Engine builders: How "hot" are your cams?

[mylesm260]

I am running the stock truck cam in my 4.3.
My stock cam specs are:

This cam produces 200 HP @ 4400 in the trucks. By looking at the numbers, this cam is cold as hell.

intake: 179 @ .050 peak lift .350
Exhaust: 195 @ .050 peak lift .383
Lobe seperation 110


Here is an example of what I can get from summit:

inake: 224 @ .050 peak lift: .525
exhauste: 224 @ .050 peak lift: .525
Lober Serperation 110

http://store.summitracing.com/partdetail.asp?part=CCA-56-430-8&autoview=sku


The cam from summit looks WAY WAY hooter than mine, and it says power is 2000 - 5500 rpms... it sounds perfect for my application... I saw a post earlier of someone sugesting an even HOTTER cam for a v8.... anyone have any experience/suggestions?



Right now my 21' boat is maxing out at 56 mph @ 4400 rpms (peak hp for my current cam)

 

[John_S]

Re: Engine builders: How "hot" are your cams?

I am not a V6 guy, but your cam selection appears to have too much lift and duration. I also see it is a single pattern cam. A dual pattern with more duration and lift on the exhaust vs intake (like your truck cam), work better in boats which have restrictive exhaust systems.

For the V6 guys that will follow, provide additional input on heads (vortec, non-vortec, aftermarket), intake, carb, compression, etc, so a matching cam can be suggested.

If it is a stock truck engine: I don't have the numbers for the marine V6 cam, but would not stray too far from it on duration or lift. I expect that the V6 truck cam is similiar to the sbc truck cam and is slightly less than the marine.

 

[Bondo]

Re: Engine builders: How "hot" are your cams?

and it says power is 2000 - 5500 rpms...

Ayuh,...And it'll be a Dog out of the hole....

Hot Cams,+ boats usually Don't mix...

 

[Maclin]

Re: Engine builders: How "hot" are your cams?

Your in-boat performance is pretty good as is dude.

I do not think you want to go to a cam that "starts" at 2000 rpm. To get the speed you want and to keep the drive below 5000 rpm you would need to up-pitch the prop some and that would make the hole shot worse, and coupled with a rumpy soggy bottom end cam, well, I see a poor performer in there somewhere.

 

[mylesm260]

Re: Engine builders: How "hot" are your cams?

2000 astro van AWD motor

vortec heads, roller/hydrollic valvetrane


Last week someone was sugesting a v8 cam with 244 duration.... I though that was way way too hot for a boat.
http://forums.iboats.com/showthread.php?t=273165&highlight=cam

http://store.summitracing.com/partdetail.asp?part=SUM-1107&autoview=sku

He said "It is a RV/Marine cam designed for low end torgue which is exactlly what you need for a marine application."


it is
234 @ 050 intake peak lift: .488
244 @ 050 exhaust peak lift .510

Power range 3000-6000

That cam looks way way too hot for a boat in my opinon




I agree that the particular cam I'm looking at is probably too hot, I was wondering if any of the v6 guys have sugestions.

Remember the v6's are just v8's with 2 less cylinders (same block/head design, etc etc)

I would like to gain another 600 rpms of speed... so I Would like to top out at around 5000 rpms and 63 mph or so....

And right now my peak torque (peak brake specific fuel consumption) is at 2200 rpms, I generally cruise at around 3000-3300 rpms (35 mph)

 

[Bondo]

Re: Engine builders: How "hot" are your cams?

I was wondering if any of the v6 guys have sugestions.

Ayuh,.... I'm running the 1 Mercruiser put in the 1st block, in the 1st place....

 

[mylesm260]

Re: Engine builders: How "hot" are your cams?

How did I know you'd say that, bond-o? =P

 

[John_S]

Re: Engine builders: How "hot" are your cams?

..and my comments in that thread are the same here.

I assume an Astro van had FI, so do you have a dual-plane intake with marine 4brl?

Merc service manual doesn't give duration, but lift is: I 0.394 / E 0.404

 

[mylesm260]

Re: Engine builders: How "hot" are your cams?

I'm running the automotive FI from the van

Runs great!

 

[mylesm260]

Re: Engine builders: How "hot" are your cams?

Those duration numbers seem really high to me... You must be refering to "total" or "advertised" duration

Most people use .050 inches as the ruler because it's easier to compair profiles (how many degrees your cam spends open more that .050 inches)

Honestly, Even if you are talking "advertised" duration, that cam sounds way way to hot for a boat. You would have absolutly no hole-shot! You still need SOME torque off idle. The specs you just gave me would make no toque whatsoever until around 3000 rpms.


The lift looks about right....

 

[JustJason]

Re: Engine builders: How "hot" are your cams?

First I'm callin ya out... do you know what those numbers mean and how to read a cam profile?

2ndly.... what's ya point?
and i mean....

