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1970 Mustang Fastback x2, 302, c6, 3.80 rear w/ posi, front wildwood disc brakes, corbeau seats
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Discussion Starter · #1 ·
In my Deathtrap Trans Am Build (1970 Mustang Fastback Restomod), I plan on building a high revving 302 that puts out around 500-525hp (I'd like 460 wheel) and has 10.5:1 compression. The max rpm goal is 8k. I will be using a tremec 6 spd so I won't be shifting over 7,200. I just want the extra rpm for safe measure. If I can rev it to 6-7k and not have to worry about it splitting down the block, I'll be happy. I plan on using Holley efi. I've read that similar applications have used the Dart SHP 302, forged internally balanced crank, crank girdle, h-beam rods, flat top pistons, and a Victor Jr. Intake. What do I need for the top end to meet this goal and keep the engine reliable? I'd like to do what I can myself, but obviously machine work and porting will be done out of house. I know that the engine will be pricey, but I'd like to spend less rather than more (if something doesn't have to be billet, I won't get it in billet!) This engine build will be in a few years so I'm trying to spend the time now to figure everything out to build this as best as possible. Thanks for the help in advance.
 

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Spammer Hammer
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Are you trying to build within vintage racing rules? If so, you will be on a very different path than just building your standard "cheater" motor. It will also be very costly. For instance, Cobra Automotive and Lozano Brothers Porting are two examples that build engines mostly within vintage racing rules. Their engines are $25K-$30K.

If you plan to build a "cheater" motor, it will be less expensive because you can do things like increased stroke, roller cam, and aftermarket heads.
 

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Not going to happen at 10.5:1. I also think you're looking at individual throttle bodies, not a 4bbl. 500hp would be exponentially easier than 525, and 475 would be dead easy compared to 500hp. But it's still going to require a lot of compression, valvetrain stability, and you can't ignore things like windage that a guy building a 400hp 302 wouldn't even need to pay attention to.

As soon as you say, "I'd like to spend less rather than more," you're heading down the wrong path.
 

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Getting over 500 horsepower is easy, if as others stated, you’re not bound by a sanctioning body racing rules by simply adhering to the old adage “no replacement for displacement.” A 363 stroker will get you the horsepower but probably not the RPM. Getting 500+ horsepower and the RPM will require all sorts of tricks and will be much more expensive because you’ll be needing high compression, lightened rotating assembly, shaft mounted valvetrain, and a camshaft profile that will probably be unstreetable. At this point forget reliability and start counting engine operating in hours rather than mileage. Decide if you want the horsepower or if your building a race engine for the track where the added RPMs can be used effectively.
 

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In my Deathtrap Trans Am Build (1970 Mustang Fastback Restomod), I plan on building a high revving 302 that puts out around 500-525hp (I'd like 460 wheel) and has 10.5:1 compression. The max rpm goal is 8k. I will be using a tremec 6 spd so I won't be shifting over 7,200. I just want the extra rpm for safe measure. If I can rev it to 6-7k and not have to worry about it splitting down the block, I'll be happy. I plan on using Holley efi. I've read that similar applications have used the Dart SHP 302, forged internally balanced crank, crank girdle, h-beam rods, flat top pistons, and a Victor Jr. Intake. What do I need for the top end to meet this goal and keep the engine reliable? I'd like to do what I can myself, but obviously machine work and porting will be done out of house. I know that the engine will be pricey, but I'd like to spend less rather than more (if something doesn't have to be billet, I won't get it in billet!) This engine build will be in a few years so I'm trying to spend the time now to figure everything out to build this as best as possible. Thanks for the help in advance.
What’s your goal for the car?

It’s your car, so ultimately if you want to have an 8k rpm 525hp 302 just to go get ice cream, more power to you. (Not saying that’s what you’ll use the car for, just a point that you haven’t stated it)

Recommend that what engine you build should match your intended use. If you plan to road race your “Deathtrap Trans Am” (love the name), then what you’re looking for is appropriate. Some of your parameters may need to change (as both patrick and jdub stated), but otherwise makes sense. And, if you’re planning to road race, checking with the rule book of the sanctioning body governing the races you want to enter. A complete waste to build a motor (or any part of the car) that isn’t race legal.

If you’re goal is more towards canyon carving or autocross… perhaps consider a stroker motor. 500hp becomes a lot more affordable and reliable with more cubes, and a little less rpm. A supercharger is also a nice option.

But if you’re thinking “nah bro, I want my motor to scream all day everyday!” Then hell yes, open that wallet super wide, sell a kidney, and let us help you spend! $$$$$$ maybe look at a reputable engine builder and have them put together a bad a$$ combo for you like this
Doesn’t quite meet your RPM, but obliterates your power goal. But it’s also a stroker, so there’s that.




Sent from the interwebs... where else?
 

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I'd assumed he wanted to stick with 302 cubic inches. No way to know though. I wonder if he'll be back.
 

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Dimples
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With the full disclosure that I’m no engine builder, it sounds like this plan will require fairy dust and unicorn tears to make it happen. In other words, while that power level may be possible, I don’t think it’s reasonable to include “reliability” in the equation. This sort of goal usually comes with a race team and a willingness/necessity to rebuild in between races.
 

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And a six figure engine program.
 

