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| Increasing 318 power- most simple sol... |
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Scott Fuller
New member
Username: roto
Post Number: 2
Registered: 07-2009
| | Posted on Tuesday, November 03, 2009 - 07:53 pm: | 
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Hi from Sydney. I have a 225hp 318 SeaBee e and find the power is not enough. I have read if I replace the heads I will get an improvement... is this so? What specifically do I ask for? I am after the most simple solution please. Head Gaskets? Also where do I source a new intake manifold as mine has seen better days.
regards,
Scott. |
Buehler Jet
Member
Username: bogdenz
Post Number: 97
Registered: 06-2009
| | Posted on Tuesday, November 03, 2009 - 09:13 pm: |
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Greetings Scott.
It's true that the power potential of the 318 is in the heads. Unfortunately, head modification or replacement may not be as simple as what you're hoping for.
In the Mopar automotive world, many people will bolt 340/360 heads onto 318...for the larger intake/exhaust runners and valves. However, given that they're designed for larger displacement motors, they also come with larger combustion chabers....which will lower the already-low compression ratio of the 318. Overcoming this problem requires significant milling of the head to reduce combustion chamber volume and, in turn, get the compression ratio up to a performance level. Even with doing that, some would argue that the large runners and valves will reduce intake velocity unless you're operating in very high rpm ranges....subsequently hurting low-end hp/tq.
The second head option is to port and polish the 318 heads. While a do-it-yourselfer can take on this task with the right tools and instruction, you really need to know what you're doing....as you're removing decent amounts of metal and thinning areas around water passages, etc. If you're going to pay someone to do this work (with full valve job, etc.), you may find that it makes more financial sense to buy a bigger engine (unfortunately, that's not a joke).
Regarding your question about intake manifolds....almost all performance manifolds (Edelbrock, etc.) are designed to marry up to 340/360 heads. The smaller intake ports on the 318 will need to be "gasket matched" to the 340/360 size to properly take advantage of such a manifold. In addition, if you're in salt water, you're best to stay away from aluminum manifolds. The factory cast iron factory manifold is actually pretty good.
It's worth adding that other factors are going to contribute to how much power you really unlock with head modifications. One of the best qualities of the 318 is it's ability to comfortably rev up into the 6,000 rpm range....and that's where the big horsepower gains will be found. Finding that rpm range will require camshaft changes and, the type of cam required is not going to work in a prop-driven boat (vs. a jet). You'll sacrifice idle quality and the low-end power needed to get you on plane.
I know that's a long-winded response to someone looking for a simple answer....but it's to demonstrate that it's actually pretty complex.
At the end of the day, unless you have the engine-building skills or resources, you'll probably discover that upgrading to a 360 long-block is cheaper and more reliable than modifying a 318. |
Fastjeff
Senior Member
Username: fastjeff
Post Number: 7079
Registered: 09-2003
| | Posted on Wednesday, November 04, 2009 - 06:15 am: |
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In my old drag racing hop up days, we used to put larger valves in. That's the easiest way to get more power out of restrictive heads.
A modern intake with a nice 4 barrel will also help but, as stated above, a 360 would be your best choice.
Jeff |
Buehler Jet
Member
Username: bogdenz
Post Number: 98
Registered: 06-2009
| | Posted on Wednesday, November 04, 2009 - 09:27 am: |
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Is your Seabee a jet drive? |
Scott Fuller
New member
Username: roto
Post Number: 3
Registered: 07-2009
| | Posted on Thursday, November 05, 2009 - 01:38 am: |
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Hi All.... I will stay with the 225 hp. Its a sterndrive. Photo attatched. Has electronic ignition.
So my questions are: what do I ask for and where do I find a replacemetn intake manifold.. it has a Carter AFB 4 bbl carby on top. And any tricks for timing the engine. I know 5 degrees BTC.
Finally what symptoms would a bad coil cause and how do you measure primary and secondary resistance? 9I can only rev to about 3000 max.
Thanks,
Scott.
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Fastjeff
Senior Member
Username: fastjeff
Post Number: 7083
Registered: 09-2003
| | Posted on Thursday, November 05, 2009 - 06:47 am: |
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Seeing you have fresh water cooling, then any good aluminum intake can be used--I'd recommend a racing street setup since it's designed for max power at lower revs. Top that with a 750 Edelbrock MARINE carby and you'll be golden.
