Engine Mods.

[fullthrottle]

Anyone change out their older (non-Vortec) heads with newer ones?

I have 1995 350Mag's, so they don't have vortec heads.

I heard this could give me a quick 40 - 50 horse. Is that correct?

How difficult are they to change, and what other mods would I need to make full use of the new heads?

Anyone work with this place
www.sallee-chevrolet.com/...ortec.html
They seem to have the best prices..
Thanks
FT

[Ratchet]

Never done it....40-50 horse may be a bit high, without any other mods (exhaust, etc). Remember the more air in...the more has to come out.

I believe that you may need to change the intake (or modify an existung one because of the bolt holes). Call them & see.

[mopower]

FT,
Will also need a new intake to match the heads OR re drill the holes in the heads to match your old intake , as the bolt pattern is different. Been there , done that. It's not that hard , but I have a friend with a machine shop
Keep in mind after all this work and expense your looking at 1 MAYBE 2 mph additional and you can see this much difference between the # of people or fuel in the boat or a 72* day as compared to a 90* and humid day
Another friend did the same thing with his because he heard the same thing. When all was said and done , he didn't really think it was worth it
His next step was to do a warmed over 406 sbc with the vortecs and it dynoed @ 490 hp. He picked up 5 to 6 mph over the stock 350 mag. This was in a 20'6" bowrider.

Hello, fullthrottle,
I have done several swaps, more on cars, but they are the same.
You will need an intake made for the purpose. The bolt holes are VERY different. The heads are a big improvement and the local roundtrackers say they will outrun ANY other GM iron head-even the turbo head. My experience agrees. You will also need to do something about rocker arms. The Vortech has no provision for pushrod guides so you will probably need self aligning rockers. Comp Cams makes roller tip rockers that work great and are inexpensive-might try 1.52's on the exhaust, 1.6's on the intakes You may also need valve springs. I have always machined the spring seats for bigger springs, but I heard that some manufacturers are making springs that will fit-Isky, maybe?? Even with the extras, this has GOT to be a good deal
If you are going this far, How about a cam? If you do the right combo, it will make a difference. It will not make it a 406 or run with a blower, but it does help in acceleration, fuel ceonomy, and speed.

[fullthrottle]

Thanks everyone for your response. I assumed that the intake would need to be changed. I was looking a an Eldb. Air Gap intake. (Not sure how it will hold up in a marine app.)

blown1500.. What cam would you recommend going with?

What does everyone think about new exhaust. I was thinking if I kept the same cam I could keep stock exhaust.

My other option was to through a low Holley or Wieland blower (144) on and that would give me the 80 to 100 horse..

Thanks again,
FT

BLOWERS!!
The head swap will help. The Edelbrock air gap is my favorite for this. They live and work great on a boat, esp. if you coat it or at least paint it (clear maybe?). Really NEEDS cam. Need more specifics for cam selection.
No matter what you do without the blower, it would be hard to keep up with the same motor with a blower.
Exhaust would really help, no matter what else you do, but the more you do, the more you need to change. The blower will really like more exhaust
If you do go to a blower, think about the compression difference you are going to get with the Vortech head. It might be too much!! You will be in the danger zone with Vortech heads and flat pistons. I don't remember which piston you have Help Guys

[bobl]

Hey Fullthrottle, your login's the name of my business (Full Throttle Marine) so you've got to be cool. LOL Anyway, I've done a bunch of these swaps. The heads alone are worth about 40 HP. But, if you do a little bowl blending, mild cam and the air gap intake it will put you up near 400 HP. There are 2 problems though. The bottom end should really be beefed up to live at that HP level. At the minimum, good rod bolts. The pistons in that engine are flat tops. The Vortec heads have 62 cc chambers, which will put you around 10:1 compression. Kind of high. You really need to change to a dished piston and get the compression around 9.2:1. Set the timing at no more than 32 degrees, which will probably require recurving the distributor so you can run around 12-14 initial advance. Those heads also respond well to bigger valves. I've done these mods to 2 seperate 5.7 2bbl engines. One boat picked up a solid 5 MPH and the other picked up 8 MPH once we got the propping correct. And these were 250HP Vortec engines to begin with! You need to spin them about 5200 RPM to benefit from the changes.

Bob

[fullthrottle]

That's a cool name, I tried to think of what I like to do when I'm out boating and that's where the name came from.

Cams...... That's painful, I would need to pull engines. Sounds like that the heads are just one small part and without doing all the mods you might as well stay stock. (At least with the heads).

I was thinking of maybe going with a small blower like a Holley 144 or a Wieland. Anyone have any experince with this blower?

It's small enough to not obstruct the hatch and should give me some gains without all the other mods. (Is this true).

What's installation like?

Thanks
FT

Full Throtle, the small blowers work great and are pretty easy to bolt on. BE SURE TO KEEP UP WITH THE SPARK PLUGS UNTILL YOU GET A HANDLE ON MIXTURE AND TIMING!! Detonation is you deadly enemy but "boost is your friend"