Small block - vortec or aluminum heads
01-24-2013, 07:23 AM
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Small block - vortec or aluminum heads
I have a 355 (.030 over 350) that I built and it's only got a couple dozen hours on it but I've got to pull it out this spring to find a nagging oil leak (that I suspect is the seal retainer in the rear). Since it's got to come out I'm thinking about switching up the combo a little bit.
Right now it's just a basic build that replaced an anemic 2bbl 305. A 94-ish 1-ton truck block that was cleaned, bored .030 and has new cam bearings, freeze plugs, etc. Pistons are flat tops with ~8cc 4-valve reliefs, block wasn't decked so they sit down in the hole a bit (.018-.020 iirc), cam is a comp extreme marine XM270H (270/286 dur, 226/[email protected], .480/.489", 112*lsa). Heads are stock '94 TBI castings that have upgraded exhaust valves and valvesprings.
The engine pulls good to about 52-5300, cam's power range is listed as 1600-5800 but I'm guessing that the heads are bottle-necking it quite a bit so since it's going to be out I've got a couple of heads sitting around - the first is a set of vortec iron heads that have low miles since rebuilt for a pickup - they would need to have work done to fit better springs (or use the drop-in beehives) and I've got some 1.6 roller rockers that fit them (self-aligning) but otherwise should be good to go, and I would need to get a vortec manifold (probably an edelbrock performer RPM?) The next is the top end of an old Holley SysteMAX kit that doesn't have too many miles on it - I'd run it with 1.6 roller rockers and have to get perimiter valvecovers.
From what I've been able to find the vortec's and the old SystemMax heads flow almost the same with the vortec's having a 64cc chamber and the Holley's having a 68cc. Both would put me about 9.6:1 static / 7.6:1 Dynamic compression ratio so it's almost a wash there.
The main reason I'd go the aluminum is to get weight off the rear and pair it with a set of HGE aluminum exhaust manifolds and risers. Is that reason enough to go aluminum heads? I only boat on lakes in the midwest so salt isn't a concern but I also don't want to have to do any real maintenance after pulling the boat out of the water every weekend.
Anyone have any experience with similar combo's and would recommend one over the other?
Right now it's just a basic build that replaced an anemic 2bbl 305. A 94-ish 1-ton truck block that was cleaned, bored .030 and has new cam bearings, freeze plugs, etc. Pistons are flat tops with ~8cc 4-valve reliefs, block wasn't decked so they sit down in the hole a bit (.018-.020 iirc), cam is a comp extreme marine XM270H (270/286 dur, 226/[email protected], .480/.489", 112*lsa). Heads are stock '94 TBI castings that have upgraded exhaust valves and valvesprings.
The engine pulls good to about 52-5300, cam's power range is listed as 1600-5800 but I'm guessing that the heads are bottle-necking it quite a bit so since it's going to be out I've got a couple of heads sitting around - the first is a set of vortec iron heads that have low miles since rebuilt for a pickup - they would need to have work done to fit better springs (or use the drop-in beehives) and I've got some 1.6 roller rockers that fit them (self-aligning) but otherwise should be good to go, and I would need to get a vortec manifold (probably an edelbrock performer RPM?) The next is the top end of an old Holley SysteMAX kit that doesn't have too many miles on it - I'd run it with 1.6 roller rockers and have to get perimiter valvecovers.
From what I've been able to find the vortec's and the old SystemMax heads flow almost the same with the vortec's having a 64cc chamber and the Holley's having a 68cc. Both would put me about 9.6:1 static / 7.6:1 Dynamic compression ratio so it's almost a wash there.
The main reason I'd go the aluminum is to get weight off the rear and pair it with a set of HGE aluminum exhaust manifolds and risers. Is that reason enough to go aluminum heads? I only boat on lakes in the midwest so salt isn't a concern but I also don't want to have to do any real maintenance after pulling the boat out of the water every weekend.
Anyone have any experience with similar combo's and would recommend one over the other?
01-26-2013, 08:28 AM
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I have a 355 (.030 over 350) that I built and it's only got a couple dozen hours on it but I've got to pull it out this spring to find a nagging oil leak (that I suspect is the seal retainer in the rear). Since it's got to come out I'm thinking about switching up the combo a little bit.
