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motoman

mercruiser 454 head and cam info 330hp upgrades or mods

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I'd like too know if any of are tech guys around the forum have did any up grading too the older 454ci motor"s 330hp like swapping out the peanut port heads too oval or rectangle port or installing a newer 454 mag camshaft or after market cams with same or close  lift or duration, intake carb set ups, and your experiences with doing so, i'm not talking go fast boats and big rpms or hot rod car stuff, im talking bigger heavier fishing boats.single or twin screw.? 

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It's not that I don't want to give you advise, I'm not familiar with the big blocks, I did my own, with a lot of help from my uncle who builds dirt modified engines, I went from a 305 to a 350 bored 30 which comes to 355 cid. with lots of new goodies, like Dart heads and a full roller cam and heads and of course a 4 bolt main. The heads were cut 60thos, to boost compression and with the roller heads and cam and a Baker carb 2 barrel carb that flows over 600cfm she pushes over 300hp on the dyno. I only use the main to get me to and from, and I can get off the water in a hurry should bad weather come upon us, I have a 21ft Sea Ray cuddy. I did a shake down run on a local lake with a 45mph speed limit and had no problem reaching that speed with throttle to go and around 4700 rpm which I found interesting, the rpms were about same as my speed, I don't foresee myself needing to go that speed to go fishing LOL but it's nice to know I can get off the water in a hurry should I need to. 

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The motor heads I have talked to make a big deal about what era the 454 is from. Like "borderline 350" used to say, "no hencho stuff".  The older 454's are legendary workhorses, there's a handful of Oak captains that have logged 10,000 plus hours on an engine, and lots of old time motorhomes have them piling up the miles. Many guys are getting away from the Rochester carbs and going to the edelbrocks, but there are fans and naysayers for both.

There are national outfits online that make incredible claims of rebuilding 454's for more power and economy, but when I needed to rebuild one I had it rebuilt the traditional way using the best components possible.

I know one thing, I will use only pure gas whenever I can get it. Not only is it better for all engines, the added economy offsets the additional price. 

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The motor heads I have talked to make a big deal about what era the 454 is from. Like "borderline 350" used to say, "no hencho stuff".  The older 454's are legendary workhorses, there's a handful of Oak captains that have logged 10,000 plus hours on an engine, and lots of old time motorhomes have them piling up the miles. Many guys are getting away from the Rochester carbs and going to the edelbrocks, but there are fans and naysayers for both.

There are national outfits online that make incredible claims of rebuilding 454's for more power and economy, but when I needed to rebuild one I had it rebuilt the traditional way using the best components possible.

I know one thing, I will use only pure gas whenever I can get it. Not only is it better for all engines, the added economy offsets the additional price. 

yes you were correct on the era of heads ( some being better than others) its all about the cfm or flow that they make but you must have all your ducks in a row with these parts being matched up well or you defeat the purposes of making a more powerful and efficient motor with stock compression and cam lift & duration. you also mentioned company's offering motor's with more power and economy  of the same C.I and that's the info that is kept to them self's and not all over the net . point is if you have a perfectly good running motor why buy one of these H.O motor's for 7500 when ya can do heads intake carb and cam and save 5k, I've pretty much got the info on doing this now thx for the reply's .  

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here is a little cam info that's well know old school stuff in the 330hp I think its 1991 and back motors that have the older technology .  

 

The flat lifter 7.4/330 horsepower camshaft is an old design camshaft from the 60's with 213/217 duration .460/.480 lift 114 LSA.

The 454/502 Magnum flat lifter camshaft has 224/224 duration .510/.510 lift 115.5 LSA

