4.3 Marine upgrade
have gotten the bug. There is no better way to describe it.
Here is what i am working on, a 2001 volvo brand a 4.3 gm push rod. It is all factory and my goal is of course higher speeds without to much sacrifice. After a lot of research and I-net gabbing i do believe i have some sort of plan, one that will give me higher speeds and not much of a down side.
This is what i have to work with and again its all stock. TBI with 2" bore's...mated to a stock 4 barrel manifold...there is some kind of spacer that bridges the gap. Vortec heads 12557113 with fulcrum rockers.
Production period 1999-2000
Cylinder configuration V-6
Bore (in.) 4
Stroke (in.) 3.48
Compression ratio 9.41:1
Displacement (cu. in.) 262
Power (hp) 205
Max engine speed (rpm) 4400-4800
What i intend to do is as follow's
CS XM 270 HR-12
Basic Operating RPM Range: 1,200-5,200
Intake Duration at 050 inch Lift: 218
Exhaust Duration at 050 inch Lift: 224
Duration at 050 inch Lift: 218 int./224 exh.
Advertised Intake Duration: 270
Advertised Exhaust Duration: 276
Advertised Duration: 270 int./276 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.495 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.503 in.
Valve Lift with Factory Rocker Arm Ratio: 0.495 int./0.503 exh. lift
Lobe Separation (degrees): 112
THE ABOVE CAM WAS EDITED TO THE FOLLOWING:
Part Number: CCA-56-450-8
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 1,800-5,000
Intake Duration at 050 inch Lift: 210
Exhaust Duration at 050 inch Lift: 215
Duration at 050 inch Lift: 210 int./215 exh.-----
Advertised Intake Duration: 266
Advertised Exhaust Duration: 270
Advertised Duration: 266 int./270 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.500 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.500 in.
Valve Lift with Factory Rocker Arm Ratio: 0.500 int./0.500 exh. lift
Lobe Separation (degrees): 112
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: No
Grind Number: C6 266HR-12
Quantity: Sold individually.
Notes: Adjustable valvetrain required.
Camshaft, Hydraulic Roller Tappet, Advertised Duration 266/270, Lift .500/.500
This was due in part to Curtis's concern for reversion and the close proximity of the riser dumping water into the exhaust flow...even after moving the water flow down stream.
Springs: COMP Cams 26918-12
Retainers: COMP Cams 787-12
Locks: COMP Cams 611-12
As per this article: http://www.carcraft.com/techarticles...ade/index.html
Keeping the stock TBI and marine 4v manifold
And having OBD flash a new maps for the changes....MEFI-3 prom
Opinions and suggestion are welcome... Opps that is what i have to work with
Last edited by Tail_Gunner; 03-26-2009 at 01:14 PM.
Here is my issue, the casr number on the head is 12557113 that number reflects just a plain old 99-2000 vortec head made for v6's....but the last three 113 indicates it is a l-98 head...Here's some pics..
Is it possilbe that someone being Gm modded the v6 head or is that a old ls head
What specifically is your question? The links don't work for me, so I'm at a loss.
From what I can see, the rockers look to be roller fulcrum and non adjustable. Looks like an "under rocker" stud girdle, but I'm sure I've not seen that deal before. Might be common for all I know, but it's news to me! Possibly, that set-up is a Volvo deal in conjunction w/GM for marine use.
In any event, an adjustable valve train is needed whenever you swap camshafts in order for the geometry to be set correctly, as well as for correct lifter adjustment. Possibly those rockers can be converted to adjustable, but I can't say w/any certainty.
From Hot Rod mag.: "Crane Cams offers an adjustable conversion stud (PN 99148-2, six required), but for serious work, all these should be drilled and tapped for V-8-type screw-in rocker studs and roller rockers."
That Crane kit would be for conventional rockers, don't know if it will work with your rockers.
Flow-wise, the "real" Vortec heads began production in '96 like the V8 engines.
I hope this helps.
Last edited by cobalt327; 03-20-2009 at 03:03 PM.
Yes it does thank you, stud girdle hmm. I have had one hell of time with all of the casting numbers and it has been years since ive done this. Opening it up caught me a little off gaurd i no ideal what i was looking at all. It would be nice if that rail is just a bolt on with modified rockers
The links should be working again...and again i thank you.
Those bee hive springs are popular with guys who run the Vortec heads on V8's, so I'll bet they're good for your engine, too. But you still need to address the non-adjustability of your valve train.
I would suggest that you remove a rocker arm to see what's up w/them as well as the girdle? or whatever that actually is.
Only problem w/that is not knowing to what torque to re tighten the bolt to. I'd say 20-25 ft/lbs. but that's a total guess.
