Cam Upgrade

[CharlieB]

Re: Cam Upgrade

Lobe centers at 113 or more, lift under .500

Cam timing, advancing the cam timing can lower the RPM range that peak torque and HP occur, depending on the power curves of the cam you select you may advance the cam 2 - 4, even 6 degrees to bring the power more into the RPM range that the motor is operated at (4600 - 4800).

Lift under 500

Mild valve springs, you are not going to be turning enough RPM to need much spring pressure.

Edelbrock makes Marine intakes, see if they have an Marine RPM Air-gap.

More compression may need reduced ignition timing, initially set timing retarded 2 degrees and be alert to ANY pinging.

If your distributor is 'points' style, consider upgrading to breakerless and a hotter coil.

Cyl Heads, some truck engines used a cast iron equivalent of the large valve GT 40 alum heads. Clean up and port match, DO NOT POLISH intakes, the rough finish actually helps keep fuel in suspension and provides more power for torque motors. Polishing is for RPM motors.

Carb, Marine version, 750 or less, a 600 - 660 will provide surprising performance. Bigger is NOT better for torque. Vacuum secondaries.

 

[HT32BSX115]

Re: Cam Upgrade

havasu, while I do appreciate your input, I would like you to explain to me how stronger pistons/rods with all new bearings, and a new top end with a slightly upgraded cam is going to affect the reliability of the engine. It doesn't make any sense; it's like saying that we should have never started designing improvements to any engine design since the 60's because it would just result in shorter engine lifespan and less efficiency.

Example: My old 98 F150 w/5.4L had 230HP, my 08 F150 w/5.4L has 300HP. Well they didn't add displacement, there's no forced induction . . . sooo, it has to be with improvements to the original parts list (honestly it's due in part to a 3rd valve per cylinder).

In any case, you don't seem to understand where I'm coming from. I'm not trying to build a fire-breathing monster capable of planing out in 1 second and hitting speeds of 60+. The ONLY reason I know the boat does 50mph is because my father and I did it ONE TIME back when we first got the boat and tried it out. My goal is to build a good strong engine that performs as good or better than the old one. The intake/carb upgrade should be worth it alone, but why reuse the old cam and have it be the one remaining item in the engine block that didn't get replaced?

Howdy,


Just about anything you do to that engine will probably make it more efficient!

I love the old Mark Twains! I had a 1966 V-Sonic that Dad bought new and I (very reluctantly) sold in 2005!


If you haven't, inspect the floor and stringers VERY closely for rot.....Just about ALL the MT's had a rot problem from water intrusion in the floor, stringers, and transom!

Also, check out the following site! http://www.marktwainboats.org/.....Um....never mind! Just saw you there!!!


Cheers,


Rick

 

[wca_tim]

Re: Cam Upgrade

I've been watching this with some interest and sounds like you've got a good handle on what you want to do. You're being very conservative with a 9: compression ratio and cam selection - you'll be absolutely fine and I bet it'll run great. enjoy it!

 

[haulnazz15]

Re: Cam Upgrade

I've been watching this with some interest and sounds like you've got a good handle on what you want to do. You're being very conservative with a 9: compression ratio and cam selection - you'll be absolutely fine and I bet it'll run great. enjoy it!

I appreciate the compliment, I hope it works out well. Just trying to give a good 'ol boat a new heart!

 

[mkast]

Re: Cam Upgrade

According to Mercruiser, mid seventies, the 188, 225 and the 255 horsepower engines all used the same cam (P/N 447-5098).
Mercruiser lists the lift @ the lobe as:
Intake .278 measured at .002 lobe lift
Exhaust .283 measured at .002 lobe lift

 

[haulnazz15]

Re: Cam Upgrade

According to Mercruiser, mid seventies, the 188, 225 and the 255 horsepower engines all used the same cam (P/N 447-5098).
Mercruiser lists the lift @ the lobe as:
Intake .278 measured at .002 lobe lift
Exhaust .283 measured at .002 lobe lift

Aren't those all Chevy motors though? The 351W was a 233HP, and the 302W was 188HP though. Either way, I may have to have the stock cam inspected when we remove it and see if they can spec it out to see what the numbers are.

 

[mkast]

Re: Cam Upgrade

Aren't those all Chevy motors though?

No, 302/188 & 225 horsepower, 351/233 & 255 horsepower.
All used the same cam.

 

[haulnazz15]

Re: Cam Upgrade

No, 302/188 & 225 horsepower, 351/233 & 255 horsepower.
All used the same cam.

Ahh, must've been the 2bbl/4bbl that makes the HP difference for the most part.

