Procharged small block, boom.
 

To much timing, not enough octane, 7psi of boost = blown head gasket, damaged block and head between cyl 4&6. All my fault
:( and now it's time to move on :D

I currently have an all forged 383 short block under construction. I used up most of my budget on the 4 bolt block, Eagle rotating assy w\JE pistons. Can you guys recommend some cyl head options? I will be keeping the Vortec intake with the MPI. I'm not sure if I will be changing the cam yet but would like some opinions there also.

My 22.5' Crownline ran just over 70 gps before my mistake and I'm not looking for a lot more speed. But what self respecting hp junkie wouldn't take this opportunity to pick up a mph or 5 :drink:

Re: Procharged small block, boom.
 

Tom,
I have wondered the same thing, what heads could be swapped in and still use the factiory MPI. Keep me posted what you find. I am on my second season so far with the twin 350 mpi pro-charger setep, however I am running 5 psi and stock timing. I have the set and forget it setup and it "seems" bulletproof at this point. Did you make the crownline run at cumberland a couple weeks ago or were your already broke?


You may want to contact Steve ([email protected]) I think he built a couple 383's and used the stock injection as well. Mark at Percision did the dyno work and programmed his ecm's.

Brian

Re: Procharged small block, boom.
 

That's where I broke it (Cumberland Crownline Rally). I bumped the timing up for the radar run and forgot to bring it back. Got gas the next day, asked to $100 of premium. After cleaning up the boat I when back to the pump to find he wasn't pumping premium. I stopped him at $60 and finished with the good stuff. I would have been fine if I had brought the timing back down but....BRAIN FART. Anyway I did get about 130 hours out of that set up so I'm not to :mad: . I would have preferred this to happen at the end of the season though.

I may just put a set of stock Vortec heads back on for now until I can spring for some good aluminum ones. Anyone have any?

Re: Procharged small block, boom.
 

How much more timing were you running? Were you ok with 7psi with stock timing? I still have the original 5 psi pulley on mine. Is that what are motors have now, Vortec heads?

Re: Procharged small block, boom.
 

I had bumped the base timing to 10* (my ecu takes out 1*of timing for every # of boost), stock is 8. I had run the 7psi pulley for about 20 hrs with no problem. I do drive the boat very hard. The 350 Mag MPI does have Vortec heads.

Re: Procharged small block, boom.
 

Looks like there are two choices in Aluminum, GM performance parts and Edlebrock makes a set as well. GM performance also has a cheap set of cast irons that may even work better then what we have.

Re: Procharged small block, boom.
 

Go with aluminum heads to lower combustion temps. Don't bother with any port work on the intake side. Make sure to open up the exhaust side huge so that you have around 80% intake to exhaust ratio. Then you will make some power as long as you have a good exhaust system.

Re: Procharged small block, boom.
 

The GM Fast Burns (aluminum)should surely add much more muscle to these engines.

GM also makes a small port and large port Bowtie Vortec cast iron head.

So........there are good choices/alternatives out there. Just make sure to get it reprogrammed when making these changes. Live (vs phone) is always better !

Re: Procharged small block, boom.
 

GM. Fastburn heads are angled plugs, may be an issue with your exhaust. The Edelbrock E-tech heads are straight plug, but are 64cc just like the Fastburn heads. What JE pistons are you using?

Re: Procharged small block, boom.
 

I'm not sure exactly what piston my builder is using he just recommended the JE for my combo. I'm sure they are dished, just not sure how much. I have the Revolution Marine manifolds.

Re: Procharged small block, boom.
 

blowncrown and tssteph - how much hp were you putting out with the Prochargers??.....what kind of increases did you guys see??

signed - small block lover

Re: Procharged small block, boom.
 

Procharger claims 490hp with the 5psi kit on the 350 Mag MPI, I would call it 450ish. I went from about 52 mph(gps) to 64. When I added the Stern Jack I got to 68 and then the 7 psi pulley got me 70.

Re: Procharged small block, boom.
 

The E-tec 200's from Edelbrock outperform both the GM fastburns and their bowtie iron vortecs.

If you want to continue on the quest for more reliable hp then it may be time for a aftermarket ECU like FAST or Big Stuff3. There is no way to beat a cutom tune. Also I do not even know if the Merc PCM takes into account IAT, or coolant temperature correction for timing. This could be fairly dangerous as well, esp when running for extended periods of time at WOT opr under boost.

Re: Procharged small block, boom.
 

A old wise man once told me "When it breaks.... fix it faster!"
And I don't think he meant repair it quickly! :D :D

Re: Procharged small block, boom.
 

I agree.

I am not looking to go much faster with this hull, but sense I had to build a motor anyway I might as well build it better that stock. The cost to build a forged 383 isn't much more than a 350 and the added torque will be nice.

I do use a LM1 air/fuel ratio meter to make sure she isn't to lean.

Re: Procharged small block, boom.
 

Yes the torque is nice but it comes at the price of reliability with the larger stroke.

Re: Procharged small block, boom.
 

What is a safe RPM for an all forged and balanced 383?

Re: Procharged small block, boom.
 

I had an old sea ray 207 srv that I put a 383 in, used canfield aluminum heads, roller cam. I ran it hard, propped to top out at 5500 rpm, that engine is now in a friends boat with 5-6 75 hr seasons on it and it's still running great. Alpha drive with Merc heavy duty upper gearset stayed with the engine and it also has given trouble free service since day one.

Re: Procharged small block, boom.
 

