Inliners International Forums General Discussion Blown and Injected 250 with centrifugal supercharger???

Hello all! Been lurking awhile and have read every thread on the site about superchargers, and mostof the ones on turbos. I have a 69 chevy swb with a 250 and would like to run an Offy intake, Edelbrock 500 (w/adjustable secondaries), a mild cam, a little headwork and headers. I was gonna put a supercharger off of a 4.6l Mustang (easy to find) and figured with a little adjustment and some cool brackets like MBHD had on that blue engine, I would be in business. I am looking for any and all tips, suggestions, and info. I was thinking turbo at first, and I know it has some advantages, but I really like the sound with the dual exhaust, and the looks of the blower. I would be curious how much power the charger would add, and how much is attainable wit natural aspiration. This truck isn't a daily driver, but I would like it to be streetable and reliable enough to travel to some shows. I have really enjoyed reading all the info on this site, and look forward to picking brains,and maybe helping someone out, too. Thanks!

Cubber,
welcome to the site.
IMO, you should jump on that Larrowe & sons blower manifold.
As far as being a bit easyier to install.

Otherwise, if you can fab up some brackets as I did, use a centrifugal supercharger, they can pump much more air than the smaller superchargers & heat the air less.

http://prostores1.carrierzone.com/servle...hevrolet/Detail


I am trying to remember, if it has a 271 blower pattern or a 471,can't remember for sure?

Run a 144 Weiand blower or other supercharger that will fit & can pump enough air..

If you build a purpose built engine for a supercharger & use a big enough blower, you can make 300-450 HP faily easy enough.
Don't know how much power you are hoping to make?

My Paxton supercharger was the older ball driven blower & I could only make 8-10 PSI max.

I estimated about 400 HP to the wheels, never took it to a dyno or a track but I raced friends cars that raced there cars on a regular basis.
1/4 mile was approx 12.6-12.3 range.
Maybe these pics can give you some ideas?





















MBHD

Wow! Thanks for all the pics. That is where I think I would like to mount mine. (matter of fact, I saw those on the forum before I joined which is how I got the idea.) I had looked at that Larrowe & sons manifold, but have an aftermarket p/s bracket that puts the pump about where yours is, and it seems like they would conflict?? Also, I have read that the centrifugals have more adiabatic (i think thats how you spell it) efficiency, and create less heat. One unit I have considered buying I found here on my local cl. It's a vortech capable of 5-10 lbs of boost and is a complete kit for $750. I know it wont just bolt on, but there is a bracket with it that looks a lot like the flat piece your blower is mounted to. I am looking to make as much power as I can, but I will probably build it like you would maybe just one step above a daily driver. If I could get in the 400 range, I would be delirious with joy. Also, I plan on pulling the engine to replace all the gaskets soon, so since I'm gonna have it out, I could go ahead and build it. Just for the sake of discussion, what could a guy expect to get power wise out of a streetable, naturally aspirated engine??
Thanks again for the pics and info!

Here is my new power steering bump & brackets.







Mock-up phase pics below:








MBHD

That's impressive! Mine is just a $150 semi-universal deal off of ebay. It takes a Saginaw Type II (I think- it's the one from the 70's-80's) p/s pump. It has worked well so far. Would that setup you have work with that Larrowe& sons manifold?

So I found a vortech v-1 a trim off of a mustang for $500. For a little more, I could get the whole kit, which looks like I could use or modify and use at least some ofe the parts. Also, I was planning on converting an edelbrock 500 to blow through. Is this something I could do, or should I just pay the carb shop?? I have good skills and a lot of tools, but I don't really have any specialty tools. Thanks.

You can mod the carb, there are websites on how to for that carb.

Change the floats to plastic & other things you need to do.

Or run a complete carb bonnet that has the carb in a sealed box basically.

Paying a shop to mod the carb usually cost a lot.

MBHD

I think it costs close to $500 for the carb mod, and that's after I buy the carb. I really want to do all of the work I can myself, but I want to take precautions to avoid burning a piston or rings. I know there will be some risk involved, but I don't want to start without a plan. Do you think that supercharger will be a good choice? I thought I could afford to try it out b/c of the low cost, and swap it for a purpose built one somewhere down the road.

