turbo 200 build


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I understand about the no further need for speculation but you should go to the dyno with certain expectations.
Here is the compressor map for your turbo. It is more aggressive than the GT2860R turbo that was originally discussed

The red load line represents 15 lbs of boost from 3000 to 5500 rpm. 380 HP @ 5500
The orange line represents 10 lbs of boost from 3000 to 5500 rpm. 330 HP @ 5500

This is assuming a very high VE at 5500 rpm due to the long duration cam you presently have along with an air to air intercooler with at least a 50% effiency.

What is important and expected from looking at the load line is that full target boost can be aquired by 3000 engine rpm. (Or close to it)
If you have to wait past 3000 rpm to get full boost then the cam profile is a mismatch.
You are looking for the widest power band possible and should use as much of the dynamic range of the turbocharger as possible

Also note that running the engine rpm much past 6000 will drive the turbo close to the choke zone.

We all will be anxiously waiting for dyno results.
You are doing an Outstanding Job!


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I'm on the same page and with you all. On big turbos, the critical surge zone is where the cam and the engines exhaust fails to give enough excitation to the turbo off idle to 2500rpm, and the turbo 200 becomes a dangerous combination if the cam is too large as well. Sixes don't do that like OHC Fours do, so you'll have to try real hard to mess up the lower part of the abdiactic curve with what pmuller9 has in the graph above. But at wideh open throttle, it might be a risk. I'm pretty sure you'll have more than 155 cfm at 520 lift.

The turbo size waranings I've gotten are from David Vizard's SOHC Pinto engine book.

Going back to a known good idling 250 turbo EFI engine build.

With 44 to 48 pound per hour injectors, an intake of 552thou lift and 221degrees at 50 thou, Exhaust 578 thou and 231 degrees at 50 thou on a 112 lobe center line. About 220 cfm at the ports, and 250 cubes with a 4 stage auto and you use a big butt turbo.

Borg Warner SX 300 60 mm twin scroll turbocharger, with T4 0.88 A/R ratio.

it makes insane boost from less than 3000 rpm

This all goes back to what works being a lot more radical than you'd expect.

Knocking off 50 cubes, reducing the over scavaging but adding some intake lift, putting in a manual, and going back to a Stone Age Iron head means you can use some extra duration.

I see nothing to worry about here. The 1.68 and 2.02:1 boost ratios (what 10 and 15 psi are without the heat factor)....they are kind of right at the low end even with a tame 60mm T4 0.88 A/R ratio.

I keep comming back to how big a 3.3 liter engine with short rods and some serious fuel and ignition ramps can be. Its goes back to the ancient 1972-1973 9 port Holden Torana engine getting a shot in the arm development in 1985...., becoming a 12 port EFi engine, making 142 hp and 198 lb-ft. Which is what 190 hp Gross and something like 200 lb-ft gross is in SAE net with the very basic 260 degee, 185 degree at 50 thou early cam. The EFI Commodore used ALMOST the same cam as the base model XU1 Torana

This is a 1972 triple carb 3.3 liter engine with a small 260 degree cam. The additional power of the 312 degree cam was unreported, but it was 216 hp net on an open iron header race car, and the best seen with Strombergs or SU's and the stock kind of iron twin outlet header was 238 hp net. With beeter carbs, 250 to 300 hp easy.

So the right cam and induction system makes the 200 or 202 six an excpetional device. A cam with 240 thou duration at 50 thou over a 185 to 195 degree cam is worth, literally, 40 hp, with no major loss of torque down low. The torque curve is just fattened out and moved upwards. Its worth a huge amouht of boost in a turbo car.

That base could make It REALLY produce the goods on a little 3.3 liter six that normally is restricted to about 300 hp at 7000 rpm without an aluminum cylinder head. With the best cylinder head around (zjello's remastered knock off of the Phil Irving 12 port Heron head), they go up to 370 hp at 7000rpm.

