DonMan

No, actually I didn`t rebuild at all (engine has 250 hrs). I basically just removed the intake and all associated fuel injection parts, installed the Edelbrock intake and Holley carb. I plumbed in an electric Carter Racing fuel pump and fired it up. I ran the Delco distributor for a few weeks, but recently swapped it for a MSD Pro Billet Marine distributor, box, coil, etc...
The MSD doesn`t help much except to give a better throttle response and crisper idle.
It was pretty easy.........
I am swapping in a bigger cam this Fall along with some head work.

bobl

Pat, I did that exact project for a customer this winter. The L29 has flat top pistons and a 9:1 compression already. I ported the heads & installed larger valves and a mild cam. We messed with the injection for a long time. We reprogrammed the ECU several times. The stock injectors are 22 lbs and didn't flow enough for the modifications. Switched to 40 lb. injectors and reprogammed the ECU. Finally got it sorted out and running very good. Net gain??? 4 MPH! The stock EFI just doesn't flow enough to support any more HP. We did pick up a ton of torque though. It just died at about 4500 RPM. Tyler Crockett told me he had done a lot of dyno testing on one of these motors and could not get over 375 HP on the dyno. He swapped to a carb and picked up about 75 HP! So, based on these experiences I would not do anything to it unless you're will to change the fuel system.

Griff

Hey LFarr, a roots type supercharger makes boost depending on LOAD.
If you are under full acceleration out of the hole, you may see full boost at 2000 rpms. If you are cruising at 3500 rpms, you will see about half of that.
I see the boost readings every time I go out. Also have had SC'd ProStreet cars that would make 10#'s all the way down the 1/4 mile. Yet driving them at 3400 rpms on the road without a LOAD you would see 2#'s.

Pat McPherson

OK Guys,
The fuel injection is coming off, an Air-gap intake and four barrel carb going on. I bought another set of L-29 heads that are going to the machine shop next week. I also bought a set of used Stainless marine manifolds for her.
Any suggestions on the cam??? I plan to install captain's call when I pull the engine so I don't think I can go that big. Any body know if the 425HP/454HO cam would be the right call? I also think Crane makes some Gen 6 marine cams.
Thanks for all the help.

DonMan

Patrick,
I have purchased a camshaft for my engine. I plan on installing during the winter. It is a GM Performance Parts hydraulic roller. It is the camshaft for the ZZ502 crate engine, also known as the 502/502. I don`t have the specs in front of me, but it is something like .544"/.544" with something like 230* duration. I was told by experts that it is the biggest cam you can run with the L29 non-adjustable valvetrain. If I remember correctly, I paid $125 for it from Scoggin-Dickey. It was a new "pullout". I also bought matched springs, brand-new, still in box for $75 (General Motors). You can go bigger on the cam by converting your valvetrain to a fully adjustable one. Crane sells the studs for $80.

mcollinstn

Guys,

A Whipple is not a roots blower. It is a screw blower (or more specifically, a Lysholm Screw air pump). It physically pulls air in from one END of the case and discharges it out the other END (as in back to front). It is adiabatically more efficient than any other form of positive displacement blower. With that said, it IS indeed a positive displacement pump and can be thought of as a very very efficient roots pump with none of the drawbacks or heat problems.

Now, a positive displacement blower WILL make almost full boost at low rpms. Theoretically, they "should" make full boost at 1000 rpm, but operating clearances and allowance for thermal expansion dictate an "engineered" loss of efficiency at very low rpms. These blowers pump a given VOLUME of air for each turn. This differs from a centrifugal pump (turbo, procharger, vortech, paxton, etc) which uses inertia to move air. Centrifugal blowers will make more boost with more rpm - until they reach the design limit for the flow ratings for the volute and turbine.

Now, for those who see less than max boost on their roots blower at mid rpm - this is due to the throttle plates being partially closed. Not saying that you will see 5 pounds of boost at steady 1700 rpm and 5 pounds of boost at steady 4500 rpm. What you WILL see is if you slam the sticks wide open from idle - the boost will jump to 90% of max boost and will stay there all the way to the top end. Not telling you to do it, just saying that it will. Centrifugal guys will see a different tale. Centrifugal guys will see the boost hop to 2psi by 1500 rpm and then it will continue to climb all the way to top end (turbos are different and we aren't talking about them cause they are exhaust driven and engine LOAD determines the quantity of heat energy present in the exhaust stream to drive the pump).

This heavy boat "may" do okay with a centrifugal system but my guess is that it would be best served by a low boost whipple setup. It needs guts coming out of the hole to turn the steeper prop he will be running.

