SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: el mojado on April 13, 2015, 02:19:18 PM
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What are your opinions on my cam? Engine is a 454 .030 over. 049 heads with a stock rebuild. I don't know how much was milled off. Pistons are 10:1 is compression. 1.7:1 roller rockers. Edelbrock Air Gap. MSD dizzy and 6a box 36 degrees timing in by 2500. 750 holley vac sec straight out of box. Mercruiser aluminum center rise ex manifolds with 4" stainless exit. Here's the cam specs my engine guy put in. Car Quest machine shop in Ontario near holt and euclid.
HYD. CAM
DUR @.050: INT-224 EX-224
ADV. DUR: INT-293 EX-307
VALVE LIFT: INT-.510 EX-.510
LOBE SEP: INT-114 EX-117
It's in a 20.5 Caribbean mini day cruiser from the late 70s. Jacuzzi WJ stock.
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Looks like I'm going to be the first one to say it... I think you'll be leaving a lot of performance potential on the table with that cam.
When I rebuilt my 454 a few years ago I spent a lot of time working the ports on the 049 heads, added compression but reused the Comp 280H cam that was already in the engine. The disappointment I felt when I had almost no gains in performance was horrible. So the next step was a bigger cam and addition of the Headers, the mph gain by getting a better combination of parts was amazing.
The cam I settled on was the Comp Cams Extreme Marine XM278H, but when I do it again I will be going to an even larger roller cam.
It all comes down to what you plan on doing with your ride, but if you're wanting to pick up some more umph, I'd recommend kicking it up a notch.
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I don't plan on going to headers. It's a mini day cruiser. I went with the aluminum exhaust manifolds cuz I read that they were better than logs. And they look cooler. I don't plan on doing any work on the heads. But I would like to have the best cam for my combination. If I need to step up the carb, I will. I'd like to see as much MPH as possible. Not looking for 80 or even 70. 55-60 would be nice. Is 65 to much of a reach? I would like to pull a tube once in a while too. I am willing to kick it up a notch in the cam and carb dept, as long as it's worth it.
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I agree 224 @.50 is going to get eatin' up by your cubic inches, something in the 230 to low 240. @.50 range will give you a nice lope and run hard. I just put a 218@.50 in a ford 400 and it sounds and runs just a smidge better then stock, throw 50-60 more inches at it and you'd never know it's got any cam at all.
Sent from my iPhone using SoCal Jet Boats
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I like the specs of this cam from Comp's marine line for your build.
http://www.compcams.com/Technical/Search/CamDetails.asp?PartNumber=11-314-4 (http://www.compcams.com/Technical/Search/CamDetails.asp?PartNumber=11-314-4)
As for the carb, run what you have and if you get a chance to try an 800 double pumper, try it and see if the difference is worth the cost.
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He is going to need to change his springs in his head, if he runs a hydraulic roller cam.
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Comparing the two cams, that of the OP and the Comp 280AH suggested by crewchief22:
OP
DUR @.050: INT-224 EX-224
ADV. DUR: INT-293 EX-307
VALVE LIFT: INT-.510 EX-.510
280AH
DUR @ .050: INT-232 EX-237
ADV. DUR: INT-280 EX-288
VALVE LIFT: INT-.547 EX-.547
The 280AH has a more intense lobe profile. Notice that the difference between the seat-to-seat (advertised duration) and the @ .050 duration. The difference is less on the 280AH, INT-48 EX-51 compared to that of the OP, INT-69 EX-83, the latter having a much softer "lazy" lobe profile and as they say, "less area under the curve." At each degree of crankshaft rotation, the valves actuated by the cam of the OP, will be at a lower lift compared to that of the Comp 280AH despite having an advertised duration INT-13 EX-19 degrees more. For example, the OP's cam will take approximately 34.5-degrees (69-degrees/2) to move the intake tappet .050 and 41.5-degrees (83-degrees/2) to move the exhaust tappet compared to 24 and 25.5-degrees respectively for the Comp 280AH. You can assume that the velocity of the lifter will continue at a comparable rate.
I am a fan of intense lobe profiles, but I would be careful about too much @ .050 duration because the engine will want to make power at an RPM higher than what the pump will allow. Your impeller could be cut down to allow the engine to RPM higher, but you will lose launch in a heavy boat, particularly pulling tubes and skiers. I believe that duration at .050 in the 220 range, but with an intense lobe profile and as much lift as possible will allow your engine to produce power in low 5000 RPM range.
The horsepower is directly related to lift. Your heads will flow up to .700, but you won't get there with a hydraulic flat tappet cam. Anything less than that and "you are leaving horsepower on the table." The .037 difference in lift is negligible because the valve is only open in that range for a fraction of a second. Going to a hydraulic roller is probably not in the budget, but if it is, high lift and intensity lobe profiles will make a huge difference along with the reduced friction.
I would choose a lobe profile in the mid 220 degrees @ .050 with as short an advertised duration as I could find and as much lift as possible. I would choose a lobe separation angle (LSA) of 110 to minimize overlap (and reversion) with your exhaust. If you want to be on the safe side of reversion, you could have it ground on a 112 LSA, but it will smooth out your idle though. I would install it "straight up" (rather than advanced), to start, to bias the power curve towards the upper RPM. Regardless which cam you choose, you will need the appropriate springs installed at the appropriate height.
One final thought, the Comp 280AH recommend by crewchief22 is a proven performer. It is a "safe" choice.
Good luck,
Joe
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A roller is not in the budget... YET. I will run the cam I have for this season. Then over the winter change the cam to one being suggested here. But maybe in about another year once my boat is "done", ( I know they're never done), I'll go with a roller. But wait... I thought it was done. Flusher, do u have a specific cam in mind?
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Flusher, do u have a specific cam in mind?
I do not.
Rather than buying a new cam, you could have a usable core reground and save some $ over purchasing a new cam. Probably more than 50% savings You could even send your core to Comp and have it ground into the 280AH profile. There would be zero difference in performance compared to buying a new cam. I would send in a stock pull-out while you are running your current cam.
Everyone has their favorite cam grinder. Bullet / Ultradyne has been mine although I have had great success with Crane and Lunati. http://jheinc.com/ is the current cam grinder choice of the professionals. I heard that he did all the Spintron development for NASCAR and is the current leading lobe profile designer. I hear that his valve train systems in Top Alcohol live substantially longer and make more power than anyone else. However, he may not work within this application range.
If you are going with a custom grind, you really need to know what your REAL static compression ratio is BEFORE you call the grinder.
Cheers,
Joe