With 30 pounds of boost, a moderate XU1 312 degree cam 215 hp solid lifter 3.3 with this kind of EFi intake then makes 403 rwhp and 600 hp at the flywheel on 30 pounds of boost and 20 degrees of total spark lead. The cast alloy solid skirt Mahale XU1 pistons that Repco and ACL made for the 1972-1973 Bathurst race cars can survive regular 7500 rpm use, and as long as the fuel delivery and spark advance is kept in check, a 30 pound boost engine with forged rods and those pistons can carry well over 6000 rpm thrashes. Like, 7500 rpm.

The best example was the January 2003 Australian Street Machine preview of the Western Australian Mick Munro's OVA BOOST. Just a two stage factory Powerglide auto with a high stall converter.

It was put together while he was still working for FORMAZ. On the strength of this 9.92@135 mph Power Glide and 28 x 11.5 wheeled 2400 pounder, Mick started OVA BOOST Engineering. Sadly, it became 2JZ after he eventually threw a rod in this Holden 202 in line six, but it took about 5 years of thrashing to do it.



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xctasy":1muposnn said:
So the right cam and induction system makes the 200 or 202 six an excpetional device. A cam with 240 thou duration at 50 thou over a 185 to 195 degree cam is worth, literally, 40 hp, with no major loss of torque down low. The torque curve is just fattened out and moved upwards. Its worth a huge amouht of boost in a turbo car.
We see this phenonema on the big six and is mainly due to the port flow and volume being so small with respect to the 50 cu inch cylinder volume.

The last 300 I assembled had a big valve ported head that flowed 212 cfm at .600 lift and a cam with an .050" duration of 232*, adv 288*.
It still idled at 650 rpm and pulled 17 inches of vacuum at 750 rpm which is a good indicator of the low end response.
It made more torque just above 2000 rpm than the .050" 192* stock cam stock engine.

However this is not the case here.
As you pointed out, the modified head probably flows in the 175 cfm range and no longer has a small port flow with respect to the 34 cu inch cylinder volume.
This is indicated by the rough idle and low rpm responce of the engine.

Anyway I will wait to see what the actual results are and will not speculate any further.


Well-known member
I've enjoyed reading and rereading all the posts after the cam info was posted. It's obvious that you guys are much more knowledgeable about all this than I am, so I'm digesting all the information and will try to make the best decisions I can. I've learned a lot from all your posts and appreciate all the enthusiasm.
Some posts really made me question my cam choice with the turbo I have. However, after reading all the posts and going over the turbo maps, I'm really curious on where the torque and hp curves are going to be - I have several ideas if I need to change something - there's a lot of tuning that still needs to be done. But the car IS running and for the time being I'm very happy :D


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As Sam Blumstein from Chevy Offroad and Marine said "There are no wrong cams...only wrong engine combinations."

The key part is making sure your air speed is high, your port and runner area and volumes are the minium to get the job done. What pmuller9 says about idle vacuum and low end torque growth with no loss is spot on. (y)

Specific to the 300.

pmuller9":3aztyhzv said:
We see this phenonema on the big six and is mainly due to the port flow and volume being so small with respect to the 50 cu inch cylinder volume.

Its actually the same with the 200 and 250 if port and intake ruuner volume are taken down a notch...even with a big cam. OVA BOOST uses the stock 2 liter intake runner 1985 Commodore Electronic Injection intake, and it uses what US guys would call a pretty exteme cam....the stock XU1 Bathurst cam, 312 degrees, with a big ball bearing turbo. That should be enough to convince you to look at a lower intake runner volume.

OVA BOOST was one example. I'll give you another great example.

The stock Ford 250 X flow intake runner to the head is 2.3 liters, not including the heads intake port CC's.

Most aftermarket ones are 50 to 155% of the engine volume, 6 to 6.2 liters in a common size. Like mike1157''s old intake runner.

They create huge off boost lag compared to the stock 2.3 liter intaske runner, but even so....On a drag car with a high stall Powerglide or 4 or six stage auto, they tear up the tarmac. Offbost, they are Lame-er, but excatly Lame.

