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Message |
    
jason landon
New member
Username: jlandon
Post Number: 2
Registered: 09-2009
| | Posted on Wednesday, September 16, 2009 - 07:26 am: | 
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What is considered to be a normal operating speed (RPM) for 1978 Chrysler 318s I just went through my engines completely and I don’t want to be beating on them. I know it varies by boat my boat is a 31 pacemaker weight 12000 lbs. Thanks |
Fastjeff
Senior Member
Username: fastjeff
Post Number: 6780
Registered: 09-2003
| | Posted on Wednesday, September 16, 2009 - 10:17 am: |
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The book says 4,000 to 4,400 rpms. I limit mine (via props) to 3,900 and they are happy.
Jeff |
jason landon
New member
Username: jlandon
Post Number: 3
Registered: 09-2009
| | Posted on Wednesday, September 16, 2009 - 11:40 am: |
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Thanks jeff |
Robert A. Fierro
Advanced Member
Username: sandkicker
Post Number: 894
Registered: 06-2008
| | Posted on Thursday, September 17, 2009 - 12:16 pm: |
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A clarification on that.... The 4000 to 4400 is the RPMS that the engine should get at WOT with te correct prop and normal load. THAT IS NOT the rpms to use to for "cruise".
I had a chat with a Chrysler engineer in the early 90s when I re-engined my boat with a 220HP/318. Said he (paraphrased) Engine Life at WOT RPMS is measured in tens of hours. Engine life at 80% of max WOT rpms is in the low thousands of hours. At 75% of RPMS, 3000 to 5000 hrs (if fresh water cooled and well maintained)
is possible. |
Fastjeff
Senior Member
Username: fastjeff
Post Number: 6804
Registered: 09-2003
| | Posted on Thursday, September 17, 2009 - 01:39 pm: |
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Let's see now.....I run mine at 2,500 rpms so...
Good forever!
Jeff |
Conqueror
Advanced Member
Username: 300hb
Post Number: 130
Registered: 03-2008
| | Posted on Thursday, September 17, 2009 - 08:07 pm: |
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I better keep mine under 4500......  |
David J Kidd
Member
Username: scubadjk
Post Number: 34
Registered: 12-2008
| | Posted on Thursday, September 17, 2009 - 09:01 pm: |
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Sounds like you need more pitch in your prop, or your tranny is slipping? You can rev more then 4500 in gear? Geeeeeeeeeeeeeeees |
G. Harrington
Member
Username: bogdenz
Post Number: 53
Registered: 06-2009
| | Posted on Friday, September 18, 2009 - 12:04 pm: |
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In runabouts like Conqueror's (mine as well), 318's will often spin up to 4400-4500....albeit that peak power is a couple-hundred below that.
My boat is a 1-to-1 jet drive and tops out right around 44 mph.....backing up the tach's readings.
In automotive applications, the stock rotating assemblies in 318's are well known for being able to comfortably handle revs in the 6000 range (with modifications primarily to heads, cam and intake).
When I pulled the crank from my '70 318 the casting number indicates that it's from 68-72 high-performance 340 automotive engine....and the only forged steel crank that Chrysler ever made for the small-blocks. That said, the marine division was definitely using the most-rugged of components from the Chrysler parts bin. |
Robert A. Fierro
Advanced Member
Username: sandkicker
Post Number: 898
Registered: 06-2008
| | Posted on Friday, September 18, 2009 - 12:35 pm: |
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The reason I used a 318 to repower my last boat back in then was that it was the choice of almost all of the small commercial fisherman in my area who ran gas engines. Also my car had one at the time and it ran and ran and ran. Actually family had been running MOPARS exclusively since 1956 (sometimes owning 3 at once)and NEVER had anything other than starter/water pump issues, on any of the cars. Very high mileage on all of them. Was sorry I had to resort to MERC on my last repower. Not happy with their QC. |
Conqueror
Advanced Member
Username: 300hb
Post Number: 131
Registered: 03-2008
| | Posted on Friday, September 18, 2009 - 04:37 pm: |
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..."That said, the marine division was definitely using the most-rugged of components from the Chrysler parts bin"....
Boy I hope your right....lol!