 

[Tail_Gunner]

Re: Cam Upgrade

Nope cam and heads my freind...you are being very conservative with your cam selection.. a 266 grind would put a little snap in it..Remeber this engine does not have a roller cam its a flat tappet.... Flat tappet cams do not create a lot of reversion..what you need to be careful with is lobe seperation...112 to 110..The smaller the seperation the loperier she sounds..106-108 is radical..But sounds so good is the word i will use.

 

[mkast]

Re: Cam Upgrade

Nope cam and heads my freind

Part number 447-5098 is the cam used in all small block Fords, 188, 225, 233 and 255 horsepower engines.
Part number 949-4057 is the cylinder head used in all of the above horsepower Ford engines.
The only difference is the carburetor and intake manifold, two barrel verses four barrel.

 

[Tail_Gunner]

Re: Cam Upgrade

Part number 447-5098 is the cam used in all small block Fords, 188, 225, 233 and 255 horsepower engines.
Part number 949-4057 is the cylinder head used in all of the above horsepower Ford engines.
The only difference is the carburetor and intake manifold, two barrel verses four barrel.

umm the 5.0 HO was fuel injected with a hotter cam a...No carbs bro

 

[mkast]

Re: Cam Upgrade

Well it has whatever cam came stock in the 351W when they installed it in the boat in 1976!

I don't think he's dealing with a 5L fuel injected.
Bro???

 

[Tail_Gunner]

Re: Cam Upgrade

I don't think he's dealing with a 5L fuel injected.
Bro???

No, 302/188 & 225 horsepower, 351/233 & 255 horsepower.
All used the same cam.
__________________

http://phystutor.tripod.com/stang/engines/50.html

The reference to 225hp was what trigger the above link will clear it up




[SIZE=+1]1989/92 -- 225 HP @ 4000 [/SIZE]

• Same block, heads, intake and exhaust manifolds as 1987
• Introduction of the 55 mm Mass Airflow fuel injection system. Since this system measures the actual air flowing into the engine, high performance camshafts may be used.
• These engines offer the greatest performance potential of the 5.0 H.O. series
• In stock trim, the small 55 mm MAF & revised camshaft actually limited breathing, so it was no longer producing 225 HP.

Notice the history GT 40 heads and roller camshaft Way off topic sorry i know were talking marine here..

 

[wca_tim]

Re: Cam Upgrade

Nope cam and heads my freind...you are being very conservative with your cam selection.. a 266 grind would put a little snap in it..Remeber this engine does not have a roller cam its a flat tappet.... Flat tappet cams do not create a lot of reversion..what you need to be careful with is lobe seperation...112 to 110..The smaller the seperation the loperier she sounds..106-108 is radical..But sounds so good is the word i will use.

reversion is a complex issue and if you get anywhere near the edge, it all boils down to things like exhaust pulse harmonics / constructive destructive intereference, etc... combined of course with overlap (the same thing that determines idle quality), intake and exhaust gas velocity, how well designed the manifold is (and most oem manifolds suck), how far down stream the water is injected into the exhaust, how much water is injected into the exhaust, how much drop, engine stroke (longer stroke shorter bore can be a greater problem from my niave understanding...

another huge issue is cam lobe profile - the largest variable that you can control is the cam grind. Note that some of the modern hydraulic flat tappet grinds approach being as aggressive as many of the hydraulic roller grinds...

take a look at the difference between advertised duration and duration at 0.05 lift and you'll notice that not all 266 cams are created equal. the xm cam grinds are very similar to the comp xe cam grinds except with a little different timing. take a look at the difference in specifications between the xe you like and corresponding xm cam for the small block gm and see what they changed in cam timing. they will grind you one with whatever you ask for or may even have it as a current grind number already... Just a thought...

 

[Tail_Gunner]

Re: Cam Upgrade

WCA i am not going to quibble with your thoughts they are sound..and speaking of sound i see a lot of people referencing to harnonics and wave form amplitude...

Intresting that people bring up those words..Care to elaborate...That firey display of wave form amplitude was entertaining..but i dont think there are any subharmonics going on here...Hmmm total length of the tube divided by 2..what a 12hz standing wave???

 

[wca_tim]

Re: Cam Upgrade

At one point I tried to do some reading on this, but the math was a bit beyond me...

but I think you're making a very valid point. when I think through it.. at face value, say you're turning 600 rpms at idle, that's 10 revolutions persecond and since you have 4 cylinders on a side, we're talking 40 pulses per second...

the initial pressure pulse when the exhaust falve opens is on the order of 1300fps, and the slug of exhaust gas is more like 250fps. so the harmonic frequencies would equate to rather long tubes, eh?

the problem in trying to think about this in any well defined concrtete terms, is that each cylinder has a different length or shape pathway to the multiple points where reversion pulses are going to be created... It's a chemical engineering student's nightmare (probably well beyond many professors?) way before we start worry about the hetereogeneous mixture that results when the water is injected - both cooling, changing velocity, density, etc...

so.... for a hack like me, the geometric constraints are waaaaay too complex to get a concrete handle on even without worrying about water injection and heterogeneous flow... I have to rely on the experience of others for perspective and think of it in relatively simple terms:

IF the tube length, velocity in tubes (or through an open chamber, etc...) result in enough reverse pulse anywhere in the cycle at a given rpm (and much more likely at lower rpms...) to reverse the volme between the peak in the riser and the point of water injection, then some amount of water is going to make it back to wet the valves...

