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Old 01-26-2011, 07:58 AM
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434 Twin Turbo Help

The car...
1966 skylark...Checkeredracing.com back half/drag style front half...ford 9" with a used mark williams center...spool...progear 355...28 spline moser alloys.

The engine.
Dart SHP...434 cu.in....all forged..-23 pistons...Dart iron eagle 230cc. heads..procomp intake...profuel 850 carb...compression is at 10.5 with current setup.

I am going to a twin turbo setup...My goal is over 1000hp...I have many successful naturally asperated builds...but I am blind to the boost scene....from what I have read a twin T-70 should do the trick...however i am confused with the whole trim/mapping problem...what compression is suitable to reach the big numbers..is o-ringing the block/heads critical.....as a fuel injected system is out of reach I was thinking of a blow-through carb setup..however I am open to suggestions.

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Old 01-26-2011, 08:14 AM
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Old 01-26-2011, 08:31 AM
How fast is fast enough?
 
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At 434ci to keep things relatively mild (low RPM's and mild valve train) I'd shoot for about 8:1 compression and 15psi. It may still be a little under your desired power levels on pump gas but if you run E85 or a 100+ octane racing fuel you can turn the boost up to 20psi and that will get you there with little problem.

With the current technology in turbocharging design and manufacturing there is really little reason to run a twin setup unless you just want it for looks. A single turbo is much easier to route and they can build one to meet your requirements. I wouldn't spend any time worrying about how to spec a turbo and instead have a professional build one for your application, in many cases there is no additional cost and your results will be much better than if you just tried to get it right on your first guess.

Blow through carbs work fine in racing situations but they can run into problems under part throttle operation on the street, a very talented carb builder can fix these problems but be prepared to pay for it ($1000+).

The rest of your car looks like it is built for racing, but many people are running race equipment on the street now. If it is truly a race only car then a blow through carb will work well, you can plan on running higher boost with proper fuel (20+psi), and a twin turbo system is really not needed at all. I would have your deck cut for o-rings as you'll be running some really high cylinder pressures, or you can look into specialty head gaskets which do work well if the heads and deck is prepped correctly- surface prep is VERY important though.

As with many things there is more than one way to skin a cat, but I would recommend getting your turbo built from a reputable racing professional regardless of what you decide to do with the rest of your approach. They know the business better than anyone and their advice is usually free.
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Old 01-26-2011, 08:50 AM
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Thanks...that is interesting...I hadn't thought about that approach...I will have to investigate a good turbo builder in the area...The car will rarely see the street...we have the Super Nats in town every year and drag cars are everywhere on the streets... so I am guilty of bending the rules occassionally..lol...I am mostly concentrating on the pushing as much out of this small block with the durability to eek a season out of it without catastrophic failure...then winter fresh-ups...I have learned the hard way about racing...(detonation...sprags...cracked bell housings etc.) I wish I had asked a pro before I ruined 4 transmissions... I really appreciate the advice... you just opened a new door for me!
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Old 01-26-2011, 09:00 AM
How fast is fast enough?
 
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Quote:
Originally Posted by visseratt
Thanks...that is interesting...I hadn't thought about that approach...I will have to investigate a good turbo builder in the area...The car will rarely see the street...we have the Super Nats in town every year and drag cars are everywhere on the streets... so I am guilty of bending the rules occassionally..lol...I am mostly concentrating on the pushing as much out of this small block with the durability to eek a season out of it without catastrophic failure...then winter fresh-ups...I have learned the hard way about racing...(detonation...sprags...cracked bell housings etc.) I wish I had asked a pro before I ruined 4 transmissions... I really appreciate the advice... you just opened a new door for me!

I wouldn't worry about "in the area" turbos are sort of a specialty item so I wouldn't hesitate to call some guy 1,000 miles away if I knew he was the best. Plus they ship really easily. These guys are really well known: http://www.turboneticsinc.com/
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Old 01-26-2011, 09:08 AM
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For a roots blower, 10.5 c.r. is a lot, not sure what's acceptable for a turbo setup, I would think the same, so consider what your effective c.r. will be related to the amount of boost you plan to see. Going with the Iron Eagle 76 cc chambers would bring the c.r. down to around 9.2 at zero deck and .041 gasket.

At 1,000 hp, consider 35 spline axles, I broke MW 28 splines in a 9" with an 8-71 383, street legal car, with only 12#'s, nowhere near 1k hp.

You mention sprag issues, I also run a pro spragless T-400, Griner VB and brake, almost bullet proof, think about that. for more insurance.
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Old 01-26-2011, 09:51 AM
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Well I just faxxed in the turbo request form to Turbonetics...I will post their response once it arrives...I feel confident this is the best approach...thanks again!

I bought a th350 race trans from Carl Rossler...he is a local trans builder with a great reputation...$1400.00...Coan 5000 convertor...$800.00..I broke the bell housing the first run...so Carl suggested a JW ultrabell...$500.00 later I was back in action...3 passes and a terrible shudder in the trans...the sprag drum was cracked and broken....$300.00 for a hardened 36 bearing sprag...(i got a sympathy deal) .then he suggested a g-force cross member and mount..($250.00) ..lasted another 2 passes...shudder and the sprag face was ground down to almost nothing...now I have sooooo much invested...and my parts are all th350 related... im stuck with either sell what is salvageable and cut my losses...or hope the new frame/suspension eases the abuse on the tranny...back to the drawing board..lol
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Old 01-26-2011, 09:58 AM
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