Draw Through Turbo Setup

Howdy guys,

The other day I picked up a custom homebuilt draw through 200 turbo setup from a guy dirt cheap and all I need is to size a turbo. I'm not quite sure how to chose what kind to get. I have a Holley 350cfm I'd like to run or a 1.23 Autolite. I plan to run about 8psi max, maybe 10psi. What kind of turbo and what would i need to do to the motor to safely accomplish this?

Thanks,
Ryan

Oh boy, a favorite subject:

Unlike a blow-thru setup where you may actually need a carb with less CFM than in NA operation, a Draw-thru setup requires the upstream carb to go from idle cfm to a much larger CFM under boost than in NA operation . The draw-thru turbo I used from a carbureted early 80's Buick 231 V6, used a specially designed Quadrajet with external Power Valve port for switching under boost and a WOT rating of 850 CFM while in boost... .

MacInnes makes no statement as to which method is best in his "TURBOCHARGERS" , the bible of forced induction. The problem with early draw -thru setups wasn't lack of performance as much as a warranty nightmare for the mfg. . With only enthusiast/light use of a homebrew draw-thru carbd' setup, there is not a real issue with MTBF for the setup.

The BOP 231 V6 turbo setup was simply adapted to my Ford inline 250 six. It made great power and I incrementally upped boost until @ 15-20 PSI when it lost power, the stock piston lands cracked off and a blue mist covered my windshield .

( PS - no need for return / referenced fuel supply as the carb bowl always is at atmosphere.)

have fun

.

.


After the draw-thru Buick turbo project on the Ford 250 six, now the Maverick 250 runs a Vortech SC with a Blow-Thru modified Holley 2 Bbl carburetor. With available 'reverse' power valves, modifying a Holley 2Bbl carb for blow-thru is simple...

The big reason I jumped at this was b/c it was actually draw through. Setting up a blow through I heard can be really difficult, rather with this, the carb is much easier to tune and theres no worries about referencing the fuel pump or anything. Down below is a picture of the setup the guy was running. I'm looking for a turbo with the T04 flange on it. That Buick setup you used looks pretty slick. It looks like though you need a lot of hood clearance though. As you'll see with the one I'm posting, it keeps the carb down lower. Its closer to the exhaust manifold which i don't like but i can make a heat shield. So how do I choose the right carb, and how do I make mine work? Should I go to a bigger carb rather than the 350 cfm or Autolite 2100 1.23? Should I move up to a 4bbl like the Autolite 4100 or Holley 650cfm? I will probably want to keep pushing the motor past 9 psi as we all would lol. But does the draw through setup limit my capability of running higher boost b/c of the lack of an intercooler? The turbo world is very new to me, I just don't want to destroy my 200 lol. I plan on doing a full rebuild anyway on my spare one so this will be going on that 200. Internally, what all should I do to make my 200 almost indestructible?

https://photos.app.goo.gl/U3Qu3Nb5wPfhHJ8b8

nice ...

... the specific turbo should be rated for addressing the Draw-Thru setup compressing atomized fuel - not air ,'Carbon Seals' is often mentioned.

,, turbo close as possible to exh. flange is better , will the setup fit in a car with shock towers?, previous setup looks to use a choke removed 'circle track' Holley 2300 series 350+cfm/#7448 or a 500+cfm 4412 -( parts and jets easily availble).

... with the BOP based draw-thru turbo 250, the venturi effect (?) created icing on the carb' plenum before the turbo requiring coolant/heat to keep it from icing internally - (!) .

.. started with getting engine running well NA, next added turbo and significant ignition timing mods. slowly increased boost and carb tuning for safer AFR's until becoming too optomistic ... .



With a SCR of @ 9:1, the 'Effective Compression Ratio Chart" lists the effective CR at 20lbs boost at @ 21:1.


A mild built small block six can handle modest boost with a few simple mods , unless you really need to build for the most it can deliver ...

... the current boosted SC'd 250 engine has ARP head bolts - Requested the machinist - NO milling of head to retain low SCR (@ 8:1 with new gaskets), back cut valves - V8 springs . Low mile stock bottom/Cam.