Seriously...I have 300 drive which I think is 1.5:1 and would think I could get close to 60 mph with a 21 pitch but not even close so far. I was wondering though if HP has much to do with top end since your limited by your prop? |
G. Harrington
Member
Username: bogdenz
Post Number: 54
Registered: 06-2009
| | Posted on Friday, September 18, 2009 - 05:47 pm: |
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For 318-equiped boats like yours and mine (“speedboats”), the biggest top-speed hindrance, above-and-beyond props, impellers, etc., is the engine’s powerband and rpm range. The factory valvetrain in these motors (both automotive and marine) is super-conservative. With a duration of 198/199, the marine camshaft is about as mild as they get. While it’s great for the low-end torque needed to get the big boats on-plane, and keep them cruising in the sweet spot of the powerband, it leaves guys like you and I running out of usable HP/rpms shortly after the 4000 mark.
While drive ratios, props, etc. are all variables in top-speed, there aren’t a lot of 60+ mph boats that are doing so with a peak HP at 4200 rpm……..and if they are, the gearing required to do it would leave them coming out of the hole like a rowboat.
Short of getting a different engine, the way you’ll hit 60 will be with some head and camshaft adjustments. Depending on where you want your peak HP, you may sacrifice a little bit on the low-end. However, with our boats, there often isn’t a “low-end”…….we’re either “no wake speed” or WOT.
Attached is a link to the build-up of an automotive 318. It’s a pretty good tutorial on what it takes to pull HP and revs out of these engines. While our exhaust is going to be more restrictive than headers and you may or may not be able to run an aluminum intake, the rest of the engine is no different than what we’ve got. Even with the factory, cast iron 4-barrel intake…….375 hp at 6,000 rpms isn’t too shabby. You wouldn’t have a comfortable idle, and exhaust/water reversion is a concern....you'd find 60mph and then some!
http://www.hotrod.com/howto/113_0304_318_small_block_build/index.html |
Conqueror
Advanced Member
Username: 300hb
Post Number: 132
Registered: 03-2008
| | Posted on Monday, September 21, 2009 - 08:04 pm: |
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That explains it then...I read that the 308 heads are the least restrictive. I kicked around the idea of a Offy dual port but that won't help.
I almost had my hands on a 340 earlier this year and have even thought about building one up with a new short block. |
G. Harrington
Member
Username: bogdenz
Post Number: 56
Registered: 06-2009
| | Posted on Tuesday, September 22, 2009 - 10:17 am: |
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A lot of muscle car guys will simply bolt on a set of 340/360 heads onto the 318 but all that's good for is peak HP. It'll rob you of compression and intake velocity and, in turn, low-end power/torque. The best option is to port/polish and gasket-match (to 360 intake/exahust) the 318 heads and increase the valve size to that of the 340/360. Milling a little bit off the deck of the 318 head will also kick up your compression ratio a tad. This stuff will give you a noticable power increase even with the factory camshaft and intake. Many of the cast iron 4brl intakes are from 340/360's so, gasket matching the intake ports of the 318 heads alone will improve performance (because the manifold's runners are actually larger than the 318 head's intake ports....gutter into a garden hose so to speak).
I hear you re: the 340.....they were the best of the bunch when it came to the Chrysler small blocks. It had the same stroke as the 318 (which is more ideal for performance build-up and rpm potential than the 360's) and, obviously, larger bore.
I kind of recall that one of the Chrylser boats that David Kain featured on his website (Hurrikain.com) had a 340. Might be wrong though. |
Conqueror
Advanced Member
Username: 300hb
Post Number: 134
Registered: 03-2008
| | Posted on Tuesday, September 22, 2009 - 04:27 pm: |
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I'm looking for a different intake to replace the Performer on it now. Something that will allow me to run the plumbing like it was meant too.
The early 70's boats did in fact come with 340's, right up until '74. They called them the Super Bee III. They had the 'bee' decal right off the Coronets on the the flame arrestor. They were replace by the 360 just like the cars. One thing I've noticed though, is just about every Chryler marine intake is a single plane right to about the time they started useing Q-jets. |
G. Harrington
Member
Username: bogdenz
Post Number: 58
Registered: 06-2009
| | Posted on Tuesday, September 22, 2009 - 07:39 pm: |
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What about the performer is Preventing you from running stock plumbing set up?