If you take it off, check the diameter of the threaded part of the bolt and that'll indicate about what the torque should be (at least how much you could put on it, less may be needed).
Have you looked for Volvo marine sites/forums? I'm thinking that this is a Volvo marine deal...
First, that cam is a big no-no. Water reversion with wet manifolds is surprisingly easy to do. Keep your @50 overlap to no more than -11*. That cam is at -3*. On a larger engine like a 350 you can push it to -9, but no more for an I/O cruiser. And DON'T listen to cam manufacturers about I/O cams. I asked Comp about a cam for my 350 and asked how that cam avoided water reversion. Their response was, "water reversion? what's that?" They do a fair job of creating lobes and profiles that suit boat's torque needs, but they suck at knowing actual marine engine parameters.
You don't want to go wild with a cam anyway. Boats need torque, not HP. I've seen guys shift their torque peak up with a cam and they can't even get on plane anymore despite adding 100 hp.
You need to increase the average TQ and HP under the curve without shifting your peak HP above 5000 rpms. Improved head flow without going too big on port size, slightly larger cam than the one that's in there, better aftermarket exhaust manifolds like ones available from GLM, and a few other tweaks, but the LAST thing you want to do is reduce torque in the low RPM range. That 4.3 is already a little crippled down there anyway.
The other thing to consider is cost. Marine performance parts aren't cheap, and for $1000 you can drop in a 350. The other thing to consider is that even if you add 40 hp, you'll only gain a few MPH. Make sure its worth the investment.
In a car, if you want to add HP to an existing engine, you are going to have to shift the peaks up. If you want more HP, you lose low end torque, period. In a boat, the best and most logical way to gain HP is to increase displacement. That way you retain the same low end torque, but add HP. Another consideration is to artificially add displacement - use forced induction. The rule on the water is keep it simple, so most forced induction is left to race boats and trailer queens, but if you're willing to put up with the reduced reliability, go for it. Again, weigh the costs of just dropping in a 350.
Just for comparing... my 19' baja was good for about 50 mph with the 305. I upgraded to a 350 vortec, and until I added the late-model coupler, added performance manifolds, rejetted the holley, bought a new prop, and remortgaged the house, I had added 110 hp and a whopping 8 mph.
Last edited by curtis73; 03-20-2009 at 04:17 PM.
I believe i will not have reversion issues with this cam it has been run successfully on many I/O's...But you puzzle me somewhat are you saying a 6 cyl will produce more vacuum than a 8. Bore and stroke are the same along with engine height and riser height.
Here is some very good info on the subject and this cam
Actual overlap cannot accurately be calculated using .050 figures.
Using seat to seat (.006 SAE standard) the
XM 262 H-12 41 deg overlap
XM 270 H-12 54 deg overlap
XM 278 H-12 61 deg overlap
XM 264 HR-12 43 deg overlap
XM 270 HR-12 49 deg overlap
Isky 281-12 51 deg overlap
The XM 270 HR-12 has Int .030 and Ex .018 more lift than the Isky with 2 deg less overlap. Isky does calculate their advertised duration figures @.020 rather than .006 like Comp Cams so in apples to apples the XM 270 HR-12 could be closer to 4 deg less overlap.
Hope this helps,
As to the cost vs yield i can afford this and i truly believe just recalibrating the ecm's fuel mapping and timing curves would get 4-5 mph.. We have different approaches to this i am sure..
But i do thank you for your input and will do some further research on this....By the way i do have some Corsa exhaust sitting in the garage. But have you ever heard a v-6 or v-10..notes on a open header exhaust or high perfromance exhasut...
Last edited by Tail_Gunner; 03-22-2009 at 12:31 AM.
Were you able to find out any details on your rocker arms yet?
I looked at several Volvo Penta sites but saw nothing like them. I thought I had found a manual on line, but they weren't for your engine. In fact your engine number 4.3GIPEFS has gotten me nowhere, so far.
gotta agree with J on this.
its also why GM on the 325,330HP marinized engines use the ball and fulcrum setup with roller tips.
the point is when the rocker arm travels from closed to open and back to closed the tip actually travels in an arc not straight up and down.
this tends to wipe acrossed the valve stem actually pulling and pushing the tip of the stem.
a roller tip rocker greatly reduces the side loading of the valve stem and aides in stem life and oil leaking past the stem into the cyl.
So i am going to try and retain the setup It all depends on how Gm set it up. if there is no variance on spring size's between that setup vs one with out it should work just as described in the article...If there is a difference then rod size will have to change or Poof there gone...I had Intended to put new rockers and stud's on any how.
