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Discussion Starter #1
I am planning on building a dart 347 and since it will be turbo'd. I was told don't worry about getting a different intake or heads since the turbo will push the air through anyway. I have a ported cobra intake but I also have an untouched Holley systemax 2 intake and also 170cc tw heads that I was thinking of having ported to 205cc but again I was told by the turbo supplier that the intake and 205 heads would be so little difference on power just keep the 170 heads and cobra intake. I would be using a 67mm turbo and looking for 650-700 rwhp. Since you guys have turbo's and know more about it then me is he correct or should I using higher flowing heads and intake? Thanks
 

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Lol who is the turbo supplier that told you to keep small heads and intake on a dart motor?? If you keep bottlenecks like that on your engine then you'll be forced to use high boost to produce the power, which will require either a different fuel, meth injection, etc.

If it were me, I'd sell the intake and heads and buy bigger stuff (hopefully for near the same price) and that way you'd make 700 on lower boost and keep heat/wear/detonation off the engine.
 

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Discussion Starter #3
Well I thinking of porting my heads to 205cc and my holly intake also ported would be big enough rght or should I go larger? I thought the same thing about my current intake and heads
 

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I don't know much about the systemax intakes but I think you'd want a 190-205cc head on that 347 for that power goal on moderate boost. I'm thinking 10-15psi on 8-8.5:1 comp.
 

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700hp is 700hp. Whether it's at 10psi or 21psi it's still the same cylinder pressure required to make 700hp on how many ever cylinders you have...the size of tuning window changes but heat, wear and tear would practically be the same for the same cubic inch short block making the same power level regardless of the boost level to reach that power level. With forced induction, you always have a "bottleneck" hence the positive intake pressure.

You can make 650-700hp with those heads and the Holley intake untouched but I think a 67mm compressor is a bit on the small side for a healthy 347 to get that done but it would depend on the camshaft, compression ratio and the turbo. If it's a badass ball bearing billet wheel 67mm with a large turbine then yeah but if it's just a regular run of the mill 67mm turbo then I'm not sure it would be as easy to hit your goal if your stated goal is at the tire. What are the cam specs and what size turbine is on the turbo you're looking at? Turbo manufacturer? Are we talking 650-700 crank or wheel hp?
 

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I'd only build an 8-8.5:1 compression turbo engine if I were looking to put 35-50psi of boost to it, solid lift cam, billet heads, Q16 fuel....if it's a street car on pump fuel then 9.5:1 and get you a custom camshaft cut for combo. If you're on E85 then no reason why 10-11:1 can't be done. My previous turbo setup was 10.4:1 347 with the TW 170 heads and track heat intake on pump fuel running 10 pounds of boost. I drove the car every day, and even road tripped it 3-4 hours sometimes. Boost was instant, and it wasn't any harder to tune even though I didn't have methanol injection on it.
 

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Discussion Starter #9
I am looking at a precision turbo 67 or 76 ball bearing turbo. I would have a steel crank diamond pistons and some h beam rods. all the exact parts are unknown but it would be build to handle the power. I was thinking 9.5cr. Do you guys think 76mm with ported holley and 205cc heads I could make 650 rwhp with aod at around 10-15 psi? that would be my goal and maybe 6k rpm? I would also like to be able to do it on pump gas without meth or e85
 

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I'd only build an 8-8.5:1 compression turbo engine if I were looking to put 35-50psi of boost to it, solid lift cam, billet heads, Q16 fuel....if it's a street car on pump fuel then 9.5:1 and get you a custom camshaft cut for combo. If you're on E85 then no reason why 10-11:1 can't be done. My previous turbo setup was 10.4:1 347 with the TW 170 heads and track heat intake on pump fuel running 10 pounds of boost. I drove the car every day, and even road tripped it 3-4 hours sometimes. Boost was instant, and it wasn't any harder to tune even though I didn't have methanol injection on it.

Nice! That's an answer I been looking for?
 

