Intake swap thought

[0xDEADBEEF]

I have seen the dyno test on a LS between the Holley dual plane 2x4 manifold and Edelbrock Victor single 4 single plane. HUGE difference in torque and the same HP. I do not see why a single 4 barrel dual plane would make much if any less. I saw the same kind of low-speed gain running the single 4bbl dual plane L31 Marine intake.

It is a bigger difference than you are making it out to be. Dual plane is going to make considerably more torque than a single plane even with fuel being added at the end of the runners. The manifold manufacturers need to create proper manifolds for 95% of the vehicles on the road. Single plane intakes suck on the street in heavy vehicles with tight converters and tall gearing.

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We agree. If you aren't building something that spends a lot of time at the drag strip, the dual plane is a better choice.

 

[Pro439]

I have seen the dyno test on a LS between the Holley dual plane 2x4 manifold and Edelbrock Victor single 4 single plane. HUGE difference in torque and the same HP. I do not see why a single 4 barrel dual plane would make much if any less. I saw the same kind of low-speed gain running the single 4bbl dual plane L31 Marine intake.

It is a bigger difference than you are making it out to be. Dual plane is going to make considerably more torque than a single plane even with fuel being added at the end of the runners. The manifold manufacturers need to create proper manifolds for 95% of the vehicles on the road. Single plane intakes suck on the street in heavy vehicles with tight converters and tall gearing.

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The problem with this is that the LS cylinder head flows better numbers than any stock and most aftermarket cylinder heads so this chart is not apples to apples

 

[MrOverCast]

I ended up going with the Holley EFI SBC 300 263 cid 4150 Single Plane Fuel Injection Intake Manifold. My motor is a pre tbi 350 but it works pretty damn well. Holley sells the same intake for the L31 vortec. Its not the best intake for street use but it beats the 900$ marine intake

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[L31MaxExpress]

The problem with this is that the LS cylinder head flows better numbers than any stock and most aftermarket cylinder heads so this chart is not apples to apples

Depends on which LS cylinder head you are talking about. A real OE L31 head not the Mexican garbage ones outflow 4.8/5.3L heads by nearly 15-20 cfm stock for stock.

My aftermarket heads flow far better than any factory cathederal port head and close to what a stock LS3 head flows. So that chart would not be far off on my 383.

 

[L31MaxExpress]

I ended up going with the Holley EFI SBC 300 263 cid 4150 Single Plane Fuel Injection Intake Manifold. My motor is a pre tbi 350 but it works pretty damn well. Holley sells the same intake for the L31 vortec. Its not the best intake for street use but it beats the 900$ marine intake

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$900 for a marine intake. I see them for $400-500 at times and have bought 2 of them for that. I bought a complete pullout 6.3L a week ago for $1200. Two 8" long freeze cracks on the block but it only had 150 hours on a 2018 and ran perfectly. It has all the marine goodies I am selling off like exhaust manifolds with water jacketed cats and 4 02 sensors, both water pumps, both fuel pumps, ECU, harness and what not. The boat was repowered with a big block. The marine 6.3L is exactly equivalent to the HT383E, same engine. Same $$$$ GM 3.80" stroke forged 4340 crank, the special rods that allow for the long throw to go into an 880 block without alot of grinding, etc. The whole rotating assembly is going into the clean standard bore 880 4-bolt main 350 block that came out of my van. The crank alone is nearly $1,800 new from GM. Even the rods and mains look perfect in this 383. I am considering even reusing the bearings and maybe the rings from the junk 6.3L block and rotating assembly. My neighbor swapped the whole rotating assembly from one 5.3L to another when he cracked the bellhousing on his drag car. The re-used bearings and rings have held ~1200 hp for a season already.

 

[MrOverCast]

$900 for a marine intake. I see them for $400-500 at times and have bought 2 of them for that. I bought a complete pullout 6.3L a week ago for $1200. Two 8" long freeze cracks on the block but it only had 150 hours on a 2018 and ran perfectly. It has all the marine goodies I am selling off like exhaust manifolds with water jacketed cats and 4 02 sensors, both water pumps, both fuel pumps, ECU, harness and what not. The boat was repowered with a big block. The marine 6.3L is exactly equivalent to the HT383E, same engine. Same $$$$ GM 3.80" stroke forged 4340 crank, the special rods that allow for the long throw to go into an 880 block without alot of grinding, etc. The whole rotating assembly is going into the clean standard bore 880 4-bolt main 350 block that came out of my van. The crank alone is nearly $1,800 new from GM. Even the rods and mains look perfect in this 383. I am considering even reusing the bearings and maybe the rings from the junk 6.3L block and rotating assembly. My neighbor swapped the whole rotating assembly from one 5.3L to another when he cracked the bellhousing on his drag car. The re-used bearings and rings have held ~1200 hp for a season already.

