Want to build a boss 302 or 331....

Want to build a boss 302 or 331....

Joined: January 15th, 2009, 1:00 am

August 7th, 2012, 4:37 pm #1

I have a 79 mustang and I really want to build a 8.2 deck boss 302 or 331....

I know I can do the 302 with stock crank, 289 length rods, and a boss piston. Or 5.4 rod and 1.3 piston
331 would be 3.25 crank, 5.325 rods, and a 1.250 compression Cleveland piston.

I want this for mainly a street car... Car has 4.30 gears already...Built Aod so overdrive is nice with the 4.30s
Looking to have the same caratistics as a old boss 302...high revving etc
Hoping to get 3200lbs down the 1/4 in low 12s high 11s
Be able to jump in and head down the road... Two pumps of the carb and I'm off...
Pump gas/reliable 93

Things I have already... Which lead me to this build...

Clevor modded 351 4v cc heads
Mexican 302 block bored 30 over fresh
Stock crank
Buddy of mine has a boss 302 intake I can borrow until I find a track boss or another intake
2 sets of forged Cleveland pistons (gotta measure compression height)


Basically I need help making a good combo with the smaller cubes... Should I go high revving 302? 7500rpm...since torque shouldn't be to bad with 4.30 gears...

I think I read go small duration/high lift to get a boss 302 to run? Like 225/230@50 with like 580/595 lift on a 111 intake center line? Trying to get 12-14 vacuum at idle...


Thanks! How did you guys get your old bosses up and moving?!?

Some help would be appreciated....
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Joined: May 20th, 2005, 4:48 pm

August 7th, 2012, 5:05 pm #2

Anytime you put 302 cubes with a 235-240cc head, you're going to have to spin the pee out of it to get anywhere. Yes, the 4.30 gear will help and yes the light weight will help, but keep in mind that a 7500 rpm engine is not a street engine and will absolutely be a dog on the bottom end.

If you do plan to turn that many rpms, you will need duration and a ton of it. No vacuum.

I do Boss 302's for vintage Mustang stuff and the engines have no butt to them.

I would throw as much stroke as you can to it, skip the 331 and go with a 347, and stay away from the 7500 rpm goals. Lower duration and ADVANCED cam timing, not 111-112 ICL's. If you can, I would put port tongues in the heads and cut the CSA way down.

Brent Lykins
B2 Motorsports, LLC






Last edited by blykins on August 7th, 2012, 5:06 pm, edited 1 time in total.
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Joined: October 1st, 2004, 8:05 pm

August 7th, 2012, 5:41 pm #3

I have a 79 mustang and I really want to build a 8.2 deck boss 302 or 331....

I know I can do the 302 with stock crank, 289 length rods, and a boss piston. Or 5.4 rod and 1.3 piston
331 would be 3.25 crank, 5.325 rods, and a 1.250 compression Cleveland piston.

I want this for mainly a street car... Car has 4.30 gears already...Built Aod so overdrive is nice with the 4.30s
Looking to have the same caratistics as a old boss 302...high revving etc
Hoping to get 3200lbs down the 1/4 in low 12s high 11s
Be able to jump in and head down the road... Two pumps of the carb and I'm off...
Pump gas/reliable 93

Things I have already... Which lead me to this build...

Clevor modded 351 4v cc heads
Mexican 302 block bored 30 over fresh
Stock crank
Buddy of mine has a boss 302 intake I can borrow until I find a track boss or another intake
2 sets of forged Cleveland pistons (gotta measure compression height)


Basically I need help making a good combo with the smaller cubes... Should I go high revving 302? 7500rpm...since torque shouldn't be to bad with 4.30 gears...

I think I read go small duration/high lift to get a boss 302 to run? Like 225/230@50 with like 580/595 lift on a 111 intake center line? Trying to get 12-14 vacuum at idle...


Thanks! How did you guys get your old bosses up and moving?!?

Some help would be appreciated....
I've driven the factory cars and they ran just fine, even with the stock 3.50:1 gearing. I think stuffing one in your '79 is a great idea; 4.30s are the right gear for a 26" tire, according to Ford.

You don't have to ask "should I build a high rpm motor"? Because the moment you decide to bolt the 4V heads on the 302 you've already set that in motion. Its unavoidable, it shall be a high rpm motor. So don't fight it, and don't try to make it somethng it isn't.

Basically the Boss 302 does everything 800 rpm higher than a 351C 4V. But the same Cleveland principles apply. Everything is 180 degrees backwards from motors with small ports and small valves. The Cleveland heads build the high rpm power, and the cam and intake manifold build the low rpm power. So spec a cam with relatively short intake duration and limited overlap, and use a dual plane intake manifold with a full height (un-cut) plenum divider. Carb & ignition calibration are also critical to running smoothly on the bottom end. Your 4V heads have either 63cc chambers or 66cc chambers, whereas the Boss 302 heads had 58cc chambers, so you'll have to make up that difference in volume somehow.