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I am looking at a precision turbo 67 or 76 ball bearing turbo. I would have a steel crank diamond pistons and some h beam rods. all the exact parts are unknown but it would be build to handle the power. I was thinking 9.5cr. Do you guys think 76mm with ported holley and 205cc heads I could make 650 rwhp with aod at around 10-15 psi? that would be my goal and maybe 6k rpm? I would also like to be able to do it on pump gas without meth or e85

Cast steel crank? Forged crank?
 

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I am looking at a precision turbo 67 or 76 ball bearing turbo. I would have a steel crank diamond pistons and some h beam rods. all the exact parts are unknown but it would be build to handle the power. I was thinking 9.5cr. Do you guys think 76mm with ported holley and 205cc heads I could make 650 rwhp with aod at around 10-15 psi? that would be my goal and maybe 6k rpm? I would also like to be able to do it on pump gas without meth or e85
Since you're looking at compact Precision units, go with the 7675CEA. I'd just stay with a journal bearing to save money unless you really plan on pushing the turbo to its limit later on down the road. You could put the money not spent on the ball bearing unit towards getting the heads opened up. TEA charges right at $1000 to run the 205 CNC program on the TW170 heads. That turbo has made 750 and up on 8.2 deck engines in this forum. And with 347ci you won't have any trouble spooling it. 9.5:1 on pump fuel would get the job done, and you'd get it done easy with that intake and 205cc TW heads. 6k redline sounds good too. You'd hit 650 for sure in the boost range you're looking at.
 

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Discussion Starter #13
Yes they charge 1000 to port to 205. and I hear the systemax 2 intakes need to be matched to the tw heads. You don't think I need ball bearing? I was told it will help spool up slightly quicker but will make the turbo last a lot longer
 

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Yes they charge 1000 to port to 205. and I hear the systemax 2 intakes need to be matched to the tw heads. You don't think I need ball bearing? I was told it will help spool up slightly quicker but will make the turbo last a lot longer
Yeah port matching is always a good idea.

If you've got the money to spend on the ball bearing option then by all means! I was just saying it wasn't necessary to hit the conservative power goal you mentioned. I doubt you'll see any verifiable spool time differences between the two units on what I assume is a street car. With the right camshaft, that turbo should be spooling right off idle, and into peak boost (10-15psi) at no later than 3500RPM. It's a small and efficient turbine even without the ball bearing option. If it's a street car then any spool time gained with the ball bearing option will be offset by the traction available haha!

As far as longevity, I honestly haven't considered that aspect of the ball bearing option...How many miles do you plan to put on the car in a given year? As long as you keep the oil changed, and don't overheat the oil or turbo then I would say that you wouldn't run into bearing life issues before you wanted to upgrade the turbo. But yeah going with the ball bearing only strains the finances otherwise it's an option that has zero downfall. If you can spend it, and want to then spend it.
 

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I am looking at a precision turbo 67 or 76 ball bearing turbo. I would have a steel crank diamond pistons and some h beam rods. all the exact parts are unknown but it would be build to handle the power. I was thinking 9.5cr. Do you guys think 76mm with ported holley and 205cc heads I could make 650 rwhp with aod at around 10-15 psi? that would be my goal and maybe 6k rpm? I would also like to be able to do it on pump gas without meth or e85
I had a PT7675CEA on my 363 with 205 CNC heads, Super Vic, solid roller, and it was over 1000. I just weighed my car, I thought it was 3150 with me, but it was like 3225. With that weight and a power glide, the PT7675CEA ran consistent 5.4's in the 1/8 over and over, and ran 8.5's in the 1/4. That's over 20 psi, but is through mufflers and dumps by the back axle.

Off shelf Diamond pistons in the 363 5.4 rod were unreliable at any power over 800 because they are thin at the valve relief. I've had a couple crack right where the intake relief hangs over the ring. I'd look at a piston with minimal valve relief.

At 15 psi my motor made around 900 at the tires.

