I have read on someone's web site that you only get boost from a KB supercharger at WOT. This contradicts what I have read previously about being able to melt tires at 1/2 throttle, etc. Here's the page I'm talking about:
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It's down under "Drivability." Is this statement correct?
I have a Procharger but aside from one being a positive displacement compressor, the "workings" are about the same. There's a bypass valve that bleeds off boost and it stays open with vacuum. Push down on the pedal, vacuum goes down, valve closes, whoosh! I don't think you have to wait for WOT to get boost though, I'm sure M.J. will chime in on this one.
The KB's make boost dependent on throttle position and not rpm. It also comes on instantaneously. When the throttle lets in more air into the blower than the engine in consuming then it makes boost. The KB's basically amplify and flatten the N/A torque curve of the engine.
I have a KB 2200 with Flowzilla manifolds and I can see full boost at about 1/2 throttle. This makes the power delivery from a KB very, very smooth. It feels like a big block engine that revs strong to redline. You'll have significant power available in any gear and at any rpm over
1,500. I can melt the tires at will through the first three gears. It's a great blower for torque junkies like me. :)
The 455 is now in the Skylark. We broke in the cam last Saturday. Hopefully all linkage issues will be fixed on Sunday and I'll be able to drive it. It's pretty nasty sounding!
Michael, Thanks for confirming that. I've been seriously considering a KB for my car but when I read this thing about WOT, I was taken aback. I think I should send him an email and suggest that he revise that page.
Another assumption I have made is that with the KB, I'm better off keeping my stock gears (3.08), would you agree? I've sort of narrowed things down to two paths: Get the KB and keep stock gears, or keep engine stock and get 3.73.
A good rule of thumb is that the gear ratio that works best normally aspirated will work best boosted.
Boost won't come in until the engine's vacuum passes through zero. The 3.08 will develop boost lower in the rev range than a 3.73 at the same throttle opening and speed when accelerating at the same rate. The 3.73 will produce more boost however as the blower is spinning faster to begin with. This was determined on a '95 GT that got a SVO S/C and then was re-geared to 3.73s.
Gears would be WAYYYYYY cheaper by thousands and easier to install. I'm running 3.73's in my '69. I've looked into a KB marine setup for carbureted engines. BADASS!! I'd have to cut my hood though, DAMN!
We'll see how it goes. It ain't pretty, but it will do. I hope to have it on the track on Oct 23rd. If not, it won't be until next year. I do have a variety of pics, but they aren't posted anywhere.
KB's are smooth and quite. You wouldn't even know there was a blower on the car unless you looked under the hood. They make a 302 feel like a stroked 460.
I have 3.55's which work well. Many times I wish I still had the stock
Not with a KB blower. My car makes 460+ ft-lbs of torque at the wheels at 2,500 rpm. With that much torque available any gear ratio over 3.55 is a waste IMO.
Boost from a KB is not rpm dependent. If the tach is over 2,000 rpm then you will have full boost available at the flick of the throttle. A KB delivers 70%-80% of full boost right off idle. When I mash the pedal I can see full boost before the accelerator hits the floor. It's instantaneous.
Well I forgot to renew the plates on it so it's still sitting in the garage. I plan to have it legal this month and take it to a garage to find the problem. I haven't found it myself. I think it's something minor. The compression is OK and when it runs it doesn't smoke. There's also no mixing of water and oil. I miss driving it.
Trouble is that I'm up to my eyeballs working on the projects we talked about and I don't have time for much else. I still plan to do the 427W swap either late this fall or in the winter. I want the reliability of a N/A engine but the torque of the KB.
I'm glad one of us has made progress. There's nothing like a big block to put a smile on your face. :)
I was pretty scared before we fired it for cam break-in. Because of the money I had to put into a motor for the Ranger, I just took the stock 1976
455 I have and put my good heads, etc... on it and a decent cam. I was afraid it would grenade. Other than a couple small valve cover oil leaks, the break in went fine.
The car is at a friend's house. He did the same thing, but with a higher compression 1970 block. He went 12.00's with it the first time out. He did freshen bearings and used a different cam than I did.
This is the day I brought it home. The tires had to go back, they weren't part of the $300 deal for the car: home.earthlink.net/~seeverist/day1.jpg
This is a before and after of the core support rust out. A friend of mine, who's house it is currently at, did a great job of removing the rusted out area and fabbing up a new core support for it. He even donated a body bushing that is supposed to go in his frame-off convertible. I'll have to buy a set for this car and give him one: home.earthlink.net/~seeverist/coresupport.jpg
This is a picture of the trunk as it was upon bringing the car home (nice pillow, and even a TH350 core trans in there). The pillow is gone, but the trans has been rebuilt and will be there for a while. Hopefully a TH400 will go in before I can blow it up!: home.earthlink.net/~seeverist/trunk.jpg
This is a picture of the engine compartment right after pulling the grenaded
350 2bbl and after the 455 was set in it. He also steam cleaned the compartment, sanded, and did some repaint for me. He doesn't like working in dirty engine compartments. The headers were donated by another friend. They had sat for years and developed surface rust. I had them coated at Performance Coatings in Kent, WA. The color is satin titanium, which is supposed to look like a raw titanium:
This is the motor completed after we broke in the cam. I didn't take this one, so the size is a little small. What started out as a $300 car now has about 9 times that into it. The heads alone were $1400, and that was a complete steal! They've seen mid 10's and have some serious modifications done to the intake ports. The intake is matched to them:
Gears sure would be easier on the wallet. I'm guessing though that comparing the end results of the two, I'll get lots more fun factor from the supercharger? (I think that must be the case, or everyone would opt for gears in lieu of supercharger.)
I have an 89 LX 5.0 with 3.73 and Lentech upgraded AOD. Together about 2/3 the price of the SC. Seems great for street use. I believe (but don't know) that it is easier on gas than a SC would be. Main problem is keeping rear tires adhering in 1st and 2nd during acceleration (yes I do have Griggs racing suspension mods).. SC car would certainly walk away from me above
35mph. I can't answer your question other than to say that for me the stock
5.0/3.73 pushes the limits of tire adhesion in a fox body set up for street use. In the land of 65mph speed limit long gears and high RPM power increase seems less useful than 3.73 gears.
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