Truck, Car or Marine Motor Differences

[alldodge]

So not to hijack a thread I'm starting this one for some discussion on the topic. There are thousands of threads here and other places which keep saying use a truck engine instead of a car. This topic is not about the gaskets, core plugs or any exterior components.

The end point (as I took it) in the other thread was the SBC long block is the same SBC long block that has been used in any and all Boat, Car and Trucks. There does not concern the gaskets or core plugs. I still believe the cam would be the same for Truck and Boat, but different for a Car.

I think we can all agree that Merc does not build the standard BBC or SBC motors, they come direct from GM.

http://www.boatfix.com/how/marineeng.html

 

[Bondo]

My thought was if its a car cam and not a truck type the torque would come on higher in the rpm range. Boats need low end torque to get them up. Hope Bondo is correct

Ayuh,.... My thoughts are,......

That motor is the basic run of the mill factory standard replacement motor for a direct replacement of the run of the mill 350 that was originally installed in millions of standard run of the mill pickups, sedans, wagons, etc from Chevy, 'n the rest of the GM's that ran the Chevy motor,....
Also the same motor that's been powerin' boats since the SBC came to be, in the standard run of the mill Oem installations by various Marine power convertors, ei: Merc, Omc, Volvo, Crusader, etc,.....

The automotive cam, Vs: truck, RV, marine cam is as usual an overblown internet wife's tale,....
It should be a discussion 'bout Hot Rod cams, Vs: standard auto/ pickup/ truck/ RV/ marine cams,....

That motor should be a dependable replacement 260 hp V8, as much as a 10 hp B/S replacement motor is for a 10 hp B/S Oem motor,...

That's a C&P from the thread that prompted you to start this thread, which I'm gonna move to the I/O general forum,.....

 

[alldodge]

What I'm finding still leans me toward the older thoughts. Going to be doing some more looking but seam to remember that there were different HP ratings for the same cubic inch motor and the only difference was the vehicle it was installed. Has there been anything found which caused you to change your mind in this area?

 

[muc]

I've only torn down a couple of 350 Chev truck engines, but I have torn down quite a few boat engines.
The 2 truck engines didn't have a windage tray, but all the boat engines did.
So I have always wondered, do car and truck engines normally have a windage tray?
As far as cams, the machine shop I mostly used for 30 years told me the cams are different. But they also ground cams as part of their business. He did call me once on a rebuild job and told me the 454 I had dropped off had a auto cam and asked me to get an OK from the customer for a extra $30 to regrind it.

 

[Scott Danforth]

Windiage trays are oil pan dependant. Most sbc car installations have a small oil pan to clear crossmembers and steering as well as a shallow pan for ground clearance. High performance applications normally have a windiage tray. Truck pans are a bit larger, and the heavy duty (3/4 ton and larger) often have a windiage tray along with oil coolers.

Marine motors come out of the GM industrial parts bin. The marine motors have the industrial oil pan and windiage tray. The same oil pan is on trash pump motors, genset motors, natural gas motors as well as the marine motors.

Marine motor cams are determined by PCM, Ilmor, Indmar, Volvo and Mercruiser and are specific to each. Mercury racing cams are installed at the high performance division and had been supplied by Crane

Volvo, PCM, Ilmore and Indmar received the motors as a longblock less the intake. Mercruiser received the motors complete, and piecemealed the performance motors

Today, Mercruiser is making their own block and head castings.

Standard automotive cams have too tight of a lobe separation for marine use with wet exhaust That lobe separation is increased on high torque applications (truck and rv) and even wider lobe separation for marine applications.