Not sure of the flow capabilities of the "A" trim?
Probably good for low boost.

I know the early Vortechs sounded like they were coming apart just ideling. Very noisy.

Carb encloser: http://www.ebay.com/itm/Paxton-Carb-Box-...728a6f3&vxp=mtr

MBHD

I looked up the a trim, and it is a low boost charger. I have heard as low as 5lbs, and as high as 10 lbs. I also have heard that they are noisy. i'm not worried about noise, I am into power. I am just rying to make the most i can while keeping gthe 6. What is the max power available naturally aspirated while keeping an engine streetable?

There really isn't a set HP # that defines a limitation for streetability. Its just a matter of compromise of what you are willing to tolerate in driveability characteristics in your engine.

what cnc-dude said there's not a horse power limit it;s just how everything is set up. my sbc drag radial turbo car has 627 naturally aspirated but makes 1375 to the tire's on a chassie dyno.and i drive my car on the streets now this is by no means a daily driver but it is street able

I see what y'all are saying. I won't ever use my truck as a daily driver, but I would like it to be able to drive to car shows, some of which are far away. Maybe even do the Hotrod power tour. I was just curious about how much power I could get by building the engine (boring .030-.040, opeening up the heads some, maybe larger valves, a decent cam, and a 4 barrel intake and carb, and headers. I would want to build it to handle a blower, but also be a decent engine without the blower. I guess I was hoping to use the supercharger as icing on the cake of a well built engine, rather than centering everything around the charger, or just sticking a charger on a motor that can't take it, and cause a catastrophic engine failure.

If you can find the threads on here about the dyno testing done a while back, you will see the 292 that made 300 HP with 8.8:1 compression using basically just bolt on performance parts commonly available to anyone. I think that engine would still be rather streetable for most peoples taste. If you plan to use it for both N/A and forced induction, you will need to observe a compression ratio at or near the 8.5:1 range as this engine has, but still 300 HP or more is relatively easy to achieve with pump gas level compression, which was the main premise of the dyno testing to begin with. Tlowe has a street driven 292 that makes upwards of 450 HP with a turbo, so you can get some impressive power out of a 292 or even a 250 with the right combo of parts. A 250 was even dynoed with a budget turbo setup using only 5 psi boost and yielded 350 HP. And it didn't even use a turbo specific camshaft. So with a more refined specific cam and higher boost level, 400 HP+ is not hard to achieve, and still be driveable on the street.

thanks, CNC!! I plan to pull my motor this fall, but I am going to get as many of the parts I can before I pull it. This is my first inline, and I think that with the help of this site, I may be able to avoid some common errors.

No disrespect to Tlowe but...I am pretty sure Tlowes turbo, efi,intercooled, 292 does not make 450 HP, the fastest it ran a 1/4 mile was what, 13.8 @ 98 MPH? & last time out was running 14's? Not sure what 450 HP equals to 1/4 mile et's & MPH but a 1970 LS6 454 70 Chevelle (heavier vehicle) would be faster than 13's no?

Tlowe did dyno his Elky years ago & I was dissappointed of the results, not sure if he was?


MBHD

There will be significant differences between a N/A motor and a blower motor if you expect anything more than 300: relative valve sizes, header primary ID, and especially a performance N/A cam will have much tighter LSA. The stock L6 cam works pretty well in a blown application because it's very mild with few RPM-sensitive characteristics and small overlap.

I believe you can run the stock camshaft for low power output on a turbo set-up. You can get high boost pressure really easy & fast , HP will not increase as much as the torque output will.

It would be a worse choice to run a stock cam w/a supercharger application over a turboed engine.

With the stock cam specs, it does severely choke the breathing of the engine.

Just my 2 cents..

MBHD

He only drives it ultra-conservative since it only has stock rods in it, so you wont be able to use any ET he has run as a gauge for power output.

cubber, for more information check out Turbo.com they have a section on the Edelbrocks' and how to modify them for blow thru applications.