I would not leave the driveway with a turbo/SC boosted car without a reliable AFR gauge.


optomistic' MacInnes excerpt:

One very important thing on your Turbo short block prep is to be sure that you have the correct amount of ring gap (this needs to be more than a NA motor) especially when using the stock type cast Pistons even if it's only at the lower boost levels. But if you want to make your 200 six indestructible think about investing in a good set of aftermarket rods and set of custom forged pistons. Best of luck on your build up

StarD

Like you I'm building a 200 to revisit the BOP derived draw-thru turbo I had on the 250 . Hoping you and others can add to this discussion on Draw-Thru turbo setups.

With some forum help, 'modern' ignition control capabilities, and Wideband AFR gauges the 'vintage' Draw-thru setup is even more workable. How much power you target the build to handle - lower end, rods etc. depends on your goals and resources ..., my friendly machinist says : "it's all about Horsepower per cubic dollar ... "

.


have fun

bubba22349":iwmf049h said:

One very important thing on your Turbo short block prep is to be sure that you have the correct amount of ring gap (this needs to be more than a NA motor) especially when using the stock type cast Pistons even if it's only at the lower boost levels. But if you want to make your 200 six indestructible think about investing in a good set of aftermarket rods and set of custom forged pistons. Best of luck on your build up

Click to expand...

I do know about gapping the rings larger. Factory is .010". What would a turbo one be? Like .02 or .03? I have no idea how to calculate it. Maybe do some thermodynamics to come up with a rough number. Is there a general rule for gapping vs boost psi? I definitely don't mind going with nice rods and pistons. The 2JZ rods can be made to fit, right? Those would be high quality stuff. Heres some I saw from Aussie speed, would these be correct? Is this the same 200 that I'm thinking of? Where do I go for custom pistons? This is a world I know not much about

https://www.revhigh.com.au/product-page ... e-con-rods

powerband":11k4rndy said:

StarD

Like you I'm building a 200 to revisit the BOP derived draw-thru turbo I had on the 250 . Hoping you and others can add to this discussion on Draw-Thru turbo setups.

With some forum help, 'modern' ignition control capabilities, and Wideband AFR gauges the 'vintage' Draw-thru setup is even more workable. How much power you target the build to handle - lower end, rods etc. depends on your goals and resources ..., my friendly machinist says : "it's all about Horsepower per cubic dollar ... "

.


have fun

Click to expand...

When setting up timing, is it done the same way as when blow through? A DSII with an MSD module is the way to go,right?

Power wise, i would love to see 300 hp. I would kill to see 315+. (My dads 2008 Bullitt Mustang has 315hp and I'd love to have as much just to show him what a I6 can do). What all do I need to do to accomplish that? Will 300hp be beyond what draw through can do and will blow through be the only way? I already have the parts minus the turbo for the draw through so I'm commited to that. What kind of power/boost can I push for and still utilize the draw through well?

Thanks

1. Richard Holdener Gaptize. The application for Gap 14:52 minutes on YouTube.

2.Ford sixes are an interferance engine if its a 200 7.8 deck engine...the cam and rods can touch if the timing chain is out just 4 degress from what the designers intended.

Cam vs rod= Big Bang.

Back to No 1 for a moment. Ring land clearance is additionally wrong for an engine with 7 pound of boost or a 50% boost in nitrous oxide...the piston tops come off when the ring freezes against the bore. So ring gap must suit your target peak horsepower. So any good breathing modifications take a Ford 200 six from 87 flywheel hp net at 4200 rpm to 130 hp, then you add a boost ratio of (7 psi + 14.7 psi atomospheric )/ 14.7 psi atomospheric. Thats a peak power boost of about 1.5.

130 hp becomes 65 hp more or 195 hp.Your ring gap target. You cannot go above that unless your gage boost level is matched by a rising rate fuel supply 4 pounds greater than your boost. To go to 315 hp requires proper, Uniform, Equal amounts of fuel supply to all six cylinders. To get 315 hp requires a boost ratio of 2.5, or well over 17 pounds of boost, which would then require 21 pounds of fuel pressure. You cannot, Ever run a turbo of any type out of fuel, or it will tourch down. Gas axe the pistons and thats fatal.

4.Carbs in draw throughs show fuel distribution problems at 9 psi of boost because one turbo is trying to fan out half a Us gallon of gasoline a minute into six 28 ounce jugs. Each must at all times have more than 12 parts of air to one pary of gasoline. Each cylinder must not lean out.

