How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

[bruceb58]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

BUT the 1.2mph drop up top tells me at full speed I may have pushed the motor a hair past the power curve by going to 5,200.

If you got a speed loss by going up to 5200 RPM it has nothing to do with your motor. It got it up to 5200RPM just fine. Something is occurring with the trim/hull/prop at that RPM.

 

[craze1cars]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

Here's my thinking in saying that...my boat in original trim is rated at max HP 4,400 to 4,800. Anytime you push a motor past peak, the HP curve starts to come down. So if running past peak, there is less power to push the boat up to speed. Which is why I believe that over-revving with a prop of too small of a pitch would cause a drop in top speed....and I think that might be happening when I push my engine to 5,200 with the 19 pitch.

I do not understand why this thinking would be wrong? Please explain more. Thanks.

 

[honeys money]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

You are rite, it is camed and carbed for that RPM range, going with more pitch should get you back there, and also more MPH.

 

[bruceb58]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

I do not understand why this thinking would be wrong? Please explain more. Thanks.

Your prop is spinning faster when the engine is spinning faster right?

Just to make sure we are talking the same thing here. You are saying the boat goes slower at 5200 RPM than at 4800 RPM with the exact same prop right? Everything else is also the same?

 

[craze1cars]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

Your prop is spinning faster when the engine is spinning faster right?

Just to make sure we are talking the same thing here. You are saying the boat goes slower at 5200 RPM than at 4800 RPM with the exact same prop right? Everything else is also the same?

Nope...that's the mistunderstanding. Reread my 3rd to last paragraph in my post #78 above where I am now essentially done tuning the motor and now fine-tuning with prop changes...maybe I wasn't entirely clear, but I did change from a 21 to 19 pitch in same prop model/style. And that's the only reason my RPMS went from 4775 to 5200 and speed dropped 1.2 mph. I was NOT using the same prop.

I purposely went down in pitch (with identical model prop), to get my RPMS up to see which direction my top speed would go, and to see if maybe the extra RPMS might get me deeper into 4bbl secondaries by pulling more air & threfore more fuel which woudl possibly = more power. The answer was no. I was (still am) looking for the peak of my HP curve that I believe may have changed from factory due to my changes. The only thing I concluded was that my peak is clearly not at 5,200, I believe that's on the downswing of the HP curve. I was making more speed (and therefore more power) at 4775 than at 5200. So I'm now going to come back down a bit in RPMS by going back higher in pitch to try again...with a 20...with the hope of testing my power output at approx 5,000 rpms. I'm basically slowly trying to find my HP curve. I am very much in fine-tuning mode. I can no longer assume that my original Volvo 5.0GL 4,400 to 4,800 RPM range is correct anymore (although it could be)...so I figure I just gotta find the acutal peak myself, and I'm using the lake as my dyno since I'm way too cheap to have the motor dyno'd...plus doing the testing myself is more fun.

 

[bruceb58]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

Just put the 21 on it and call it good if you are getting into the recommended RPM range.

 

[craze1cars]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

My recommended range? That just loops me back around to the question I'm working on answering right now:

What exactly IS the recommended range for a 1999 Volvo 5.0GL Vortec that has now been converted to a 4bbl, carb spacer, 1.6 roller ratio rockers on intake, and 1.5's on exhaust? I find it entirely possible that I've changed it...

As far as I know, Volvo never built the setup I have...therefore I certainly don't know the range...so I'm trying to find it/confirm it. I do know that the newer EFI models with higher HP output are recommending 4,600 to 5,000, and a few of the new 5.7's are now saying 4,800 to 5,200. My original 2 bbl setup was 4400 to 4800. The pre-vortec mills mine called for 4200 to 4600.

Obviously I can roll the dice and just call it "good enough"...but us tuners NEVER do that...instead, we figure it out first, THEN we know we can call it "perfect." Heck, my boat performed 'good enough' way back before I started this project...where's the fun in that?

Besides, never in my life have I seen peak HP listed as a "range"....only in the marine world do they do that. Every motor I've ever seen on a dyno has a specific RPM "peak", not a 400 rpm "range". So I'm seeking the peak....it's what good performance engine tuners do, even if it's not what most boat mfrs do....

 

[bruceb58]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

So what are you doing to the engine to "Tune" it? Sounds like you are just finding the right prop at this point.

 

[Don S]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

Besides, never in my life have I seen peak HP listed as a "range"....only in the marine world do they do that.

The rpm range on a marine engine has nothing to do with the HP rating, it's a range for propping the engine to prevent excessive engine rpm (and shortens engine life) and lugging the engine due to not getting full use of the engines available HP and torque which also shortens the engines life.
Also, the engine specs are for the majority of boat owners and making the product last as long as possible, not the hot rod that wants to tinker with everything and look for that extra .5 mph in the boat.

If you want to discuss props and how to get the most speed and rpm out of a prop, we have a prop forum just for that type of discussions.

 

[craze1cars]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

I agree 100% with both of your last posts. Engine tuning is essentially done for now. I am indeed now searching for the perfect prop pitch for my very mildly modified engine in its current state of tune, and in order to do that for my hot-rodder standards, I need to know my motor's perfect peak RPM...and I'm looking for it...a generic range is not good enough for me, though I agree it usually is for the average boat owner.