With a big total runner volume, After cooming on boost, they then make simply epic horsepower.

Even with a 6 liter intake volume, the old Glia Monster still had sublime off turbo response because the cam was so small for its cylinder capacity, and the cylinder heads ports were small, with very high gas speeds.

Que your intake.....

I guess it is a sectioned down 3 by 5 RHS section, 24 long. By my estimates, it is less than 5715 cc's. It looks like 20% has been cut off. So its gotta be 4572 cc's or so perhaps.

with six 1-3/8 by 2-1/2" runners 4" deap = 1386 cc's

Total has to be about 6 liters (6000 cc's or 366 cubic inches or less). That's 188% of the engine volume if its a 3.3 liter engine.

The key thing is the short side radius has been tidied up, and the effective runner volume is really only 1386 cc's. The 3 by 5 log at the top is really just a stagnant flow supplier to six very short ruuners which feed pockets in the head that are less than 110 ccs at the runner.

If it cammy, you can fill in the top runner with an alloy plate to reduce the total volume back. You only need 2690 cc's at the top, for a total runner volume of 2690 cc plus 1386, or about 4076, or 123% of your engine size.You can go down to about 3315 cc's if you make an effective throat size of 63.5 mm in the top of the T that feeds the six leg ins. Thats 100% of the engine capacity as it stands.

You open up the top of the 3 by 5, and put in an alloy or Poly Ethelyne spacer to approimate the internal throad of the throttle body you are using.

As you get down to 2.3 liters, the off boost performance improves a whole heap. Due to the stroke differences between a 250 and 200, there is only a 9% difference in peak power rpm, and the off boost idle and transition to boost is fixed up.

Just cut a 3 by 5 by 24 slot in the top of the runner, and replace it with a nice piee of alloy plate allen bolted or cap screwed in, (and maybee put "Power by Ford 200 " on it!).

Start with a plate that necks down the top one US gallon, 3785 cc's. That will fix any off boost camminess your worried about.

The other bits of kit are then putting tied in tongues to the lower port floor going into the six 1.65" effective diameter ports. The runners can be necked down about 12 cc for the depth of each approx 4 inch runner, taking 72 cc's off the total 1386 cc the six runners might be sized at right now. Low speed flow will go up, and air speed will go up, and camminess reduced. The bottom 1/8" of each port needs to be filled in like a 4V Boss 302 head or a 4V 351 head "back in the day". That can be done by alloy spacers or fillers that ey can be bolted in by cap screw. Then you can fiddle with the cam retard or advance, lifter clearances, and dial the engine combination to suit the cam.


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67Straightsix":1k059g5o said:
pmuller The rocker arms are adjustable 1.6 ratio.

x you are close on the plenum dimensions. 3.5 x 3 3.5x4.5 22 long

Oh yeah, transition from top 3 x 3.5 to bottom 3.5 by 4.5.

I guess about 500 cc's off those totals might be bang on.

I'm sorry if the comparisons seam pure speculation.

But it goes like this.

The X-flows run 1.73, or 1.7-1.75 if you use the aftermarket rockers.

So the little 200 can take and needs more intensive cam that needs to make up for the lack of lift.

The so called 202 Holden has 1.5:1 lifters, and a lot less lift, as well as having a smaller 845 thou GM lifter.

The Ford 144-250 lifter is the SBF lifter diameter, and like all of them compared to Chevy lifters, it can make take and make a lot more intense lift, but its still less than what I've used. Most cams are sadly ground off Chevy profile masters, and don't allways take advantage of the lifter diameter.

A real factor in reducing "camminess" is the lousy 1.5:1 rod length to stroke ratio. 4.715 over 3.126. It hurts the peak power rpm level. Fords Aussie in line six development engineer found in 1969 that as you cam up the engine, the rev range didn't increase the way a normal 1.7 to 2:1 rod ratio engine did. This is not particular to the Ford six; all engines that have reduced rod ratios do the same thing. You would pour more duration and lift, but even with big ports, the power peak wouln't go up much past 4800 rpm. But it can rev to 7500 rpm.

