Merc 420 spec's ??? What is it??
 

I have discovered my new/old Sonic (88-31SS) has a Gen V & Gen IV 454's. One of them is labeled as a 420. Exactly what does the 420 designate?The other engine has no visible tag on the valve covers. Both engines have roller rockers and appear to be factory stock (sealed). According to the boat survey, both engines were replaced in '97-98. Is it likely that both engines are 420's? Were 420's made in both Gen IV & V versions? One electric fuel pump/no boss & one mechanical !! Both engines also have the Merc aluminum high rise intakes.......???
If they are 420's what are the specs and do they have "all the goodies" -forged crank, rods & pistons, roller lifters & rockers???
A search on 420's revealed some info but the links put up by
NW JIM in March are no longer any good. Help!!

I am considering a "freshening" & cam change if the internals are the good stuff.... always, the need for speed...... I'm just getting started finishing Too Old's project and already I'm going for the engine mods....:rolleyes:
Help me please!!

Geez That deal is getting better and better. If I knew it had 420's I might have looked at it a little harder. I believe 420's were Mark 4's. Not sure but I dont think they ever made a Mark 5 420. The 420 has all the goddies, 8.8-1 compression,Rect port heads, 4 bolt main, forged rods pistons and steel crank, roller rockers and aluminum high rise intake. A ittle head work and a better cam and exhaust and its good to go. I dont know what to make of the one with no fuel pump boss. It has to be a mark 5 or 6. Post the serial numbers.

I'll check the numbers next week end. My engine guy was the one who spotted the different Gen configurations and plainly the starboard engine has no mechanical pump, electric only. Thanks for that other info though. I have a two set of Stainless Marine exhaust on the way now.....just gettin' started!!

420 is horsepower. Is a 454. Hydraulic flat tappet cam. Crane gold roller rockers. Only made them in MkIV's. Thru 1989 or 1990.

420 camshafts
 

I have had a little experience with the 420's and have found that they are poor running engines because they are WAY overcammed. If I remember correctly they have Crane cams with 240 - 250 degrees of duration @ .050 lift.
Whomever (at Merc High Performance) chose these cams was stupid, plain and simple!
They also have the worlds worst ignition system the Mercruiser CD (not the Thunderbolt IV or V).
Changing these two things would turn the 420's into respectable performers.
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

So, Dennis (or others) what cam should be used? Should I go to a roller lifters & cam? I would like to get about 450hp out of these engines..... with maybe a little head work...

The 420s were only Mark IV bocks. A 425 hp Gen V motor was made in 93. My guess is that they blew a motor and replaced the Mark IV with whatever was available, a Gen V motor. Since some parts are not interchangable between the 2 motors, I would have them checked out VERY carefully. Be sure it's actually a marine engine and the specs match the other motor. Keep in mind that they rigged it with an electric (marine?) fuel pump. A Merc Gen V motor runs the fuel pump off the water pump. There may be a lot of other things that were put together as a matter of convenience.
Also be sure the Mark IV engine was actually rebuilt. You may have one motor with A LOT more hrs than the other.
Gary

According to the survey, BOTH engines were replaced, but I don't see how I could have different Gen blocks if they did. You may be correct. It is for that very reason, I am going to go thru them both...... still looking for help on cam selection

If 450 hp is all you want I wouldnt go the extra expense (lots)and less reliability of a roller cam. The flat tappet cam should be around 224, 232 duration at .050 with .525 to .550 lift. I use the Edelbrock torker cam because I am using silent choice with short risers. It has a 114 degree seperation with hurts its power some. You could go to 112 or even 110 degree seperation if your risers are long enough. If you have the money, the roller cam with give you more horepower but on a mark 4 I think you need to have the lifter holes bored true and bushed to use a roller lifter. There are special roller lifters made for these older engines. You may have a roller cam in the mark 5 engine.

I agree with Formula 31
 

If you really want maximum power and fuel economy (you should use Formula 31's cam specs but) use a hydraulic roller camshaft.

The engine will idle smoother and make more HP with a roller camshaft than a flat based camshaft with similar specs.

Remember that all new engines come from the factory with roller cams (even stock automotive and truck engines) and durability is not a problem for them!

The use of synthetic oil on a roller lifter camshaft is NOT a problem. If it were then we would have thousands of cars and trucks (with roller lifters that are using synthetic oil) failing every day. The synthetic oil manufacturers would be buried in lawsuits!

Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE

Dennis, Ive never done it but doesnt the Mark 4 blocks lifter bores have to be bored perpendicular to the cam centerline to use rollers? Thats what I was told a few years ago. maybe they have better roller lifters now.