I would like to gain another 600 rpms of speed... so I Would like to top out at around 5000 rpms and 63 mph or so....

a 4.3 will hit 5K.... but it's not going to like it, and it's not going to run all day like that. Especially if it's a gen 1 4.3.
Ask any guy that works on fountains or Donzi's.... lots of owners cook their motors at a mere 100 hours.
WOT should be for brief usage only. WOT beyond manufactors specs... first of all shouldn't even happen if the boat is set up correctly. and secondly, is going to cook any motor pretty quickly.

I think ya need to do some reading about cam profiles and water reversion as well. You can't go sticking any old cam in a boat.... this isn't a car.

I'm totally gonna scold ya on using an automotive non CG approves FI system in your boat.... shame shame shame on you!!! Seriously... I hope you don't blow up.

and lastly.... as Maclin said...

Your in-boat performance is pretty good as is dude.

and who really knows how your boat is going to act at 63.....
Ever push through a chine walk??

 

[mylesm260]

Re: Engine builders: How "hot" are your cams?

First of all, I am running the marine starter and alternator. The rest of the automotive EFI components are all completely igntion proff by their very nature.

I do also have a blower motor that I use to keep the gas funes out of my bilge.


In terms of cam profiles, of course I understand how they work. More lift and duration moves your peak torque higher, which results in more horsepower HP=tq @ rpms/5252.

I have a pretty extensive automotive background with lots of experience with turbochargine and fuel injecting engines (I was one of the first people to build and install a megasquirt)



And yes, I understand that you don't want to sacrifise too much bottom end torque or your boat will never get on plane. And YES I know you can't spend all day at WOT.

Looking at the specs of different marine engine manufactures, people use all kinds of different cam profiles, however. I'm looking to find a profile that will give me more HP up top, without sacrificing too much bottom end TQ.

http://pbgpreview.com/engines_performance.php
here is an example of someone running .457 lift and 218 duration. Much more than I am currently running.. They are claiming 262 HP and 300 ft/lbs (but not giving RPMS)

Also Egines are most fuel efficient at their peak torque (Peak brake specific fuel consumption)

Look at any modern automobile. It will make peak torque in top gear at whatever speed the EPA test's their vehicle at. So for example. if the EPA is testing a car at 55 MPH highway. And that car's engine has peak torque at 2500 rpms, it will be geared to run at 2500 rpms at 55 mph in top gear.


Right now my motor makes peak torque at 2200 rpms. I cruise my boat generally at around 3100-3300 rpms. It makes sense fuel economy wise to have peak torque closer to my cruising speed/rpm.

And yes, rpms do wear on a motor (engine wear is equal to the square of engine Rpms)

so at 3000 rpms, your engine has a wear rate of 9000000
and at 5000 rpms your engine has a wear rate of 25000000

So your engine wears 2.7 times faster at 5K than it does at 3k

 

[MikDee]

Re: Engine builders: How "hot" are your cams?

I hang out at the Chevy S-10 forum a lot, and 4.3V6 camshafts are always discussed there, there is a bunch of good info there, but if you have a 1st generation 4.3, no balance shaft, no roller lifters, & no true (96' and newer) Vortec heads, there's a bunch of performance cams available, Factory, & aftermarket, you just have to decide how hot you wanna go?

http://www.s10forum.com/forum/

Here's some factory offerings:
http://www.gmpartsdirect.com/performance_parts/store/catalog/Category.jhtmlCATID=304.html

If this is not enough, Comp cams, Crane Cams, Lunati, & others all have great offerings at their websites, I think you can find a few good marine cams here as well, But remember these will have more duration, & lift, requiring machine work on the valve guide bosses I believe, if your lift is over .480", then you also have to check valve to piston clearance, once you get too radical.

I'm looking at possibly upgrading my 95' S-10 TBI as well, because I have a crappy cam like yours too, but cam selection is very limited with the balance shaft, roller cam engines, most of them have .500" lift and definitely require machining, or beehive springs, with special thin retainers.

 

[MikDee]

Re: Engine builders: How "hot" are your cams?

Wait! Forget It! I just looked you have a 2000 Astro van motor, it must be a balance shaft, roller lifter motor, with Vortec heads!,,, It's a 2nd generation true Vortec motor, ever since 1996! Definitely Max lift is .480 on those heads, and there ain't too many cams made for balance shaft motors! Plus, Most of them are over .500 lift, check around yourself, Good Luck with that I know from watching the angst at the S-10 forum!

 

[John_S]

Re: Engine builders: How "hot" are your cams?

MikDee's explaination explains why I was having problems finding a cam with "reasonable" specs. Sounds like a lightly used stock marine cam is your best bet. It won't provide any big improvement though.

Wouldn't a "hot" cam require FI re-mapping?

 

[wca_tim]

Re: Engine builders: How "hot" are your cams?

I'm not an engine builder, but play and read a lot, have put a few together, and paid to have others put together...

I'm pretty sure that the stock marine roller cam in a 4.3 is 202/213 @ .050, valve lift .404/.410 and LSA of 112. would have to dig to check where I wound up on that when thinking through building one last year. If that's not spot on, it's pretty close and is a healthy cam compared to most car engines. I think you could go a little more, the 4.3 I had last year would run out of cam around 4800 - probably about where should stop rpm wise, but i think it would be fine to spin it to 5000 - especially if enouhg cam to support more and higher peak hp. I think a small step up would be perfect if it matched everything else...