Why not just toss out the coil? And if you do, be sure to get the right one: If there's a ballast resistor in the system, then you need a coil designed to go with an "external resistor". If not, you'll need a full 12 volt coil.
Jeff |
Freshwater Fred
Advanced Member
Username: fred70
Post Number: 199
Registered: 01-2009
| | Posted on Thursday, November 05, 2009 - 07:42 am: |
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Hey Jeff,
Scott is at the "I can only rev to about 3000 max." + he's only been a member for 4 months, (no offense Scott).
You need to (at least) run him thru the dist. advance mech. first, 3k isn't right.
I thinking any 225hp 318 should turn up 4200 - 4500 rpm in a plaining hull boat , if it still has the factory setup. (I'm not familiar with a "SeaBee" but from the pic , it doesn't look that big). What kind of speeds are you getting?
Scott, how long av you had the boat? Has the boat ever turned up a decent rpm at wide open throttle?
I think we need to run him thru some of the basics before we help him start spending his money.
Fred 156-M |
Scott Fuller
Member
Username: roto
Post Number: 4
Registered: 07-2009
| | Posted on Thursday, November 05, 2009 - 09:21 am: |
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Thank you everyone. I have owned the boat 12 years. It has not had enough use these past 4 years. Hoverever about 7 years ago it could get top 4000RPM and 30 knots. Perfromance has declined since then.
I am now doing it up again to use as my fishing boat. Its a 24' flybridge.
I am in the process of putting on new manifolds and risers next week, the intake manifold has seen better days and is rusting out around the port and starboard sides of the carby... so its time to replace it.
280 volvo stern drive has been serviced.. original leg was chrysler 300, but swapped it out 10 years ago cutting the Chrysler bell housing in half and welding on the rear end of Volvo bell housing. Works just great. It was interesting to see the engineers do this, especially welding hte Chrysler and Volvo shafts together to make it all work.
I've had the carby serviced just recently. Boat being antifouled next week. Propeller diameter being cut down 2" this week (it was a 15 x 15 Volvo clover leaf and I reckon always to big. I have tried many diffrent props over the years and most recently a 4 blade 15 x 15, but still on 3000 and boat sluggish.
All new fuel in tanks with octane boost additive and lead substitute.
So next critical task is to work out why RPMs are not going over 3000 under load. Freely revs quickly to 4000+ in neutral, so dont think its the fuel pump. I understand about freeing up the distributor by rocking the rotor and will do this on the weekend. I'll also get a standard timing light over the weekend and check for the 5 degrees and make sure that it advances as the power is applied... looking for a metered timing light at present. Timing plate next to harmonic balancer in good condition. I'll get a new coil (with ballast resistor). Spark plugs are newish. Reluctor distance has beens set. New rotor installed.
So timing and intake manifold and my next issues.. I'm in Sydney so genuine intake manifold may be hard to come by. Will any car one work with my Carter AFB? Due to cost I'll keep the Carter AFB.
Regards,
Scott.
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Buehler Jet
Member
Username: bogdenz
Post Number: 99
Registered: 06-2009
| | Posted on Thursday, November 05, 2009 - 11:04 am: |
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Hi again Scott – speaking only from a knowledge of what’s available to us in the states, the only aftermarket automotive intake manifold that will work properly on your 318 is an Edelbrock Performer (model 2176). The name’s a little deceiving because it’s really not much of a “performer”…..it’s more of an aluminum replacement for a factory 4-barrell manifold. It’s a dual plane so, if you currently have one of the single planes that came on marine 318’s, you may notice a little improvement in low-end responsiveness.
Unfortunately, the best performance manifolds (Edelbrock RPM Air Gap, Professional Products Crosswind and Mopar Performance M1) are all designed to marry up with the larger intake ports of 340 and 360 cylinder heads. While they’ll bolt right up to a 318, performance will be very poor…..as intake velocity will be disrupted/obstructed in the transition from larger manifold ports to the smaller cylinder head ports. So, unless you're going to change or modify your heads, stay away from these models.
There are plenty of Performer intakes on ebay but, considering the fairly reasonable cost of a brand new one, you may have better luck seeing if some of the larger online retailers (JEGS or Summit Racing) offer good international shipping rates. A quick tip if you do go this route……hold off on stripping down or tossing your existing intake until the new one arrives. It’ll serve as a good reference for how the cooling connections need to be set up on the new manifold. The raw-water cooled marine set up will require plugging of some water passages. In addition, I believe that the Edelbrock Performer reuses the splash guard from the factory manifold (something you don’t want to omit).