Blow throughs always work better than draw throughs. Draw throughs have a flow distribution problem. Always. Fine at 7 psi, then declining rapidly as boost rises. Anyone who thinks a draw through is easier is wrong. The carb is a pressure calibrated device and it works in pressure differential for both Air and Fuel. There must always be excess air and excess fuel in equal, richer than stoichometery measure. The way to do that is raise fuel pressure with a NASCAR piston mechanical fuel pump, and by profiling the geometery of the fuel delivery below the turbo. Twin turbos administering more fuel to two parts of the intake with two 2bbl carbs under less than 9 pounds of boost with 13 pounds of fuel pressure with work. Two Dual Jets on are Qjet float bowl carbs able to take 13 psi of fuel pressure at.peak boost, and they come on 2bbl junk 262s or anemic Olds V8s from the mid 70s

GM moved to Garret T03B turbos like the 79-80 Mustang and Capri turbos. You can reconditons those. The GoPro Turbo shop sells the o-ring and seals can compressior parts.


5. All US OEM 6 cylinder pistons have slotted ring lands that arent able to support the skirts of the piston. Its a potentially catastrophic problem which is mis diagnosed as "gudgeon pin freeze" On a short rod engine...it can take out a cylinder wall.

'Vintage" Draw-Thru conversions were usually add-on modifications of selected - robust - engine platforms. Aftermarket vendors and home garage fabricating' amateurs fueled the interest in what still amounts to the simplest way to significantly boost OEM performance.

I'm not too discouraged with a little less than tripling the 200's stock output. Along with increased HP, the lower RPM torque capability of the blown small block six shouldn't be underestimated. Your 300+HP goal may not be easily attainable ( $$ ) but since you already have the bones, a suitable Turbo and a few simple basic mods should get you partly there and a huge performance boost compared to major NA upgrades ...

A simple way to start is to measure the cyl. head compression chamber to get a baseline for target CR ...

Using a Turbo already spec'd for Draw-Thru use is a plus like the TO3 on the BOP GM Pushrod V6's and the Ford 4's as mentioned.

. .

.




have fun

StarDiero75":1l208oup said:

bubba22349":1l208oup said:

One very important thing on your Turbo short block prep is to be sure that you have the correct amount of ring gap (this needs to be more than a NA motor) especially when using the stock type cast Pistons even if it's only at the lower boost levels. But if you want to make your 200 six indestructible think about investing in a good set of aftermarket rods and set of custom forged pistons. Best of luck on your build up

Click to expand...

I do know about gapping the rings larger. Factory is .010". What would a turbo one be? Like .02 or .03? I have no idea how to calculate it. Maybe do some thermodynamics to come up with a rough number. Is there a general rule for gapping vs boost psi? I definitely don't mind going with nice rods and pistons. The 2JZ rods can be made to fit, right? Those would be high quality stuff. Heres some I saw from Aussie speed, would these be correct? Is this the same 200 that I'm thinking of? Where do I go for custom pistons? This is a world I know not much about

https://www.revhigh.com.au/product-page ... e-con-rods

Click to expand...

There are cast Pistons that look like the boxed set pictured above and have that type of sloted oil ring groves they are a known for their weakness and can come apart even in NA engines there are much better ones made by aftermarket companies back in the day such as Jahns and others today like Mauhle.

The most reasonable custom forged pistions in the USA are made by AutoTeh / RaceTeh at about $500.00 Or $550.00 a set last time I checked. You get to pick out your pin size, dish CC, and ring pack size too. There are also many more available at a little higher cost such as RaceTeh's. Yes the 2JZ rods might fit when using a custom piston. There is a sticky on the top of the small six forum with the info of what can work in a 200. Yes you could get that 315 rear horse power with a enough of a parts budget, but do you really need that much? I use to race a 1964 Ranchero with my uncle back in the early 1970's you might check the actual weight of your dads car my guess is it's around 3600 to 4000 lbs. Your Rachero is much lighter so in my opion you could probally match or beat your dads cars performance at around 225 to 250 rear wheel horse power, with the actual weights of both cars we could drill down on more accurately on the power needed to match or exceed his. Best of luck on the turbo build up. Edited

Revisit our earlier discussion.

viewtopic.php?f=22&t=80234&p=622717#p622717

TO3B's were sold in five cars from 1979 to 1982, the 4.9 Firebird TA Turbo, 3.8 T type Rivera and Regal, the 2.3 carb turbo Ford Mustang and Mercury Capri. 130,000 from 79 to 82.