The summit cam you list in your first post has way too much overlap for a stock 4.3 and will very likely suck water back into the engine from the exhaust unless you go with long aftermarket risers (reversion)... Also, depending on which heads you have and how much you've done to them, there's a good chance that they either don't flow worth a darn at lifts over 0.5, OR they won't support that much lift at all (the newer vortec heads flow pretty well but can't handle .500 lift without modifications).

The cam in the motor you linked to is probably the upper end of what would work in a 4.3 engine that isn't highly modified. I also agree with don that split duration and lift cams generally have a reputation for working a good bit better.

One thing to consider is that I am guessing you have a balance shaft engine. that robs a bit of horsepower and limits output some. It also limits parts availability (cams?). If it were me, building one from scratch or looking for a starting point, get the non balance shaft, earlier design bottom end, put vortec heads on it and choose pistons to get the compression in the 9.0 - 9.5:1 range.

If you already have the balance shaft bottom end, might
have the heads touched up / lightly ported, port match the intake, go with an edelbrock performer manifold and a 1409 600 cfm carb jetted two steps fatter with metering rods and one step lighter springs. main and secondary jets 0.89. (supplied with 4.3 jetting kit). Choose a cam on par with the specs I listed above for a marine cam or perhaps with more lift and a tiny bit more duration. Lose the stock flame arrestor and go with a k & n or better. That?s probably good for 230 - 240 hp on a non balance shaft engine ? oh and you?ll need aftermarket exhaust to get the most out of it. The only one that would offer the potential for any gain (I don?t know if they do or not, haven?t run them, but imco makes a great product) is the imco aluminum manifolds. GLM makes a set, but my impression is that they don?t really flow any better than stock. They?re a lot lighter and that is worth the cost by itself. If you go with any real increase in cam duration you?ll have to have long risers as well

The y pipe and factory through hull shouldn't be limiting...

Hope this is helpful?

 

[wca_tim]

Re: Engine builders: How "hot" are your cams?

sheesh... I was sitting her spacing out and working on something else while you guys were layin it out...

 

[MikDee]

Re: Engine builders: How "hot" are your cams?

How to break in your mild Chevy Hi-perf Cam! I came across this while searching for a marine V6 cam. I got a "Stirring in my Loin" hearing that groovy, slightly lopey idle

http://www.truveo.com/Chevy-marine-engine-camshaft-breakin/id/777811631

Theirs only 2 cams here with less then .500 lift:
http://www.cranecams.com/index.php?...ne_Make=CHEVROLET&Year=2000&Engine_Size=4.3 L

Theirs nothing here with less then .500 lift, But Comp will custom grind the lift you want, no charge! You just have to know what you want?
http://www.compcams.com/Cam_Specs/Browse.aspx

A Final note here, remember if going with any of these cams, over the stock offerings, you'd want to get new springs, (and maybe new heavy pushrods, plus you might need adjustable rockers, & studs as well, and the machine work to put the studs in) with the extra lift, & duration, most of the 96' up V6's have non adjustable rockers It can be Quite an extensive, expensive, Quagmire! Thats why I advocate the stock GM hi-perf cams, be used when possible, especially on the Chevy 4.3 V6

 

[MikDee]

Re: Engine builders: How "hot" are your cams?

Here's the cam I'm looking to get, once I decide to tackle the job!
my 95' S-10 is a Vin Z TBI (2WD), and I want to put the 95' Vin W (4WD CPI version) cam in, as you can see it's the hottest stock factory cam here,
as long as there's no difference in base circle? and I'm not sure if I need to go to an adjustable valve train? Yes, I've been searching for a cam for quite awhile now:

Factory 4.3L Cam Specs
* '96-'00, VIN W, w/ balance shaft
- Lift (I/E) - .415/.429
- Dur @ .050 (I/E) - .191/.195

* '93-'96, VIN Z, w/ balance shaft
- Lift (I/E) - .376/.402
- Dur @ .050 (I/E) - .183/.193

* '92-'95, Vin W, w/ balance shaft
- Lift (I/E) - .432/.440
- Dur @ .050 (I/E) - .208/.208

* '91-'93, ZR9/Z79, Syclone/Typhoon
- Lift (I/E) - .351/.386
- Dur @ .050 (I/E) - .179/.195 (Ductile)

* '90-'91, VIN Z, Astro/Safari
- Lift (I/E) - .403/.450
- Dur @ .050 (I/E) - .202/.213 (Steel)

* '87-'94, Vin Z, w/o balance shaft
- Lift (I/E) - .351/.386
- Dur @ .050 (I/E) - .179/.195 (Ductile)

found this on s10 forum
__________________

 

[wca_tim]

Re: Engine builders: How "hot" are your cams?

http://www.youtube.com/watch?v=33aWuP1K6o8

oh, but wait, that's not a v-6.... Right after cam break in though...