Since we're talking about reversion as a function of camshaft duration, the main contributer is going to be overlap that puts the intake and exhaust open at the same time - the area under the overlap region is going to be the primary factor that determines how much volume we need between the peak in the riser and the point of water injection. (Obviously there's more to it or merc wouldn't have had to add the little "turbulators" to the 496 exhaust systems to keep it from happening!)

My bottom line assumptions when worrying aobut exhaust reversion (my understanding - not gospel from anyone).

overlap bad - more duration requires wider lobe angle separation, steeper lobe geometry is going to be less forgiving (more overlap per degree of overlap)

Long risers good

Fre flowing exhaust without a lot of sharp bends (to generate reversion pulses) Good

I've been told (and read more than once) that the only way to tell for sure when you're on the edge, is to idle for a while (NOT on muffs... changes the water flow rate....) and then pull a manifold and see if there's any whater where it's not supposed to be....

IF you're close on reversion, your fuel mixture is right and you feel like it's loading up and running like crap at low idle... that's a big hint to pull a manifold and see...

in the extreme case, you draw enough liquid up to put a slug of water in one or more cylinders while another fires and your done... more likely is just wetting things... valves, seats, cylendar walls, don't like rust...

Why have i thought about this a ton lately?

I'm waffling (agonizing??) over where to drill my risers to weld in a bung for a wideband oxygen sensor... if I get it to close to the engine, it'll get too hot and die, if I get it to close to the water injection, it'll get wet (and die instantly)... dry pipes are just tooo dang loud...

have fun and if you want to giveus a math lesson, I've got a couple books and journal articles for you to chew on... (Green's function, Helmholz equation, eigenfrequencies, modified bessel functions etc.. I know my way around Matlab pretty well, but it was greek to me...)

WCA i am not going to quibble with your thoughts they are sound..and speaking of sound i see a lot of people referencing to harnonics and wave form amplitude...

Intresting that people bring up those words..Care to elaborate...That firey display of wave form amplitude was entertaining..but i dont think there are any subharmonics going on here...Hmmm total length of the tube divided by 2..what a 12hz standing wave???

 

[TimeBandit]

Re: Cam Upgrade

I agree there are so many variables that It's impossible to predict the outcome when pushing into the grey area of too much overlap. And the shut-down and dis-assemble proceedure is the only sure way to know (when pushing it). I don't think HaulinAzz is even considering camming into that grey area... His needs/wants are pretty mild.
One good thing about his engine (351W), is that it has good long rods (just under 6") which is a good rod length to stroke ratio which causes the pistons to dwell longer at and close to TDC, vs a stock and somewhat short SBC rod length. If it were a 302 that would be a different story as they have a very short rod length because of the very short deck height.

I'm thinking about installing ball-valves just ahead of where the water enters my exhaust manifolds so I can shut them off right before shut down at the end of the day. Not necessary, but I'm kind of anal about stuff. I don't want to take a chance on rusting up the cylinders between outings. Shut down is when the engine has the best chance of ingesting exhaust water, or if nothing else, humidity.

 

[haulnazz15]

Re: Cam Upgrade

It just seems like if they would have extended the riserss a bit (not up, just out) so that the water injection point is 6-8" further down, this likely wouldn't be much of an issue. Wish I had the money to go wth dry stacks, but $2K+ for water injected headers isn't my cup 'o' tea when the entire engine would have hardly $2K in it!

 

[wca_tim]

Re: Cam Upgrade

It just seems like if they would have extended the riserss a bit (not up, just out) so that the water injection point is 6-8" further down, this likely wouldn't be much of an issue. Wish I had the money to go wth dry stacks, but $2K+ for water injected headers isn't my cup 'o' tea when the entire engine would have hardly $2K in it!

You're not even close to reversion issues with the cam specs your thinking about... imho...

if you look at where the exhaust and through prop exhaust routing goes, there really isn't room on a stock system to move the water injection further downstream without major changes and expense...

 

[haulnazz15]

Re: Cam Upgrade

You're not even close to reversion issues with the cam specs your thinking about... imho...

if you look at where the exhaust and through prop exhaust routing goes, there really isn't room on a stock system to move the water injection further downstream without major changes and expense...

Oh, i know that; I meant it as a reference to the original design of the risers.