306 or 347 stroker kit

beanplant · Apr 29, 2004

I'm not sure which to go with. Either way, I think I'm going to get this 302 motor for $500. It's got everythign but the intake and carb. I was planning on going with the edelbrock 4 barrel intake and carb for it. Its already rebuilt, and bored .030 over.
The question is... Should I bore it to .040 over and go 306, and use the extra money I save to buy some sweet ass AFR heads. Or should I get the 302, and get a 347 stroker kit for around $1200. The only question I have is, the re-rebuilding. Don't you have to rebuild strokers because of the way the pistons run?
How would a 306 with some nice pistons, and aluminum heads run? What kidn of numbers? Thanks!

-Shaun

skywalker · Apr 29, 2004

I couldn't justify paying for a stroker kit for 4 cubic inches of displacement, but that's just me. The downside to the 347 is (IIRC) that it needs to be notched for clearance.

rebel65 · Apr 29, 2004

he isnt getting a stroker kit for the 306, thats the bore increase.

beanplant · Apr 29, 2004

I guess I should clarify.... Should I bore the 302 to a 306.... and spend the extra $1000+ on a sweet set of heads, pistons and such?..... or should I buy a stroker kit for the 302?

-Shaun

3spd on floor · Apr 29, 2004

uh...you already have a 306. a .030 overbore 302 IS a 306. If its already been rebuilt, why would you need to do it again? if the rebuild thats on it is with quality parts, i'd just throw some nice heads, a hot cam and an intake and carb on it and you'll be set. there is NO reason to bore again to .040 over to make it a 308.

jesserose17 · Apr 29, 2004

Actually, .030 overbore with 302 is a 304 - .060 overbore is a 306.

3spd on floor · Apr 29, 2004

ACTUALLY a .030 overbore is a 306.134,

and
a std bore is a 301.593,
a .010 overbore is a 303.103,
a .020 overbore is a 304.616,
a .040 overbore is a 307.655
a .050 overbore is a 309.179
a .060 overbore is a 310.709

do the math (Pi*bore^2)/4 * stroke * # of cylinders

SadbutTrue · Apr 30, 2004

The argument is between AFR heads and a stroker. If it needs a rebuild, you will be boring it either way. If not, you do not need to bore it either way. Make sure you need to bore it, even if it needs a rebuild (some times a $70 re-ring is enough). I would go with AFR heads versus a stroker, given the rest of the engine is built equally in both cases. Without aftermarket heads, a stroker is severely choked, whereas aftermarket heads can be very effective on a normal 302, and only be more effective if you stroke it in the future.

jesserose17 · Apr 30, 2004

3spd on floor said:
ACTUALLY

do the math (Pi*bore^2)/4 * stroke * # of cylinders

I thought it was Pi*bore*stroke*# of cylinders... thanks for clarifying this.

allcarfan · Apr 30, 2004

If it has been rebuilt, no need to do it again. With some AFR 165s and a healthy cam, you can make 400hp. However, we dont know what kind of pistons you have and how good the reliefs are. $1200 is way too much for a 347 kit. You can get one several hundred dollars cheaper. Ever consider a 331?

Its up to you as to what you want. If you build the bottom end as a stroker....you have something to grow on in the future and can 'add' everything later on without having to pull the engine. If you add heads to your current setup, you will make a good bit more hp, however, if you want a stroker in the future, you will have to pull the engine in order to install it.

Id put some AFRs on that baby with a healthy cam and intake and be happy.

3spd on floor · Apr 30, 2004

jesserose17 said:
I thought it was Pi*bore*stroke*# of cylinders... thanks for clarifying this.

no, that formula will give you the surface area of the cylinders. that formula actually gives you the same numbers if you have a 4 inch bore, but it is still not the correct way to do it.

beanplant · May 1, 2004

Well, now I have another proposal..... I've decided I'm either going with the 302 bored .030 over ($500, everything but intake and carb).... and putting some AFR heads with a nice cam... probably about 400 HP.

OR Get another guy's motor and tranny. He came in to my work today (O'Reilly), and he was telling me about his motor he had in his old stang. He had it dynoed at 650 HP. It's a 302, and has the whole edelbrock RPM package. HE said he'd give me the motor and everything, with the tranny for $1500. Its been rebuilt about 5000 miles ago by my local performance shop (Bill's Performance). AHhhhh decisions decisions.

Would it be cheaper and easier for me to maybe... i say MAYBE talk the latter guy down to $1000 cash, or should I still try the 306 of the previous? Need some opinions and advice! Thanks guys!

-Shaun

allcarfan · May 1, 2004

he made 650 HP with a 302? Was he sprying? Turbo? or Supercharger? Even with an edelbrock RPM package...he would have to come up with another 300HP to get those numbers.

As for your 306 idea....just remember, you will have to upgrade pistons to run a 202 valve.

washMO66 · May 1, 2004

He's blowing smoke or something is blowing a whole lot of air or spray into that 302 to make 650HP. That would be tough to do on pump gas NA.

I'm running a 347ci that was balanced & blueprinted, seriously worked AFR 185's with a Vic Jr that has been opened up and I'm only making 455HP at the crank on Pump gas. Not saying that you can't get good numbers out of an NA 302 but it would be some serious high compression and serious head work.

Remember when used motors go up for sale their HP jumps by 10% every other day.

beanplant · May 1, 2004

I'm gonna call the guy with the "650" HP motor. I'm not sure how he would of gotten it, but he said it was dyno tested. My guess is that he lost the dyno sheet lol. I'm not for sure. I also found a guy with a 9 inch posi rear end with 4.11s from a 67 cougar that he's gonna sell me when he pulls it out.

-Shaun

Mustang67Coupe · May 1, 2004

Hey blkfrd what kind of compression ratio do you end up with the setup you just named? low enough for a no2 later or not?

Your setup caught my eye, seems enexpensive and a performer

washMO66 · May 1, 2004

That is a damn nice fast back blk frd. My only advice speaking from experience is to get rid of that Street Avenger and get something else. I have a 670 out in a box in my garage that spent about 2 months on my 347 and it got replaced with a 650 Mighty Demon and boy did it wake it up.......

allcarfan · May 2, 2004

Blkford...interesting homework you did there. I have no doubts about your combo, but Id like to point out that the pistons are hyper....I think. That being said...any kind of power adder is not a good idea. Also, the rod/stroke ratio of a 331 made the 'traditional' way...is better than the rod/stroke ratio of the combo you mentioned or a 347.

306 or 347 stroker kit

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