302 stroker 347
- Thread starter lxhatch91
- Start date
-
Sponsors (?)
Never had it on a dyno, but according to ET and MPH, my car was making around 305-310 rwhp. Combo was a stock block 331, home ported gt40 heads with dual springs and valve job. Edelbrock performer intake and anderson n41 cam. Compression was just over 10:1.
Joe
Joe
mikestang63
SN Certified Technician
a 347 with GT40 heads is a terrible combination. You should go with at least a 205CC head for a 347 .
For anyone starting from scratch, I'd recommend either a Dart block or a stock 351 block. Either of these will be able to handle way more power should future aspirations take you there. HP is addictive and the stock 302 will be limited to maybe 500 before catastrophic failures are common.
It's not going to make great numbers, but it's not going to hurt anything either. When I did mine 8 years ago, my bottom end was toast and needed a rebuild. I couldn't afford an entire engine, so I built the stroker and worked over my existing heads. Car ran very well and went well into the 12's. 3 years later, I was able to afford a new HCI combo and already had the bottom end in place.
I would never recommend the combo, but if the heads and intake are already there and you cannot afford all new stuff, go for it. Just have reasonable expectations for the outcome.
I will warn this, a 347 with small 59cc gt40p chambers will be a little more difficult to run on pump gas without detonation. Its doable, but will require some planning which may not be cost effective if on a budget. This is the reason I went 331 vs 347 at the time of the build. I would have preferred the extra cubes.
Joe
Lol, I don't think anyone believes that they are going to rotate the Earth with the power they make, but they are not going to cause an engine to catastrophically fail as some would lead you to believe. While a turd, 351 lightning trucks came equipped with them and they operated just fine.
Yes, buy the absolute best head you can afford. But if he can't afford aluminum heads, they will work. Now, I wouldn't advocate for the building of a stroker if he never plans an upgrade on the HCI, or if he doesn't need a new rotating assembly. But, building a stroker is not much more than a 306, literally about $400 more in my case.
Joe
HCI = heads, cam, intake
Stroker is an engine that has an aftermarket crankshaft that increases the distance the pistons travel up and down in the bore.
Cubic inch displacement is the volume of the bore when the piston is at the bottom of its stroke.
Total displacement ie, 302-306-331 etc, is calculated by this. Bore x stroke x number of cylinders.
Stroker is an engine that has an aftermarket crankshaft that increases the distance the pistons travel up and down in the bore.
Cubic inch displacement is the volume of the bore when the piston is at the bottom of its stroke.
Total displacement ie, 302-306-331 etc, is calculated by this. Bore x stroke x number of cylinders.
No matter what the nay Sayers say if you can run 11,79 @117 MPH your combination is doing OK. GT 40 heads are not the best but your numbers are showing
that they do the job. I know some one that runs a 331 that runs 9 seconds but he is not on a budget and has all the best parts.
Thanks. The 11's came with afr heads, it went 12's on the gt40's and old suspension setup. I think it had 12.50 in it if I had the current suspension in it then.
Joe
To get 331 or 347, you would need to buy an aftermarket crankshaft. Boring alone will not get you to 331 or 347. I not totally sure but a 331 is a 302 bored out .030" with a longer stroke crankshaft. The 347 is a 302 bored out .060" with a longer stroke crank.
A 302 with a stock stroke crank that is bored out .030" is a 306
A 302 with a stock stroke crank that is bored out .030" is a 306
302 is a 3" stroke, 4" bore.
306 is a 3" stroke with a 4.03 bore, can use stock crank, rods and larger pistons.
331 is a 3.25" stroke with a 4.03 bore, needs a different crank, rods and pistons.
347 is a 3.4 stroke, 4.03 bore and also needs different crank, rods and pistons.
You can make your existing engine any of these sizes depending on what you need/desire.
What do you need/desire?
Joe
306 is a 3" stroke with a 4.03 bore, can use stock crank, rods and larger pistons.
331 is a 3.25" stroke with a 4.03 bore, needs a different crank, rods and pistons.
347 is a 3.4 stroke, 4.03 bore and also needs different crank, rods and pistons.
You can make your existing engine any of these sizes depending on what you need/desire.
What do you need/desire?
Joe