The idealised engine analyser calculations correct for it when the cam durations and lifts are put in, I've had a 15 year long quest for understanding how engines like this have to be tuned. The asnwer is more cam lift on intake and changing the overscavenging of the exhaust profile to suit the engine cobination. Clay Smit has done that with your cam, and the other cam SynchromeshWines got recommned to him by Jerry does it too.

I'm pretty sure all cam suppliers do a limitmus test.... does this client really need a bigger cam. If he is a normal conservative Ford sixer, probaly not. But if its a real hard core performance guy with a light car and some real modifications, then, YES YES YES.

On the the over square nature of the engine...it doesn't really do a thing to stop the 200 still being a tractor engine.

Based on the calculations, you engine is still air flow limited, and could possibly take even more 50 thou figures than what you have. Most of the EFI guys are still using bnak fire, not fully sequential injection like the old Cal Pack GM injection, where as the HP Holley is fully sequential, like the first 5.0 Ford port EFI. Modern EFI systems have a lot more tricks than the old style Second generation Tuned Port systems. Holley's HP module has facilty for 12 sequentially driven 8:2 peak and hold injector drivers....you could even dual layer the injectors with some tiny ones for low speed, and some killer big ones for higher speed. Meantime, it's just a case of getting it running, adjusting the fuel and sequential pulse widths, and if its raggard, reduce the plenumb volume or rephase the cam on the crank. 109 to 112, there is normally 3 degrees in it. You have a whole range of good options to tie off any low end "raggardness".

Even alternating fire on an I6 (like bank fire in a Cal Pack or EECIV 5.0/5.8/7.5 truck engine), a little in line six in the 200 to 265 sizes with little compression a big cam and a big turbo....its got a great idle if your exhaust is muffled and the pipe sizes aren't to big.

Porsche 911 Turbos in the first 3 liter rendition had 6.5:1 compression Later cams can be subbed into these, 964 series (that is the C2 and C4, '1989-'1994) camshaft duration figures 280 I. 262 E .470 .430. Porsche figured out how to tame big cams was less exhasut duration on turbo engines as well.

These turbo cars were stated as hating extra cam lift. That's not strictly true.

So on a engine that doesn't breath as well, your safe


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If the engine is limited to 5500 rpm because of the Turbocharger's compressor size and a person really wants torque from and idle (which is the case here) then why not use a short duration, high lift cam and take advantage of a higher Dynamic Compression Ratio which will produce much better low rpm torque.

With the present 300 degree cam the DCR is between 5.7 and 5.9 depending on where the intake lobe center was set at.
It was intended to be around 7 for this project.

This engine was designed with a low 8:1 static compression ratio with a short duration cam profile in mind.
The turbocharger was also chosen with the same low rpm power band as part of the criteria.


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I'm curious:
The reason I went with 8-1 compression is because the fuel octane available is 93 - I didn't want to have to buy race gas. I always thought with a turbo you want a low compression engine, but after reading these last posts, could I have gone with a higher compression ratio and been ok? (especially with the cam that's currently in the car) Just trying to be more knowledgeable about how all the components in an engine relate to each other. Thanks :)


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The previous conversation was about Volumtric Efficiency at low rpm rather than compression ratio.

Xctasy was pointing out that if the intake port is undersized for the cylinder volume then there is high enough intake charge velocity to continue cylinder fill way after BDC and a late closing intake valve has less effect on low rpm torque because there is less intake port reversion at low rpm than one would normally expect with a long duration cam.
Also the long duration cam will naturally maintain a high VE at high rpm and the engine will rev beyond peak power.

What I pointed out is that your engine is rev limited by the turbocharger which was chosen for a low rpm power band.
Looking at the compressor map shows a recommended engine rpm limit at 5500 rpm which gives margin before running into the choke zone where the turbo can be damaged.
So if I have to limit the engine rpm to 5500 rpm then why would I want a cam that maintains a high VE above that point.
Wouldn't it be better if I used a short duration cam and closed the intake valve before port reversion to maximize low rpm torque while allowing the VE to drop off after 5500 rpm.

