Cam Timing question

[Underdog88]

I'm running new cams I've just put in last fall. I know you guys will tell me they're all wrong but it is what I have... I was running almost the same cams with 10* less duration prior and they worked well. I have about 10 hrs now on these motors with no reversion issues with them or the last ones. I have the motors back out for the winter.

Here are the specs:
Hydraulic flat tappet
Basic Operating RPM Range 3,000-6,500
Duration at 050 inch Lift 238 int./248 exh.
Advertised Duration 296 int./306 exh.
Valve Lift with Factory Rocker Arm Ratio 0.540 int./0.540 exh.
Lobe Separation (degrees) 114

I don't want to spin much over 5k rpm and have just under 9:1 compression with aluminum heads and small dome pistons -100cc and 118cc chambers. The cams should have 10:1 compression as recomended by mfgr.

Eldelbrock 750s, RPM air gap, 030over 454s w/100cc domes. Alum heads w/118cc chambers, 2.25/1.88 valves. EMI thunder with long stainless tails(see EGT thread for pics)

They ran well and sound awsome at idle but think I'm leaving some on the table.
My best end of the year run was 79.2 and still climbing slowly at 5k rpm before I hit the no wake zone with a very light load(ran outa gas on the next pass trying to hit 80 ) 28 stock Bravo props. 30 Velocity w/-2" IMCO lowers.

The question is...
I've advanced the cam timimg 4* to bring the power band down and this should also increase cylinder pressure, if my thinking is right. This should tame the idle which is pretty radical now, create more dynamic compression and bring the power down closer to the RPM range I plan to run.
Is this a good idea? Am I thinking right? Do you forsee any problems with this?

Thanks for your input!
Mark

[BUIZILLA]

I would confirm the IC installed is at 110* now after you advanced them 4*, assuming both lobes were 114 and you don't have a 110 intake and 118 exhaust lobe to make the 114 number

ya might find the cam already had 4* advance ground into it

ALWAYS degree a cam, no matter what

[Underdog88]

Will do that as it's on the stand and not assembled. I've yet to do the other motor.
But... does the general idea make scense? Am I barking up the right tree?
Thanks
BUI zilla... I jus can't get past that Not wishing ANYTHING bad on you brother!

[Boat1]

I would agree with your thinking. Generally advancing a cam will bring peak torque down the rpm scale, help cylinder pressure, and help fill velocity. You must degree the camshaft to be sure everything is accurate. Your lift is not real big but also be sure to verify intake valve to piston clearance. Use the cam card timing and verify the intake centerline is in fact advanced from the card data. Most manufacturers grind in 4 degrees advance in a split camshaft. Your 114 LSA cam now likely has a 110 Intake centerline. Do not trust the multi-keyway advance gears, they are rarely accurate. If you would like an expert opinion I suggest calling Bob Madera @ Marine KInetics, 585-654-8583. Be sure to have all your engine info when you call. I don't think you are overcammed for your application.

[ROGUE]

Our engines are very similar, i have less duration and more lift and I got my best power out of 106 ICL. However, due to reversion issues since my overlap is 75 degrees and running the short Gil risers, I detuned them to 110 ICL and have 3 years on them now (knock on wood). I used to blow one up every year, mostly due to valve problems. BTW, I run around 5200-5400 rpm with Edelbrock Torker 2 intakes and holleys. OH , and that 114 is lobe seperation and not ICL, someone who responded was missing that. Verify the ICL, then make sure you have at least .100 intake valve to piston clearance. Ive gotten away with less but one stick and boom. As you bring the ICL earlier, your valve to piston clearance will drop. And I doubt that you are leaving anything on the table, i think you are running too much prop, try those engines around 5400 or so. That duration cam will not like lower rpms.

Oh, Im going to install 731's soon and my reversion will drop and I expect a lot better performance due to the rollers. Not cheap but safer in the long run.

[Underdog88]

First, Thanks for all your input. It is appreciated very much. Tom, you have helped before so, thanks again.

Second, ALWAYS degree your cams! You guys are so right. Being a drag bike racer used to double OH cams and slotted cam sprockets, it was a givin and often tinkered with. Occasionally between rounds for weather and track conditions. I looked at car cams as being non adjustable. Throw em in and go cuz not much you can do w/em.

After spending last night and a bottle of wine TRYING to get some consistent numbers, I got discouraged (and a blister from the breaker bar turning and turning) then did some homework. I was trying to get readings off of the spring retainers like a bike. Then trying to use the pushrod end of the rocker arm. After some research I've learned. I wish I had done this while I had my alum heads off so I could have used my magnetic base but too late.

Finally learned I could use the push rod w/rocker removed and got a solid mount with my clamp on mount. Nuther lesson learned...

