Engine Build Questions
Logistics Pro
Joined: Aug 2010
Posts: 3,716
Likes: 583
From: Chillicothe
The "big port" heads on the LS engines are a result of the "advertised hp sells" motto that the engine designers have to take into account (meaning it's ok to sacrifice some low end), AND they have the advantage of using a long runner EFI intake manifold to increase inertia of the intake charge to make up for some of the loss in velocity that resulted in them shooting to achieve a marketable hp figure. I am an advocate of big port small cam for truck engines, but in his case, running a carb intake on a trail rig, he will definitely be feeling a larger diameter intake runner in the head.
Lead Driver
Joined: May 2011
Posts: 5,771
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Yea, we are kinda spoiled with expectations when it comes to modern engines....cams that would make a 350 sbc run like ****, super long intake runners that flow great and have a small footprint, cam phasers, etc. I have wondered what modern engines would be like if they designed them to have 50 less peak hp and more off-idle hp. It would be more suitable for the application but they wouldn't be able to make hp claims vs one another (and they also have to "compete" internally with the diesels that now come with well over 400 hp).
5th Wheeling
Joined: Jul 2012
Posts: 25
Likes: 7
From: Camby, IN
Thanks for the info!
Going Carb because it is simpler. Trying to get away from electronics as much as possible. Bugs in electronics are hard to source/find.
This is going in a Bronco II that I have done a full size Dana44/9” solid axle swap.
yeah, I mis-typed the cam I want. Looking at the 224/232 Extreme Energy CompCam offers. That has the 112 LSA you mention.
Going Carb because it is simpler. Trying to get away from electronics as much as possible. Bugs in electronics are hard to source/find.
This is going in a Bronco II that I have done a full size Dana44/9” solid axle swap.
yeah, I mis-typed the cam I want. Looking at the 224/232 Extreme Energy CompCam offers. That has the 112 LSA you mention.
BTW, I have an '89 Bronco II with a 5.0 swap. If you're running trails, you don't need high rpm power. Keep it low end.
Just my $.02
Last edited by chazzone; Nov 29, 2024 at 11:58 AM. Reason: adding to...
Tuned
Joined: May 2024
Posts: 300
Likes: 149
Yea, we are kinda spoiled with expectations when it comes to modern engines....cams that would make a 350 sbc run like ****, super long intake runners that flow great and have a small footprint, cam phasers, etc. I have wondered what modern engines would be like if they designed them to have 50 less peak hp and more off-idle hp. It would be more suitable for the application but they wouldn't be able to make hp claims vs one another (and they also have to "compete" internally with the diesels that now come with well over 400 hp).
Lead Driver
Joined: May 2011
Posts: 5,771
Likes: 441
In the days of the SBC you had a 2,48:1 1st gear. The 727's were 2.54. Motors had to make off-idle torque because of that. It's just not needed any longer. 6R80 and 10R80 have 4.16:1 and 4.7:1 respectively. These were ratios relegated to dump trucks back then. Modern trucks outperform old trucks at any speed today because of the sum of all the parts.
Another disadvantage of the sacrificing of low end hp on the trails, even with modern combos, are situations where you need wheel speed of "the next gear" but can't get it because it bogs instead of sings. If we are just talking about creeping around on hard dirt in 1st LOW, yea, obviously the power band is irrelevant.
Laughing Gas
Joined: Jul 2009
Posts: 999
Likes: 402
From: NE Ohio
In the days of the SBC you had a 2,48:1 1st gear. The 727's were 2.54. Motors had to make off-idle torque because of that. It's just not needed any longer. 6R80 and 10R80 have 4.16:1 and 4.7:1 respectively. These were ratios relegated to dump trucks back then. Modern trucks outperform old trucks at any speed today because of the sum of all the parts.
THEN for got rid of the SBF in cars and used weak 3.8L V-6 and the 4.6L V-8 mod motor. 281 inches? Yeah, not much torque there. Ford quickly came out with the 4R70W with the W indicating the Wider gear ratios than the AOD-E it was based on. That gave the 4R70W a 18% lower First gear to 2.84, the 1.55 Second, 1:1 Third, and a 0.70 OD.
Lead Driver
Joined: May 2011
Posts: 5,771
Likes: 441
Ford's three-speed trans used 2.40 First, 1.45 Second and of course 1:1 Third. Ford's first OD transmissions also used those gear ratio, but added the 0.67 OD gear.
THEN for got rid of the SBF in cars and used weak 3.8L V-6 and the 4.6L V-8 mod motor. 281 inches? Yeah, not much torque there. Ford quickly came out with the 4R70W with the W indicating the Wider gear ratios than the AOD-E it was based on. That gave the 4R70W a 18% lower First gear to 2.84, the 1.55 Second, 1:1 Third, and a 0.70 OD.
THEN for got rid of the SBF in cars and used weak 3.8L V-6 and the 4.6L V-8 mod motor. 281 inches? Yeah, not much torque there. Ford quickly came out with the 4R70W with the W indicating the Wider gear ratios than the AOD-E it was based on. That gave the 4R70W a 18% lower First gear to 2.84, the 1.55 Second, 1:1 Third, and a 0.70 OD.
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