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'66GT350H - '67 Ranchero 545ci 460 - '68.5 Mustang 428CJ '74 and 78 F350 "Oleynik" enclosed haulers
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As several have mentioned , you will NOT make 500-525 hp for a 10.5-1 flat top 302. MANY have tried for years! One or two Super Stock ( drag race) engine builders have done it but these are 10,000 RPM dedicated 1/4 mile engines with .800+ lift solid roller cams and custom sheet metal intake manifolds. Just a couple of money saving items. A Dart SHP block does not need a main stud girdle. It already has 4 bolt mains. EFI will not get you 500 HP either , you will need a carburetor. A wiser choice is to go the stroker route as others have suggested . A 347 or 363 can do what you want and still be street friendly. My 331 makes 525ish and is NOT street friendly. Yes I turn it 8,000 rpm to do it and it is a solid roller with titanium valves and VicJr aluminum heads with 11.5-1cr.
 
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^^^^Yes, power or high reliable revs.
I would like a high winding screamer myself but wouldn't care where the HP fell. My understanding is that absent a crazy HP goal (500 is crazy) that almost generic HP, balanced and shot peened rods can handle the revs.
Rods, rockers and springs, titanium filled valves, light pistons and flywheels...? Where to spend and where to save? At that level even the most well regarded parts can fail 0.99% of the time. Not to mention build tolerances.

*sodium filled valves.
 

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It sounds like youre going to the restomod format, so vintage spec road racing is not your goal. If plan to go to a Dart block, stroke it out to 363 and enjoy 500+ reliable horsepower. With my supercharged 363 EFI car, it's a very docile 'going to the Cold Stone Creamery' car. If I get the pistachio, I'll open it up on the way home and hold on for dear life. ;)
 

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1970 Mustang Fastback x2, 302, c6, 3.80 rear w/ posi, front wildwood disc brakes, corbeau seats
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Discussion Starter · #16 ·
Are you trying to build within vintage racing rules? If so, you will be on a very different path than just building your standard "cheater" motor. It will also be very costly. For instance, Cobra Automotive and Lozano Brothers Porting are two examples that build engines mostly within vintage racing rules. Their engines are $25K-$30K.

If you plan to build a "cheater" motor, it will be less expensive because you can do things like increased stroke, roller cam, and aftermarket heads.
I'm not trying to build it within the rules, but to the same specs for the most part. For example I'd like to keep it at 302ci and naturally aspirated (not a big fan of boost in my cars). I know I will need a roller cam and aftermarket heads. I just want to know what I will have to get or change to get an engine to make close to those numbers. Even if the engine doesn't rev to 8k and only revs to 7.5k, I want an engine that I can spin to 6,500 all day long and not have to worry about it blowing up.
 

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1970 Mustang Fastback x2, 302, c6, 3.80 rear w/ posi, front wildwood disc brakes, corbeau seats
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Discussion Starter · #18 ·
Not going to happen at 10.5:1. I also think you're looking at individual throttle bodies, not a 4bbl. 500hp would be exponentially easier than 525, and 475 would be dead easy compared to 500hp. But it's still going to require a lot of compression, valvetrain stability, and you can't ignore things like windage that a guy building a 400hp 302 wouldn't even need to pay attention to.

As soon as you say, "I'd like to spend less rather than more," you're heading down the wrong path.
When I mentioned keeping the cost down I meant doing things myself that don't necessarily HAVE to be done by an engine builder, materials used (not using billet if I don't have to), stuff like that. I know this is going to be an expensive engine, but for the most part I'd like to keep the costs down that I can.
 

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1970 Mustang Fastback x2, 302, c6, 3.80 rear w/ posi, front wildwood disc brakes, corbeau seats
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Discussion Starter · #19 ·
Getting over 500 horsepower is easy, if as others stated, you’re not bound by a sanctioning body racing rules by simply adhering to the old adage “no replacement for displacement.” A 363 stroker will get you the horsepower but probably not the RPM. Getting 500+ horsepower and the RPM will require all sorts of tricks and will be much more expensive because you’ll be needing high compression, lightened rotating assembly, shaft mounted valvetrain, and a camshaft profile that will probably be unstreetable. At this point forget reliability and start counting engine operating in hours rather than mileage. Decide if you want the horsepower or if your building a race engine for the track where the added RPMs can be used effectively.
This is what I was looking to hear. I guess depending on all the numbers my rpm's will be a little lower than expected. Would this work vise versa? If I was looking to make say 475hp at 7k rpm?
 

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Posted this years ago, it will give you an idea what it takes to get that HP out of a small NA motor.. How to Build a 479hp Ford 302 for $4,991 - Car Craft Magazine
479hp but won't idle below 1300 RPM and pulls six inches of vacuum. Also 13.8:1 compression ratio.

If you want to maximize a reliable 302 that works on the street don't chase a number. Just build it right and see what happens.

306ci
Dart SHP Block
11.0:1 compression
TFS 190cc 11R Heads
.600-.625ish lift roller cam with around 236-248 duration @0.050
The best Morel hydraulic lifters
Harland Sharp rockers for 11R heads with stud girdle (or shaft rockers)
1-7/8" Headers
Ported Super Victor
750cfm Double Pumper with all the tricks in the book and the tallest spacer you can fit

Should be dead reliable to 7000 RPM and almost be streetable (which is subjective). I don't know how much power it would make but in my mind it's a decent compromise between a max power 302 and something streetable/reliable (whatever those words mean).
 
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