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

[Mischief Managed]

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

A cheap and quick way to tell if a bigger carb will give more HP is to install a vacuum gauge on the manifold and go out and drive at WOT. If you have 1.5 inches-Hg or more vacuum at WOT, the carb is restricting the engine and you'll make more power with a bigger carb.

 

[John_S]

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

Just a point of conversation and interest...continuing the manifold discussion. Not sure how long this will be viewable, but this ebayer is selling my exact manifold, and it has a few decent pictures that shows the design a bit better than my pics did:
http://cgi.ebay.com/ebaymotors/Merc...6165083QQptZBoatQ5fPartsQ5fAccessoriesQ5fGear

Part # is 3856270. In searching at Volvo Penta Store, it appears this exact same manifold has been in use on pretty much EVERY single 5.0L and 5.7L vortec motor, carb'd and TBI injected, from 1996-ish thru 2006-ish.

Is this one better or worse for this application than the Edelbrock offerings? I have no idea. I suppose aluminum would be nice if only to remove a little bit of stern weight. All I know for sure is that I will not buy or test one. I will be running stock Volvo manifold.

In my model year range, the options for the 5.0 were either 220hp 2bbl carb, or 250hp 2bbl TBI. I will be curious if a 4bbl carb can be set on my manifold to produce about the same HP as the 2bbl TBI did. How will I figure this out? I won't. I'm too durn cheap to pay for dyno time on a stupid runabout, so I'm just gonna drive my boat really really fast until I run out of lake. Then I'll guess.

So what is my point in writing this particular post? I don't have a point.

Good info.

- Volvo must have had the intakes made for them (casting logo).

- I still don't see anything that says this will be inferior to Edelbrock Performer.

- Both are aluminum (no weight advantage), but couldn't see clearly enough to see if water passages were bronze. Maybe they are just hard anodized.

- The correct carb and tuning should get all or most of the HP that a TBI with same manifold. If comparing to an MPI, than no.

I wouldn't count on that one selling too quick!

 

[83Evinrude]

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

Part # is 3856270

I suppose aluminum would be nice if only to remove a little bit of stern weight

Just checked my engine and yes, that is the manifold part number that's factory installed on it. My magnet confirms that these are indeed aluminum.

 

[dannyual767]

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

They are indeed aluminum. I changed the thermostat on mine today since I've been fighting a pesky cooling problem. I noticed a nice bronze coloring right under the thermostat housing. I think these Volvo manifolds have coated water passages for corrosion resistance.

 

[craze1cars]

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

Cool...It never really crossed my mind they were all aluminum. Just gives me another reason to not bother changing it out.

Update: Friend-of-a-friend carb did NOT pan out to be as it was represented to me. So no dirt-cheap lucky steal there. Minor bummer.

I'm still carb shoppin'...

 

[83Evinrude]

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

I'm still carb shoppin'...

Looks like the cheapest spreadbore I can find is a rebuilt Quadrajet on eBay. Not sure why, but the Holley 4175 is much less plentiful and also more expensive.

 

[craze1cars]

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

OK. Enought talk. Time to either s**t or get off the pot. So I got one:
http://cgi.ebay.com/ebaymotors/ws/e...0509765564&viewitem=&sspagename=STRK:MEWAX:IT

Holley factory reman...direct from Holley themselves. They had it on Ebay for $299.99 or best offer. I typed in $259.99 and they accepted it instantly. DANG IT!! I should have tried to go lower first!! LOL...

Oh well, even with $20 shipping it still seems like a great deal to me since the new ones all sell for $450-ish and up. So I'm a little over my $200-ish budget now, but the curiosity is simply too much for me to ignore. At least I'm gettin a totally fresh one and I won't even need to bother opening it up to clean it...bolt it on and put fire in the hole, maybe rejet if even that. I figure it's hard to beat a 90 day warranty, and I will now have no guilt over calling Holley tech support for assistance if I have questions on dialing it in.

And if it just doesn't work out, I can probably get most of my money back by selling it again on Ebay...

I did call them and asked what they recommended for my specific setup...and I didn't steer them at all. And this is the one they told me I should buy. He said it would work better than a square bore with an adaptor. He also said it will probably be jetted very very close to accurate for my motor straight out of the box, but he said if anything at all, it might be set a little too rich. We shall see.

Guess I'm gonna try this mod much sooner than I anticipated! Should have some performance answers within a few weeks if my schedule allows it.