Take the BBC marine motor for example. A gen 6 motor had 290hp in truck configuration, and 310hp and 330hp with the same block and heads in a marine application (different cam). Install rectangular port heads and its rated at 385hp. Install forged pistons and a higher duration can and its 420hp. Bump the compression a point, a further bump in duration and lift and you have 465hp

The 350 cubic inch small block for 1996 had 260hp to 330hp in marine trim, 260hp to 330hp in automotive trim, and 215hp-255hp in truck trim. Induction and cam along with compression ratio changes are what differ.

generally, most I/O boat applications can be replaced with a truck longblock without more than a head gasket and core plug change. Car motors can be used, however the cam should be changed. However the best is a marine specific coctail of parts with regards to combustion chamber, valve size, compression ratio, cam lift and duration and oil pan

Marine motors are rated at the prop these days meaning the flywheel rating will be about 30hp higher.

Fuel systems, ignition systems and exhaust systems are the biggest difference between marine and automotive

 

[Baylinerchuck]

Great information. Very educational to say the least.

 

[Fun Times]

Just sharing some basic info from GM regarding marinized engines I had run across in the past,

Marine Engine Introduction - GM Powertrain Torino

GM Marine Engines | GM Powertrain Marine

 

[HT32BSX115]

The automotive cam, Vs: truck, RV, marine cam is as usual an overblown internet wife's tale,....
It should be a discussion 'bout Hot Rod cams, Vs: standard auto/ pickup/ truck/ RV/ marine cams,....

I agree that my last comment on this should have really been a hotrod "thang" regarding reversion.

But didn't GM (in OEM installations) use a different cam in SBC 305/350 powered cars vs pickup trucks and vans etc that might be used for towing?

 

[Scott Danforth]

yes they did.

the F-body cars received different cams than the B-body cars which received different cams than the trucks. they also have different heads in some applications within the same year as well as different pistons.

 

[mr300z87]

Hi all, I find this topic interesting and wanted to add to this my recent experience that basically confirms what is said above. I am currently working on replacing the 5.7L 260 HP QJet 4 barrel 1988/89 engine in my Invader, I have documentation confirming that this is the OE engine installed in my boat. When searching the head casting #s on the internet, they come up as the same # as an 1987-1989 5.7 IROC Camaro. If my aging memory serves me correctly the 5.7L IROC/Z28 engine was rated at like 230ish HP with FI and that was a hot rod back then. The block's casting lists as an 1988-1995 5.7L. I recently purchased a (I was told running) TB injected 5.7L engine from a 1994/95 1500 series truck and it carries the same block casting number as the MerCruiser 5.7L being replaced. Do not know the head casting #s yet since I have not pulled valve covers. My plan is to swap all the MerCruiser specific hard was including the cam and windage tray. I would guess the 454/7.4L MerCruiser engine also shares most if it's long block components with their truck variant.

One question that keep coming up n my mind is did MerCruiser/Volvo/Crusader/other marinizers spec their own cams and pistons or did GM use off the self hardware and let MerCrusier and others market replacement parts at a elevated marine price.

 

[alldodge]

Talking from days of sort of old, not the last 10 or so years in motors. I really do see how the marine industry needs enough motors to change the way motors are manufactured. No matter how many they have use, its just a drop in the bucket so far as numbers. The SBC world produces so many that I have found only two variants, car and truck. Do find where Merc has engines produced with their spec cam, but the standard run of the mill is still the standard run of the mill truck long block.

Unable to say with certainty but have not found a 454 produced with 502 heads other then the marine industry. Doing this needs a cam change and install 502 heads on a 454 block. Bore of 502 is 4.466 and 454 is 4.250

I'm still listening for others which could show the old assumptions to be incorrect, but so far old is still good from where I read

 

[Scott Danforth]

AD, the 502 simply comes with rectangular port heads. these were the standard Hi Po offerings for the 454 in years back. GM realized the 454 works best with the smaller oval ports in most towing applications as they quit putting 454's in cars in 1974 (first few months of 1975 model year production of the chevelle to be exact), however they quit bore notching the 454 like they did in the mid 70's as trucks received smaller valves in the oval port heads because the RPM range was much lower