Regarding your overall performance, I agree with Fred....I think I'd start by focusing on some general "tune up" items before trying to get back to stock-level output via performance modifications. Get it as close to factory performance specs as possible and, if still desired, modify from there. |
Ricardo E.
Advanced Member
Username: ricardomarine_vp
Post Number: 742
Registered: 03-2009
| | Posted on Thursday, November 05, 2009 - 11:30 am: |
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Scott, this is a Volvo Penta I/O, correct (Chrysler name on the V/P drive)?
Some people under-estimate the Duo Prop performance gain!
The Duo Prop lower unit will do as much or more than if you were to install the 360 engine, IMO.
All lower units within the range that you may have (250/270 or later) will adapt with the correct shimming being performed.
The ratio that your engine will require would be the 1.95:1.
Select props using the WOT RPM testing just as you would for a single prop drive.
If doing exhaust mans, consider going to a center rise type manifold.
Also, timing is critical for top performance. Setting BASE alone often will not cut the mustard. You need to also check and make sure that TA (total advance) is correct for your engine. You may gain a tremendous amount of performance if this has been OFF!
(see your OEM specs for this, and tune accordingly)
. |
Freshwater Fred
Advanced Member
Username: fred70
Post Number: 201
Registered: 01-2009
| | Posted on Thursday, November 05, 2009 - 12:12 pm: |
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Search Jeff's back posts for stuff on freeing up the advance mechinisums in the distributers. make sure your getting distributer advance.
there's a whole lot of them. Jeff goes over it time, & time again, and after people swear theirs are right,,,, suddenly they see the light & it cures their problems...!!!
Its not the boat that you have but,,
1976 24 foot AMF Slick
195 HP (318 2-bbl) 1200 hrs
Chrysler 300 out drive (1.75 : 1)
16 X 16 wheel, 36 mph WOT @ 4,800 rpm
or
14 X 21 wheel, 36 mph, WOT @ 4,400 rpm
26 - 28 mph, @ 3,800 rpm
you shouldn't be that far behind.
Fred 156-M |
Buehler Jet
Member
Username: bogdenz
Post Number: 100
Registered: 06-2009
| | Posted on Thursday, November 05, 2009 - 01:06 pm: |
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That's a nice top speed for 195hp in a 24' cuddy. Goes to show how so much lies in the setup. |
Scott Fuller
Member
Username: roto
Post Number: 5
Registered: 07-2009
| | Posted on Thursday, November 05, 2009 - 04:32 pm: |
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Thanks again everyone... I have found the Edelbrock 2176 intake manifold on ebay... perfect and in my budget.
Question 1... on the starboard side of the Carter AFB is a thermocoupling device that opens the choke as the engine warms. Its like a small vertical rod that goes into the intake manifold. As the device expands within the intake manifold due to heat it pulls on the choke linkage. Will it work on the 2176?
Question 2.... The sales pitch for the 2176 say not to use it in salt water. My boat is used in Sydney Harbour (salt water) and the engine is FRESH water cooled so this should not be an issue with the aluminium 2176???? I presume the header tank will bolt on.
Obtaining the timing light today and getting ready to twiddle the distributor.
Best, Scott. |
Buehler Jet
Advanced Member
Username: bogdenz
Post Number: 101
Registered: 06-2009
| | Posted on Thursday, November 05, 2009 - 05:20 pm: |
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I don’t think that the Edelbrock is compatible with the mechanical choke. You can, however, buy an inexpensive kit to convert your choke to electric. You may be able to search this forum or post a question on this subject (or simply search the web for “carter electric choke conversions”).
I’d suggest giving Edelbrock’s tech line a call. You can find the number on their website and, in general, their techs are very knowledgeable/helpful. Tell them what you’ve got and what you’re doing and they’ll point you in the right direction. Might be worth the cost of the long-distance call!
Regarding the salt water……you’re okay as long as your fresh water cooled. The outside of the manifold may oxidize more quickly from the salt air. Many people paint aluminum manifolds to make them look like factory equipment…..so that’s an option to protect against oxidation. Not too sure about the header tank. Again, best to wait to break down the old one until you have the new one in-hand for comparison.