With parts back-up. 20 dollars for O rings, 24 dollars for Combustion seals.
"http://vb.foureyedpride.com/showthread.php?92600-Carb-Turbo-M81-Mclaren-ready-to-start-after-15-years!/page10"

m81mclaren":1mx39kad said:

G-Pop Shop delivered and looks beautiful! Picked up the FelPro o-ring kit and now the last item to source is the gasket for the hot side manifold that I didn't need to split open in the first place:fp:

Does anyone know where to source this last piece that goes between the hot side housing to exhaust manifold?

Click to expand...

https://gpopshop.com/garrett-kits.html

Find two Ford 2.3 carb turbos and put two Buick or Pontiac intakes on them. And two turbos on that log with two Dual Jet carbs. One 2bbl direct mont hole gets fed by one turbo in the stock position Powerband used. And another turbo and intake forward, with its feeder to the direct mount intake reversed.

Use a Strip Dominator 400 hp Chevy diaphragm fuel pump which makes in excess of 10.5 psi fuel pressure. And set the turbos to 7 psi. Use an Aeromotive or Malpassi boost fuel pressure regulator. Full boost, 10.5 -12.5 psi fuel pressure. Idle and part throttle no boost, 7 psi.

The old Olds 262 or 307 or Pontiac 301 Dual Jets have a small primary 2bbl, about 1.16s, with simple metering rods for 110 to 130 hp each, but able to supply 315 hp net if the metering rods and jetting is adequate. Fuel pressure must be adequate.

Its VERY important to know Why and What you need TO3B turbos for. In the Triple K/Schwitzer/ Rotomaster/Garret turbo OEM supply wars in supplier info from 1976 to 1984, the information was insufficient from the supplier to help the back yard conversion industry. The Draw through wasnt bad technology...it was killed off by the electronic Fuel Injection. When the 1976 Cadillac Seville and the one Oldsmobile released the EFI 350 gasoline engine, and the engineer for the Carb turbo Mustang said it was going EFi fir the next turbo install, draw throughs got killed off. Best induction system for draw through us programmed electronic Fuel Injection. Two CFi 3.8 or 5.0 Ford fuel injection throttke bodies. They are able to be run off any MegaSquirt system. Stock 2 bar map sensor and an F250 electric fuel pump and your into a midern draw through. But it has to be twin turbo to feed both legs of the log evenly.

Draw throughs are an art form. Ak Millers 1972-73 Pangra (Pinto 2.0 based) was draw through. Ak Millers 250 Maverick used a draw through gasoline engine with 4bbl carb feeding the single 1.75 inch log intake in 1977, but he wasnt allowed to fit twin carbs on a California car.

His Propane turbos were always blow through. Any emerging US EFi engine used blow through technology.

The gap in bolt on turbos was draw through. Huge MacInnes prevented any great information being circulated on TO3 and TO4 turbo draw throughs because he was a Rotomaster engineer. No disrespect for his work was exceptional. But we all work for The Man, and even in the 2nd Turbocharging book revision by Hugh, draw throughs were going out of fashion...Fast!

A reminder the 1jz rod is the one...Fast64Ranchreo has I nice turbo build with those rods in the AL head section.
46 years ago I did the draw-thru, I would not do it today and i am not...MPEFI is the safe way, control and logging of air fuel , boost and timing etc...But you do what you can...A blow-thru 350 holley 2 barrel and intercooler would be better than the draw-thru.
The more boost, the more octane you will have to use, water-alcohol inj. can help,
Get, A. GRAHAM BELL book Forced induction performance tuning, it covers every thing plus engine building for boost.

The boxed set of cast pistons pictured have the slotted oil ring groves above are a know weakness that can come apart even in NA engines there are much better ones made by aftermarket companies such as Jahns.

the boxed set in the pic' do have slotted oil ring grooves but are Forged TRW L2217F



200 with moderate boost ranges , adequate ignition advance control, close monitored AFR's , Forged pistons, stock rods and a healthy bottom end should sustain reasonable boost levels .

.. querying Jahns may not yield much current info .. years ago I contacted someone who supposedly bough the existing stock asking about 250 pistons . "Egge Machine" kinda' fills in as the main vintage ring vendor source but no forged Pistons currently manufactured for vendors AFAIK.' ...

https://egge.com/



have fun

powerband":1h2vpz2o said:

The boxed set of cast pistons pictured have the slotted oil ring groves above are a know weakness that can come apart even in NA engines there are much better ones made by aftermarket companies such as Jahns.

the boxed set in the pic' do have slotted oil ring grooves but are Forged TRW L2217F



200 with moderate boost ranges , adequate ignition advance control, close monitored AFR's , Forged pistons, stock rods and a healthy bottom end should sustain reasonable boost levels .

