Advice on used 347 motor (Dyno Attached)

[Ol'Blue]

Found this used 347 motor that has bout 1600 miles on it since built. Was properly broke in then chassis dyno attached. I had planned on a new crate motor some day but getting the funds together is taking forever so looking a good used motor. What are your thoughts in this dyno sheet? Seems like the torque comes on early and in a good range for an early bronco. My rig is mostly street driven, some rocks and dunes.

 

[DirtDonk]

Seems oddly high strung to me. Not that it’s a bad motor, and not that it doesn’t probably still put out more power down low than a stock motor did, but that particular one appears strangely biased a little to the higher rpm range.

For an engine that isn’t developing huge numbers, it seems to ramp up slowly. Torque is in the 350 range and fairly level, but only after 3000 RPM. Horsepower is down in the 300 range which is kind of a sweet spot for a low rpm motor really, but shows a long ramp up as well.

Maybe the bottom end below 2500 on that chart is because it’s just coming up and it might be the way the dyno operator was working the controls? But if not, it’s actually fairly weak down low and doesn’t come into its own until 3000 and above. Finally peaking horsepower at 6000 RPM-ish.

Still, if it’s a good deal and you can keep it tuned well induction wise, it could be a nice upgrade from stock.

Wait for a lot more opinions however. A lot of people have built motors similar to this in recent years, so should have more direct experience than I do.
It’s actual peak numbers look very similar to the blueprint engines “bronco” model engine. Don’t they?

Any way to find out what cam is in it?

 

[Ol'Blue]

Hi Paul, ya I think its more of a street/strip motor but thought the numbers weren't too bad for RWHP numbers. I have the builder contact info, I could try and see if they still have the spec sheet on it for cam etc.

I should probably keep looking as my original plan is a nice 351-408 motor.

Thanks for the input.

 

[Broncobowsher]

Looks OK, not great. I wonder where the compression is on this one. I always wonder when someone sells something so quick. Was it really not that good? Unless it was dirt cheap I don't see a reason to jump.

 

[BUCKWILD]

I would like to know gearing and tire size. A mustang with 4:11s and little tires make those numbers look good. Bigger tires and the numbers wont look to good. 347s are fun but not practical in a bronco in my eyes. a 351 is a much better choice i think and a stroker 351 even better

 

[DirtDonk]

Yes, is this for the '70 with 35's and 4.30 gears? Or the '68 with what gearing?

BUCKWILD, what's the difference that makes a 347 anything more than just 4 cubic inches smaller than a 351? Isn't a hopped up 302 still potentially better than a stock one just about everywhere?
Isn't a 347 just a bored and stroked 302? And with a 351 being basically a stroked 302 in the first place, is it the slightly shorter stroke (and rod?) that are the limitations for building torque down low?

I'm just bringing it up because my thinking is that if a 302 was a decent enough engine in a Bronco, then a 347 should just be more. If built correctly that is.
Are they peaky because they can't be anything else, or because the're just typically built with the wrong cam for a truck? And "peaky" brings me back to the dyno chart. It's not actually peaky in the traditional sense. Just does not seem to make much down low. Especially considering it's not all that powerful a build in the first place. Seems like mild cam territory. I wonder if they put a Thumper cam in it for the lope and lost some low end in the process?
Seems to me, that just like any other build, it's all about the cam, heads, exhaust and induction. The "tune" if you will.

Or is there more to it?
Thanks

Paul

 

[TX-ZACH]

Yes be careful when considering new engine choices. I am one of the noobs that bought a very expensive 351 roller build with all a ton of performance i will never be able to use unless I turn it into a mud truck. After getting a good education on the topic here I would have went a different route. Buyer beware...

 

[Ol'Blue]

hey Paul, Yes, its the '70 with 35's and 4.30 gears.

Thanks for the input gents. I think I will keep looking for a mild 351 and above and keep saving. My current motor runs well, just looking for some more hp/torque.

 

[sprdv1]

Seems oddly high strung to me. Not that it’s a bad motor, and not that it doesn’t probably still put out more power down low than a stock motor did, but that particular one appears strangely biased a little to the higher rpm range.

For an engine that isn’t developing huge numbers, it seems to ramp up slowly. Torque is in the 350 range and fairly level, but only after 3000 RPM. Horsepower is down in the 300 range which is kind of a sweet spot for a low rpm motor really, but shows a long ramp up as well.

Maybe the bottom end below 2500 on that chart is because it’s just coming up and it might be the way the dyno operator was working the controls? But if not, it’s actually fairly weak down low and doesn’t come into its own until 3000 and above. Finally peaking horsepower at 6000 RPM-ish.

Still, if it’s a good deal and you can keep it tuned well induction wise, it could be a nice upgrade from stock.

Wait for a lot more opinions however. A lot of people have built motors similar to this in recent years, so should have more direct experience than I do.
It’s actual peak numbers look very similar to the blueprint engines “bronco” model engine. Don’t they?

Any way to find out what cam is in it?

All about that price and fit...

 

[sprdv1]

Yes, its the '70 with 35's and 4.30 gears.

Thanks for the input gents. I think I will keep looking for a mild 351 and above and keep saving. My current motor runs well, just looking for some more hp/torque.

Good plan.. the hardest part is just having the patience