PS, careful with those plastic fuel filters mounted in such close proximity to the engine. Plastic melts a lot easier than steel. |
Dan Finnelly
Member
Username: tolly_family
Post Number: 87
Registered: 07-2006
| | Posted on Thursday, November 05, 2009 - 05:37 pm: |
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Replacing the intake is not going to give you your RPM back. Rebuild the dist first. I helped a friend on a 26 Tollycraft yesterday who could only get 3300 RPM and after a new dist was installed it turned 4800. |
Scott Fuller
Member
Username: roto
Post Number: 6
Registered: 07-2009
| | Posted on Thursday, November 05, 2009 - 05:45 pm: |
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Hi All,
Metal fuel filter is installed... photo is 5 years old.
Also the old cast iron intake manifold is flaking iron peices around the port and starboard side of the carby and will need to be replaced int he near future, but not next week.
Scott. |
Conqueror
Advanced Member
Username: 300hb
Post Number: 143
Registered: 03-2008
| | Posted on Thursday, November 05, 2009 - 08:15 pm: |
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You can also consider the Weiand intake. They have 2 models #8007 & #8022. They were re-designed for Holley by the original designer of the Edelbrock however what's a little more user friendly is the thermostat housing is like your stock manifold were the Edelbrock is on an angle meaning you'll have to add elbows to get your water lines to line up.
If your not in a big hurry stock manifolds pop up on ebay too. |
Scott Fuller
Member
Username: roto
Post Number: 7
Registered: 07-2009
| | Posted on Monday, November 09, 2009 - 12:33 am: |
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OK. I purchased a new replacement distributor from Chicago on Friday night and it walked into my house in Sydney today Monday. Amazing. So I will install this later in the week. Boat is being hauled out on Friday.
New distributor is:
"YLM Series Magnetic Breakerless Electronic Distributors
CHRYSLER V8/LH 273, 318 (67 and up), 340 and 360 “LA” Engines YL579AV MI 9-26305"
It does away with the ECU and the balast resistor.
On Friday I also did a timing light check with the old distributor... photo A shows timing at 500rpm. Photo B at 2500 and 3000 RPM is in following post.. The problem is there are no marks on the timing plate so I dont know what is correct. Where should 5 degrees be? Timing did advance when throttle was applied.
Regards,
scott.
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Scott Fuller
Member
Username: roto
Post Number: 8
Registered: 07-2009
| | Posted on Monday, November 09, 2009 - 12:35 am: |
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Photo of timing at 2500 and 3000 RPM.
Regards,
scott.
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Fastjeff
Senior Member
Username: fastjeff
Post Number: 7102
Registered: 09-2003
| | Posted on Monday, November 09, 2009 - 06:08 am: |
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Fabulous photography! It looks like it's getting about enough advance, but I guy smart as you are (see photos!) can make sure by degreeing the pulley.
Measure its diameter, multiply that number by 3.14 and divide that figure by 360. That will give you the length around the pulley for one degree. Mark the pulley and fire it up!
Jeff |
Ricardo E.
Advanced Member
Username: ricardomarine_vp
Post Number: 761
Registered: 03-2009
| | Posted on Monday, November 09, 2009 - 07:32 am: |
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Scott, great choice on an ignition distributor. The YLM series (VR Magnetic) is one of my favored choices where mechanical advance is desired.
Looks like you will need to positively locate TDC and also mark off your balancer in order to set/check TA.
IMO, there is no need to mark the entire perimeter of the "Balancer" unless you plan to use this for setting cam followers or checking cam specs, for example.
If you know the diameter, you can purchase a Mr. Gasket self adhesive decal for this. (must be specific for the diameter....... Clean the surface well, or it will come off!)
The one mark on the tab is likely your TDC..... (I'm not as familiar with this engine as I am with the SBC.)
If that is TDC, or ZERO, then the rest can be marked off on the harmonic balancer clockwise of the groove. (If you do not use the decal, at least mark it up to 34-36 degrees BTDC or so!)
This can be transferred from a 360* wheel!
Do not guess at the degrees on this..... it is too important!
I'd make sure to use my OEM specs for BASE and TA settings, and I'd make sure that it is NOT coming on TOO SOON, nor too much!
(IMO, 2,500 rpm may be a little too early for FULL-IN TA. Check the OEM specs!)
Detonation can be one of a gasoline marine engine's worst enemies!
I recommend that we use a standard strobe type timing light when setting TAT. (real time/real degrees)
Good luck.
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