Here are Tlowes dyno results.
1st run 235 hp @ 4550 rpm torq was above 300 from 2700-4700 rpm. max tq was 320
2nd run 243 hp with 1 more degree of timing 26 total
3 rd run 240hp @ 27 degrees timing.

Kinda hard to guestimate 450 HP w/those results .

Maybe there are unpublished 450 HP dyno results?





MBHD

Dont think your going to see those #'s anywhere. Those you listed are from so long ago, the Statue of Liberty was a little girl, not from his 292 anytime recently, there unpublished as you said.

Lets just say I'm from Missouri, the show me state.

MBHD

Tom is probably the highest contributing member this forum has ever had. He has logged over 200 dyno runs on both the 250 and 292 engines....you know this, he also has countless of videos documenting that as well. Why would you think that producing 450 HP from a 292 with a turbo would have to be proven by anyone. Just because you haven't done it doesn't mean it cant be done. He has also been contacted by Car Craft magazine as you also know, because of his accomplishments with these engines, to give his advice to the magazine on some turbocharging questions....who has ever called you! You obviously cant get past the fact that Tom is making a mark in the Inliner world and that many members here as well as the club president and forum administrator have a high regard for his knowledge and his achievements.

All I am saying is show me his Elky makes 450 HP.

I would be very disappointed if my built 250 only made 450 HP.

Don't understand why you keep stating his 292 makes 450 HP.

Where is this info of his engine made 450 HP?
I think all of the forum members would like to hear it from Tom him self.

MBHD

I think one of the main items you have to consider is an El Camino is a poor choice tor a drag car because of the weight distribution and to make any engine work will require a suspension rework that will completely ruin any streetability. 450 HP is attainable from a 292 but what would you have him do? Pull the engine and dyno it, chassis dyno?? It runs and goes like stink and can be driven to the store or cross country, nuff said.

His is in the process of building a purpose built 65 Elky for drag racing.

Even if the Elky does just spin the tires, the MPH will show the HP it is making & IIRC, the best MPH it ever made was 98 or 99 MPH.

Guys have made more power from a 250 turbo engine, so of course 450 HP is attainable from a 292, even N.A 292 engine can.

Heck, Tlowes turbo 250 made good power w/only 5 psi 340 HP?

Tlowe already had dynoed & published the results.

Are there more dyno results not published?

All I keep seeing is it makes 450 HP on posts here.

He does not have to prove anything, but if someone states Tlowes 292 makes 450 & runs low 14's last time @ the track w/dyno results of
"1st run 235 hp @ 4550 rpm torq was above 300 from 2700-4700 rpm. max tq was 320
2nd run 243 hp with 1 more degree of timing 26 total
3 rd run 240hp @ 27 degrees timing."
it's a little hard to imagine the posts here are spot on.


With those dyno results, it is making about what his turbo 250 engine made, so it seems. About 340 HP @ the crank?

I think he is making 350-400 ft lbs of torque.

MBHD

That 450 hp # was put out by me when the engine was first put together and I was thrilled with the way it ran. Since then I did chassis dyno it and came up with very respectable #'s. But not 450hp. The torgue when driving is a thrill. I do not rev it over 5000 rpm, so no real hp can be made without massive tq.

I do like to have a very respectable, streetable car and my recomendations to people reflect the same. For me to make 20+ PSI of boost on the brakes is not going to make a streetable car.

Don't care to argue about it either.

The main thing is, a turbo is probably a better choice over a supercharger on a inline 6 like the Chevy's. It is hard to mount the super charger and drive it from the crank.
A turbo is easier to package, easier on gas and can make more power.


I do have a question about the J&S safeguard knock sensor with regards to our six's. Where do you plan on mounting the sensor? There are not many attacking points that are good for this on these engines.

Tlowe ,

thank you for your honesty.

I am curious to your newer HP & torque numbers, but you dont have to post it if you don't want to.

The 20 PSI of boost on the brakes is just a launching technique.
My Syclone is a stock, very smooth idleing engine & is very steetable.