I'm just writing my findings and explorations on this whole project for those select few are/were interested in reading it and seeing it. Given that there has been 3,361 views thusfar, it seems someone out there had an interest...

I'm not really asking any questions anymore as I'm just exploring, thinking out loud, and sharing my findings from start to finish. Non-hot-rodders, and anyone else out there who is not interested in this topic as a whole...you are welcome to not read it and/or not post in it...and moderators are welcome to move it to wherever they see fit, if it bothers you to see it here.

Those who do have an interest, you're welcome to continue commenting as you see fit...

 

[ramster]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

The cam in the 2BBL 5.0 is very mild, so peak power will be around 4600-4800, a cam swap will make a big differance, it is a roller so you can reuse everthing, lifters, pushrods etc. put in a Ramjet cam or "495" as its sometimes referred to, it's the same cam used in the 270 HP injected motors, but will work fine with a carb too. As for my 5.7 conversion, had the boat out for a quick shake down run, usind a Stilleto 3 blade 21 she storms right to 61 MPH at near 5000 RPM. My jetting is too lean so I knows theres more left once that's sorted out.

 

[rbchristian2]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

I think this is absolutely great... I am in the process of doing this now and it is very helpful. I am going to put a quadrajet on but I didn't know about the spacer. I assumed that you could reuse the flexible fuel line but I was going to look at the this weekend, but if you say no, then I will make a new one. I am not going to do the roller rockers but great idea.

This all started with the boat popping on hard acceleration and only getting 4200-4300 RPM's (tune up done). I did rebuild the 2 barrel but kind of half @ss and no RPM increase with stock prop. So I figured it was time and you can't find many people that have done this. So hats off to you for reassuring me! Thanks for the confidence.

By the way, mine is a 2002 Four Winns. I am only seeing 46 MPH out of the stock 50 I should see, so if I get that back and 2 MPH more or so I will be VERY happy. Plus the fuel economy should be a hair better on cruising or stay the same... Great for a performance upgrade when it usually goes down!

 

[craze1cars]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

Please share how it goes, it will be interesting to hear your results. Regarding fuel line, you and I are comparing apples to oranges as I used a Holley and you are using Q-jet, so most certainly they have different locations and possibly different sizes of inlets.

But having said that, I will be 98% certain in saying that you will probably need to fabricate yourself a new fuel line to fit the Qjet...

 

[rbchristian2]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

Please share how it goes, it will be interesting to hear your results. Regarding fuel line, you and I are comparing apples to oranges as I used a Holley and you are using Q-jet, so most certainly they have different locations and possibly different sizes of inlets.

But having said that, I will be 98% certain in saying that you will probably need to fabricate yourself a new fuel line to fit the Qjet...

I will keep you posted! It will be within the next 2-3 weeks.

 

[SeanMcl]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

I am only seeing 46 MPH out of the stock 50 I should see

Keep in mind that if you are significantly above sea level, you will not see the rated speed. At 4000 feet, you lose about 15% of your rated HP and it gets worse the higher up you go.

 

[E4ODnut]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

Great Thread!

So refreshing to see a tuner out there not afraid to try something different and document the real results.

If you ever feel you've reached your limit with carbs and conventional ignition, and want to venture into the mystic world of programmable EFI, I'd love some company.

Keep up the good work!

 

[rbchristian2]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

Keep in mind that if you are significantly above sea level, you will not see the rated speed. At 4000 feet, you lose about 15% of your rated HP and it gets worse the higher up you go.

Thanks but I am in the Chicagoland so I am not above sea level. 46 is the best that I saw with a normal of 44-46 and I am only getting 4000-4200 RPM's and it sputters slightly on acceleration sometimes, plus the last part of the throttle gives me nothing. There is an issue in the carb and it is easier to do this with a gain that to play with the old one.

 

[ramster]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

My latest test after swapping some jets netted me 63 MPH and then it starts to get a bit squirrely. My jetting for the Q-jet is 74 primary jets with 44 rods, and DH secondary rods, and an E hanger. Getting pretty close with that combo, still a little fine tuning to do. I'll have to admit that the four barrels works better with a 350 under it VS. the 305. I now have to tweak my Smart Tabs to sort out the handling issues.

 

[rbchristian2]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

My latest test after swapping some jets netted me 63 MPH and then it starts to get a bit squirrely. My jetting for the Q-jet is 74 primary jets with 44 rods, and DH secondary rods, and an E hanger. Getting pretty close with that combo, still a little fine tuning to do. I'll have to admit that the four barrels works better with a 350 under it VS. the 305. I now have to tweak my Smart Tabs to sort out the handling issues.

When you had it on your stock 5.0GL, did you have the Quadrajet set up stock out of the box to see your 2-3 MPH difference? I am doing this tomorrow (weather permitting) so it is set for Memorial Day weekend. Did you notice any gas mileage difference either way? Anything else you remember?

This is the most informative thread and very detailed thanks to you,craze1cars and mikeneal (if I am forgetting someone, sorry!). Thanks!

 

[John_S]

Re: How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

Thanks for coming back and updating. Almost missed it since the last board change and thread moves.

PS: I would be interested in what your compressed gap measurement was with the 1.6 rockers on both the the intake and exhaust valves that proved you didn't have a binding issue. thx