Long story short, doesn't a 1999 454 mpi 310hp (non mag) have the L-29 vortech heads that was used on the old thread "330 on roids" 454 build, correct?? Since there's so much info coming from all types of people on the web it gets quite confusing. Some people knowing what there talking about and yet plenty just repeating what they've read but getting thingies mixed up along the way.

99% of threads about the 7.4 mpi (non mag) is 1st of course the cast enternals are junk I get that yea there weak. 2nd thing people say is that the heads garbage and can't make sufficient power. Well the 330 on roids would contradict that as it's making close to 500hp with um!?

Things What I've noticed from reading countless threads over years.

Also there referred to as the L-29 peanut port heads by people who shoot them down.
There aren't many positive threads about them but the few out there refer to them as the l-29 vortech head saying that they flow better in comparison to some other stock heads.

you see my confusion. Maybe I just confused my self reading people's personal thoughts. If 454 mpi 310hp has the heads used on the roids motor that will answer al my questions. Also I'm fully aware he machine work done on the heads to produce better numbers. I Just wanna know if the mpi heads will support 450hp with effort and machining?

Thanks!

If I recall correctly, the L29 heads (casting # 12560241) do use the larger oval intake port as opposed to the small round "peanut port" truck head that was common on the prior generation 7.4L's. However, these heads differ from the "old school" variety oval port heads from the 60's and 70's in that they employ a sizable "ski jump" intrusion in the intake port to enhance swirl, and they have a much smaller 100 cc heart shaped fast-burn chamber. The small chamber could be beneficial if you want to bump up compression on one of the older 7.4's, but some have said that the swirl design in the intake port hinders flow at high RPM's. Dennis Moore was pretty high on the L29 heads in his book about marine BBC's, but he also recommends adding the larger 2.19 / 1.88 valves and better springs.

Also, I think the heads referred to by the "330 on roids" thread were probably the 781 or 049 castings from the 70's. Another oval port casting to consider is the 3993820, which also has the large oval ports but has a 113 cc chamber that could bump your compression if so desired. I would not go over 9.0:1 CR on an iron headed marine big block with the crap gas we have available today.

Budman, Thanks for the input! I'm positive the roids motor used L-29.
However I'm still unclear on weather or not the 454mpi non mag motors come factory with this the L-29 head. my original understanding was that the 1998-2000 7.4 310hp mpi is the l-29 motor used in gm truck's.just Set up for marine us by merc obviously. But like I said the threads I read contradict that.

I think you are correct on the MPI engine, but I also think the original "330 on Roids" thread referred specifically to the 049 and 781 casting heads as upgrades over the peanut ports.

Best bet would be to check casting numbers on your block and heads. That will tell you what you have. Also, I think you may be limited on the mods you can do to a fuel injected motor without getting into remapping the ECU or switching to carb.

The L-29 is not the peanut port head but a little bit
Larger oval port. My casting number was 279 if I recall. I did install a set on my 2000 L-29 7.4 with success... It is a cruiser and runs very well. I did upgrade to forged pistons and h-beam rods and the stock cast crank is plenty tough. I did install the larger 2.19/1.88 valves and did some bowl blending but left the ski ramp alone. Motor redlines at 4.400rpm with a 24P B3 drive at 51MPH. Stock motor was 47mph 22P prop but I never cruise for than 35-40mph. I did did upgrade to the 454 HO cam .510/.540 lift with stock roller lifters and valve train with new springs of course. I used the stock crappy exhaust and should have upgraded to the 496 style but overall it runs great but the extra power really is not that noticeable at all. These heads are ideal where max torque is needed at lower rpm's.... Fwiw, I built a 502 with aluminum rect port heads, ported, good exhaust and alot more cam and it is a freakin jet compared to the L-29motor.... If you want performance above 4,500rpm than the 279 Vortec head is not a good choice but might be about the best choice for a torquey, lower rpm cruiser.... TBF

No "330 on Roids" used L-29 heads with the 99cc chambers. I know because I was going to copy his build before scrapping my 330. I actually bought the vortec L-29 heads and was going to have my head guy port them. Very good low rpm heads, and from that build did very well. However, you need to look at how much you are going to spend on a restricting cast iron design vs new aluminum heads.

The rods need arp bolts, crank is ok in the 400hp range, and obviously pistons need to be tossed into the trash.... You can see how for your money, sometimes people just opt to leave it alone it build something more reliable with the added HP.

That said, it can be done and as you know, has been countless times. Just gotta be sure you can accomplish your goals within budget with the 330 base.

I also had to Run an adjustable fuel pressure regulator to get my air/fuel ratio safe. With stock settings it ran lean above 3,000 so I bumped up the pressure about 3 or 4 psi and all is good. Well, the downside is that is runs rich at really low idle speeds but remapping the ECU would be the right way to go..... If you have a Donzi I would consider a rebuild using. 4.25" crank and Aluminum heads.... 600HP easy! Lets just say my well raft cruiser is for sale and I am keeping my Donzi!

I have wondered how my 489 with the AFR 265's would run in a cruiser. It is developing almost 600 ft/lbs from below 3000 almost all the way up to the power peak at 5400 RPM.

I haven’t found a single person running these afrs but I want to grab a set this next season for the next stage. My L-29 in my 236 rinker with stand-alone efi, mild marine cam, flat tops, 9.5.1, bravo1 and 4b 24p b1 will spring out of the water and run up to 61mph at 4300.