Still a bit confused with the results on the advanced motor. Went ahead and checked the other untouched motor to compair "straight up" to my advanced one and got crazy numbers! 13-15* advanced w/132-7 lobe centers! Double checked TDC then tore down to find it one tooth off on the cam... felt like a dumb azz... musta had too much wine that night too. Can't believe it ran so well. Gonna leak it to make sure no valves touched.

Now it's straight up with ICL 115.75 opening 9.5 BT and closing at 47 ABDC with a duration of 236.5 and the ExCL is 118 open at 62 BBc and closing at 5ATDC giving a 247 duration. This is close to the cam card specs but how is this a 114 lobe center cam?

Now the cam I advanced 4* on the crank gear is a nuther story... Does this advance the cam 8*??? I have an InCL of 101.75 opening at 17* BT and closing at 40* ABDC The Exhaust has a centerline of 123 opening at 69 BBDC and closing at 3 BTDC??? This is closer to 8* advanced... what gives?

I expect I should put this one back to straight up like the other... Have to believe I'll gain a little by having the one tooth off cam back where it belongs. Still can't believe it sounded and ran so well. Had I done this on a dragbike I'd have a junk head...

Sorry so long winded but, I value all your advice and know you can't give it w/out complete information.

1- the 4* slot on crank gear is 8* on the cam? I know it turns 2 to 1 but thought the marks were for cam timing use.

2- 115.75 / 118 centerlines gives me 117LC right? Not 114 advertised

3-The advanced motor with 101.75 ICL and 123 ExCL would be 112.5 Lobe Center? That just sounds like a bad combo to even a bike guy closing exhaust 3*BTC. Am I doing bad math again?

Thanks for your time and input guys. All opinions welcomed!
Mark

Oh and the advice to call Bob M. is solid advice I know but, not being a paying customer, I wouldn't feel right.

[cdail28590]

Definately call Bob. It doesn't matter if you didn't buy anything from him he will still help you and believe me you will eventually buy something from him. He did the cam for my engine and when I posted the hp it made on the dyno he called me within 20 minutes saying something was not right with the dyno. I gave him the dyno #'s and he rechecked it and the dyno was off by 34 hp. Not many cam guys would take that time do that. His cams are awesome and he can definately help you out.

[MILD THUNDER]

Is there any reason you dont want to spin a higher rpm? You have a nice setup, that much cam in a 454 to take advantage you should really be turning at least 5400. That cam should make power to 6000-6500 RPM. I think you are correct in advancing the cam timing to bring the powerband down a bit, but kind of defeating the purpose a little, if power is the ultimate goal. Even if it was a 502CI with your cam specs, i would still shoot for 5400-5600RPM.

I have a dyno sheet from my old setup. 454's, cams that had less duration than yours, dart iron eagle heads, that made around 50 more HP at 5500 vs 5000. Peak torque was right around 4600 i think. I would guess you are propped where your motors make peak torque right now.

I would guess, that if you called bob, and had him spec you out a hydraulic Roller for your application, you would see somewhere in the 30-60HP per motor motor, and probably more on the table if you spin it faster. Of course the roller free's up some horsepower, and then some power gains just from his cam profiles.

[Underdog88]

>>>Is there any reason you dont want to spin a higher rpm?
Only reason being I have cast cranks, SP Hyper pistons, stock rods w/3/8 ARP bolt in one motor. Better rods w/7/16 bolts in the other.

I've broke a few motors over the years and am a bit gun shy. I did have a good builder resize all rods and assemble my short blocks this time after doing the others myself. The first was a dropped valve right after buying the boat with leaky stock manifolds. The last 2 ran outa oil due to junk stock gages and too small of pans spinning then breaking rods.

I've got new exhaust, all new gages with many added and 10+ qt pans now. Great oil pressure too. I guess I'm just a little bit chicken of breaking anuthr...

It did just start sounding really good at 5k and just getting up on the pad nicely. Maybe lab my props... didn't get to run it much as (9-10hrs) this fall and had timing backed up and breaking in things gently. Havn't really tuned the carbs yet either. I know it has more in it. I have vaccume gages but didn't even look at them close enuff on my few short WFO runs. I also have EGT yet to install. 750 Ebrocks and RPM air gaps. Too small? 850DP w/Torker manifolds for sale on the other site look tempting...

Thanks again for the replys!

[MILD THUNDER]

>>>Is there any reason you dont want to spin a higher rpm?
Only reason being I have cast cranks, SP Hyper pistons, stock rods w/3/8 ARP bolt in one motor. Better rods w/7/16 bolts in the other.

I've broke a few motors over the years and am a bit gun shy. I did have a good builder resize all rods and assemble my short blocks this time after doing the others myself. The first was a dropped valve right after buying the boat with leaky stock manifolds. The last 2 ran outa oil due to junk stock gages and too small of pans spinning then breaking rods.

