4.3 Vortec build up and traps

[Tail_Gunner]

2000 4.3 tbi setup http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=576&sb=0

I know that cam is a bit hot for a boat but will reversion be a big issue here???

Revised to:

http://store.summitracing.com/partdetail.asp?part=CCA-08-417-8&autoview=sku

Milder duration with less chance of reversion, thats a v8 cam but comp cams will grind it for the 6

 

[Fishermark]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

Cam selection is like black magic to me - I try to stay away from guessing what is best and stick with the "experts." Having said that, I have a copy of Dennis Moore's book "Small Block Chevy Marine Performance," and he recommends a lobe separation angle of between 113 - 116 degrees in order to keep down the chance of water injestion. So it looks like you are okay with that cam based on the information given of a lobe angle of 114 degrees ... that's IF I'm reading the chart correctly!

 

[Fishermark]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

One more note, for what it's worth, to quote from Dennis' book:
"If the lobe separation angle is more than 112 degrees, maximum power will be down, but the engine will idle very smooth. If it is less than 109 degrees, the engine will idle very rough and suck water into the cylinders at low rpm."

He goes on to add:
"In any case, when choosing a high performance camshft for a marine engine, anything wider than 112 degrees LSA will not give much of a power increase over the stock marine camshaft."

My disclaimer: Back to what I wrote earlier - it is black magic, and I stay away from it!

 

[180shabah]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

That cam has too much lift for stock vortec heads. Without machine work you can't go any more than .478 IIRC.

Best bet is to call the cam manufacturer, tell them your plans and get a suggestion from them. But there is little power to be gained under 5000rpm without getting into the reversion zone.

 

[Tail_Gunner]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

Im going to have them machined....What your opinion on 1.60 rockers followed with springs???

Better ideal...whole system..600 marine carb... eldo intake... that cam and (maybe exhaust..pure astheics quality)

 

[180shabah]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

250-260hp (220-230 at the prop) how much is all of this going to cost?

Thru hulls on a 4.3 really DO NOT sound good at all, and they provide zero benefit until you start approaching 375-400 hp.

You might be better off swapping in a v8.

 

[Tail_Gunner]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

250-260hp (220-230 at the prop) how much is all of this going to cost?

Thru hulls on a 4.3 really DO NOT sound good at all, and they provide zero benefit until you start approaching 375-400 hp.

You might be better off swapping in a v8.

Mabye 1200...If i take the tbi system off fuel cell and all probably 500 out of pocket.

No v-8 if done correctly its 4000-5000 and the boats hull is not going to run at that speed...or at least not with me in it..

Its a volvo motor tbi 205 maybe very weak at the top end of band....I was hoping for 275-285hp and a much broader tourqe band..I may shave the heads a bit and up the comp a little..

 

[Don S]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

One thing to keep in mind. Both Mercruiser and Volvo run right on the edge with a V6. They are worse than a V8. Volvo actually put some flared exhaust elbows (not risers) between the risers and Y pipes. Must have worked, because they still use them on the MPI 4.3's with 220 hp.
We replaced a 4.3 one time with a TBI 4.3 in an older Volvo setup and didn't use that type of elbow. Got lots of reversion. Ended hand building the exhaust with the flared elbows and the problem was cured.

Here is a picture from the iboats parts page with a fair picture of the elbow (Item #19)
You can see how it's flattened at the back and wider . Kind of looks like the head of a King Cobra snake (not outdrive )

 

[Tail_Gunner]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

Don do you know by chance or know where i could find the cam profile for the existing cam?? I looked for 4 hours trying to find it..some kind of deep dark secret i assume..and your above post worry's me a bit in that the cam is as far as it go already...

Playing with some props has show me the current cam is one weak sob at the top...aka 19p 3bl alum @ wot gets a very occasional rev limiter pop.. yet a 21p ss can run her to the same rpm on calm water.... and still get the occasional pop ..but i do get a 5 mph speed gain..

Or maybe it's just the tbi body limiting air flow...i will find out.

Thank you for the illustration...good info i see the flare..did they also angle it back a few degrees??

2001 pefs tbi black anchor.

 

[Don S]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

Don do you know by chance or know where i could find the cam profile for the existing cam??