the rectangular port heads on the 454 really do not start to shine until you get the RPM over 5000 RPM and into the 7 or 8k range (much higher than the marine world uses in cruisers). they work better on larger displacement motors. the large oval ports work well on the 454 up to about 6500 RPM where their smaller port advantage drops off as port velocities max out, however really shine in the mid-range RPM where the oval port velocities significantly help cylinder filling. using rectangular port heads on a 454 would require a cam change to make use of the heads flow characteristics. this cam would have an operating range of 2500-7500 or so. it also will benefit from bore notching to unshroud the valves a typical oval port head has an intake plenum volume of about 270cc a typical rectangular port head has an intake plenum volume of about 310cc

the rectangular port heads have been around since the big block "mystery motor" of 1963. todays "088" 502 heads can trace their lineage back to the famed "LS6" big block of 1969 for its port shape and combustion chamber. casing changes were made along the way for steam hole relocation, etc.

the plethora of cylinder heads available for the big block is staggering. then again, the mr potato head small block has a large number as well. Mr300z87 was discussing his tracing of casting numbers on his 1988 mercruiser motor. in 1988, GM had about 15 active head casting numbers for the small block ranging from 52cc heads (305 cubic inch) up to 76cc heads (truck 350 cubic inch) and valve sizes all over the map. the marine world received 3 different 64cc casting numbers alone. Volvo used a different casting number (police / hi-po crate) than Mercruiser (Iroc Z). the difference is slight variation in intake plenum, and both using the same casting for the 305

one of my go-to engine casting number sites http://www.mortec.com/castnum.htm and this doesnt include the aftermarket world of Dart, Merlin, AFR, etc.

 

[alldodge]

My Merc 502 head comment comes from taking a few 454 MPI motors apart. The head casting number on the heads are the same ones used on the 502. I know your correct I'm just matching casting numbers. Do see some rectangular port aluminum and some LS heads, so my bad

 

[Scott Danforth]

The non-performance marine 502's came with two different rectangular port heads. the 14097088 from 1991 up and the 12562934 from 2000 up. the 12562934 is a "marine only" head were the 14097088 came on genset motors, trash pump motors, crate motors and marine motors (but not the truck motors) Truck motors were year dependent and received 14081045 from 1978 - 1990, 10114156 from 1991-1995 (Gen V peanut port ) and 10141279 from 1996-2000 (small oval, closed chamber Gen 6 L29 vortec combustion chamber).

the Mercury Racing 502's came with Edelbroch aluminum heads for a while then GM performance aluminum heads when available

the 088 heads are the gen V version of the Mark IV 14096188. the difference being the steam holes. since GM intended the 454 truck motors to all be oval ports, the 088 heads were the first BBC heads to get the differentiation of 502 only, yet they can be ordered on the 454.

I believe the 12562934 marine head is the 088 head with the 188 steam holes to make it Mk IV/ Gen V / Gen IV compatible, however as of today, I can not confirm.

the 8.1 liter was used by GM from 2001 to 2008. (Gen VII BBC) Mercruiser decided to build a detuned version of the 525 (502 GM performance block) to fill the 425hp slot and volvo had 3 years worth of inventory of the 8.1's prior to switching to the LS motors for the 425hp slot.

most of my information on casting numbers comes from my recent research for my BBC build that I have bookmarked

 

[alldodge]

Most cases I use Mortec to get my numbers. Still have a 454 MPI in a Merc shipping crate in the barn. We pulled it apart after it spun a bearing. One of these days we'll get it rebuilt if something is found to put it in

 

[Scott Danforth]

Most cases I use Mortec to get my numbers. Still have a 454 MPI in a Merc shipping crate in the barn. We pulled it apart after it spun a bearing. One of these days we'll get it rebuilt if something is found to put it in

Your seadoo doesn't have a bbc......yet

 

[GA_Boater]

Your seadoo doesn't have a bbc......yet

A hold my beer moment for sure!

 

[alldodge]

Your seadoo doesn't have a bbc......yet

A hold my beer moment for sure!

Things that make you wonder

 

[Scott Danforth]

I would even help with a custom adapter

 

[GA_Boater]

We need a build thread with a lotta pitchers.