I run a full forged 383.. around 560 hp N/A. Spin it 6000-6300 all day long. You build it good and it will run like a crazzzyyy ***** :D Spend some coin on some AFR heads. you will love them. this is hooked to a alpha that just loves it... no problems 3 yrs running.

Re: Procharged small block, boom.
 

I wound up with the Eagle 12106(forged crank, rods and 31cc dish JE pistons) that should put me at 8.5:1 with a 64cc chamber. Also ordered the Edelbrock Etech 200 heads. Does anyone know what # injectors are stock in the 350 Mag? Also, are the bigger EFI engine injectors compatible for an upgrade on mine?

Re: Procharged small block, boom.
 

Have you tested these or seen some build ups comparing these heads ?

I've never used the E-Tec's, thus why my question.

Re: Procharged small block, boom.
 

No, but they seem to be the best option for the Vortec style intake. I let you know how they work out.

Re: Procharged small block, boom.
 

How can I get a hold of Mark at Percision? Thanks

Re: Procharged small block, boom.
 

Call Mark @ Precision Marine at 504-469-7463

Re: Procharged small block, boom.
 

Well I got the long block all put together and someone asked me if my Edelbrock heads had Inconel valves.... Not! So here I am asking the advice of the OSO tech wizards, where can I get Inconel valves for these small block heads?

Oh, and does anyone know the # rating of the stock 350 Mag (MEFI III system) fuel injectors?

Re: Procharged small block, boom.
 

Good luck. I tried to find them, they are out there but you'll have to dig deep.

Personally, for a small block, I think a good quality stainless is good enough, but severe duty rated are what I would use.

Re: Procharged small block, boom.
 

Blowncrown, I cross referenced the injectors in your 350 and they are the same part number as the 502 Mag, using the MEFI 3 ECU. So they are indeed 42 lb. REV will custom make a set of inconel exhaust valves for you. I just installed a set in some Whippled 383's I'm building.

Bob

Re: Procharged small block, boom.
 

1.6 Exhaust or 1.5 Exhaust? Head diameter of the valve.

Re: Procharged small block, boom.
 

1.6

Re: Procharged small block, boom.
 

Thanks alot Bob! Who is REV?

Re: Procharged small block, boom.
 

REV is in Ft. Lauderdale....just got off the phone with Al. Check your e-mail.

Re: Procharged small block, boom.
 

In regards to injectors. I have a modified 454 mag that is ProCharged 7 PSI. Call Arizona Seed And Marine and talk to a technician not a sales clerk about injectors and your current set up. You may also consider a remap on your ECM.

Re: Procharged small block, boom.
 

I FedExed my ECU and one injector to them yesterday. They are setting it up to eliminate the FMU and to compensated for the additional cubic inches.

Re: Procharged small block, boom.
 

Well it runs! I finished the install and turned the key this afternoon. Probably not going to see any water test for another week though, I'm headed out of town.
All in all not a bad project. Took a little extra time getting the unexpected stuff like Inconel valves and different length pushrods but realistically right on schedule. I will post a build sheet with $ when I get a chance. The boat ran 70 with the stock 350 Mag and Procharger, hopping for 75 with the 383 and good heads, but will settle for just getting back on the water. Thanks for all of your input, I will let you know what she does.

Re: Procharged small block, boom.
 

I think this is the right answer. Sell your supercharger to help fund the rebuild then pick the right heads (AFR's are great), build up a solid bottom end, cam and intake to match the heads and you should have +500hp easy NA - which means no more problems like you just had.

BTW, the September issue of Hot Rod magazine has a 500hp 383 built up for $5k. Cheap reliable power by being smart with your purchases.

Re: Procharged small block, boom.
 

Although I have learned many a lesson the hard way a blower motor can be a reliable turnkey product, they are built by Merc and others every day.
When it comes to any performance project the weakest link will always fail regardless of it being naturally aspirated or not.
When it comes to this type of project it is important to pay attention to the details engine build, ECM, parts, and money. don't skimp it will cost dough. If you can't afford to break don,t modify you will always find the weak part.
Homework first pay later. You will win in the long run.

Re: Procharged small block, boom.
 

Took her to the Cumberland Poker Run over the weekend and she ran great. I've got about 10 hours on the meter sense the install and everything is going good. I did take it to wot a few times and it pulls like a freight train, but (there is always a "but") it seems to be finished at about 5000 rpm. I am turning a 25p Mirage Plus which I could turn 5000 before the engine upgrade, although it was a dog out of the hole. Now the 25 feels great all the way from idle to 70 mph but just seems to stop there. The fuel mixture is 12.5:1 at wot and the plugs look good. Is the stock 350Mag cam just not going to do it? Do I need to drop the prop pitch to get into the higher revs. I am seeing 6 psi of boost.

Re: Procharged small block, boom.
 

The stock cam is not helping but are you hitting the rev limiter. Where did you tell them to put it. You say you are running 7lbs boost and getting 6 you could probably use 200 more rpm to get max boost. You say fuel mixter is 12.5:1 how about fuel pressure. There are still a couple variables.
What was your maximum speed and boost before, same prop or did you bump up one?
Bob

Re: Procharged small block, boom.
 

Same prop. Boost was 7 psi before. I had the rev limiter removed from the ECU, I have a 5700 chip in the MSD box. 40 psi of fuel pressure.
I could run 70 before, it just took longer to get there.

Re: Procharged small block, boom.
 

Can you also detail you fuel mixture meter installation? Is your 40 psi at wide open throttle? Shouldn't you have quite a bit more then that?