Yes that motor seem to be a bunch of parts all piled together, but Volvo does put that assy on there GXI which is cpi motor. and discontinued that head and assy on the GI
There you have the updated Gi PEFS see part 10..
Ok here's a 2002-6 gxi and poof.
The valve overlap has everything to do with exhaust reversion. The same cam that might produce a silky-smooth idle with no reversion in a 350 V8 will provide a choppy and unsuitable marine idle in a smaller V6.
I really can't stress this enough, RESPECTFULLY ... the fact that you used the word vacuum when talking about exhaust reversion means that you haven't really fully understood the dynamics when it comes to overlap reversion.
I've been building marine engines for many years now, so you can disagree all you want... or you can choose to build on experience. If you doubt my advice, post your concerns at one of these boating forums.
They have some of the brightest minds in marine engineering. If that's not enough, try www.eng-tips.com
suffice it to say, I wouldn't run that cam in my 355 V8. WAY too much overlap. In a 4.3 V6, that cam has a very serious risk of hydrolocking the engine in very short order. Many people think that for exhaust reversion to occur they need to suck water up from the lake, all the way up the huge 4" exhaust tubes, and into the engine. That is NOT the case. All it has to do is suck water from the wet exhaust manifolds back about 2". Then it falls down the manifolds and does one of two things; either contacts the exhaust valves causing them to splinter, or creeping into the chamber causing it to hydrolock.
Some stock marine cams have LSAs in the 117* range. To suddenly jump to 218/224 on a 112* LSA is a pretty definite suicide move for a 5.7, let alone a 4.3.
Be open-minded, do your research, and if you feel strongly that I'm incorrect, build it and good luck.
Here is my experiance with boat performance. A Ski Nautique, a tournament ski boat with a 350, or 351, and around 310 horsepower will go about 47 miles per hour top speed. I also have driven the same hull with a 430 hp GM 502 motor. It's top speed, about 53 or 54 miles per hour. Know the 502 also put out a lot more torque.
I am thinking you could spend a lot of time and money to gain not very much.
By the way, I had a 16 foot boat with a 135 outboars that would do about 48 to 50 mph, depending on how full the tank was.
My understanding is that the 4.3 liter GM V6 3/4 of a GM V8. Would it be possible to put a 350 V-8 in the boat instead of the GM 4.3L V6?
Gaining HP in a car is simple... shift the torque and HP curves up in RPM. In a boat, that is suicide. Not only do you lose the low end torque required to pop out of the hole, but you create increased exhaust reversion which can kill the engine pretty quick.
Dry exhaust is a whole different critter... as long as you have enough displacement to make the torque to get out of the hole, go nuts with a cam, but if you have a wet exhaust, keeping the cam mild is absolutely imperative.
Just finished reading the last of 87(!) posts made on your project at iboats forum, titled “Re: 4.3 Vortec build up and traps”. There were other topics on your project that I didn’t read.
I doubt there’s anything I personally could add to all the advice, so best wishes on the project and good luck.
Opps absolutely did not mean to offend you far from it. And yes you brought some very interesting points. This has not been guess work by myself at all, some very intelligent people have helped me along the way.
As to vacuum and reversion I might be way off the beaten path here but does not the exhaust valve stay open slightly while the intake stroke beings and the piston pulls (vacuum) from both valves reversing the exhaust flow and pulls both exhaust and water into the engine.... That is my understanding or maybe was..
Description Hydraulic flat tappet Hydraulic flat tappet Hydraulic roller tappet Hydraulic roller tappet
Crankshaft Duration at Lash Point (degrees) I: 294
E: 306 I: 320
E: 320 I: 318
E: 318 I: 321
Crankshaft Duration at .050" Tappet Lift (degrees) I: 202
E: 210 I: 222
E: 222 I: 222
E: 222 I: 224
Maximum Lift with 1.5:1 Rocker Ratio I: 410"
E: 410" I: 447"
E: 447" I: 447"
E: 447" I: 450"
Valve Lash --- --- --- ---
Lobe Centerlines (degrees) 113 114 114 112
Notes Marine cam for 229ci V6 with 108-132 degrees semi-even fire crankshaft. Good street performance cam. V6/90 degree version of L-79 small-block V8 cam for 4.3L even-fire engine. Excellent power and torque. For engine without balance shift. V6/90 degree version of L-79 small-block V8 cam for 4.3L even-fire engine. Use only with roller tappet block. For engine without balance shaft. High-performance street and marine cam for 4.3L even-fire engine. Use only with roller tappet block. For engine without balance shaft.
No 117 lsa there but i will follow up carefully what you have said, And again i thank you
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