 

[ECVCHAMP]

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

We knew you couldn't wait, keep us posted.

 

[Utahboatnut]

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

I run a Merc but wanted the same out of the hole pop that you do. Tried a 4 blade stainless with good results, then bumped up to a merc hi five 21 pitch. Better make sure your shoulders are in good shape cause it will rip your arms off in a hurry. I did lose some off the top (prob 3-4 mph) but man is that low end worth it. Two 200+lb slalom skiers bring it no problems at all. I don't know if there is a hub conversion kit for a VP but I do know the hi five is THE prop for watersports OR tug boats. I know you want to do the carb switch I just thought I would relate my personal experience.

 

[83Evinrude]

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

Guess I'm gonna try this mod much sooner than I anticipated! Should have some performance answers within a few weeks if my schedule allows it.

Sounds like you got a good deal on the carb, looking forward to seeing how it works for you.

I did lose some off the top (prob 3-4 mph) but man is that low end worth it.

That's more top end than I'd like to lose. Unless work stops me, I'm finally heading to the lake tomorrow and will test the 20p 4 blade BayPro II prop I bought in March. Ours pulls skiers great now but I think it could hook up in corners better.

 

[mikeneal]

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

I have the jetting somewhere, I do recall it ended up nearly or exactly same as out of the box so I think your reman from Holley will be same. I bought the AN stainless fuel lines and fittings and made my own fuel line. No way to get my OEM fuel line to work. I can take a pic of it if you want. My perfect pass I modified the throttle cable attachment to shift the fixed end. (I think, it has been a while). There again if you get into trouble I can snap a couple pics.

I use a couple different props on the boat, I wanna say I added a couple hundred RPMs to the 19" prop, I don't ever WOT the 17" prop (wakeboard prop) top end because boat is under proped for high end). My boat is pretty heavy, (19' chris craft) and almost always has some ballast in it and with the carb change is runs almost 50, added about 3-4 MPH. And it has about 1200 hrs on it so not "fresh" by any means.

I would leave the manifold, factory is good bronze lined aluminum, IMO no benefit to a aftermarket. I assume since you are searching for performance upgrades you have a good stainless prop? If not spend your manifold on a good prop.

 

[craze1cars]

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

Thank you mikeneal...helpful.

I do have a very good prop. Brand new 4 blade Stainess Solas Titan HR-4. I love that prop, and in large part it is the very reason I am trying to make my motor strong enough to bump it up from my current peak 4,570 peak RPM. If adding this carb gains me 200-ish RPMS with this existing prop, I'll be incredibly happy...that would be better than repitching or having to drop in pitch.

Just got the carb from Holley today. Now I'm even more glad I bought from them...looks absolutely brand new, never installed...AND it came with a complete install kit, big beefy base gasket, studs/nuts, etc., and install instructions. I wouldn't have got any of that stuff with a used one that I had to rebuild myself.

Heck, I didn't expect a base gasket at all, and I had already bought a Fel-pro 1902 from NAPA in anticipation of getting this carb. Guess I'll be making a return run to NAPA since I won't need it!

And as fully expected, installation takes a back seat for a bit. Today is BEAUTIFUL weather and is an official WATERSKI/WAKEBOARDING day! Friends and I are hitting the water about 4:00 this evening, and we will be running my perfectly tuned stock 2bbl carb and prioritizing FUN over a tuning session. So the new carb will sit in a box on my workbench for a little while...we'll see if I can find a window of non-watersports time to get it installed in the next few weeks...

 

[wire2]

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

Thank you mikeneal...helpful.

...that would be better than repitching or having to drop in pitch....

Repitching can be iffy. A dealer sold me a 19" ss repitched to 21". It was fine out of the hole, but once on plane, just a slight turn of the steering wheel caused severe cavitation and loss of plane. A big PITA. I got a new 21" ss, no problems since.

 

[craze1cars]

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

Update: Carb's installed. Took about an hour. VERY straightforward and easy once I got a new fuel line made. Pics attached.