To answer your question, Yes
The engine as it stands now with the long duration cam could be run with a higher compression ratio but what we find is the tune-up becomes more critical and for the little amount of torque gained with a higher compression ratio can easily be made up for with a little more boost.

We ran NHRA Top Sportsman class with a 300 degree advertised duration cam but .900" valve lift.
At 2000 HP, 430 cid SBF our compression ratio was 9:1 with VP C16 race gas, 25 lbs of boost and an ice water intercooler.


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drag-200stang":220j641w said:
You are planing on supplementing that 93 with a water meth kit?

Most likely yes. It's one of the things that will be installed if needed after the car has been run on the road.Been going between controlling it with the Holley or a stand alone system. I'm also trying to decide where to place the oil catch can. Considering I have a small six there is not going to be much empty space in the engine compartment when it's finished.


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Mazda and some of the Aussies have understood what the Millers brothers knew back in the 30's....combustion is controlled by Exhaust and intake overlap, and principally, the exhaust event and total boost. I'm sure Rotary guy's learn a lot more than us dancin knitting needle piston engine guys because they don't loose valve gear when over reverd or leaned out to tourch down levels, where a lean out takes to the exhasut valve like a gas axe to an old iron tube. There is a very conservative approach grounded in traditional V8 cam theory that caps in line six cylinder power in the United States. This is not a criticism, its an observation. Since we are six cylinder guys, most of us like the concept of V8 style grunt, but never want to pay as much as V8 guys for it. We are all generally into a protection mode, and that doesn't help the science of creating power. This is excatly as things were in the areo engine area in the USA before World War II. Everything areo piston engind supplied to the government was designed to use a standard compound charge US turbo charger to meet the altitude requirements. The key then became making the turbo live, not making the engine as great as it could be. In 2018, we need to see the turbo as a variable that needs to change, and make the piston engine tough enoug enough. The turbo is not to be a door stop to performance aspirations.

So the cold cranking compression ratio just has to be low enough to make a worakable idle, and you can fiddle around with detonation measures by curbing peak ignition advance with boost, or playing with ignition tip and an air fuel. Then, last resort, droping exhaust timing by cam and lash repositiong.

In a competition environment, low octane makes better hp and torque than higher octane if you can modulate ignition and air fuel ratio. The octane rating has been critical since 1971, when the Petrochemcial industry found lower octane was a better use of crude. GM's trimetal catalytic converter ment leaded gasoline was OUT. Dropping lead has created a major problem for everyone. It was the easiest way to boost octane. The problem is.... traditionalists think that the Iso Octane and Research octane numbers are what give reliable power and better economy, the focus has been on adding it to the combustion event all the time. Its like running Nitrous Oxide all the time....an effective octane boost is only need in certain situatons, not all the time.

I haven't seen anything change in Turbo engine or gasoline engine building except for running higher compression rations and finding that low octane gas makes more power. Toyo Kogyo's SkyActive X, (supercharged gasoline engine) and General Motors SIDI semi diesel "air limited" non turbo gasoline engines can run on 80 octane pool gas if it were around.

Back to pmuller9's point. The issue is one of matching and blance. The idea is for a given turbo, avoid destroying turbo impellors. Match octane to expected boost, and get the best of both worlds. Thing is....a turbo is just a gas turbine that shares its combustion chamber with a gasoline engine. Despite the total importance of the turbo sizing, it'is still much easier to destroy an engine than a turbo. Eddy Tassone and Active Automotive in Australia hit the right formula in the Noughties with a 1376 rwhp pull in a 6.3 liter 308 stroked to 383 twin turbo Holden Commodore....

Anthony Rodriguez at Maztech of Melbourne tuned it.


Antony had a method that dumped timing, leaned it out, and then over fueled it to create what everyone else thought was a hidden N20 kit. As a result, Eddy was hooked on turbos. and this guy does 189 mph at the 2626 foot mark before deploying the parachut in a street '1300hp daily-driven VZ HSV GTOPontiac GTO (the Monaro one).

