454Mercruiser Intake question
 

I have to believe this is not a from the factory set-up, just bought this 454 gen 5 motor and was taking it apart,suppose to be a 1996 300 horse motor. With all the motors I've built for racing I have never seen anyone put an aluminum square port intake on a set of peanut port heads? I understand the opposite way to build up alot of low end power. These are the pictures of the intake and of the head. the intake has a casting of 6269315 or 6269318.
Any help with this one. i am putting new heads and an intake on it but this is bazarre.

wonder how good it ran like that?

i dont beleive it came from the factory lke that,it must have been a real mut.:party-smiley-004:

Heads look correct for that engine. intake is a surprise.

You have a mag intake, which I'm sure you guessed, on peanut port heads. Not a good idea!

thanks for confirming my thoughts,it amazes me that people just don't pay attention to what they are doing!!!!

Alot of people don't care...........Unfortunately.

I would be willing to bet someone got their hands on the aluminum high rise intake and weber/carter carb and thought that they were making a performance upgrade.

They probably figured that was the difference between the 7.4 Bravo and 454 Mag.

I know it is a little different but just as an example I do tons of work and sales with outboards and you wouldn't believe how many people think that they just slap the carb from a larger model on their motor and it becomes that hp!! I see it and hear it all the time!

Or they repowered with a cheaper long block and didn' t realize that the intake/fuel system was different. See that alot too!

yeap Merc did some that way....seen a few..just worked on one recently that was all original, thats the way it was..that intake was the one with the bronze lined water passage....they seemed to run ok...but not a great setup for sure !!!

WOW,wonder why ,i wonder if maybe they needed to fill an order,so they just used what they had,i think it would run better with the small oval port manifold.do you think it came from gm like that?

They didn't come from GM like that, but lots came from Merc. I think it's when they started using the truck long block but weren't using the MPI truck intake. Must've had lots of the square port intakes in stock. Lol.

weird how some people try and piece garbage together and pass it off for something its not!! at least this was advertised as a 454 300

That combo worked better with the carter carb. The only intake they had with the small port was the cast iron junk that did not work well with the adapter and the carter. It filled the gap until the gen 6 efi

mercury is all about making money,if they wanted to do it right,they could have bought aftermarket manifold for them,but i guess that would have cut there profit margin.:party-smiley-004:

no, I think they just wanted to have one intake to use on a few different engines..they used that intake on a bunch..thats why they were done for holley & Q-jet's 1st one I saw I said no way came that way...then ran into a few more, some I knew were never apart...nobody said merc never did dumb stuff...

Nothing surprises me anymore, after working for G.M. for about 25 years and having my transmission shop, most of these company's are just about the profit margin and using what they have hanging around.

Exactly! A freind of mine was a quality control manager at GM from the 70-90's and he said you NEVER stopped the line for any reason! You were told to do what ever was needed to keep the line running! Looks like Merc had the same attiitude! I have to say that is shocking, especially considering what Merc charges for an engine!

Merc built them this way on purpose on the early Bravo III engines - called it the Performance Tuned engine. Had the Mag intake on small oval heads, different carb calibration and a recurved distrubutor. Supposedly increased mid range torque for cruisers, etc that used the BIII. I have one in my PQ.

From the August '93 PowerBoat:

I can see where they would need to play around with the carb and advance as this combo must have leaned out the @@@@ on the motor, funny because the motor actually has a burned valve in it!!!!!!!!!
I know I'm fairly new to the whole boat engine thing but a drag motor would never survive with that combo,let alone have any kind of performance.

Correct, I bought one around 97 from our Mercruiser distributor, on a B3.

Drag motors are set up for WFO high rpm. Boats (especially cruisers) need mid range torque to get on plane. Different beasts altogether.

BTW, from the rods in mine (Weber carb) they did fatten it in the midrange a small amount, then leaned it up slightly at the top end. Not a lot of change there, though - Merc generally runs things fat. Compared to the std 7.4L, timing ramped faster in the midrange (2000-3000 rpm), then ramped slower to max timing at 4800.

I forgot to mention that in contrast to the stock 7.4, these also got forged pistons and crank.

Actually works quite well. While we often think the Merc engineers were on acid from some of the things they did, they worked from a different perspective - that of producing _reliable_ power to meet specific demands (like for cruisers) while maintaining cost. When we re-build these, we give up one part of that equation - either reliability or cost go out the window. Sometimes both!

This last post makes me feel better about this thing(having the forged internals), the motor is actually getting a set of oval port aluminum heads,r.p.m. performer intake, 800 holley carb,MSD ignition,have aftermarket exhaust with silent choice, was thinking about the 420 hp mag camshaft?

don't count on the forged stuff...seen many low HP mercs all cast small stuff..sorry

Yep, double check the forged - even if it was a PT engine, the short block could have been changed out for one with cast internals. Ask me how I know.

Looking at your valve covers, it looks like a GenV, which the PT engine should be. Double check everything, though. No telling what the PO did.

Lots better cams out there since the 420. Many folks have had good luck with the ISKY MEGA 270/280. Also consider calling Bob Madera (rmbuilder on here) for cam - it will be about the same cost, and you'll get great advice.

Thats a given making sure first, does the combo I was talking about seem like a good mix of parts

The combo all depends on what you are doing with it. If you are looking for good midrange with some expanded top end, your combo is going to be pretty good for that. I'd consider the air gap intake unless you need the heat (boat often in low temps?).

It's essentially what I'm doing based on advice from some very knowledgable folks on another site:

Zero deck block, flat top pistons
Large oval iron heads, 2.19/1.88 valves
RPM air gap intake
ISKY MEGA 270/280 cam
Crane gold roller rockers
750 Weber carb (upgrade later)
Stock ignition
Stock exhaust (needed for noise)

Max rpm should be around 5000. This will be perfect for me as I need mid range for pulling the kids, ect and am not looking for max top end.

If, however, you are going for max top end (or you will want to eventually), you need to re-think. This is where talking to someone like Bob Madera will help - he will first ask what you want.

Looking for something thats a little better than the original 330hp that came with the boat,I still don't know how long I will keep the boat,have allways wanted something with twin bigblocks to play around with.

As long as it will end up somewhere in the mid 50 mph range and get me through this season and maybe next season.

The combination will be going in a 1988 26' Nova Spyder, has a Bravo One drive. do have to figure out a prop as it doesn't have one at right now.

What speed are you running now? My 26' PQ does 56 all day long with the 300 hp 7.4. Although it does have the BII, so a low slip number (7% or so). I'd think with the right prop, you should be low 50's now.

If you are thinking about trading it in, I'm not sure I'd sink the $ for alum heads. You can get a good set of take off iron heads with larger valves for $4-500 a pair. Don't know if these are still around:
http://forums.boatfreaks.org/showthr...highlight=head

BTW, my rationale for going through mine is that I have a replacement long block of unknown pedigree. Maybe a truck replacement block for all I know.

But, while I'm in there...

Allready have the aluminum heads from a project a customer never picked up(surprise,surprise) I was thinking about starting with what the boat came with in stainless as far as the prop goes.

If anyone else has any ideas I am definatly open to them.

I've had this thing for 2 years now and never got it into the water last season,don't plan on making the same mistake this summer