Cheap Go-fast parts (vortec head swap)

[Scott Danforth]

Re: Cheap Go-fast parts (vortec head swap)

the sucking sound is the secondaries

once you get your motor healthy and if you want to go from there with performance increases, my recommendation is as follows:

vortec heads with stainless valves (look on racingjunk.com - its end of racing season, people need money for x-mas gifts)
vortec manifold - ebay or elsewhere. if your in salt water, stick with cast iron or aluminum bronze dual alloy intakes. if your in fresh water, aluminum is fine.
1.52:1 rockers
I also recommend a cam change. Do not go above 268/270 degrees duration with wet exhaust. stick with a marine grind
new timing set
brand new melling oil pump, pump shaft, and pickup
New gasket set

 

[jumpjets]

Re: Cheap Go-fast parts (vortec head swap)

Sounds like your electronic advance is not working correctly. With an 8-10 initial, you should be getting 30-34 total advance at 4000rpm.

View attachment 170216

John_S: Are you sure about the electronic advance? The ignition curve chart I found in the merc service manual and posted above is contradictory to your diagnosis. I'm fine with replacing it, but I'm not convinced it's broken. Based on what the chart says, it sounds like I'm in the zone. I'd love for someone else to chime in though.

the sucking sound is the secondaries

once you get your motor healthy and if you want to go from there with performance increases, my recommendation is as follows:

vortec heads with stainless valves (look on racingjunk.com - its end of racing season, people need money for x-mas gifts)
vortec manifold - ebay or elsewhere. if your in salt water, stick with cast iron or aluminum bronze dual alloy intakes. if your in fresh water, aluminum is fine.
1.52:1 rockers
I also recommend a cam change. Do not go above 268/270 degrees duration with wet exhaust. stick with a marine grind
new timing set
brand new melling oil pump, pump shaft, and pickup
New gasket set

I'm pretty convinced my engine is "healthy" again. It's rated for 4200-4600 max RPM, and I'm at 4400 RPM right now. I'm satisfied with that based on my prop.

Good call on racingjunk.com! I've never been there before. So far I've been looking on ebay, and I've seen some pretty good deals on vortec heads.

I did not know there was such a thing as an aluminum bronze dual alloy intake. I boat exclusively in salt water, with an open cooling system, so I'll try to find one of those.

Why do you recommend 1.52 rockers vs. 1.6?

I'll shop around for a cam as well. I believe there are marine cam grinds by comp and crower, aren't there? Is the stock merc 5.7 a roller or a flat tappet? It'd be cool to upgrade to a roller if applicable, but it might not be worth the $$$.

I don't really want to tear apart the bottom end to change the oil pump. I think that would require pulling the engine. I'm not going to do that until I have the time/resources to build myself a bulletproof 383. Maybe next winter.

 

[Scott Danforth]

Re: Cheap Go-fast parts (vortec head swap)

volvo and PCM have manifolds that are dual alloy cast, and very similar to the edelbroch. I found mine on ebay for a great price.

you can also coat the inside of the water passages as well as where the intake meets the head at the rear with enecon, however be prepared to spend a bit of money.

 

[John_S]

Re: Cheap Go-fast parts (vortec head swap)

That advance curve is MINUS the initial (base) timing. Your TOTAL advance is the curve PLUS the INITIAL. 8 + 22 = 30 BTDC

I wouldn't jump on buying a new module (expensive and non-returnable). Need to verify your top dead center, check all connections, etc. Make sure someone hasn't replaced module with the wrong one. Are you using an advance timing light or estimatemating or using timing tape?

 

[jumpjets]

Re: Cheap Go-fast parts (vortec head swap)

That advance curve is MINUS the initial (base) timing. Your TOTAL advance is the curve PLUS the INITIAL. 8 + 22 = 30 BTDC

I wouldn't jump on buying a new module (expensive and non-returnable). Need to verify your top dead center, check all connections, etc. Make sure someone hasn't replaced module with the wrong one. Are you using an advance timing light or estimatemating or using timing tape?

I figured I needed to add the 8* to the curve. I used a digital timing light. At idle I set the light to 16*, 8* initial plus 8* as indicated on the timing curve chart. I shot the timing at idle and rotated the distributor until the harmonic balancer mark was at the 0* mark on the little metal indexer tab. At 2500rpm, I set the timing to 32* on the light, and ensured it was at zero on the balancer.

 

[John_S]

Re: Cheap Go-fast parts (vortec head swap)

By verify TDC, should check to make sure that #1 piston is at the very top of the stroke and that the harmonic balancer zero lines up with the tab zero.

At idle, the module should be adding zero advance. So intial should be 8 degree BTDC. From your chart the module should advance from 20-24 degrees at 2400 rpms. So, you should read somewhere between 28 and 32 degrees BTDC. Running it at 16 would put you at 36 - 40. That is too high for 87 octane and stock motor. If the module is bad, the cost is high enough to consider switching to an aftermarket ignition. Check the module part number. Someone might have installed a V6 or other module to get it running.

I don't know the weight/hull, but your prop slip numbers are good. Given you mentioned chine walking, you might not want the extra HP. You will probably want some sort of tabs to help control that, if you go forward. This mod will be more than a grand, doing all your own work, but without the distributer and tabs. I'd do a compression test, and leakdown, to feel confident the engine is in good shape. Make sure the boat hull, floor, transom, stringers are in good shape before doing. Once you start, its all the harder to stop!