i have a hard time finding them. I usually find them for like 900$ not saying it a bad intake or anything I was just spitballing ideas for others hahah

 

[L31MaxExpress]

i have a hard time finding them. I usually find them for like 900$ not saying it a bad intake or anything I was just spitballing ideas for others hahah

It is the only intake I know that has a spitball chance of not being noticed in a visual inspection. Lit looks so much like the normal intake if one painted the fuel rails black it hides out very nicely.

 

[Pro439]

It is the only intake I know that has a spitball chance of not being noticed in a visual inspection. Lit looks so much like the normal intake if one painted the fuel rails black it hides out very nicely.

I didn’t realize that they are making the marine manifold with cats on them. If you do the math for the 3.8 stroke a stock block is too short to put a long enough rod in it to achieve the better rod ratio. The 3.75 stroke w/a 6” rod gets you close to stock ratio of a 5.7 and unless you can find that intake on a deal you’d be better off with a aftermarket one IMO. GM had a lot of trouble with the 400 sbc the bores wore excessively piston pin failures that was because of the rod to stroke ratio wasn’t enough. It’s also why there is a tail deck block because once you calculate the rod ratio you end up with a longer rod and then you don’t have enough room on the piston for the ring set w/o going into the pin bore. The taller deck gives you the room for the correct piston and it also to an extent changes where the engine makes power and it also looses efficiency with a shorter rod. The guys running big cubes don’t worry about a budget or how long the engine will survive. I took the stock L31 intake and ground it more or less flat on the bottom and filled in the low spot opened the ports up to the gasket I got from edelbrock and pinned it so it couldn’t slide all over. Plugged the egr off. I didn’t take any pictures because I don’t know that it’s going to work that well or not and may eventually have to go aftermarket. The biggest issue with an aftermarket intake is the distributor cap plug wire terminals line up with the fuel rails luckily MSD makes a distributor that uses top terminals with a cam position sensor to run the gm ECM. Do you plan on dynoing this when it’s finished?

 

[JeremyNH]

I didn’t realize that they are making the marine manifold with cats on them. If you do the math for the 3.8 stroke a stock block is too short to put a long enough rod in it to achieve the better rod ratio. The 3.75 stroke w/a 6” rod gets you close to stock ratio of a 5.7 and unless you can find that intake on a deal you’d be better off with a aftermarket one IMO. GM had a lot of trouble with the 400 sbc the bores wore excessively piston pin failures that was because of the rod to stroke ratio wasn’t enough. It’s also why there is a tail deck block because once you calculate the rod ratio you end up with a longer rod and then you don’t have enough room on the piston for the ring set w/o going into the pin bore. The taller deck gives you the room for the correct piston and it also to an extent changes where the engine makes power and it also looses efficiency with a shorter rod. The guys running big cubes don’t worry about a budget or how long the engine will survive.

There are a number of pistons that work with a 6" rod on a long stroke. It's true the oil ring is into the pin height but they come with oil ring retainers so it shouldn't be an issue. I have a 390 stroker in the shop now being clearanced for a Scat 4-350-3800-5700-L crank (same as GM HT383), KB 164-40 pistons, and Eagle CRS6000BST rods. Compression height is 9.030" so 0.005" out of the hole at nominal deck height. With Felpro 1003 gaskets I get a near perfect 0.036" quench.

 

[Pro439]

There are a number of pistons that work with a 6" rod on a long stroke. It's true the oil ring is into the pin height but they come with oil ring retainers so it shouldn't be an issue. I have a 390 stroker in the shop now being clearanced for a Scat 4-350-3800-5700-L crank (same as GM HT383), KB 164-40 pistons, and Eagle CRS6000BST rods. Compression height is 9.030" so 0.005" out of the hole at nominal deck height. With Felpro 1003 gaskets I get a near perfect 0.036" quench.

Yes I know that they make pistons but is it worth the cost versus the availability of the pistons?