4/7 cam swap?
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From: washington state
4/7 cam swap? what happens if you do a 4/7 cam swap on a pontiac? does it work the same as a sbc? the firing order on a pontiac engine is 1-8-4-3-6-5-7-2. the same as a SBC but counter clockwise. the swap on a Small block chevy makes about a 30hp differance.
it does not make a 30 hp difference... if its a massive cam as opposed to a smaller on ethan yea but if the cams have otherwise similar specs you wont get 30 out of it. i would belive you can switch the firing order just the same.
i seen where hp tv picked up 30 hp but that is on the extreme side.i'd say in the real world 10-15 is more likely.i did the 4/7 swap because they claim it is easier on the crank also.
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From: washington state
Originally Posted by Wnts2Go10O
it does not make a 30 hp difference... if its a massive cam as opposed to a smaller on ethan yea but if the cams have otherwise similar specs you wont get 30 out of it. i would belive you can switch the firing order just the same.
well, it was HP tv and they just got their new engine dyno set up, they put in a 500 hp smc, pulled the cam, had one made with the same specs only with a 4/7 swap and it made 30 flywheel hp.
so the cam may of been around a 600 lift or so, but either way its still a hp gain with no downside.
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Originally Posted by firechicken76
well, it was HP tv and they just got their new engine dyno set up, they put in a 500 hp smc, pulled the cam, had one made with the same specs only with a 4/7 swap and it made 30 flywheel hp.
so the cam may of been around a 600 lift or so, but either way its still a hp gain with no downside.
so the cam may of been around a 600 lift or so, but either way its still a hp gain with no downside.
And all along i was told the 4 / 7 swap was to get the overtemp problem the 7 cylinder has ( Lean condition ) from following the # 5 cylinder at the back of the block -- away from the direct flow of the water pump that the # 2 has with the switch following the #4 in the SBC firing order -- i hate it when a TV show selling **** for their sponcers who sell this stuff --- get it right and now we know all that we have learned on the 100s of hours of dyno work -- all i had to do was call HP TV wow what a dope i have been and we only seen 3s and 5s in HP and only after setting the motor in a venue it could not be used in real time racing i need to go back to my desk top dyno and screw the 75 thousand dollar monster we bought just for this sort of thing wow -- jz
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From: Illinois, RT 66 dragway area
I have been doing this a long time, and we have been using swap cam's in dragracing before all these magazines even knew we were, I have never heard of anyone getting anything close to 5-10% more HP. We do it to get less heat build up in 5-7 area, and with all the HP we have it puts less stress on the crank. Like it was said, the force being applied to the piston is still the same. Yes I run swaps in all my engines, and I never pick up anything close to those numbers. Good luck.
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Found this post on another web site and thought it'd fit in here perfectly.
"Any horsepower gain with a firing order swap is simply icing on the cake. The real benefits in swapping firing orders is in how the crankshaft is loaded in a dynamic running condition, and also in the air motion in the plenum of the intake manifold, which can provide a dramatic impact in carburetor signal. The different firing order provides more uniform loading on the crankshaft, resulting in less twist and stress, as well as smoothing out plenum pulsation in the manifold, providing for a more stable signal at the carburetor boosters, ultimately leading to a smoother running engine. From personal experience, the LS1 firing order seems to be the most effective; try a 536-inch Pontiac with a cam that was low-280 intake duration/low-300 exhaust duration @ .050" , and a 1400+ CFM Dominator, with absolutely zero vibration of any kind from idle to 7,500+ RPM, and glass-smooth drivability right off idle with absolutely no choppiness at any driving RPM. Anybody that has driven a conventional firing order large-cammed GM engine with a Dominator on the street knows that the engine is kind of choppy while cruising under light to moderate loads, usually up to around 3,000 RPM, give or take a few hundred RPM depending on the combo."
"Any horsepower gain with a firing order swap is simply icing on the cake. The real benefits in swapping firing orders is in how the crankshaft is loaded in a dynamic running condition, and also in the air motion in the plenum of the intake manifold, which can provide a dramatic impact in carburetor signal. The different firing order provides more uniform loading on the crankshaft, resulting in less twist and stress, as well as smoothing out plenum pulsation in the manifold, providing for a more stable signal at the carburetor boosters, ultimately leading to a smoother running engine. From personal experience, the LS1 firing order seems to be the most effective; try a 536-inch Pontiac with a cam that was low-280 intake duration/low-300 exhaust duration @ .050" , and a 1400+ CFM Dominator, with absolutely zero vibration of any kind from idle to 7,500+ RPM, and glass-smooth drivability right off idle with absolutely no choppiness at any driving RPM. Anybody that has driven a conventional firing order large-cammed GM engine with a Dominator on the street knows that the engine is kind of choppy while cruising under light to moderate loads, usually up to around 3,000 RPM, give or take a few hundred RPM depending on the combo."
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The posts on this issue are all correct --- we have not found cracking in footbrake cars a problem only trans brake or stick shift both with very big violent leaving motors --- we have a few guys who have a cam swap combo and cant say on the dyno or in the car you can feel the difference in vibes ?? but a cam swap has that sound -- hahahah -- but sounding real good doesent win anything hahahah good post to all -- jz