My PT7675CEA spooled off a fast idle to 15 psi in one second. At 1.1 seconds it was over 20 psi. I wish this miserable 8280 on it now spooled that fast. The 8280 takes 2.5 seconds to 25 psi, although I think I found an issue. I'm still sorting the 8280 out.
 
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To put it simply, the better flowing your engine is NA, the better it will be boosted. I'm doing a Dart 331 w/ AFR 205's, and a 76-80mm. Looking for a streetable 650-750. You should be fine.
 

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700hp is 700hp. Whether it's at 10psi or 21psi it's still the same cylinder pressure required to make 700hp on how many ever cylinders you have...the size of tuning window changes but heat, wear and tear would practically be the same for the same cubic inch short block making the same power level regardless of the boost level to reach that power level. With forced induction, you always have a "bottleneck" hence the positive intake pressure.

You can make 650-700hp with those heads and the Holley intake untouched but I think a 67mm compressor is a bit on the small side for a healthy 347 to get that done but it would depend on the camshaft, compression ratio and the turbo. If it's a badass ball bearing billet wheel 67mm with a large turbine then yeah but if it's just a regular run of the mill 67mm turbo then I'm not sure it would be as easy to hit your goal if your stated goal is at the tire. What are the cam specs and what size turbine is on the turbo you're looking at? Turbo manufacturer? Are we talking 650-700 crank or wheel hp?
I can't help but think that something important is missing here. 700hp is 700hp, yes, and the cylinder pressure is the *same* regardless of the bottlenecks before the cylinder but cramming tons of air mass through smaller ports (assuming small heads and higher boost) will generate heat in the charge that I imagine will lead to detonation quicker than if he had a free-flowing engine at low boost. This will require higher octane fuels, as mentioned in my first post. Is this guy okay with running C10 or e85 in the car? If so, by all means, go ahead but if he's stuck to 91-93 unleaded, I don't see why it would make sense to keep the current setup when he could get bigger stuff for very little money.

thousand dollar set of heads with a thousand dollars in machining vs selling the 170's for a thousand and buying 205's for about a thousand. Seems like a solution to me.

If he does stick with 170's on a 9.5CR 347 i doubt he'll make 700 through an AOD on 91-93 unleaded gas. If he does, he should write a book about it.
 

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Discussion Starter #19
when I looked 205cc tw heads were $2000 so it's the same money to port mine as buy new. might as well keep mine since selling and shipping would be a pita. I will be moving to AZ where the premium gas is only 91! so that's what I was hoping to make the power on without meth injection.

Maybe I'm crazy thinking in hot Arizona and ####ty gas it can be done. Can anyone from that part of the country chime in on 91 octane and turbo's?
 

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when I looked 205cc tw heads were $2000 so it's the same money to port mine as buy new. might as well keep mine since selling and shipping would be a pita. I will be moving to AZ where the premium gas is only 91! so that's what I was hoping to make the power on without meth injection.

Maybe I'm crazy thinking in hot Arizona and ####ty gas it can be done. Can anyone from that part of the country chime in on 91 octane and turbo's?
i'm in texas and it gets up to 110+ in the summers sometimes. We have 87-91 pretty much everywhere with 93 in all the big cities that I know of. As I understand it, lower octane number means the fuel has a lower flash point, so it requires less heat/pressure to make it combust. This means that if pressures are too high or temp too hot, it will flash early/incorrectly and "detonate" within the cylinder. Race gas and ethanol fuels have a higher flash temp that allows for greater heat or combustion pressure, which gives us the ability to make more horsepower.

It sounds like you'll be going with a 205cc intake runner regardless so that will help you make easier power. All in all, you can make the setup work with whatever octane fuel you have available. It will just require keeping the boost low enough to eliminate the possibility of detonation. It's all about the tune. You can probably squeeze good power out of it but don't be mad if it doesn't hit 650-700. I'm not trying to bring you down or anything. I just wouldn't be super optimistic given those conditions.
 
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