Right now it's just a basic build that replaced an anemic 2bbl 305. A 94-ish 1-ton truck block that was cleaned, bored .030 and has new cam bearings, freeze plugs, etc. Pistons are flat tops with ~8cc 4-valve reliefs, block wasn't decked so they sit down in the hole a bit (.018-.020 iirc), cam is a comp extreme marine XM270H (270/286 dur, 226/[email protected], .480/.489", 112*lsa). Heads are stock '94 TBI castings that have upgraded exhaust valves and valvesprings.
The engine pulls good to about 52-5300, cam's power range is listed as 1600-5800 but I'm guessing that the heads are bottle-necking it quite a bit so since it's going to be out I've got a couple of heads sitting around - the first is a set of vortec iron heads that have low miles since rebuilt for a pickup - they would need to have work done to fit better springs (or use the drop-in beehives) and I've got some 1.6 roller rockers that fit them (self-aligning) but otherwise should be good to go, and I would need to get a vortec manifold (probably an edelbrock performer RPM?) The next is the top end of an old Holley SysteMAX kit that doesn't have too many miles on it - I'd run it with 1.6 roller rockers and have to get perimiter valvecovers.
From what I've been able to find the vortec's and the old SystemMax heads flow almost the same with the vortec's having a 64cc chamber and the Holley's having a 68cc. Both would put me about 9.6:1 static / 7.6:1 Dynamic compression ratio so it's almost a wash there.
The main reason I'd go the aluminum is to get weight off the rear and pair it with a set of HGE aluminum exhaust manifolds and risers. Is that reason enough to go aluminum heads? I only boat on lakes in the midwest so salt isn't a concern but I also don't want to have to do any real maintenance after pulling the boat out of the water every weekend.
Anyone have any experience with similar combo's and would recommend one over the other?
Right now it's just a basic build that replaced an anemic 2bbl 305. A 94-ish 1-ton truck block that was cleaned, bored .030 and has new cam bearings, freeze plugs, etc. Pistons are flat tops with ~8cc 4-valve reliefs, block wasn't decked so they sit down in the hole a bit (.018-.020 iirc), cam is a comp extreme marine XM270H (270/286 dur, 226/[email protected], .480/.489", 112*lsa). Heads are stock '94 TBI castings that have upgraded exhaust valves and valvesprings.
The engine pulls good to about 52-5300, cam's power range is listed as 1600-5800 but I'm guessing that the heads are bottle-necking it quite a bit so since it's going to be out I've got a couple of heads sitting around - the first is a set of vortec iron heads that have low miles since rebuilt for a pickup - they would need to have work done to fit better springs (or use the drop-in beehives) and I've got some 1.6 roller rockers that fit them (self-aligning) but otherwise should be good to go, and I would need to get a vortec manifold (probably an edelbrock performer RPM?) The next is the top end of an old Holley SysteMAX kit that doesn't have too many miles on it - I'd run it with 1.6 roller rockers and have to get perimiter valvecovers.
From what I've been able to find the vortec's and the old SystemMax heads flow almost the same with the vortec's having a 64cc chamber and the Holley's having a 68cc. Both would put me about 9.6:1 static / 7.6:1 Dynamic compression ratio so it's almost a wash there.
The main reason I'd go the aluminum is to get weight off the rear and pair it with a set of HGE aluminum exhaust manifolds and risers. Is that reason enough to go aluminum heads? I only boat on lakes in the midwest so salt isn't a concern but I also don't want to have to do any real maintenance after pulling the boat out of the water every weekend.
Anyone have any experience with similar combo's and would recommend one over the other?
Flow numbers are close between the two so its a washup there. Aluminum heads, manifolds, intake will make a substantial weight savings and handling difference.
Mill the Holley heads to get you around 10-1 static, valve lap the seats and check the spring pressures. Performer RPM intake and the 1.6 rockers should make for a nice combo.
In freshwater, you should have no problem with aluminum heads. I've been running them for years with no problems on my small blocks.
01-26-2013, 09:08 AM
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I have a 355 (.030 over 350) that I built and it's only got a couple dozen hours on it but I've got to pull it out this spring to find a nagging oil leak (that I suspect is the seal retainer in the rear). Since it's got to come out I'm thinking about switching up the combo a little bit.
Right now it's just a basic build that replaced an anemic 2bbl 305. A 94-ish 1-ton truck block that was cleaned, bored .030 and has new cam bearings, freeze plugs, etc. Pistons are flat tops with ~8cc 4-valve reliefs, block wasn't decked so they sit down in the hole a bit (.018-.020 iirc), cam is a comp extreme marine XM270H (270/286 dur, 226/[email protected], .480/.489", 112*lsa). Heads are stock '94 TBI castings that have upgraded exhaust valves and valvesprings.