Neither Volvo, nor Mercruiser will publish cam profiles. Not even to dealers. Proprietary information

2001 pefs tbi black anchor.

Say what??? PEFS sounds like Volvo black anchor sounds like Mercruiser
What do you have?

Thank you for the illustration...good info is see the flare..did they also angle it back a few degrees??

Depends on what you mean by angled back.

 

[Tail_Gunner]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

Neither Volvo, nor Mercruiser will publish cam profiles. Not even to dealers. Proprietary information



Say what??? PEFS sounds like Volvo black anchor sounds like Mercruiser
What do you have?



Depends on what you mean by angled back.

That be a black volvo.. as to the cam profile i thought something was up there...nothing a mic cant undress......

 

[Don S]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

That be a black volvo.. as to the cam profile i thought something was up there...nothing a mic cant undress......

And a degree wheel, egg shaped is the only thing you will get with a micrometer.

That black is actually DARK GRAY, not black

Then you should have the those flared elbows and be able to see how they set.
With the V8's, they just make a corner and straight down. The V6 has to work at it a bit.

 

[wca_tim]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

you might do best with good 1.6 rockers a little porting work on the heads, the carb and intake and aftermarket exhaust. the weight savings alone makes a set of imcos or emis worth the money. I have the numbers for two of the years v-6 cam profiles around here somewhere. i remember that the non-balance shaft one (similar engine to the v-6 I was playing with) was pretty close to the v8. once I got to the point where was considering head work, it made more sense to go to a v-8...

I was pleased with the effect, but honestly a little more (but not a lot more) cam would have been nice - especially when it ran out of air about 4800 - 4900... that being said, i can imagine that it doesn't take much cam for a 4.3 to be a dog on the bottom end.

I've still got that engine sitting in the garadge, haven't had the time and energy to get around to selling it. who knows, maybe i'll pickk up a boat that someone froze this winter. good luck with the upgrade.

 

[WizeOne]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

2000 4.3 tbi setup (Carbs coming)

http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=576&sb=0

I know that cam is a bit hot for a boat but will reversion be a big issue here???

Oooh! What lengths we'll go to!

Hey! GM's down to FoMoCo levels. Which is a better bet?

 

[Tail_Gunner]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

Oooh! What lengths we'll go to!

Hey! GM's down to FoMoCo levels. Which is a better bet?

Ford my good man... bet the farm if you have any spare assets 2010 will be a amazing year for them.....

 

[Tail_Gunner]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

One thing to keep in mind. Both Mercruiser and Volvo run right on the edge with a V6. They are worse than a V8. Volvo actually put some flared exhaust elbows (not risers) between the risers and Y pipes. Must have worked, because they still use them on the MPI 4.3's with 220 hp.
We replaced a 4.3 one time with a TBI 4.3 in an older Volvo setup and didn't use that type of elbow. Got lots of reversion. Ended hand building the exhaust with the flared elbows and the problem was cured.

Here is a picture from the iboats parts page with a fair picture of the elbow (Item #19)
You can see how it's flattened at the back and wider . Kind of looks like the head of a King Cobra snake (not outdrive )

Yes i do have those elbows and flares that are not shown in the above illustration's. i will post pic's later tommorow. Bondo once told me that all of the head work would be nill without a exhaust system...i can see why now.

http://videos.streetfire.net/video/rebuilt-43-comp-270ahr-no_52565.htm

Lumpy lttle bugger isnt it..

Some peoples kids...


Engine types: http://www.bucksengines.com/Data/24.pdf

 

[Mkos1980]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

You can use Comp Beehive springs and retainers and get away with .550 on stock unmachined Vortec heads. Thats what I'm using with good results. I'm also running a hotter cam then the compucam and have no issues at all with the stock merc exhaust setup.

 

[Tail_Gunner]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

now thats some damm good news...Thanks mike..but just how do you get by the lift issue using behive spring's.... and 1.6 rocker's..

 

[Mkos1980]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

The retainers for the beehives are alot thinner then the standard 4.3 and SBC valve spring retainers. This results in a greater distance between retainer and valve guide. Thus allowing more lift.

 

[Mkos1980]

Re: Cam profile ( reversion)

Re: Cam profile ( reversion)

Link to the article. http://www.carcraft.com/techarticles/vortec_valve_spring_upgrade/index.html