I've got new exhaust, all new gages with many added and 10+ qt pans now. Great oil pressure too. I guess I'm just a little bit chicken of breaking anuthr...

It did just start sounding really good at 5k and just getting up on the pad nicely. Maybe lab my props... didn't get to run it much as (9-10hrs) this fall and had timing backed up and breaking in things gently. Havn't really tuned the carbs yet either. I know it has more in it. I have vaccume gages but didn't even look at them close enuff on my few short WFO runs. I also have EGT yet to install. 750 Ebrocks and RPM air gaps. Too small? 850DP w/Torker manifolds for sale on the other site look tempting...

Thanks again for the replys!

Ahh, ok. Cast internals. Since you are running hyd flat tappets, you might just be better of going with a new cam, better suited to that setup. They're cheap enough. You can go with some "sealed power" cams, cheaper and good cams. Not sure what heads you have, but some small CC oval intake runners, a cam spec'd with that application, would probably work best. From cruising speed, to top speed, to fuel economy.

The 750 holley and intake you have a fine for a 5000RPM max engine. Your power gains will be in the heads and cam. In this situation, less is more, in my opinion.

You said your old cam's with 10* less duration worked well, I bet even a few more degrees less duration than your old cam would yield more power at 5000.

The current cam is just way too much for a 5000RPM boat motor thats only 454CI. Probably be a great cam in a 540CI or larger. I think you may be getting ahead of yourself trying to make that cam work for you. I'll dig thru my old sealed power book, and see what grinds they have to offer. Keep us posted

[ROGUE]

Sealed Power CS 1139R.

[MILD THUNDER]

Sealed Power CS 1139R.

Yep. Here ya go, 100 bucks for the stick.

http://www.northernautoparts.com/Pro...tModelId=15056

[Underdog88]

Thanks for the recomendation. Kinda confused tho... advertised duration is more than I have now but less at .050? Don't get that part. Less intake lift but more exhaust lift than I have now. Same lobe center. You think that's the stick for me? You guys know better than this dumb ol drag bike racer. I like the price too...

I can go up to .580 lift w/these heads and springs. I was searching a few mins ago for more lift w/less duration. Was looking at these while away from here.
http://www.summitracing.com/parts/CCA-11-236-4/
http://www.summitracing.com/parts/CCA-11-240-4/

Also I sent an email to Bob M before reading this as many recomended. Didn't want to bother him w/a call. Any Idea what he charges for a cam?

I hate to throw away 2 new cam/lifter sets as well... Kinda bullheaded and a tight azz. But it's too hard to try and change em later in the boat as I want to get a full season this year and also get all I can outa my lil ol motors. It did run pretty good considering one was a tooth off. I have to wonder what that will give me now that it's back in place.

YOUR TIME AND INPUT IS VERY MUCH APPRECIATED GUYS! THANKS!

[Boat1]

Glad you found some issues. First you really should be reading the lift numbers at the lifter, I reccommend buying a flat tappet lifter and welding a flat surface to the top of it so the dial indicator has a correct surface to work with. The pushrod system you are using will allow some varience. Second how big is your degree wheel and how accurate are you at setting the TDC reference of the degree wheel. Spend all your time an energy setting TDC for your wheel, this is very critical, and use the largest wheel you can afford to buy. Finally all your degree readings should be taken with all other rocker arms loose. Any play in the timing chain will be magnafied with additional load. When I assemble an engine I install #1 piston, then degree the cam, then install the remaining rotating assembly. If you are getting calasses on your hands and using a breaker bar to turn the engine over, reduce the load on the cam, this will help give you re-peatable numbers. Finally the cam card should specify the intake centerline, if it does not then call the manufacturer to get that info. You must have the manufacturer Intake Centerline to check all other cam timing data. I suspect you are in the process of dicovering what I tell alot of people about timing sets, "Just because it is new in the box and wrapped in shrink wrap doesn't mean its any good!" Good luck

[Boat1]

Forgot to mention the best way to get accurate timing changes is with the degree buttons that install in the cam gear and on the cam pin. They are sold in muti-timing packs, you drill an oversized hole in the cam gear to install them. If you build another engine next time spend $45.00 extra bucks and use the Cloyes Hex-A-Just timing set. This is a high quality set that allows accurate cam timing changes. Good Luck. Post the cam card details so we can accurately help you out.