The engine pulls good to about 52-5300, cam's power range is listed as 1600-5800 but I'm guessing that the heads are bottle-necking it quite a bit so since it's going to be out I've got a couple of heads sitting around - the first is a set of vortec iron heads that have low miles since rebuilt for a pickup - they would need to have work done to fit better springs (or use the drop-in beehives) and I've got some 1.6 roller rockers that fit them (self-aligning) but otherwise should be good to go, and I would need to get a vortec manifold (probably an edelbrock performer RPM?) The next is the top end of an old Holley SysteMAX kit that doesn't have too many miles on it - I'd run it with 1.6 roller rockers and have to get perimiter valvecovers.
From what I've been able to find the vortec's and the old SystemMax heads flow almost the same with the vortec's having a 64cc chamber and the Holley's having a 68cc. Both would put me about 9.6:1 static / 7.6:1 Dynamic compression ratio so it's almost a wash there.
The main reason I'd go the aluminum is to get weight off the rear and pair it with a set of HGE aluminum exhaust manifolds and risers. Is that reason enough to go aluminum heads? I only boat on lakes in the midwest so salt isn't a concern but I also don't want to have to do any real maintenance after pulling the boat out of the water every weekend.
Anyone have any experience with similar combo's and would recommend one over the other?
Right now it's just a basic build that replaced an anemic 2bbl 305. A 94-ish 1-ton truck block that was cleaned, bored .030 and has new cam bearings, freeze plugs, etc. Pistons are flat tops with ~8cc 4-valve reliefs, block wasn't decked so they sit down in the hole a bit (.018-.020 iirc), cam is a comp extreme marine XM270H (270/286 dur, 226/[email protected], .480/.489", 112*lsa). Heads are stock '94 TBI castings that have upgraded exhaust valves and valvesprings.
The engine pulls good to about 52-5300, cam's power range is listed as 1600-5800 but I'm guessing that the heads are bottle-necking it quite a bit so since it's going to be out I've got a couple of heads sitting around - the first is a set of vortec iron heads that have low miles since rebuilt for a pickup - they would need to have work done to fit better springs (or use the drop-in beehives) and I've got some 1.6 roller rockers that fit them (self-aligning) but otherwise should be good to go, and I would need to get a vortec manifold (probably an edelbrock performer RPM?) The next is the top end of an old Holley SysteMAX kit that doesn't have too many miles on it - I'd run it with 1.6 roller rockers and have to get perimiter valvecovers.
From what I've been able to find the vortec's and the old SystemMax heads flow almost the same with the vortec's having a 64cc chamber and the Holley's having a 68cc. Both would put me about 9.6:1 static / 7.6:1 Dynamic compression ratio so it's almost a wash there.
The main reason I'd go the aluminum is to get weight off the rear and pair it with a set of HGE aluminum exhaust manifolds and risers. Is that reason enough to go aluminum heads? I only boat on lakes in the midwest so salt isn't a concern but I also don't want to have to do any real maintenance after pulling the boat out of the water every weekend.
Anyone have any experience with similar combo's and would recommend one over the other?
If you shave the heads make sure you remember to shim the distributor the proper amount so it doesn't run too deep into the cam gear.
01-26-2013, 02:31 PM
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I don't think I'd mill either head - the compression ratios would be real safe on premium pump gas, but with the vortec's more efficient burn chamber design can I get it safe to run 87 octane pump gas vs the Holley's traditional wedge design?
What are you guys running for ignition? I've got the stock Thunderbolt IV setup and am hoping it's not holding me back RPM wise on the top end.
The real question is how much weight can I shave off the tail end with aluminum heads and aluminum exhaust manifolds and how much of a difference is speed/acceleration would it make (assuming that the iron headed / exhaust makes exactly the same HP curve)
What are you guys running for ignition? I've got the stock Thunderbolt IV setup and am hoping it's not holding me back RPM wise on the top end.
The real question is how much weight can I shave off the tail end with aluminum heads and aluminum exhaust manifolds and how much of a difference is speed/acceleration would it make (assuming that the iron headed / exhaust makes exactly the same HP curve)
01-26-2013, 04:00 PM
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I do not like aluminum heads on boats without closed cooling..even fresh water kills them quicker than most think...vortecs are great heads, you may need to mill down the guides with that cam...some sell them prepped with that done pretty cheap...keep in mind less timing and they take a long reach spark plug...