Any IRS car is a risk on the track, Eddy has wrecked his, but its been raced and tuned, and he's lynched on to understanding the basics of making traditional OHV US engines with a turbo stand up and beg. Most of that info has come the A Rodriguez.

The Holden Torana was tuned by the same company. The in line six made much more power safely than people expected.

Eddy Tassone":32ps4qih said:
With drag racing under our belt we decided to give HorsePower Hero's at Summernats a try and being from the West Coast we were referred to as the underdogs...That all changed when we walked away with HP Heroes trophy in the highly scrutinised event with 1376rwhp on unleaded pump fuel and the first time 1000+rwkw was recorded on a Dyno Dynamics dyno.

2003 Eddy Tassone VH Commodore 1376rwhp

Eddy Tassone took this car to the 2003 Summernats, ran up 1376 HP on the dyno and the Eastern Staters spat the dummy.
"Your running nitros!" they cried.
No he wasn't and he took off the manifold to prove it.

The Summernats dyno shoot out goes to a Sand Groper.

From there it was nonstop controversy, critics saying the car could not sustain multiple runs and would not run mph etc.
Straight to the track again to prove the critics wrong the car run a massive 8.11@176mph to become the fastest 10 inch tyred, standard suspension car in the world at the time and and breaking the Super Sedan MPH record at the Motorplex.

Then with a series of Dyno comps around Australia, both the AME and Holden Vs Ford shows, the car went on to win 3 years straight, as well as being the first car to make over 1000rwhp in every state bar Northern Terriotory, with a combined 120 1000+hp dyno pulls for crowds all around Australia putting to rest the reliability rumours including another Summernats win at Summernats 18


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Very interesting read!

So he retarded the timing and leaned it out? Then added timing and fuel?

Why did that work?


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Mark Arblaster from Australian Street Machine in March 2003 explained it better than I. IIRC, Eddy created an aligmighty lean condition with little advance that almost stalled the turbo, almost holed pistions. then dumped fuel in while it was just starting to explode. Then the timing got changed. The result was like a statified charge, with a real rich layer of low octane gas in the cylinder chamber. The results were eruptive...50 psi of boost when all he could get in the past was 35 psi, and hp up from 1238 to 1376, probably more due to tire losses and wheelspin.

An engine isn't a steady state, you can almost blow it up in a lean torch down, then add fuel. The turbo is in lag, so you avoid surge by sudden, non constant retarding of ignition and then dumping rich fuel loads.

While off boost, you treat a turbo engine like any other. The exhaust timing governs what happens at the turbo. The turbo is a jet engine sharing the piston engines combustion chamber, but the gasoline engine is the parent unless you put injectors down stream of the engine, upstream of the turbo.

Some of the Rotary guys, they have learned how you can time the lean to rich sequence, the ignition and the exhaust shut to intake opening "overlap" to play agianst the turbo sizing. Bob broke the ice back in 2003.

I've got a few pages to read sometime, I have the quote on how its done from Australian Street Machine...


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pmuller9":3cdglsbc said:
Did you get the car running on the road?
Not yet. Once I got the engine running in the car I felt like the car should be just about finished! When I focused on the rest of the car I realized there was a lot more to do than I'd thought! Since I posted the video, I've installed the brakes - that took more fabrication then expected. I got Wilwood disc brakes "complete with brackets" from a buddy - the brackets were for a different spindle so I had to make my own. Ran new brake lines from front to rear. My engine is shoved back more than most so I had to find a driveshaft four inches shorter than stock. Found a driveshaft and installed that. Still need to finish the interior, install the bumper, valance and grill, install exhaust system, and get it aligned - etc, etc, etc... I've been working on it everyday for the last two months and I'm finally seeing a light at the end of the tunnel! It should be on the road in the next week or so.


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Quick update. Took the Mustang on its first test drive to the gas station and back :D It ran a little rich - need to do some real world tuning - that will be tomorrow. So far, so good (y)