The cam specs are smaller than your 292 cam, like 175 degrees duration @ .050 & .380 lift? It's stock, as in a stock Chevy Astro Van 4.3 camshaft stock.

In regards to the J&S, I have not mounted mine yet, but plan on making a bracket screw in the knock sensor on the bracket & attach the bracket to the side of the block, or even on the cylinder head. An unused or even a used threaded bolt boss will work.

My Syclones knock sensor is located top of the block close to the distributor.

Are you thinking of getting a J&S?

MBHD

No really looking to buy one, just have messed with a knock sensor on my engine and had difficulties with a good location.

Something interesting though. I do own a new design vortec 3000 4 cyl. Maybe a 2008 model. It has all the good bells and whistles.
One piece rear seal
individual intake ports
Injectors bungs cast into head
Location on driverside of block for knock sensor.
Crank position sensor
4" bore
This engine still shares our head block bolt pattern and front cover.

I had looked at these engines (Vortec 3000) for the dragster and with a modified ECM and bigger injectors they should be able to pump out close to 300 HP N/A. The redesigned intake ports are a big help too. If it's the same as this PDF file the water pump is also an interesting rediesign, http://pdf.nauticexpo.com/pdf/marinepower/vortec-3000/22171-12476.html

I was pretty excited when I first posted this thread with the information given, and also the helpful spirit in which it was given. after not being able to check in for a few days, however, it seems my post has degraded itself to a good old pissing contest. For what its worth, I thought we were all on here to share info and tips. As far as dyno tests go (at least Where I come from), the best test is to line your ride up next to the other guy's, and see who gets over yonder the fastest. If it ain't you, then its time to sit down and SHUT UP. No disrespect to anyone, cause I don't know any of you, but I don't have much faith in all of the tough typing that goes on on all these sites. Seems like peoples cars run differently behind the keyboard than they do behind the wheel.

Anyway, I am going to build two 250's, and have decided to put the supercharger on the back burner. If anyone still wants to help or advise, I would like to know what is possible with an N/A 250, everything from mild to wild. I would like to retain the original block and head, but I am willing to modify them in whatever fashion necessary. I would like to make 350-450 HP. Can it be done? If so, how? If not, then what IS possible?
Thanks,
Matt

I personally liked to run side draft Weber DCOEs.

I tried the Clifford, Offy intake w/various carbs, from 2 barrels to four barrels & the best intake & carb combo I ever ran was a Clifford side draft intake manifold.

It ran so much faster & smoothed out the idle, the best! I.M.O.

BTW, it ran the best w/a 194 cyl head milled down & 12:0 compression.
220-230 PSI cranking pressure.

MBHD

Thanks, Hank. As I said earlier, I have 2 complete engines. Someone gave me one earlier this week that they pulled out of a truck just like mine to (of course) put a 350 in. My engine runs pretty good, but leaks like a sieve and has what I believe is a wrist pin knock. I just put electronic ignition on it last night, and it seemed to make a big difference. I am planning on fixing the oil leaks this fall/winter and it seems like as easy as that engine is to pull, it would be best to pull it to fix 'em. I also wanted to paint the engine and underhood area, so I thought while i had it out I might as well go through it, since I will be basically tearing it down to replace all the gaskets anyway. I was thinking of going with an Offy intake, and and Edelbrock 500 because they are easy to get, and I would like to save my big dollars for my upcoming supercharged build. Also, I have never messed with side draft carbs. I would like to run on pump gas, but I don't mind buying premium (93). I guess I was kinda hoping someone could give me something like a spec sheet so I can tell the machine shop what to do with the head. I am cool with lumping and changing valves/spings/rockers and porting. I will probably bore the cylinders .030 over. I will use long tube headers from Summit. All of this will be going into and old truck, so it probably won't be on the strip a lot, but I want it to be fun to drive, and if I can give on of these guys with an sbc a run, that would be great. I don't want this thread to go in circles, so I guess I'll just ask for what I need help with. I know what I want, but I'm just not sure how to accomplish it. Santucci's book (read it cover to cover) jumps around a little for me, and I can't just ask ol' Leo for advice like I can you guys. I would really like to know what head work I need done, piston and rod recommendations, and cam recommendation for an engine that is as hot as possible on pump gas.
Thanks and keep it inline (haha I'm hilarious),
Matt

