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Turbo Build Help - 331 Stroker w 78/75 On3 Turbo

10K views 32 replies 14 participants last post by  PerformanceAndStyle 
#1 ·
I searched through the forums and couldn't find a post that really answered all my needs so hopefully this doesn't break any rules and sorry if I do but I am in highschool and I'm new to building cars. I am getting started to build a 331 stroker turbo build that's mainly a street car but I will take it to the drag strip every once and a while. The build that I'm making will go into my 1983 Notchback. I'm on a budget but I'm looking to make around 400-600hp with the turbo. I don't know if I should buy a stock 302 block and bore it out or if I should save up a lot of money and buy a stronger 331 already made. I'm going to an automotive school in a few months so I am able to do all machine work, rear end, trans, and any work you can imagine for "free". Also I'm not sure what type of head or size chamber of heads to buy. Also if I should upgrade the type of rollers and push rods. I was thinking about running an F303 cam or maybe even an X303 because I have heard they are really good for boosted applications. I've heard some people running stock everything (except a tire) with a 302 and making 10 second passes with a 70mm turbo but I'd rather be safe than sorry so I want decently strong internals. The stroker kit I was going to get was the Scat 331 with the I-beam rods. I can't figure out how much power they can hold but it's gotta be better than stock and also its $1000 cheaper than next option with the H-beams. Sooo pretty much I'm asking on tips on how to make good power for decently cheap but not blow it. Anything helps thank you!
 
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#3 ·
If the automotive school you are going to is SAM in Tx. Do yourself a favor and just hold off till you get to school before you purchase anything.
The amount of knowledge and help you will recieve there if your willing to listen and learn will be priceless, and those guys will help you make wise desicions to put a detailed plan together for exactly what your goals and budget are. The key is having a good plan together before you randomly start buying parts.
Plus students usually get a pretty good discount from most of the sponsors of the school. So If SAM is the school you are attending i would recommend take the next 4 months do some research and mainly begin to stash your spare cash for when you get to school and are ready to start the project.

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#5 ·
If the automotive school you are going to is SAM in Tx. Do yourself a favor and just hold off till you get to school before you purchase anything.
The amount of knowledge and help you will recieve there if your willing to listen and learn will be priceless, and those guys will help you make wise desicions to put a detailed plan together for exactly what your goals and budget are. The key is having a good plan together before you randomly start buying parts.
Plus students usually get a pretty good discount from most of the sponsors of the school. So If SAM is the school you are attending i would recommend take the next 4 months do some research and mainly begin to stash your spare cash for when you get to school and are ready to start the project.

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I am going to a school in Exton PA but one of the teachers there builds mustangs and has a ton of knowledge so I will save my money until then. Thank you for the help!
 
#10 ·
Yes 9.5 is 351W. As said DSS is just a machined factory block. No amount of machining is going to make a factory block stronger. It will likely eliminate points of issues starting, or perhaps delay the issue from starting, but either way you will be holding the pin in one hand and the grenade in the other. At some point it will blow up.

The rest of your expressed goal is well within the limits of the factory 351W block and sound "budget" oriented. Keep the same goals and build a stock stroke/bore turbo 351W. All the 351W blocks are pretty much equally strong. At that power level the OE crank and rods will suffice even.
 
#11 ·
Im currently building a Fox with a 331 single 76/75 for a customer. Customer went with a Man O War block. Its got 4 bolt splayed nodular cast main caps good to about 750hp. You can get it with billet main caps that will bring the motor potential up to about 2,500 hp. You can also go big bore with it. Its also got 2 extra holes per cylinder so you can run 6 bolt heads. Pretty nice piece. Although you probably would be fine with something like a Boss block for your power goal.

Rest of the setup is AFR 205 Renegades, custom solid roller camshaft, super victor 4150 intake, holley super sniper blow thru, hyper spark ignition, and On-3 turbo kit with the upgraded stainless steel option and upgraded 76/75 Precision turbo. Pump gas and water meth injection.
 
#12 ·
Saving your money for a good block is probably the best choice, but you can be successful with a stock 302 block combo as long as you keep your power/rpm reasonable. 20 years ago, I ran a stock block, stock crank/rods 306 into the high 9s with a 66 mm turbo (maybe 550+ fwhp?). It ran for 3 years before the block cracked. Another option is to go with a 351W block to build your turbo combo, like TJM73 mentioned. Do some searches on here and other turbo Mustang-oriented sites and you'll find quite a few people that have built rather cost-effect 351W turbo combos that really run well...just another option. Good luck with your project!
 
#17 ·
You can make 500 on the stock block no problem as long as the tune is right and you do not spin the motor to high.
Don't go aftermarket block unless you plan to match it with a forged rotating assembly. This ends up not budget friendly lol.

Stock 351 blocks break just the same as the 8.2 deck 302s, so keep that in mind.
Personally I would save your money and atleast build a stout short block. Get a good Dart block or similar, and good 4340 rotating assembly.
This way, you can grow and not worry about being power limited when you get greedy and want to push 20+ boost.
 
#18 ·
You can make 500 on the stock block no problem as long as the tune is right and you do not spin the motor to high.
Don't go aftermarket block unless you plan to match it with a forged rotating assembly. This ends up not budget friendly lol.