If you can fit an RPM Air Gap (or Professional Products knock-off version) under your engine cover, it's a great manifold for performance boats (assuming you're fresh water since you're already running a Performer). The air gap would, however, require the aforementioned gasket-matching on the heads.
You're right about the single plane. My '70 is a single. Low-rise single plane is a little odd. A dual plane is a better fit for the 318.
I've got a set of good-condition heads from my original 318 (which I'd replaced with a long block). I'm thinking about having some of that work done over the winter.....giving me the option of bolting them on with an air gap in the future. |
Conqueror
Advanced Member
Username: 300hb
Post Number: 135
Registered: 03-2008
| | Posted on Thursday, September 24, 2009 - 09:43 pm: |
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It's just odd the way the thermostat housing is angled so you need a few extra elbows. I run raw water but never run in salt.
I assumed they stuck with the single plane for a flatter power band or more power since they are square bore and didn't have a need to change until the spread bore Q-jets became the standard carb. It's funny they never used the Thermoquad on them, probably because that plastic body wouldn't meet regs.
I'll look into the air gap....Did you consider a 360 when you replaced the motor? |
Fastjeff
Senior Member
Username: fastjeff
Post Number: 6823
Registered: 09-2003
| | Posted on Friday, September 25, 2009 - 06:39 am: |
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On those 318/ 360 marine engine heads...
The exhaust ports are the same tiny ones used on the original 273 cube V-8. (I use gaskets from that motor. Car-type 318/ 360 exhaust manifold gaskets are WAY larger in opening size and don't work.) The valve sizes are also tiny compared to car-type heads, though the intake ports look the same. Also, from wehat I've seen, the 318/ 360 marine heads are identical.
My conclusion? The 273 V-8 heads were used on the 318/ 360 motors to improve mid-range torque. Bolt on some 340 or later car-type 360 heads and an automotive cam and I'll bet one could pick up 50 hp!
Jeff |
Buehler Jet
Member
Username: bogdenz
Post Number: 63
Registered: 06-2009
| | Posted on Friday, September 25, 2009 - 10:58 am: |
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Here’s the scoop on heads....when Chrysler kicked the 273 up to 318, they didn’t change the heads. The general specs (port size, runner size, valve size and chamber volumes) are the exact same. In other words, there’s no distinction between 273 and 318 heads. The first major changes that Chrysler made to the 318 heads were in the early/mid 80’s. In 85-86, they introduced the swirl port head (302 casting) which they referred to as the “fast burn” head. In 83-86, they also had a “police” head that contained 360 size valves.
All of the marine components (sans exhaust manifolds of course) are automotive castings. The heads I pulled from my ’70 318 have the same valve size, etc. as the automotive heads. The only difference that I suspect/assume is that the valve springs are slightly different as the cam is specific to marine/RV applications. If you were to call a company like First Mate marine engines (which I did), and ask them to give you the casting numbers used in assembly, they’ll be straight-up automotive numbers/specs. I have found that, early 80’s “225’s” actually had slightly LARGER valves than their automotive versions….potentially stemming from the development of the aforementioned fast burn and police heads of the time.
Also while the 273/318 heads appear to be the same as the 360 heads, they are significantly different. The 360 heads have much larger ports, runners, valves and chamber volume. If you were to put 318 heads on a 360, it would suffocate. In addition the smaller chamber volume of the 318 heads would kick the 360’s compression ratio way up (probably into the 10’s). This is the opposite of the problem people have with putting 360 heads on a 318…..the larger ports/runners lower intake/exhaust velocity and the larger chamber volume lowers compression.
The gaskets are tricky because of some of the mix-matching that went into the marine engines (via the Chrysler automotive parts bin). Chrysler only made one-size-fits-all exhaust manifolds for the marine engine……which may be why you notice the difference when it comes to that particular gasket. |
Conqueror
Advanced Member
Username: 300hb
Post Number: 136
Registered: 03-2008
| | Posted on Friday, September 25, 2009 - 12:42 pm: |
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I think the 'police' head is the 308 I read about.