I would be happy to have more than 450 hp per engine, but I also want maximum reliability without having to replace valve springs every season. That is a real hassle!! and broken engines in the middle of the season is not good either...
:mad: :D

I hear that, been there, done that. I think the problems that people were having with the hp500 were the valve springs causing failure of the roller lifters. Crane and/or Merc screwed up and used a valve spring that was way to strong or had the wrong spring rate causing failure of the roller lifter. I would still find out about the mark 4 block and how well it accepts roller lifters before I considered that avenue. If you go the flat tappet route, break them in religiously (no idle time at all) and they will be fine for a long time.

When you are saying flat tappet, are you referring in fact to "hydraulic" flat tappets or solid ? I would think with solid lifters, the valves would continually have to be adjusted (bad in a marine setup), and higher spring pressures would be required??
Yes/No????:confused: I do not really have an objection to hydraulics as I know they are reliable but rpms are limited also, are they not? What is the limiting rpm of hydraulics? flat tappet versus roller??

Oh yea, hydraulic flat tappets, you dont want to go solid unless you are after every last pony and they are a pain. Hydraulics are totally ok to 5500 rpm, maybe more I think. I dont really know, Ive run them to 5500. It mosly depends on spring pressures I think. You wouldnt really want to push your bravo over that anyway.

So, is it possible to reliably get 500 hp out of these engines and not be tearing them down all the time? That would be nice to have a cool 1000 hp in the Sonic!!

it's easy to get 500hp out of those engines and be trouble free. i had 400 hp MARKIV's. now they are right about 500's. i used a comp cams extreme 4x4 cam to keep the low end torque and still make good hp. redline is 5800 R's. 223int /234exh .544lift intake/ .564 exhaust with 111* LSA. clean the casting flashing up on the runners and the heads are good since they flow well already. i changed to EMI thunder from stock and have no reversion problems. my boat weighs 13,600 lbs and still has plenty out of the hole( not that i use it like that). don't believe rectangular ports can't make good torque down low. :) they can.
and if you use torquer 2 springs, no machine work is needed to the head.

Re: I agree with Formula 31
 

I agree with Dennis about the hydraulic roller---they're a good and reliable way to go and will give you more HP/TQ. You also might want to take the heads and have the bowl/pockets cleaned up, have the short turns radiused, and unshroud the valves. This would usually be termed as a "street port" and might cost only about $250 per set or so. Also, something that many people don't do on a 454 is to have the cylinders "bore notched". The person doing it has to know what the heck he is doing for it to be done correctly otherwise the block could be ruined or have the cylinders sleeved. Thing about it is that it's a VERY INEXPENSIVE way to get more HP from a naturally aspirated 454. The cost of a "bore notch" is only about $50-$75 per block and takes only about an hour or so to do. A guy could even do it himself---it just has to be done correctly. When dealing with the 454" block, speed shops may know what "bore notching" is, but they may not always know the extent of what bore notching can really do and therefore they don't really think it's that big of a deal, and thus don't offer it to the customer----when actually the bennefit is worth roughly 25hp/tq or so on the dyno. It may not sound like much, but it all adds up----not a bad value for the money spent! If you decide to have it done, take it to a machine shop/speed shop that BELIEVES in bore notching and actively does so and offers it to their customers. That way the chances of having the job done correctly are much better. This is NOT a process that is needed on every engine, but makes a nice increase in power on a 454" engine that I think is worth the time and money spent.

"Tinkerboater" had done this for guys around the area on their 454's and "JimV' offers it in his shop.

Dennis, you know, you are right about the synthetic oils being used in many of the everyday cars/trucks "grocery getters" with roller cams/lifters without problems. I didn't really think about that and have over looked that point. I always thought marine engines run under a harder load and more sustained RPM's---and they do, BUT I guess it (the engine) still doesn't know whether it is in a boat or a car---right? I think I have embarassed myself and get the dunce cap :o DANG!---what was I thinking??? And here I am giving guys advice. Take it ALL with a grain of salt gang!!! I think I'm going to go BURRY myself in my room for a while! Oh well, at least I have decided to use a synthetic in my roller cam equipt boat engines next spring. Therefore, I get to save a little face----not much, but a little anyway. ;)

KAAMA,
You're a little hard on your self aren't you?
Read a couple of FAMILY AND PERFORMANCE BOATING MAGAZINES and fergetaboutit!
Dennis

Well, that's just it Dennis! I already DO buy FAPB Magazines! I even have your book----the book you authored! I had to beat myself up a little! :p

Just make sure it's a yella dunce cap.:p To match them yella motors you got in that there bote.

Ok, now I am going to compile all the info you presented and then I will post the composite for everyones approval!:D

Hey Crazyhorse! You forgot to mention that my "bote" is yella too!

blown formula----looks like I'm going to become a martyr again. But you don't have to throw me into the lion's den----just open the gate and I'll walk in.