[ROGUE]

Advertised duration is a crap shoot, Are they refering to duration at .006 or .004 or where?. However, what you are asking in the first part is likely different due to ramp speed. And this is critical. On a flat tappet you are limited on ramp speed, this makes for a more gradual sloped lobe to get to the same lift. The more gradual the slope, the easier on the parts but more duration at just open (.006). Unfortunately, there is a trade off and in wet exhaust engines that increase in .006 duration can be a problem with reversion. Like I said, that cam I showed you has 75 degrees of overlap and is real close to being a problem. But does well if the other parts are matched. It seems to like large oval ports heads and torker 2 intakes. Now a roller cam can use real steep ramps so it can get open and closed a lot faster and as a result, has less duration at .006 and even sometimes less at .050 and still have greater total usable opening than a flat tappet with much less duration. That rapid valve opening has some other issues like requiring strong springs and other potential wear and reliablility issues but for the most part make more power with less overlap and potential reversion.

The more exhaust lift seems to be common with the BBC and stock heads. The reasons for it are long and Ive typed enough.

I'm not a cam guru by any means but I think what Mild Thunder said is all very true, less can be more. I lost some power going from 2.19 to 2.30 intakes. I believe easy on the compressions and easy on the duration, get all the lift you can, keep the runners smallish to maximize charge velocity and find the right combination of carb, intake, heads and exhaust to use it.

As far as cast internals, I think they are fine up to 600 hp if things are either left stock or done correctly. My belief is, and I speak from experience, that those of us who have "cheaped" out by keeping the cast bottom ends have also unfortunately also "cheaped" out on the valve train, and thats why their engines blew up, not from a bottom end failure. At times I wish I had a couple good stock bottom ends to build some nice 500 hp engnes with and put all the money on top where it really needs it.

All that being said, It sounds like those cams are working for you, they may have less overlap than the cam I listed (which is good) and if they arent tearing the lobes or lifter up, go ahead and run em. Save your money for the rollers, thats what Im doing.

I hope Bob does reply here, I listen to his advice closely and he knows way more than me.

[Underdog88]

Great info guys

Boat1- After the first night of turning and turning with inconsistant numbers I did some research and learned some of what I was doing wrong, like where I was trying to get my numbers ect... I also learned to loosen all the other rockers(much easier duh) I had the heads off the day before and could have done even better then. The pushrod are being pretty consistant as I have dart adj guide plates keeping the p rods steady and neither of my 2 dial indicators are long enuff to reach a lifter now. All readings have been w/in .001 but I'm sure your way is even better and will keep it in mind next time. Just scrapped about 48 lifters too. Shoulda kept one or two... I have a pretty big degree wheel 12-14" Moroso. I also used a piston stop to ensure TDC.

My cam card says max lift intake 109 and ex 119 which I believe to be the same as centerline? That's close to 118 ExCL I came up with and 108.5 In CL(bad math above when posted 115.5 as I screwed up BTC w/ATC in post #6) giving me 113.25LC. All the other cam card info I have is in the first post.

Rogue- GotCha on the ramp speed/advertised duration/rollers. Good stuff. I tried to measure this and seems impossible. If my math is anygood on this(Haaa!) I came up with 73* overlap on these cams.(That's how I discovered my error w/intake centerline/duration confusing BTC and ATC opening #s drawing my circle to figure overlap) I am going to stick w/these cams for this year as they're paid for and not doing anything bad yet. Only 10hrs but... all looks good. Ran pretty well considering one tooth off on one(still embarassing)

All this said and learned so far... what do you guys think about advancing a few degrees as originally posted. And is the 4* mark on the crank sprocket 8* at the cam? I like Boat1s suggestion about the better way to advance and have saw those kits.

Again I'm a bike guy but a cam designed for 3k-6500 seems like it could be bumped up a bit to use more of its sweet spot in the range I need it while building more dynamic compression which I could use.(I'm under 9:1 static)

Should I mill the heads a bit?

You guys and this site are awsome. Thanks so much for your time to all who have posted!
Mark

[ROGUE]

Intake centerline of 109, Id set it there. But if you do decide to advance it to 105, triple check the intake valve to piston clearance. And do that before you think about milling the heads. I use the cam sprocket bushings, they are cheap, easy and you can set them right on the money using the offset bushings.

[Boat1]

Yes, maximum lift is the lobe centerline number I was looking for. Use it as reference to determine amount of advance you are putting in the set-up. I would not mill the heads, your pistons provide plenty of compression for a boat. I would recommend advancing the cam 2 - 4 degrees, I think your combination would like it. Since your using the sproket keyway don't get to hung up on exact details. If it advances 3 stay with that, try and get the engines within 2 degrees of each other, this will be better than what you had. I hope you are running minimum 89 Octane fuel, they probably would prefer a mix of 91 and 89 to allow more timing. What is your total timing? Good Luck.

[Underdog88]

Thanks Guys!
I was running 91 and only 30 degrees timing to break in. Last day out I bumped up to 33 degrees. That was the first time I really ran WFO for more than a few seconds. Like I said, only about 10hrs on them last fall Oct/Nov then the water got hard.

I'm gonna soak on this a little while... leaning towards a couple three degrees w/bushings as the sprocket keyway seems too much of a jump to me.