daveo1

Is it worth spending any money on these 1999 7.4 L-29 vortech heads (p/n 10141280) or should I just invest in some oval port Merlin's? The engines are being redone right now and I have heard many different opinions on the vortec heads...Any ideas...

Wildfire

Dennis Moore's book suggests them when you have flat top pistons in a 310 horse motor because the smaller chamber will raise the compression ratio.

Other than that, I don't know if they flow better or any other reason. Hopefully, Dennis will see this and chip in.

Pat McPherson

Hey Dave,
I have talk to a couple of engine builders on the subject.
If you retain your GM MPI system your engine can only make about 375HP.
If you loose the fuel injection and you with a carb., the engines can make more, a lot more.
Like sutphen30 said, porting and a little hotter cam will wake up the L-29, 450HP is within reach.
I had my L-29 heads ported, new valves, and springs. Going to install a cam, stainless marine exhaust, reprogram the ECU. We'll see how it goes...
If I don't gain enough to crack 70, the MPI will come off and a carb will go on...
Good Luck!

formula31

And dont forget the large difference in chamber volume. If you switch to Merlin heads, you will need different pistons or you will have a lower compression ratio.

dave-o

Thanks for all the replies. Why would I need to replace pistons? Can't I just mill the heads at bit to get closer to the 105cc I started with? I feel if I spend hundreds of dollars on upgrading the L-29 head that they will be maxed out, and when I do a major rebuild on the motors I won't have any more room as far as other upgrades go...

formula31

yes, the difference is large. I have managed to angle mill 119 cc heads enough to get down to 110 cc but it was maxed and I didnt have much valve seat left. If yo go Merlins your might as well figure on pistons. Id stick with the vortecs for now until you have to do pistons.

daveo1

Ok Ok, I get it...last question, what if I went with the edelbrock al. heads. These are only 110CC...any opinions? I can get the marine ones complete for about 725.00 ea...

formula31

http://www.offshoreonly.com/forums/s...delbrock+heads

Raylar

Daveo1:



don't forget the weight factor, taking weight out of the boat with aluminum heads is an extra benefit. As for the edelbrock heads, mercury does use them on the 525EFI as original equipment, but they spec them with special alloy seats, inconel exhausts and special springs. I doubt you'll get these features for $800 each probably more like $1000 each. Use them this way with a Cometic
.040 stainless gasket and you'll have your good high compression and a good set of heads that will make power with a good cam. Good Luck confusing yourself!
Raylar

daveo1

Thanks for the info. Flatlander has them for 1299 a set complete with Inconel exhaust valves (less shipping, springs and retainers).