Building a 450 HP engine in N/A form is going to be much harder and expensive than building one that has the same power with forced induction. A 250 with 450 HP is equivalent to a 350 making 630 HP, so any machine work you would need to perform on the 350 to help it endure that kind of stress, you would also be required to do on the 250. You may even have to dowel the main caps and use main straps if you intend to beat on the engine on a regular basis. Much more extensive headwork will need to be performed to reach this level as well. Also as Hank mentioned, a better induction setup is going to be a must. You also will need to install much more beefier rods, H-Beam or I-Beam style, billet preferably, as well as quality forged pistons. Reaching that HP level in N/A form will require you to go well beyond the compression level needed to run pump gas, also, the peak RPM range on such an engine is going to be well above the level of normal street driving also, and may make street driving altogether a disappointment in a big heavy truck.
On the other hand, using forced induction will give you many benefits over the N/A engine. It will allow you to use pump gas, which you said you would like to do. It also will give you the 450 HP in a much lower RPM range suitable for street driving, and be more pleasant and fun to drive. It will also make your engine last longer because you aren't having to run the engine so hard. You still will need to prep the engine in the same manner as far as machine work and components goes, and maybe add an intercooler and some form of alcohol injection to help fight detonation, but it will definately be the better way to reach your HP goal.

Makes sense, CNC. Thanks. It seems like these engines (and I guess most others) are affected by the law of diminishing return. The more you spend, the less power you get per $. I really want to keep the 6 because it is original to the truck, and not a lot of people would do it. I think I need to take the engine in the truck and do a mild build, so I can use it as a cruiser, and find an old nova or camaro (pretty easy around here) and build the other motor to shred the strip with. As far as the truck engine goes, money isn't much of a factor, but I don't want to spend an extra $8000 dollars to get 100 hp. What is possible with a mildly built engine (intake, headers, cam, bored, and head work) that will still run on pump gas? Racing fuel is hard to find out here I live, plus I want to be able to fill up wherever I am instead of having to make a research projct out of where to get gas.
Thanks,
Matt

You should be able to get 1 HP per cubic inch from this engine and still be streetable with no problem. Beyond that, you will need to decide if the mods necessary to get more HP still meets your needs for street driving. Another 50-75 HP can still be gotten with common parts, but the next 100 HP after that is going to be a little more involved as you already mentioned. If you can find the threads on here from the 250 dyno testing done a while back, you will see that this is easily obtainable with commonly avaialable components and basic block and head work. So no budget breakers to worry about and its also pump gas friendly.

IMHO 1 hp per inch is already past the point where it's fun to drive on the street - low speed power is weak, ignition has to be set very accurately, it's only fast when wound out.
There is a certain amount of good engineering in the maxim "increase the compression ratio when you delay the intake valve closing point to get the cranking pressure back up". The problem is that although the pressure comes back, the low speed power is still down.

I put hei on the truck last night and a tach. I already changed the gear to a 3.42. Without being scared of over revving, i laid into it pretty good, and was pleasantly surprised. It has a bad cutout when you first get on it, but I think it is b/c of the junky reman Monojet the p/o put on. It leaks gas anyway every time you shut the motor off. I think that rod is worn out. There is some valve chatter at around 4000 rpm, probably a timing issue. I am going to check those dyno results out asap. i am thinking that if I keep the six, I will keep it kinda mild, since I have another one I can go all out on. I am really enjoying this process, and will post some before pics of my engine when I can. Thanks guys for all your help!

HEI's work great.

Mono jet carbs really are the limiting factor in making power on a stock engine. A intake & 4bbl carbs makes a good difference in increased power.

A side draft carb intake will make the bigger gains, even on a stock engine, I forgot what Cliffird had said how much HP increase over a stock set-up? What is it guys, 40 more HP??

Found it, 40-60 HP increase. Oh my!

MBHD