The fuel line with the silver ends was my factory fuel line. The new carb had a different fuel inlet location, plus a different size fitting, so I couldn't re-use the old one. The line with the blue ends is one that I had made at a local speed shop. Not the cheapest fuel line, but I wanted a good one. Paid $46 for all fittings, teflon lined braided hose, and tax. They assembled it for free in about 5 minutes. If any of you want to do this at home, the Volvo electric fuel pump side is 5/8"-18 threads, and the Holley 4175 inlet end is 1/2"-20 threads. I could have PROBABLY just cut one end off the factory fuel line and got by with attaching only one end for cheaper, but after 12 years of age, I thought better to just build an all new fuel line while I had it off.

These Volvos are simply MADE to do this conversion with the 4175 marine carb...a total slam dunk. Sooooooo much easier, faster, and MUCH MUCH cheaper than doing a Mercruiser!! I had to relocate throttle linkage mount one hole forward, which involves just one bolt. The plate even has clear marks that say "2V" and "4V"...presumably for 2bbl and 4bbl carbs. I took a pic of this too. You can see the dirt outline where the mount was previously with the 2bbl. After doing this, the linkage just bolts right up just like it did to the old carb and nothing needed any adjustment.

The vacuum port for the PCV valve is moved from rear to the front of the carb. So PCV valve hose wouldn't reach. Rather than run a super long, twisty new line, I just moved the PCV valve to the other side of the motor (the opposite valve cover), and moved the vent hose that leads into the flame arrestor from that valve cover over to where the PCV valve previously was. I see no disadvantage to swapping these, and saved me from buying any parts or changing the length of either hose.

Electric choke just plugs right into factory harness...plug & play.

The ONLY parts I needed to buy were the carb itself for $280, and the fuel line for $46. All my gaskets and mount kit hardware came with the Ebay carb from Holley. I needed to buy nothing more. So I'm exactly $326 out of pocket, and as far as I can tell, I'm 100% done. Plus I have a well-tuned factory Volvo/Holley 2bbl and fuel line that I may be able to sell someday if I choose to, and offset some of this cost.

I fired it up on muffs in the drive tonight after install. Ran crappy at first and wouldn't idle, but after tweaking idle mixture screws and idle speed for a few minutes, I got it running like a top. Seems to have very good throttle reponse with no bog or anything, and a nice smooth idle. But I can only do so much in the driveway...she needs a test drive. Hopefully tomorrow? Right now it appears my schedule will allow, but if work comes in fast & furious as it sometimes does, I'll have to postpone the boat ride for about 1.5 weeks because my schedule is JAMMED after tomorrow. BUT I'm pretty sure I'll be reporting back with performance stats tomorrow! Will be kinda bummed if it runs 56 mph...or less. We shall see!

Oh, as a side note I pulled the float bowl off of this carb to take a look and it has 61 jets in it. Hopefully I don't need to rejet it leaner, because I don't have anything smaller than 64's in my stash. Worst case I'll need to buy some more jets. $10 or less. I will report back if I find it necessary to play with jetting. Most reports I've found from the few people who have installed this carb have told me it runs very well out of the box and rejetting may not be needed at all.

Go back to post #27 of this thread if you want to see my 'before' pic. 'After' pic is below...

 

[craze1cars]

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

Drum roll please! badumbadumbadaumbadumbadumbadumbadumbadum....

And the answer to the question asked in the title of this thread:
How much HP would be gained adding 4bbl to 5.0L Volvo GL Vortec?

ZERO.

That's right.

ZERO.

No gain, no loss. It ran like a top today, just like my 2bbl did. Top speed 55.8 at 4,600 rpms. With 2bbl I got 56.2 at 4,570. Too close to call...could have been a breeze or slight difference in trim setting that caused that minor diff.

After word got out that I was on the lake doing test runs alone, I ended up quickly with a boat full of 7 people! (they did NOT partake in my top speed test run...so I DID compare apples to apples on weight/load to get above result). So I bailed on playing with the carb and we just boarded and skied the rest of the day. Had a BLAST! Beautiful day and lots of fun.

BUT, I have not given up all hope just yet. Since friends appeared out of nowhere I scrapped any effort to try rejetting, determining if/when the secondaries are opening, etc. Heck, I haven't even pulled a plug yet to see if it's lean or rich. But I think it's pretty close. Smelled normal, no smoke, no soot on back of boat, no lean bog. Fuel consumption seems about the same, but I never have really measure that so I'm just guessing.

So I will play with tuning some day and hope for some improvement. Might experiment with jetting and different secondary control springs. But between work, vacations, and watersports It'll be a solid month or more before I really find time to play with it again. But I ain't holding my breath of getting much more out of it...at least not without propping down a bit to allow this carb to get more RPMS to suck some more air. And once I do that my baseline will be gone, and I'll never have a confident answer, unless I put the 2bbl back on with new prop to get a NEW baseline.