Stock 351 blocks break just the same as the 8.2 deck 302s, so keep that in mind.
Personally I would save your money and atleast build a stout short block. Get a good Dart block or similar, and good 4340 rotating assembly.
This way, you can grow and not worry about being power limited when you get greedy and want to push 20+ boost.
Thank you! I'll keep that in mind. I was probably gonna go with a dart or boss block. And yeah I like to be safe and greedy at the same time so that's what I'm gonna do
 
#21 ·
I've alway ran 373s. But 373s I think work better for centrifugal blowers, which is what I've always had.

Now with a turbo, I wish I had 355s or maybe 327s. 1st gear with a stick shift is ass. Turbo isn't doing **** until second gear.
I'd probaby keep 373s if I was running a auto, but Def not a stick car.
 
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#23 ·
There's a big thread on here where it was argued that Turbo's need load to spool versus gearing for the Camshaft..


I can tell you that the load thing is just that.. A load of shyte. You need gear to keep the Cam in the powerband.

I first went 3.27 and it drove real nice on the street and thought it was fast. It was good to have 1st gear pull longer with low revs at highway speeds but it comes at a cost of torque multiplication. You think the car is fast because it isn't spinning the tires but then somebody puts you on the trailer.. Modern cars have 10 Speeds and still run a 3.73 gear. You're at a huge disadvantage.

I then went to a 3.55 and the car is faster but I lost 10mph topped out in 4th. If I had a 6-Speed, I wouldn't think twice about running a 3.73 because you get a tall 6th gear for highway cruising. If the car was dragrace only I'd run a 3.73 on a 5-speed, but because the car is mostly street/highway driven, so I still want some mpg's..

This calculator is great to figure out your speed vs tire and gear..

 
#24 ·
The block is the weak link on a 302 build, buying a 331 is a waste of money without a DART or man o war block.

If you are on a budget a 351 is by far the safest option. I have never heard of anyone splitting a 351 down the middle at 500hp and most people say they are good to 700hp, rods and pistons being the weak links. Go to theturboforums, a lot more turbo knowledge there.

If you go 302, find a stock one in good shape and keep the boost to 10psi or so. I did that for years no issues. 445whp and 490 trq.

I assume you are working part time in college, same path I went on my build. It took me about $1800 to build my kit but I had a running engine and a way to tune the engine already. Junkyard turbo, built my own hotside, Chinese cold side parts. You need to pick a budget and stick to it. An aftermarket block build is easily $10k
 
#26 ·
The block is the weak link on a 302 build, buying a 331 is a waste of money without a DART or man o war block.

If you are on a budget a 351 is by far the safest option. I have never heard of anyone splitting a 351 down the middle at 500hp and most people say they are good to 700hp, rods and pistons being the weak links. Go to theturboforums, a lot more turbo knowledge there.

If you go 302, find a stock one in good shape and keep the boost to 10psi or so. I did that for years no issues. 445whp and 490 trq.

I assume you are working part time in college, same path I went on my build. It took me about $1800 to build my kit but I had a running engine and a way to tune the engine already. Junkyard turbo, built my own hotside, Chinese cold side parts. You need to pick a budget and stick to it. An aftermarket block build is easily $10k
Lol you were close. I'm a high school student working part time. I already have a 78/75mm turbo but not the plumbing, wastegate, BOV intercooler, etc. The fox shell that I bought already has some aftermarket suspension but I have to take a better look to see if i need to upgrade even further. It used to be a drag car and HAD a roll cage in it.No engine or trans but I got a T-5, trick flow intake (upper and lower), fuel cell, and mickey thompsons as well. Right now with everything including the car I think I have 1600 into it. Im going to buy a donor car for 700 with an engine, wire harness, front seats (i need), and other interior pieces Im missing, and some other goodies. I honestly might go with a 351. But I dont know if i need different motor mounts for the 351.And hopefully I can use the trickflow intake with the 351 If i go that route.Also I do have a second car that i use as my daily. I have a FBO and tuned 99 GT that i use but also I have a nissan altima when i want to save gas
 
#25 ·
I'll also give you some advice I learned the hard way. Having a project car as your only car is stressful and not a great idea. I can't tell you how many times I had to rush something and redo it or rely on friends and family because my only car was taken apart for a weekend project that turned into 2-3 weeks. Make sure you have a reliable form of transportation besides your project car so you can take your time and do everything the right way. I also didn't enjoy my car as much because I was worried about blowing it up all the time and not having the money to fix it. Having a second car alleviates a lot of that.

Start going to local car Hangouts, avoid the troublemakers that will get you arrested or dead, build a network of car buddies so you have help and can learn from them as well.

I ran an F cam because I wanted the cool cam lope sound. A stock engine and cam with a turbo will be plenty power to shred your block. You'll also start finding all the weak points of the car. Trans will go, suspension won't hold up, axles and rear... I will offer up that your number one priority will be improving the rear suspension. My fox was outright scary when traction broke loose until I made the rear end suspension better. It had a mind of its own, there's a reason mustangs have a reputation for burnouts going wrong. The lateral movement in the rear end makes it very unpredictable.
 
#27 ·
The motor mounts should work for both, the upper intake will usually swap but the lower intake is different for a 351. You also need a different distributor and headers if you go with a 351
 
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