Building a 393 low end torque engine

[sykanr0ng]

I can see some of his point, I wouldn't pay $1000 just to show something to someone on the internet.


But my main takeaway from this thread is I am going to just stick with a 351W, the stroker only adds a lot more to the snowball of using this part means you need to replace these parts which leads to those parts not being enough..............

 

[68ford]

I can see some of his point, I wouldn't pay $1000 just to show something to someone on the internet.


But my main takeaway from this thread is I am going to just stick with a 351W, the stroker only adds a lot more to the snowball of using this part means you need to replace these parts which leads to those parts not being enough..............

It really doesnt. Assuming you have a aftermarket intake and 4 barrel carb on a 351 and headers like 99% of people out there. The only thing you would really want to change is the cam shaft. If you tearing the engine apart enough to rebuild the short block or in your case the stroker kit, you would be buying a cam shaft and lifters anyway. Bigger heads do make big improvements, but there are people out there with iron head 408s that run real nice. Blueprint E gines even builds one for a budget. You just play with the lift and duration to make up for the small heads. Not a perfect world, but like I said, it works and makes a lot of torque

 

[pcf_mark]

I hate to break it to you, There may be at most one engine dyno in Tucson. They're may be one in everybody's garage in Penn., not here. Even if my running 351 was out of the Bronco I'd have to haul it to the builder and pay $1000+ to hook it up, for what reason? So I can get you dyno sheet. Don't hold your breath. In other words that's a ridiculous thing to say. Do you really think that's a persuasive argument? I can see that my personal experience is worthless to you and your opinion is worthless to me if you ask for a dyno sheet to make a point. You forfeit any credibility you may have had.

My only point with sharing dyno data is you claim that a smaller carb, small cam, small port installed on a larger engine is going to make more torque and make it a lower rpm. It is not a ridiculous thing to say - it is saying "if you are so convinced you are right, prove every other person on this thread wrong". I could be wrong and both admit it and own it. If I am wrong only actual facts will educate me not a "feels like" measure.


For reference you may not be very current with your dyno experience. I live a suburban area of PA and can drive to four different chassis dynamometers in 30 minutes. Each chargers $75 - $150 for 3 pulls with no tuning just baseline. If you want an engine dyno that is more rare but I can drive to two of those in an hour and they are $250-$500 for set up, engine run in, base line tuning. What I think is really, really, really funny is a guy shows up in his car or truck and he is convinced he has a monster under the hood they paid a lot of money to build. Then they get 180 hp/200 ft-lbs to the tires and put the tail between their legs. You can learn a whole lot from seeing some dyno runs.

 

[Joe473]

3 bar gt 40s. Upgraded springs and keepers with scorpion roller rockers

Joe, what heads are on your 347?

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[Joe473]

Keep in mind that 1500 - 5500 rpm range is based on the 302 cylinder volume. Your stroker will shift that rpm range lower and have more stable idle and vacuum than a 302 would with the same cam. A cam with lower LSA as suggested will shift you lower again. This is why I suggest running a software model to see the expected performance and torque curve. When you get too small for the cubic inches in VE you get peaky narrow powerbands. Just like the guy who puts in a huge cam with no supporting equipment and has a very narrow high rpm engine you could end up with a very narrow power band at very low rpm range. When things are matched well you start to see broader flatter torque curves that span a larger RPM range. A more efficient engine with a torque curve matched to your driving needs. Where is your cruise rpm going to be on the highway? Figure it out based on gears/tires and make sure if it's at 2800 rpm your torque hasnt started dropping off at 2500.

Carburetor size is something I've experimented with for many years and I found it's difficult to go too small. When a 480 runs as strong as a 600 on my 351 I can see no reason to go to 600. After all the engine is only occasionally pushed at full throttle. There's usually vehicles, red lights and speed limits keeping a light throttle as the only choice. So part throttle is where the engine lives. Smaller throttle bores and venturis are always advantageous at part throttle. So even if at full throttle a larger carb is a little better and for my engine it's not, the smaller carb is better for drive-ability, fuel economy, and resistance to bump stall off road. The Comp Cams 35-349 is designed to work from 1500-5500 RPM. My C4 shifts at 4500 and I see no reason to change that. If I had chosen to work for more HP through deep breathing heads etc. a higher shift point would be indicated. I don't need the HP I have. Why would I want or need more? As I stated in my first post the 133 HP of the stock 302 was plenty to do what I need. My "restrictive" 302 heads and exhaust manifolds worked well then and kept working well with a far more powerful 351. I'm going to try GT40 heads that don't change the original look of the engine compartment. I'll see if that does anything. The same with the roller cam and valve train. Headers can never look original that rules headers out by itself even without the noise and heat. The question of going to a 3.85 crank is contingent on things that haven't happened yet and likely won't. The point is to explore ways of gaining low RPM torque that won't break the bank. At less than 2000 RPM all the big cam, big carb, big heads, and exhaust are useless if not harmful. They certainly are not going to improve drive-ability or MPGs.

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