Ok, so here is the recipe per the thread:
assuming the engines have clean bores & pistons in spec=

454-420 base engines
hone cylinders or bore & repl pistons

Merc high rise manifolds
stock carbs...???
cam- Edlebrock torquer hydraulic roller 224-232
[email protected] .525-.550 lift
110-112 lobe sepearation (4" risers)
OR
cam-Comp Cams Extreme 4x4
223 int...234 exh .544 lift int/ .564 lift exh
111 lobe seperation
Springs- Torquer 2 ???

remove casting flashing on intakes (heads & intake), clean up the bowls, radius the turns, unshroud the valves (street port heads)

bore notch the cylinders
file to fit rings
Stainless Marine exhaust & thrull hulls 4"

Change ignition to Thunderbolt IV or V or aftermarket


does this cover it? Which cam would be best of the two?
I am after more all around use rather than absolute speed, but good usable 500hp (or more) would be nice if it is reliable!!

;)

blown,
i'm sure that cam would work well for you but that wasn't my recommendation. it was just an example and happens to be the one i use. that is the cam i like for my particular application because my boat is so heavy. there are lots of good cams to select from depending on your situation, what you will use the boat for like pulling skiiers or poker runs, rpm range, weight of the boat, etc.
my engines also came from the factory bore notched.

Blown Formula,

I don't know what your budget is for rebuilding your engines, but I would definately go with the hydraulic roller cams. Perhaps Dennis Moore can help make the suggestion on a hydraulic roller cam for you.

Also, if you really want a kick in the pants, once you get the heads off from those engines, send them to "JimV" and have the wedges installed!

The blocks/engines that come with the "factory bore notch" does help, but is still nothing like the extent of what can be done over and above the what the factory does. With the "factory bore notch" there is much more to be desired and is minimal at best. I've even seen this done from the factory on the old 396 blocks.

Ok, so I'll be the dummy here !!!

What are "wedges" & what function do they serve? :confused:

wedges are installed in the intake runner to decrease its volume and increase velocity.

Blown Formula,
I have a GM High Performance roller cam 224/234 @ .050 with .527 & .544 lift with 110LSA. This cam has about 40 hours on it and is in perfect condition.
I had it in my 502 but have since done a number of other mods to the engine and have swapped to a bigger cam .
This is one of the cams that Dennis Moore mentions in his book.
Infact, I have a buddy that installed the same cam in a 454 Magnum and it really woke it up!
The version of the cam that I have has the fuel pump lobe on it.
The cam is machined for a GenVI motor but is easily adapted to a Gen IV or V by using a retainer plate that your block is already machined for and utilizing a Gen VI timing set.
The cam is just sitting on the shelf with the box collecting dust. If you are interested I would take $75 plus shipping for it, and in fact I would throw in a GenVI timing set with about 20hrs on it for another $20.
E-mail if you are interested: [email protected]

Blown Formula,

I think you'd be doing well with that hydraulic roller cam you have listed in one of your previous posts and I think Dennis would probably agree that the 224*/232* on a 110* would work well for your application. Hydraulic roller cams/lifters are very reliable set-up these days. Usually, it's the solid/mechanical roller cams/lifters that have issues. These solids rollers require much higher spring pressures and thus are more apt to break springs and lifters and they require periodic valve adustment which can be a pain in the arse! But some guys like "Wette Vette", "26Scarab" and others believe the hassel is worth it because of the trade off in power. Solid rollers make excellent power, but at the expense of high maintenace and (some more than others and there's room for arguement on this) constant lifter and valve spring changes. Solid rollers are DEFINATELY NOT a turn-key set-up! Hydraulics rollers are MUCH easier on the valve train than solid rollers. Just thought I'd explain and straighten that out for you so that you might understand a little better. You'll be just fine with the hydraulic rollers. Just make sure that your spring pressures, installed heigth are set up and check for coil bind. This will have something to do with the lift of the cam you select. JimV can do this for you too if you have him do the head work----and he will work with your (or any) engine builder.

As far as your lifter bores go, (depending on the application) it's mostly the SBC (small block Chevy) that usually has lifter bore alignment issues and there is about a $400 machining and bushing process done to correct this. You most likely will not need this with the big block Chevy. The lifter bores should most likely be fine for the hydraulic roller lifters. Just have your machinist them checked out and have them flex honed.

BTW, Excaleagle42 did a good job of basically expaining in a "nut shell" how the wedges work.

TomR, I'm not interested in the cam, but is it a billet cast iron cam or a billet steel cam?

KAAMA,

I'm not sure, I think it's a steele cam because I had to run a "special Melonized" distributor gear with it, which I would include for anyone who would like to buy the cam.
It's a GM/ High performance cam.