350 hp and 550 lb-ft. if i can hit that, ill be happy. but im sure youve noticed, the cam is the weak link im aimin to solve, and if a gm lsx 454 gasser with an 8-71 at 9 psi can push 850 lb-ft at idle, so can my motha-f***in IDI!!
hairyboxnoogle
Full Access Member
Ya they run the db2, there was a pump on ebay that I was watching, and the auction ended while I was at work, it sold for 5.00
That bites, i wonder how different they are from ours if they are at all.
Ya, the volumetric efficiency is pretty low at low rpm, but if you aren't using the idle bypass it could make some boost.
By the way, It would only take 1psi to make 17:1 static turn into 18:1.
14.7+1=15.7 /14.7=1.068 x 17 = 18.15
Wow, nice work i knew there had to be a formula, but i had no idea what it was. Soo 14.7+40= 54.7/14.7=3.72x17= 63.24 ? Then again, thats at sea level, i think average air elevation around here in the summer is around 4200... like 12.4 AP. Been a while since i played with our airtronics thingy
429idi
Full Access Member
12.4 is where I'm at too. Of course if you wanted the real dynamic timing, you would need to figure volumetric efficiency, and some more stuff, but for comparison it works.
hairyboxnoogle
Full Access Member
As far as valve reliefs go, i dont know how far into the piston you would have to go to make it non interference. My guess is you dont want to take too much of the crown off. Thinner metal gets hotter faster. This also heats the oil by way of the piston squirters. Techniacally a 460 is actually 466 CID. I dont know where you will find a stroker kit, but if you do lemme know. I thought about offset grinding the crank to gain some stroke but thats going to come down to what my machinist says about weakening the crank and clearance. Seems kinda overkill to only hit 350hp, unless youre talking 350rwhp +. Also, a big block is turning almost twice the rpms you will even with 4400 spring. A 6-71 or 8-71 would be huge on our engine. Thats like putting a 093 turbo on a quad. 3.8L @6600rpms = 7.6L@3300 rpms. This is why i think im going to do some lookin in on the GM 3800 charger, especially since i know where one is in a backyard sittin on a blown up buick. Would have plenty of leeway to overdrive the blower without the rpms going to the moon. As far as the cam goes... $2200 will get you a fresh cam ground however you want it. However with forced induction you dont need the lift and duration a NA motor does. Regrind your cam to work with forced air and youre set. Or if youre really motivated, you can join me in finding a set of 1.7 or 1.8 rockers that can be made to work on our heads. Comparing an IDI to a BBC, well imo like comparing 2 strokes to 4 strokes, or bannanas to bowling balls. IDK about 850lb ft at an idle. Maybe at 2200 or even higher. Our race motor didnt get into the torque band till around 3200, peak was at 3900 at 710lb ft, then again its a NA 451 dodge
blown84
Full Access Member
"...over 800 lb-ft of torque just off idle..."
http://www.popularhotrodding.com/features/1104phr_1968_chevy_camaro/cherry_bomb_camaro.html
http://www.popularhotrodding.com/features/1104phr_1968_chevy_camaro/cherry_bomb_camaro.html
blown84
Full Access Member
and i said my goal is 350hp. yes thats at the rear wheels. and yes, its a lot of work for a tiny goal, but even at 350 rwhp, id be a pioneer. hell, mel only makes ~290-295 rwhp. after him its ~285-290. if anyone here is makin more, id LOVE to see dyno graphs and know how they did it. also, im not just goin for deep valve reliefs on the pistons, im wantin shorter rods, and an overall shorter piston. i want it to stay down in the hole a little bit, just to get it out of the path of the valves. granted, its NOT a high rpm motor, even after a lot of work. the heads flow plenty for the rev range, the capability for the fuel is there, but the weak link: the cam. why? because its an interference motor. the piston can hit the valves, even at stock lift. this means theres no opportunity for good duration, or overlap for scavengin. my goal is to overcome all of that. also, in readin, the cherry bomb camero isnt even a 454, its a 427. and i was wrong, its 800 lb-ft just off of idle, not 850 at idle. but still, if a gasser, with less displacement than my build can make that much torque, that low, so can my idi.
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