I have been trying to learn what Chrysler head would work for me for awhile now because if you go to a high performance head like a Edelbrock Performer you get into the HP vs Torque tug-o-war.
I thought I found my answer with a Magnum engine but how would you hook up your water pumps? I assume they have a reverse water pump because of the serpentine belt but never looked into it. |
Buehler Jet
Member
Username: bogdenz
Post Number: 64
Registered: 06-2009
| | Posted on Friday, September 25, 2009 - 02:14 pm: |
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The police heads were a 345 casting number. It may be the 302 swirl-ports that you read about. They're the most popular heads to modify for the 318's.
You're right on about the Edelbrocks. Their small-block mopar heads are really an aluminum version of the 340/360 heads (with even larger valves). Like the stock 340/360 heads, they'd kill our intake velocity and compression.
You could have your existing head's modified and pick up 30+ hp for sure. However, unless you're willing to take on some of the grinding yourself, it's going to be expensive (anywhere from $500-1,000 at a good race/maching shop).
If you're really interested in going that route, the link below is a decent option. The company is called Aerohead Racing. They sell fully-remanufactured heads with some performance upgrades. Their 318 heads are, basically, the "police" head (they have 360 valve sizes). They sell them for $399 for a complete pair (valves and springs incl). I asked them how much it would be to do some extra porting (like gasket-matching the intake runners to fit an RPM Air Gap intake) as well as milling the head for a slight compression ratio increase. They quoted another $250 for that labor and $88 for shipping. While it's a decent chunk of change, at the end of the day, that $740 may be cheaper than bringing your existing heads to a machine shop. And, where these guys are "remanufactures" (vs. just a machine shop), their process, and subsequent results, may have more integrity.
http://www.aeroheadracing.com/id6.html |
Fastjeff
Senior Member
Username: fastjeff
Post Number: 6834
Registered: 09-2003
| | Posted on Friday, September 25, 2009 - 05:41 pm: |
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My 1985 Chrysler 360 heads have the same, tiny exhaust ports as did the old 273 V-8. The valves are also relatively small (though I don't recall the actual sizes). AUTOMOTIVE 360s have better breathing heads than the MARINE 360s. Let's not confuse the two.
Jeff |
Buehler Jet
Member
Username: bogdenz
Post Number: 65
Registered: 06-2009
| | Posted on Friday, September 25, 2009 - 06:38 pm: |
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I hate to got to battle with you on this one Jeff, but there is no confusing the auto vs. marine becuase they are one in the same. Note, as an example, the link below (First Mate remanufactured MARINE heads). Scroll down to the 318's and 360's and note the casting number differences between the two. If you then go then go to a 360 automotive casting ref (online, manual, etc.), you'll see that every one of those "marine" castings numbers is the same as the automotive castings.
The 318 and 360 heads LOOK almost identical...but they're not.
http://www.marineengineparts.com/shopsite_sc/store/html/page30.html |
Fastjeff
Senior Member
Username: fastjeff
Post Number: 6837
Registered: 09-2003
| | Posted on Saturday, September 26, 2009 - 06:31 am: |
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You're making the same mistake I made on Merc 18 vs Merc 25 hp outboards. Both power heads have the same displacement, but one motor is 7 hp different. Trying to research why, I did a part number comparison: both blocks have the SAME part number! Whoopee, I concluded, it's in the carb (or whatever). Not so. The REPLACEMENT blocks are the same, that's all. (Merc chose to make only one type to lower stocking overhead.)
And that's the case here as well. Note the wording: "Fits Chrysler LM-360 Engines with casting #'s 051, 596, 974, 587, 475, 805, 830, 496, 230, and 915..." It does not say IDENTICAL to normal marine heads. Also, I can assure you (as a long time hot rodder) that I measured the 318 and 360 MARINE heads when I had them, and the valve sizes and tiny exhaust ports were identical.
One final point: Using "normal" 318/ 360 exhaust manifold gaskets on marine heads results in an exhaust leak. (Don't ask!) Likewise, using my beloved 273 V-8 gaskets on STREET 318/ 360 heads would probably do the same. (Never tried it, though.) That alone says something about the two types of heads. Interestingly, the OSCO manifolds have giant ports that would match up with the street heads.
Jeff |