.. querying Jahns may not yield much current info .. years ago I contacted someone who supposedly bough the existing stock asking about 250 pistons . "Egge Machine" kinda' fills in as the main vintage ring vendor source but no forged Pistons currently manufactured for vendors AFAIK.' ...

https://egge.com/



have fun

Click to expand...

Yes I see that now looking at the second picture expanded that they sure are forged sorry about was only focusing on the single piston in the thumbnail picture. :rolflmao: I guess I am getting blinder everyday. Mahile (German company I think probably spelled it wrong too) but their also making some great pistons to.

Its clear that there is some missing info to make an informed choice.


M10 casing TO3B

M10 CASING CONTINUED

StarDiero75":1kpbud5i said:

Howdy guys,

The other day I picked up a custom homebuilt draw through 200 turbo setup from a guy dirt cheap and all I need is to size a turbo. I'm not quite sure how to chose what kind to get. I have a Holley 350cfm I'd like to run or a 1.23 Autolite. I plan to run about 8psi max, maybe 10psi. What kind of turbo and what would i need to do to the motor to safely accomplish this?

Thanks,
Ryan

Click to expand...

Your turbo will have to have a seal to prevent oil ingress into the combustion chamber.
430108-0004 ----> https://www.turbosbytm.com/backplate-t3-carbon-seal
407516-0003 ----> https://www.turbosbytm.com/thrust-collar-t3-carbon-seal
403069-0060 ----> https://www.turbosbytm.com/o-ring-t3-carbon-seal

If you use these, its just 24 bucks




409695-0000 ----> https://www.gpopshop.com/product-one-pi ... -seal.html
(Garrett TAO3 TA31 TB41 Turbo Encapsulated Backplate Carbon Seal)

The turbo sizing process is defined best in page 133-134 of David Vizard's 1988 book, How To Modify Fords SOHC engine.

First column(Unlabeled) is the Cubic capacity
Ratio Boost is the Effective Boost Ratio @2.3, the CFM.
CI= Compressor Impellor is the cold side. Compressor Wheel
TW= Turbo Wheel is the Hot side. Exhaust Housing.


Letters like Y-4, S-4 , 2, V, are Compressor Impellor trim.
Letters like N 0.X. O-0.X, P-O.XX are Turbo Wheel Impellor trim.

AR is the Area Ratio, the rate of gearing. lower the numbers, the higher the gearing into getting boost. Bigger numbers, mean more lag.










Turbo sizing was best defined by Hugh MacInnes in his 2nd edition of Turbo Charging.




Its very clear that the advisC given is missing the dangers of breaking an engine due to lack of fuel to each cylinder. Down here, we still do Draw through turbos. Hamilton Jets.

This is a 302 Cleveland with four CDS188 Stromberg's and two Garret TO4's for a jet boat. 800 hp....

' kudos XTC for the TO3 - TBO-3 ... detailed info. I got interested in the Buick/Olds/Pontiac draw thru turbos when looking for a right angle 4 bbl plenum for a Supercharger project. I Inexpensively, picked up a few questionable used turbo's , 4bbl plenums , Pre-computer turbo QJets' and New in Box turbo' and turbo specific non-ECM Qjet. ... 'hope the simplicity of the complete - almost bolt on assembly mated to basically any stock six car encourages more forced induction tampering .


. . .




have fun


not yet

.


yet

. .

.. last word from me on the Buick/Olds/Pontiac draw-thru:

With the Draw-Thru (sp) setup, high vacuum at the carb will keep conventional Power Valve closed at all throttle positions. Carbureted draw-thru turbo's typically need a way to control the Power Valve Circuit to OPEN when the Intake manifold transitions to positive boost pressure . GM-BOP V6's and V8' turbo's used a specifically built Quadrajet that simply controlled the PV vacuum circuit externally and used a proprietary vacuum switch mounted on the intake manifold to 'switch' the carbs PV circuit to open under boost.

Center front vac' swx is for pre- ECM QJet Power Valve..



The OEM Vacuum switch is unobtanium. Generic vacuum-dependent fuel line shutoffs and one way valve 'logic' was used to control the specially built Qjet's external PV circuit on my Draw-Thru BOP setup.



have fun