5 pounds of boost on a cast 454 at 91 octane is pushing the limits. I don't know that I would advise that. 3 1/2 pounds would be trouble free.

Whipples are more expensive than most anybody elses blower kits. I feel that a whipple would be the best blower solution for this motor.

A 174 blower and a carb would be the most affordable solution and would be "almost" as good.

I like prochargers, but don't feel that they are the best option for this heavy boat and cast motor.

dhess

Bob, I've read all these expert's opinions and all have their merits. Having been around this arena for a while and tried most all the suggestions plus port nitrous, I would suggest the least attractive of the options: Opt for a 540 crate motor from a variety of manufacturers and use an Arizona Speed and Marine fuel injection system. Mercruiser uses their system on the 525 EFI motor. All the components other than the intake manifold and plenum are GM Delco Remy, available at your local Chevy dealer. www.azspd.com is their website. Talk to Dan Peloso @ 480 753-0208. They sell complete motors with all the necessary stuff. 540 CI 620 hp/650 ft lbs 9:1 CR $17,000 =/-. Ought to be worth 25 mph on Tahoe. Or... keep your short block and make the modifications mentioned previously and add the AZSPD system. This will solve the EFI problem. AZS sells a 502 motor, a little bigger than yours, that starts with the turn of the key, idles at 700 rpm, runs on 87 octane and make 520 hp @ 5000. If you used your short block should get you close to the high 400's. The low and mid range torque of these systems is impressive. I wanted the above and purchased a system this year.

Supercharging is great if you have a forged piston/rod/crank motor. Otherwise you end up with problems, i.e. lack of reliability, low power increase at low boost (3.5 lbs), lots of work to install, not that inexpensive to install ($5,000+) and in your application, in my humble opinon, the wrong option. Go with a big motor with AZS and you'll smile all the way across Tahoe.

baronbob

Wow!! I am impressed with all the knowledge and experience expressed on this subject of pumping up this low performer. I have talked with both Procharger and Whipple and they both believe that I will not have a problem with my cast componets if I keep my boost under 5-6 #s. I know they are both in the business of selling boost devices but they say they have plenty of examples of reliable installations as long as I stay low in boost and RPM's (mid 4's). There are things I can do such as cam duration and timming for futher reliability.
So here is what I am going to do. By the way thanks for all the input to you-all. Nice to hear from you Don. Operating elevation change is a big factor in my decision. Not necessarly going that fast but improving hole power are also factors here. I think I may be able to purchase a used Whipple and bolt it on to my existing EFI. Here is my reasoning. My yearly travels take me to various atmospheric conditions and I would like a computer to figuar out mixture, timming ant to watchout for detionation. I appreciate the discussion about better flow with a carburator, clean manifold anb better flowing heads however I believe that a positave displacement system covers alot of the performance gains of better flow at atmospheric conditions. I also remember the hassel of re-jetting as temp and elevation changes. Being an aviator I watch over-all manifold pressure and note that 5-6#s oh boost equates to 10-12" of manifold pressure. A hot day on Tahoe can result in a 9000' density altitude and a hot day on shasta can be in the 6000' range. Durring operation on a hot day @ Tahoe Converting boost to "s and then taking into consideration density altitude(1" per 1000') I will net only a 1/2#-1 1/2# over normally aspirated performance @ sea level (STP). Shasta would be 2-3# same conditions. I will have to watch WOT deuration durring colder and lower operation.

dhess

The whipple is a good choice if supercharging is your decision. My only caution is to stay on the light side. Whipples make a lot of torque, can break things and have an incidence of burnt/broken pistons when they get too lean. Good luck, Bob.

mcollinstn

If you setup for your low altitude operation, then you will not have any worries at higher elevations.

With an MPI you can adjust fuel mix with fuel pressure adjustments. Higher elevations will result in richer performance (which is safer then the alternative).

Don't confuse your MPI setup with a closed-loop automotive FI setup. The boat unit does have knock sensor, but does not have the ability to sniff the exhaust to properly adjust fuel mix at altitude. It uses a MAP and BARO sensor to adjust to where it "thinks" it should be. Your MPI brain might need some programming tweaks to adjust for altitude properly once boosted. (but you ARE correct in that it DOES have the capability to adjust automatically, it just won't know if it adjusted correctly or not - that will be up to the fuel curve map that whipple burns into the ECM).

Since you clearly understand the relationship of density altitude and supercharger effectiveness, you may even want to talk to Whipple about buying a "high altitude" pulley for operation in the mountains.