Printable View
Valvoline VR1 and comp cams breakin lube for cam breakin is what I use, though I'd happily sub whatever cam breakin lube is conveniently available as VR1 alone should be good. The additive is just belt and suspenders, cheap insurance. Whether you need to be concerned about having sufficient zinc and phosphorus content after cam breakin depends on what cam and springs you are using.
As said above, a .030 over bore will not product any considerable gains unless matched with different heads/cam but that can get pricey.
Like cadunkle mentioned, if you are looking for any small gains I would look at a different intake/carb setup. Obviously the big goal is low end torque, and going with a longer runner manifold can help in that department.
For example, on my 302 SBF in my 1987 Mustang (stock heads/block) I switched from the stock intake to a GT40 style that has long tube runners (granted, it is EFI) but I ended up with 24 ft.lb gains and peak torque at 700 rpm less than stock.
My opinion on changing cams on a stock bottom end and stock heads is that it will do nothing but kill your low end torque. You may improve efficiency and peak HP but in this world you are trying to get up and go.
I don't know the specs on the cam PCM used in these, but I'm certain with only 330 HP there is a lot of improvement to be had. I'd imagine the PCM cam is low lift and slow ramp rates. Changing cams for more power and efficiency does not mean an engine that idles rough at 1200 RPM and pulls to 7500 RPM unless that's what you want. Cam technology and lobe profiles have come a long way since the 80s. In any rebuild cam lifters and springs are typically replaced given how cheap these parts are. With a modern cam there can be torque improvements across the board.Quote:
Originally Posted by Supra_Comp
Do the 351's have a better cam than stock? I always thought they had higher lift/duration than a stock Ford 351.Quote:
Originally Posted by cadunkle
It's likely a different cam than Ford put in 351 truck engines in the 80s as trucks had emissions requirements whereas boats didn't. So it's quite possible the cam is a bit different and may have made a bit more power. Hard to tell since boat HP was rated at the crank and car/truck HP at the rear wheels after driveline and accessory losses.
I'd be surprised if the PCM 351 cam was at all aggressive with lift or ramp rates and I'm with a 4400 RPM max it's not going to have a lot of duration or overlap. What we'd want for a mild performance build ina towboat is more lift and faster ramp rates along with slightly more duration and overlap. Nothing excessive since we want a broad torque curve for wake sports. Slalom and barefooting you can build for higher RPM.
Also I doubt that PCM cam in either 351 or 454 is split duration. Not sure on BBC but all Ford engines benefit from longer exhaust duration due to restrictive exhaust ports as cast. BBC has pretty decent exhaust ports relative to Fords but I'm sure more exhaust duration would help BBC as well.
I've made a little progress finally.
http://unumemarketing.com/boat/lifters.jpg
http://unumemarketing.com/boat/painted_engine2.jpg
Got it back in today. Based on last time, I was expecting one hour to drop in, and one hour to connect and get running. Well, the best laid plans... It took about 6 hours in all. But she's alive! Still a lot of little things to button up, but I'm glad she's running.
Anyone have advice on the break-in? I was told to get it running and immediately get the rpms over 1,500 and don't run over 2,200, but fluctuate between those numbers for about 15 minutes. This is to break in the cam. For breaking in the rings I'll need to go to the lake and run between 1,500 and 3,000 for 10 hours. Anyone have a different procedure?
http://youtu.be/ljCoci2SuHc
How long did you have it running? Hopefully not more than a few seconds as it doesn't take long to wipe a new cam.
Before starting ensure you have smothered and cam lobes and lifter bases with moly assembly lube. Also ensure you are using a good oil of appropriate viscosity for your build with at least 1200 ppm of zinc and phosphorus. I typically use Valvoline VR1 for cam breakin, and also use Comp Cams breakin additive. Prime the oil pump with a drill or speed wrench until you have pressure. Set your timing in the ballpark, put #1 on compression stroke with timing marks where you intend to set your base timing and lock in the distributor with the rotor pointed at #1 and preferably if you can tell also set at the point at which your trigger fires the coil. You want to be sure the engine will fire quickly, cranking will wipe the cam and removes your assembly lube
Immediately bring RPM to 2000-2500 RPM and keep in this range for minimum of 20 minutes, though I typically do 25 mins. I set the idle stop to be in that range before starting and adjust from there so "idle" is at 2000 RPM. Throughout the breakin period I slowly vary RPM in that range using idle stop screw adjustments. At the end of the breakin period set idle stop to 2000 RPM and do a long slow sweep to 2500, back down to 2000, then to 3000 and down, then to 3500 and down, then bring it to normal idle RPM. Set timing, adjust carb mixture, get idle RPM where the engine likes it. Shut down and change oil using high zinc and phosphorus oil such as Valvoline VR1 for first oil change. Monitor dipstick for metal particles during first oil change and check oil for metal at next oil change when draining.
Once the engine starts do not let it idle for any reason until you've run at least 20 minutes. Do not shut it off unless absolutely necessary, such as oil leak under pressure, severe coolant leak, overheating, or any circumstance in which you foresee you cannot run for the full cam breakin period. You should be closely monitoring oil pressure and coolant temp the whole time. Again, do not let the engine idle or you are likely to wipe the cam.
Thanks Cadunkle, that's a great run down and very similar to what I did yesterday. I had lots of assembly lube on the cam, and I used the correct viscosity of oil and added Valvoline's ZDDP additive to make sure I had enough in the oil. I had the oil pump primed and distributor timed with number one at TDC.
Once started I brought it up to 2,000 rpms and varied between 1,800 and 2,500 for 20 minutes. I then fine tuned the timing and carb settings. I had great oil pressure and temp setting the whole time.
To my understanding, this breaks in the cam. But I've heard that the ring break-in can take 10-20 hours. In reading about this topic, I've found that for the next 10 hours I should: keep above idle as much as possible, change rpms often, and don't go anywhere near full throttle. Would you agree with that?
So I should change the oil before I go to the lake and do the longer break-in period, but after this oil change do I need to do another one (after the second break-in period) before declaring it good for the summer?