ok, discovered that what i was told to be a 454/330 was a L29 vortec. since this changes everything,

1. what are the stock crank, rods, and pistons made of and how much horsepower/rpm will they take?

2. what is the compression ratio?

3. recognizing the gen VI non-adjustable valvetrain, whose roller rockers should i run?

4. i have a set of 1.8 ratio harland sharp roller rockers, can the stock valvesprings handle the extra lift and ramp speed?

5. i want to swap off the efi unit that soots my transom for a carb setup, probably a vac. secondary 750 sea demon; whose intake should i buy that will line up with the vortec heads?

6. on the subject of ignition, i was thinking MSD pro billet marine distributor and 7ml-2 ICB, ideas?

7. do i need a bigger oil cooler?

8. considering the heads will be cleaned up and 2.19/1.88 valves will be installed, what cam should i run with all of this?

9. who makes an economical exhaust header setup that flows good?

10. who should i buy this stuff from? i was going to buy it from jegs but if there is someone cheaper i would entertain that idea.

any other ideas would be greatly appreciated, and thank you in advance to those of you who help me out on my quest for a mean boat!

also, since the roller 454 mag cam is so close lift-wise to the l29 cam, could i re-use my valve springs?

also, what size guide plates does this engine have, if any? 5/16"; 3/8"?

ok, this list is too damn long lol!

i've done my homework, and i've found all but a few.


2. 8:1 compression

3. crane energizer, comp stainless steel, gold race, etc. not going to take much for the wimpy spring pressures of a marine motor.

4. screw the 1.8s, i.m going to cam it this winter.

6. not sure if i'm going to pull the heads, but if i do i'll clean them up.


BIG IMPORTANT QUESTION NOW! what does the bottom end consist of?! this is the kicker for the whole project if anyone has the answer, you can pick my brain about any land-bound gasoline or diesel engine anytime! promise! lol.

also, is the "old pushrods with new rocker arms" issue of wear patterns really that big of a deal? i read that it was and i'm having trouble believing that.

That is a long list.!

1st of all, lets just ask you this. What are you trying to accomplish?, then maybe we can help you. The stock motor will run for 400-500 hours trouble free with reasonable power.......

clue us in to what you are doin.....

o yeah....... bottom end

4-bolt mains
cast crank
cast pistons
small rod bolt cast rods.

good to 425-450hp if rpm's are kept under 5K

my goal is to have a boat the will make no more than 500hp, rpm is really not as important as it's cousin, durability lol. i've got a stock bravo 1 drive that i'd rather not blow all over the lake lol

here are my main desires for this boat.

1. gain in acceleration, and time to plane

2. a more radical idle that will turn heads on the river, or loto, wherever.

3. something that i can call my own creation, i'm almost positive that the cast components will not work, besides i've got enough dimple rods and trw pistons to choke an elephant.

in my line of business (drag motors) the trw pistons are considered ashtrays. it seems as if they are more widely used in the marine world.

thanks for the info,

PS- shafiroff.com and ohiocrank.com have some of the best, and cheapest rotating assemblies around for those of you who are looking.

While I realize this thread is old some people do find interest in these topics and back into info. It's also almost 2026 and alot of things "have" changed in the world of BBC/Tuning/Performance. And I have some experience with this engine so here's some help for those caring.

I have "some" L29 knowledge. It is far superior engine wise from a 330 hp peanut port motors of earlier generations. I do currently own one in a Velocity 22. It had a "few" things going for it. Decent Stock Compression, MEFI 3 ECU in a marine application (tuneable on mefiburn or blackbear performance tuning if send ecu out). The factory head is "decent" and does respond "well" to porting, its a decently large oval port head. 230cc runner, 99cc/100cc combustion chamber The Factory intake also does respond well to this. Injectors are generic Bosch and can take in 2025 a 19 or 30 lb injector fairly easily (Fuel Injector Connection). The motor is a gen 6 and has good roller lifters from the factory with the tray along with 4 bolt mains. This helps when it comes to lifter cost. There a few decent builds online of which I can share links on of folks doing Cam setups in them with detailed parts list and great results. 500 hp is achievable. 5000 RPMS is about it (which is 400 rpms over factory redline, with mods and a tune obviously).

The "consensus" is all L29 had inconnel exhaust valves in marine as well as car applications as they were mostly used in 2500-3500 towing gas truck applications. The Valve springs are the weak area, but again in 2025 there are extensive upgrades available. Figure on a hair under $2000 in today's pricing for everything needed to upgrade the cam including a single row gm performance parts timing set (cannot run double row timing set of the comp stuff with the EFI sensors). Tuning is necessary and somewhere between $350-700. Dyno obviously optional. With the motors becoming so "cheap" in the marine area and everyone focusing on the 454/502 MAG a 7.4 MPI engine with a Mefi 3 ecu isn't a terrible place to start an EFI DIY Budget build in a cheaper boat on an alpha or bravo based platform.


1. what are the stock crank, rods, and pistons made of and how much horsepower/rpm will they take? Consensus is a non forged factory crank (cast) with cast pistons and rods. Many performance builds utilize the factory rod and crank for 5000 rpm car and towing applications.

2. what is the compression ratio? 9:1 with 100cc combustion chamber.

3. recognizing the gen VI non-adjustable valvetrain, whose roller rockers should i run? I have provided a parts list for you.

4. i have a set of 1.8 ratio harland sharp roller rockers, can the stock valvesprings handle the extra lift and ramp speed? Most folks use 1.7 or 1.8 roller rockers, but some have converted to adjustable valvetrains using stock stamped steel rockers (I would upgrade to a scorpion or a comp ultra pro rocker arm roller rocker)

5. i want to swap off the efi unit that soots my transom for a carb setup, probably a vac. secondary 750 sea demon; whose intake should i buy that will line up with the vortec heads? Alot has changed since then, tuning is easily available for this project through mefiburn, blackbear performance or other vendors to make more power, burn less fuel, and not soot transom.

6. on the subject of ignition, i was thinking MSD pro billet marine distributor and 7ml-2 ICB, ideas? Not needed if retaining EFI.

7. do i need a bigger oil cooler? I have an HP500 cooler on mine, no oil temp issues.

8. considering the heads will be cleaned up and 2.19/1.88 valves will be installed, what cam should i run with all of this? Few options, some custom, some off the shelf marine, and some decent car cams that would work with a performance exhaust or full dry depending on LSA and some other factors. Consult with others and builders based on your specific exhaust & reversion concerns.

9. who makes an economical exhaust header setup that flows good? Hardin/Lightning or Stainless Marine. CMI always work till they leak.

10. who should i buy this stuff from? i was going to buy it from jegs but if there is someone cheaper i would entertain that idea. Summit/Jegs/Amazon.

Parts list below. Some folks find the comp lifters to be noisy and agree the GM performance Part lifters seem to be the way to go. Obviously pick a cam. All of these get you near 500 hp.

356hp 486ft/lbs no accessories with a tune and headers.

Performer RPM air gap and a 650cfm holley
370hp 476ft/lbs

Comp extreme energy 276
0.510” lift
224/230 110
428hp 514ft/lbs

Need a valve spring upgrade 26120 with a rotation eliminator but he said it’s near coil bind. So he said to use something else.


With out a true full length header you could assume you’d get to 400hp with a mild cam

Chevy Vortec L29 '97-99 Iron 230/- 2.070/1.72 99 63/49 121/91 165/120 198/133 226/140 242/142

Last 2 numbers are 0.500 and 0.600.

Could make 450hp at 0.500 lift and maybe close to 500 with a healthy cam at 0.600 and a real header.

Im not sure the stock intake would support that though.