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well i dont have a heck of alot of experience with the big block, the small block 350 was built buy gm to be a turd and the 454 is basically a big version of the same idiocy's.  the pistons they use have chamfers and releifs that are way to big and useless, therefore lodge unburnt fuel which causes pinging, knocking, and all types of bad stuff.  to prevent the predetination which destroys the engine, they back out the timing and reduce compression wich greatly reduces all tourque.  this will make a pretty good reliable engine but dont expect rings to last on this type of engine build because the fuel washes the rings as its stagnant and unburned untill the engine is heat saturated.  if you build a nice engine get some true flat top pistons WITH THE CORRECT PISTON COMPRESSION DECK HEIGHT COMBINATION.  after you pick you CORRECT piston for your build, you would mill the heads of your choice prefferably the  newish alpha era stock set with some hand porting done.  the older pre alpha heads were heavier and hardly ever crack but they flow like drinkin gatorate through a coffee straw.  stock marine heads are made for torque.  wich you NEED.  mill them to get your correct dynamic compression. make sure you measure your dynamic compression using your cam intake valve openings in the value.  it matters if you want economy.  personally i would use the factory cam for the mag 502.  is is a good cam for high high torque, which you NEED.  position your heads about .040 thousands of an inch from the piston deck height at tdc.  anything over .060 is hotdog in a hallway material.  this is known as quench.  its a big deal.  you need to use a head gasket that gets the head that close to the piston.  it will make a dog of a engine withought your quench distance perfect.  now you have your piston travel and  compression figured, likely at around 8.75 to 1 dynamic comp 9.55 to 1 static comp for good marine gas.   with these ducks in a row, make damn sure your using a rochester 4 barrel carb PROPERLY tuned so that you can keep as much timing into the ignition as possible to increase torque, which you NEED.  any variables not covered in my post will cause predet and you will back your timing out to compensate for reliability and your torque goes right out the drain hole.  if you are just using the merc thunderbolt ignition alpha or fuel injected bravo you cant controll your timing and a nicely built engine will just be that much more reliable.  and with the properly built engine you can attain higher power with stock ignition just by efficiency of parts being set up properly.  dont use a high volume oil pump as it robs power.  use a new stock pump with a higher spring pressure.  use a double roller timing chain for strength and longetivity of cam timing.  single roller get better efficiency.  less power to turn it.  and no matter what what ever you do...do not reuse the old log style exhaust.  get the alpha and newer style torque header type.  still junk but miles ahead of the pre 1988 log type.  if your carb is not tuned exactly then all these little things to bring out your true efficiency are wasted effort.  i call it engine harmony.  you can hear the harmony on onieda lake all summer long!!!

Edited by kingslamon22

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good info , but .040 isn't that super tight on piston too head clearance ? i did run a race motor one time at .035 and it knocked the bearing on the crank right out of it, rod stretch at high rpms piston hit head till it cleared it self. wasn't pretty. unless you talking with out gasket and gasket will open the squish up ?

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At 9.55 cr, a cam with about 37 degrees intake closing, with tight lobe centers, and good lift would be a torque producer.

We set squish/quench with "0" deck at .030", using Cometic MLS EST gaskets, on the engines we build.

They do not crush.

 

Edited by Fish Hunter

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reed cams made a couple good cams like you mention before they they shut their doors.  they had a handle on the type of engines that people like to build.  unlike todays market who builds their cams for high rpms OR rumbley sound.  marine marked cams usually cause water reversion and should never be used for marine aplications unless your exhaust is dry.   plain idiocy if you ask me.  .035 is too tight of clearance for piston to head quench.  no less than .040 no more than .060.  if you had piston to valve problems you picked the wrong piston...OR...your rod bearing clearance was too much OR the rod was over reved or already weekend and stretched.   race engines need close scruitiny.  if what im saying is too much for you to worry about then buy a turd crate engine or pay a skilled engine builder for these types of upgrades.  fish hunter obviusly youve done this before but dont tell just anybody to use that clearance id be scared to squish em like that.   .030 can work if you heavily scrutinize your measurements and really really pay attention to details.  id be leary id made a mistake.  even rod bearing side clearance can destroy an engine with tight tolerance like that just by lowering oil pressure stability in the crank to rod bearing itself.   with your ducks in a row, tight clearance is good but  you dont want no predet with that type of quench though.  also with that tight of clearance compression can be high with the wrong head.  carefull with the dynamic ratios there too.  obviusly youve done this before and dont need a lesson but here is my 0.02 cents

Edited by kingslamon22

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Yep, you need to check, double check and machine as needed. Good points well made. :yes:  :yes:

Edited by Fish Hunter

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