Homemade 125" FED Twin-turbo SBC

I would have put a dip in the frame had I built it with a longer wheelbase. I like the look of the straight frame short wheelbase dragsters. I need to get the turbo fabrication done, build the cage and body then get it out in the open to see if I like it. I just might end up cutting some wheelbase out of it if it doesnt "do it" for me. 125" to me is a fine line between a short FED and a long one. I want it to track relatively straight but on the other hand I dont want it to be an eyesore to me.

 

Do you feel a stock sbc with stock internals can take 10lbs of boost on a consistent, say daily, basis?

That setup would be cheap hp.

 

I don't think you understood what I was saying. The wheelbase is fine. The frame rails should be tapered some. Going from 2x4 to 2x3 say from the front of the motor forward to the front end. Would not look so boxy in my opinion. Give it some streamlining in design. Just my lousy 2 cents. Can someone draw him something like I suggested? I have no computer drawing skills

 

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Back in the 70's, one of the car mags - maybe Hot Rod, Car Craft, PHR or ??? - I can't remember which one now - did an article on Zora Arkus Duntov and ran a couple of pictures and some specs and tech info on that experimental twin-turbo 283. I remember at the time thinking that using a pair of fairly cheap Corvair turbos mounted on inverted stock 'Rams head" manifolds was really slick and for a while seriously contemplated duplicating the set up, but I never did

Mart3406
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My bad, I understand now. The frame rails are actually 2"x3" from front to back. I could step it down to a 2"x2" tube from the motor forward, that would look better but I would be a little concerned with its ability to carry the load of the motor without flexing too much.
Im not sure if you can see in the pictures but I did taper the front of the frame rails from 3" down to 1 3/4" to meet with the torsion tube. I only brought that taper 12" back from the end. After seeing it on the floor and at ride height I have been considering redoing that taper. I might taper it back 24" or more.
Do you think that would help some in eliminating some of the bulky look? Thanks for looking.

 

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283's came with forged steel cranks and
I imagine if you simply added some good
forged flat-top replacement pistons that
it'd live a long time at 10 lbs. boost. 283's
if you treat them right, are pretty tough.

Mart3406
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Nice look'n project! Where in Maine are ya?
Pontiac Slim here in lovely rural Mexico... MAINE

 

I made roughly 748 HP in a Ford 302 that I built using a pair of $130 ebay turbos. The shortblock was full of stock components. Stock cast crank, stock connecting rods with ARP bolts, and stock 1987 pistons. I rebuilt the bottom end with just new bearings and rings. I set main bearing clearance to .0019" and rod bearing clearance to .0017". I had no fancy fuel injection, I modded an old 650 Holley DP to work under boost and tuned it very conservatively. I only ran 22 degrees timing total locked out, and ran 108 octane VP fuel.
Based on my experience with this 302 I think a stock bottom end SBC could take 10 pounds of boost, live a long life, and do it on 93 oct pump fuel. Keep it out of detonation and it will survive!!!

 

Thats cool. It amazes me how the turbo thing never really caught on in the drag racing world until the '90s. You can make huge power with small cubes and idle like its stock.

 

I have the basic layout of the turbos mounted on a rig. Here are a couple pictures, tell me what you think. Too low?

 

please tell me thats not how you are mounting the rear to the frame and going down the track..... thats just for mock up right?

 

I remember reading in one of the hot rod mags, back in the 70's, about Buick's first attempt at turbocharging an engine. It was a factory program from the early 60's... I'm going 100% off memory here, so take it for what it's worth.
They put a single turbo on a nailhead [401], and the damn thing made so much power, they couldn't get a transmission to survive behind it, or tires that could put the power to the street.

X2

 

Those steel plates will be welded to my uprights. Whats the issue with this???

 

a friend has a fed and was talking about installing twin turbos but had an issue with using blow through carbs. How do you do it?

 

Jim, your build is awesome, the frame is dead-on and simular to what I had planned for my Twin Engine build. I believe the rear-end requires 4 bolts per side, 7/16" minimum diameter. The other issue we have is if we run an NHRA Track (which I don't plan on) the shoulder hoop and bottom frame tubing must be a spec size and a 1 piece hoop from in front of the engine plate (2" I believe) around the driver and back to the front of the engine plate. I'm sure you searched the forum an found the great info started on here by King Ch***is and the input from alot of very knowledgeable builders like Rooman, Riceman, King Ch***is and others. I'd leave the front as I love the look and proceed Rocky
These copies of NHRA 10 sec and slower rules are 2008 but you get the idea. As fast as that bad boy is going to run you'll need the SFI Building specs if you plan on running an NHRA Track.



A drawing I did for my build.

AWESOME BUILD!

 

Jim,
to p*** NHRA or pretty much any ?hra tech the rear end needs to be mounted with 4 bolts per side, 7/16" minimum diameter. There also needs to be 1 1/2 bolt diameter of material outboard of the hole and the bracket on the housing itself needs to fit at least 180 degrees around the housing.
If you run quicker than 10 flat the frame will need to conform to the appropriate SFI spec. At the very least it will need to look something like the stuff in Rocky's post.