I think you'll like the motor, my advice is go for it.



-G
____________________________________________________________

Pantera Photos | 351C Historic Information | 351C Technical Information



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Joined: January 15th, 2009, 1:00 am

August 7th, 2012, 5:50 pm #4

I think I'm gonna go with the stock stroke... 3.0
A 5.4 rod super light 4340 I-beam... And a 1.30 Cleveland piston...light bobweight

CC 4v heads with stud girdle and roller rockers since I have them.

Intake i have the access to a stock boss 302 one for now... Probally scope eBay for a cool one.

Shooting for 10.1 compression I guess to keep it safe...

Really all I gotta do is throw the right cam at it?
What was the hopped up boss 302 catalog came way back?
I know the cam will make or break this idea... Anyway to pull 12 vacuum from it?

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Joined: May 20th, 2005, 4:48 pm

August 7th, 2012, 7:29 pm #5



Sorry, I had to.

You'll need to figure out where you want to be with the power. A factory Boss 302 cam won't get you to 7500 and you wouldn't have vacuum if you made peak hp that high.

If you want a peak hp that's lower, there are a lot better cams out there than the factory stuff. Pick the duration for the rpm you want to be at, then pick the LSA/ICL to fit the rest of it.



Brent Lykins
B2 Motorsports, LLC






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Joined: January 15th, 2009, 1:00 am

August 7th, 2012, 7:45 pm #6

Based on what I'm lookin for in the first post...
What would u grind? Small duration/big lift?

Idc where it makes the power I want... I just thought I'd have to spin it up to 7500 to get the full benefit of power...
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Joined: May 20th, 2005, 4:48 pm

August 7th, 2012, 7:52 pm #7

...to have an engine that makes peak hp at 7500 and has low end manners plus vacuum to boot.

Modern engines can do it with multivalve heads, variable valve timing, EFI, etc. However, it's not like that with big cammed carbureted engines, especially small ones.

Where would you need to be to peak at 7500? Probably with .050" durations in the 240's. That may not sound big, but for a 302, it's huge.

Again, you'll need to figure out which side of the fence you want to be on. The streetable side with plenty of vacuum and some low end power (relatively speaking, Boss 302's don't have low end power), or a 7500 screamer with no niceties down low. I don't think you'll be happy with a 7500 rpm peak on the street, even with a 4.30 gear.

Brent Lykins
B2 Motorsports, LLC






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Joined: May 20th, 2005, 4:48 pm

August 7th, 2012, 8:05 pm #8

If it were me, I'd not worry about the vacuum and the "driving" part of the engine. I'd cam it to turn some revs so that it will be efficient and make some horsepower. A solid cam with about 240-242 duration @ .050", a 108LSA on a 104ICL, and about .600" lift.

In stock form with the Boss 302 cam (about 228 deg @ .050"), it should make about 375hp at 6600-6700. You could probably get closer to 400 with a little larger cam and a higher peak, but prepared for less and less torque. A stock 5.0 Mustang had more torque than these Boss 302's did.

Brent Lykins
B2 Motorsports, LLC






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Joined: January 15th, 2009, 1:00 am

August 7th, 2012, 8:08 pm #9

...to have an engine that makes peak hp at 7500 and has low end manners plus vacuum to boot.

Modern engines can do it with multivalve heads, variable valve timing, EFI, etc. However, it's not like that with big cammed carbureted engines, especially small ones.

Where would you need to be to peak at 7500? Probably with .050" durations in the 240's. That may not sound big, but for a 302, it's huge.

Again, you'll need to figure out which side of the fence you want to be on. The streetable side with plenty of vacuum and some low end power (relatively speaking, Boss 302's don't have low end power), or a 7500 screamer with no niceties down low. I don't think you'll be happy with a 7500 rpm peak on the street, even with a 4.30 gear.

Brent Lykins
B2 Motorsports, LLC





My old 2003 Mach was kind of like a boss 302 I believe... 4.6...
Made 320 torque at 4500... Peak hp was around 5900-6100... I shifted at 6600-6700...
It had 4.10s... Ran 12.70... I loved the feel of that car... Mellow then wham... Pulled for forever it felt like...

I think that's about what I'm shooting for... Not making peak hp at 7500... More like shifting around 7200-7400...
Peak around 6600-6700
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Joined: May 20th, 2005, 4:48 pm

August 7th, 2012, 8:12 pm #10

...I wouldn't use the factory specs of course, but just similar .050" durations. The other parts of the lobe would be more modern.

Brent Lykins
B2 Motorsports, LLC






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