Homemade 125" FED Twin-turbo SBC

Interesting build for sure, keep up the good work!

 

Sorry I totally missed this question. I gave a rough explanation allready on my blow-thru carb on page 6 I think. As far as compression and boost, Im at 10.2:1 CR and I have 7 pound springs in the wastegates. 10.2:1 isnt optimal but its what I have to live with. Its a flat top motor but the cylinder heads Im using were shaved down to 57cc, I have other heads like camel humps and some #487s but I just rebuilt these ones last year.

 

Hi Jim!

Is that regular exhaust tubing you're using for the log style manifolds? Will you need to build some kind of brace to hold up the turbos or will the manifolds support them?

Why a 650 DP and not something larger like a 750 or ?

Do you not rev it that high or do you use large jets?

After rebuilding a couple holleys, I'm confident I can go through a DP no prob, but of course setting it up is the real challenge.

Do you have a pic of the new radiused ends for your log manifolds?

I have a million other questions but that'll do for now. I *wish* I could find double pumpers for $75! I've gotten 600s for free or 650s for $30, but anybody with a double pumper wants a lot for it.

 

When you compress air, you literally "compress it". The atmosphere around you is at about 14 psi at sea level, so one cubic feet of air is one cubic foot at 14 psi.

If you double the psi, you double the amount of air... Since the air your breathing is already at 14 psi, we consider that as our baseline and mark it as zero. Adding an additional 14 psi to one cubic foot of air doubles it to two cubic feet of air in a one cubic foot box.

By this same logic, a 650 carb that's being force fed air at 14 psi is effectively flowing 1300 cfm [650 X 2].

The fuel [gasoline] however is in-compressible. If you take 2 gallons of gasoline, no matter how much pressure you apply to it, you can not make it fit into a one gallon container,,, so the carb must be re-worked to flow more fuel to match the increased air charge.

I hope that makes sense...

Here's a good read about a guy's first ever turbo attempt on a buick 350 V8. He started with just basic knowledge, built his blow thru system, and has slowly tuned it into a beast over the past few years. It's a long read, but a good one if your new to blow thru setups.
http://www.v8buick.com/showthread.php?t=99527

 

Bitchin thanks for the link pirate daryl!

 

the more velocity (air flow) you have draws more fuel to keep the ratio a/f the same without going to bigger jets plus you have the pressure in the fuel bowl that increases as the boost goes up.
JM what do you set your timing at and how much does it retard as the boost goes up?
i'm just picking your brain as a friend is talking about installing twin turbo's on his 350 powered fed.

 

#1 Yes thats 2 1/2'' od exhaust tubing that Im using for the logs. Its .063'' wall thickness and is plenty strong enough to hold the weight of the turbos. I have built headers where the turbos were much further forward and didnt have to make any bracing, but it was a track only deal and didnt see any rough roads.
#2 Pir8Darryl did a good job of explaining this one but I will add that from my own experience I like the smaller carbs for blow-thru mostly because they are easier to tune. There is a stronger booster signal which makes a bigger impact on jetting changes.
#3 I will be finished the changes one of the log manifolds tonight and will post a few pictures as soon as Im done.

 

The pressure in the fuel bowls is the same as the pressure in the carb hat or in the venturis, unless you were referring to the vent tube extensions? With the vent tube extensions its possible for the fuel bowls to have a slightly higher pressure inside them compared to the venturis. This higher pressure inside the bowls goes up the more velocity you get inside the carb hat. Basically the more air that moves past the vent tube extension inlets, the more air that gets stacked up and pushed into the float bowls, thus aiding in pushing more fuel into the boosters.

 

I weld the centrifical pieces together inside the dist so there is no mechanical advance and I disable the vacuum advance mechanism. Where ever I set my base timing to is where it stays no matter what. I found that on my turbo 302 that 22 degrees on VP C12 fuel worked best. On this turbo 355 I will start at 16 degrees and work my way up until there is a noticable drop in mph then I will back it down a bit. Turbo motors dont seem to like alot of timing, and C12 fuel doesnt need much advance either.

 

I have one log manifold finished and painted. Tell me what you guys think, should I leave them painted black? Paint them a different color, if so what color? There isnt alot of paint colors for high temp header paint though. Lastly, what about wrapping them in header wrap? Maybe wrap them and then paint the wrap? I've seen that done. Remember Im trying to keep these looking as much '60s era as possible. Thanks.

 

jm that is exactly what I was saying about the carb, I had to translate from Canadian to American. the headers look better black

 

Unless you made those manifolds (which are very nice btw) out of thick tubing, don't wrap them.

 

Looks GREAT Jim!

 

Neat project. I was turned onto Winterport Dragway by your postings. That's a cool little track, and being an old airfield makes it even cooler. Butch/56sedandelivery.

 

I always thought that for turbo's the header material needed to be stainless due to the temps?

 

Thats what I thought, I just wanted to make sure we were getting the right message across.

 

The thinnest tubing on them is .063". Its all steel fence post tubing from Home Depot. Doesnt get much cheaper.

 

Its a very cool track and lots of friendly folks too. The tracks managed by some old school guys who love nostalgia drags. They are very considerate to the guys that want to race their original '60s dragsters. Single hoop stuff and all.

 

Maybe at some point in a very high end turbo motor stainless is needed but most low HP stuff like mine is built with mild steel.

 

Hah I threw out some fence post log style headers, couldn't give them away , now I need them. Go figure!

No chance you could powder coat and cover with wrap for longevity, or is that not even an issue on a race car?

Beautiful headers.

 

neat to see you jumping in, good stuff

Here's some inspiration for you...



Cheers,

Drewfus

 

Does anyone make a powdercoat that will survive on headers? I usually just strip and repaint headers after a few years anyway. If I prep them good and bake the paint on they will last a long time with just the $8 autoparts store header paint.

 

Yeah that dragster has definately given me some ideas. I found out about it a few months back and couldnt believe that somebody actually tried turbos on a dragster in the '60s. Im surprised turbo V8s never really caught on until the past 10 years.

 

Well I ended up trying a little bit of wrap only on the primary tubes. I painted over the tubes and wrap with high temp black so it definately helps blend in the wrap. I decided to wrap the tubes because I think that at speed the air moving across the tubes would have a tendency of pulling heat out of them which is what I dont want to happen. Heres a couple pictures.

 

Freaking WILD, Keep it up JIM! Rocky

 

Cool, Im glad you like em. Everything cosmetic on this dragster has been a challenge! If I was building a traditional n/a small block or a blower motor this would be easy as there are alot of pictures of what these looked like in the '60s. But trying to make a turbo small block look like it was built in the '60s is tough especially considering I was born in 1983 LOL, I can spot a fox body Mustang from 5 miles away

 

looks good, checking all the posts, it's a learning experience for me as I don't know anything about turbos

 

Neat as hell. How long till you fire the engine? I'd love to see a video of that running.