Roo

 

Keep in mind once you run under 10.0 You're gonna have strict tech to conform to. Ch***is certification, safety gear, etc. Your enthusiasm is great, but you may wanna pause just to make sure you're headed in the right direction. Are you content to run outlaw tracks or do you ever think you're gonna want to run at a NHRA/IHRA event. If so you might want to do a couple things - get an SFI book. Get a NHRA handbook (it's a rough guide only and often refer's back to SFI) and last but certainly not least get ahold of your local ch***is inspector. Talk over your plans with him - "fix" anything upfront and save yourself aggravation later.
My 2 cents!


Looks like a fun project!!!

EDIT: Rooman types faster than me!! Listen to him - he KNOWS!!

 

The plate thats welded to the rearend housing does indeed wrap 180 degrees around the housing, it wraps around from the bottom and is designed to anchor with 2 bolts in front and 2 bolts in back per side. Is this not acceptable? Im not sure I understand you on the "1 1/2" bolt diameter of material outboard of the hole". What exactly does that mean? Thanks for the help.

 

All I race are 1/8th mile outlaw tracks. I still want to this to be safe as possible though.

 

Your drawings were one of the things that inspired this build. I remember seeing those sketches of yours about a year ago and it gave me the idea to try something similar.

 

There really isnt any real issue with building and tuning blow-thru carbs. Alot of people say that it wont work or that it wont work very good and will have lots of problems, it all boils down to guys that half-***ed it and it didnt work so they blame it on the carburetor.
The basic necessities in converting a Holley DP to blow thru is solid floats, .120" needle/seats, upping the main jet sizes a bit and a basic rebuild of the carb and making certain that all the gasket surfaces are true to hold a good seal. I use vent tube extensions to keep the main jetting size small and also drill out the power valve restrictor channels to help compensate. Basically the secret to making these work without loading up under cruise is to keep the main jetting as small as possible.

 

I think this is something you should consider. I would make your axle mounts go all the way through your 2x3 framerail so that it can be welded in 2 places per framerail. Also, disregard the top section of my brackets, I would extend those into the shoulder bar on the car or something to triangulate them. If that housing comes loose, you are bound to be seriously hurt if not fatally. Does anyone know of the suggested bolt spacing for the 4 bolts?



I'm not a dragster builder, but just thought I might draw something up in CAD that you might understand. Some of the other builders, please critique my drawing as its just an idea.

 

Yes, That's what I was suggesting. I have never built anything like that either. I just know that I like things to look a little more streamlined in design. It looks like you have a handle on the situation. I'll just sit back and enjoy the show. Carry on. Work looks great. There was a Willys coupe back in the 60's that had twin turbos on it. I always thought it looked cool.

 

The 1-1/2 times the diameter means that IF you're using a 1/2 dia bolt then the EDGE of the bolt hole must be at least 3/4" from the edge of the bracket. 3/4" being the 1/2" bolt diameter times 1.5.

As for the rear end mtg plate upright - I ***ume we are seeing this WAY early in the build. I would think having it "out there in the wind" is a definite no-no. I'm not suggesting that what the OP was doing I'm just stating it for the record. If it were mine I would weld another horizontal tube to cap off the top as well as an additional vertical that the thin plte would also be welded to. Then there's the matter of the "wrap" - different inspectors seem to interpret this differently.

Even if you're not going to certify you still may want to keep it as close to 'certifiable' as possible. There's good reason for most of the stuff.

Looking at your pic - both the rear end bracket and frame mounting tab fail the 1.5 x bolt dia edge clearance rule. Not trying to burst your bubble - just pointing out what Rooman has eluded to.

Edit: Speaking of mtg schemes - consider that you're sitting on this thing - putting the bolts in double shear is a good idea - also on my bolts I used "long" bolts cut down to length so that the shank of the bolt fits thru all the plates - having loose threads in a clearance hole is a bad idea. They make special bolts for this, but cutting "standard" ones down was a cheap alternative if you're on a budget.

Also plan for a anti-rotation device. The rules are pretty insistent on it as well.

 

Im glad I posted these pictures up here, you guys have been very helpful. I am going to make a few corrections to my rearend brackets when I get the tubing for my hoop and uprights. Since the rearend is set almost perfectly in there I will cut out 1 plate at a time as to not disrupt anything and rebuild it with a larger plate and keep more material around the bolt holes. Thank you for the help!

 

How would you weld the bar stock on the top and bottom of the frame rail? Would it get inserted through? Thanks.

 

Super cool!

 

I'm no pro and I'm pretty new to this but it seems to me that you are going about it kinda backwards. I would think you should have the uprights in before you mount the rear. I could be wrong but that's the way we did it.

Here's how my 9" is mounted and I'm good for 7.50.

 

please do what the last guy posted at least. because that little flimsy piece of metal you have on there is just going to snap off the frame and either take your legs off, or kill you.