Anywho, as I acknowledged earlier, not all tuning experiments provide the results you hope for! And this was one of those experiments. Thankfully it runs as good as ever and is still a great and fast boat.

Will report back someday if I ever feel like tearing into it and trying to fine-tune further.

So my answer for today, for those of you contemplating this change? Don't bother. If I change my mind someday after more thorough carb tuning I will report back with details. But I honestly suspect those who have reported gains in making this change on their 5.0's may have been people who replaced their WORN OUT or OUT OF TUNE 2bbls with NEW 4bbls. And naturally they saw legit gains...gains they could have seen with a properly tuned 2bbl. But since I started this test with a properly and peak-tuned 2bbl, I am currently seeing no gains. But of course I'm just speculating and have no idea what others started with.

 

[fossill]

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

Oh well, it was a noble experiment in the least. If anything that carb "spruces up" the engine cosmetically.

 

[bruceb58]

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

Assuming you used the identical prop that you used before your change, you wouldn't and shouldn't expect a speed increase. The only way you would expect a speed increase is if the higher HP allowed you to swing a higher pitch prop. You may have a little better acceleration now and can tolerate more people on your boat but don't expect any speed difference unless you can change your prop.

 

[craze1cars]

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

Thanks. I mostly agree. But if this motor can't spin the same prop any faster than 4,600 right now, I wouldn't expect a HIGHER pitched prop to be able to spin this motor anywhere near it's powerband. Pretty sure more pitch would just lug it below the peak powerband.

But the prop thing has definitely been on my mind, but more in the opposite direction. I'm speculating (maybe incorrectly) that this motor may make its power peak closer to 5,000 rpm than it does at the 4,600 my current prop allows...especially with a larger carb since the whole point of larger carb is to pull more air. And pumping more air can only be done by running higher RPMS. So maybe higher RPMS may allow it to take better advantage of the extra air carb can allow? Therefore if I do anything prop-wise, I probably will change it out someday to an inch or two LOWER pitch to see if and/or how that makes any top speed diff if I let the engine spin out.

The other reason for my theoretical 5,000 rpm target is the fact that I believe the 250 hp rated 5.0 Gi TBI injected model of this boat was rated at that HP, at a max RPM of 5,000. I THINK that is accurate anyway...I've found it difficult to find specs on these Volvo motors, can anyone confirm actual HP and RPM ratings for a 1999 Volvo 5.0L Gi TBI? If you can, thank you in advance!

Plus that would clearly benefit me more for watersports anyway, even if top speed changes little in either direction. Frankly I could care less about top speed...it is just the only built-in dirt-cheap dyno I have so I'm using it for the experiment. But if I'm gonna change props in any direction it will definitely be lower, so I can pull better. We ALL know I'll gain accelleration with lower pitch...top speed will be a definite question mark until I try it.

Still quite confident that my factory exhaust is the biggest restriction to any 4bbl benefit anyhow. But I will NOT be trying thru-hull exhaust as I have always hated louder exhausts. On anything.

But to allow any definitive answer on whether or not the carb makes extra power, I would need to run with the 4bbl with any new prop, larger or smaller, then put the 2bbl back on and run with the new prop again and compare those notes. We'll just have to see how motiviated I am to do all that LOL! Of course if I don't, I'll will never have confidently answered my first question regardless of any speed change. You'll all be left hangin'!

Methinks I'll just BOAT the rest of this summer and enjoy it. It's not like my 55 mph boat is SLOW or anything! And it's fine out of the hole for everything we do. When the water gets too chilly I may play more with tuning & experimenting this fall. That's when new props get cheaper too...

 

[John_S]

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

Not the outcome I was expecting, either. I wasn't expecting allot, but 1-2 mph seemed reasonable. Maybe you will get a little from a good tuning. If you are not going to mess with it this summer, just keep a good eye on the plugs such that you are not running lean.

I'd do more research on what is different between the TBI and the 2brl carb. Given the intakes are close/same, there has to be another answer of how they are getting more hp. Cams, timing curve, something. One area to look at is rocker ratio. I believe I have seen some volvo owners state their engines were stock with 1.60 ratio.

 

[craze1cars]

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

Not the outcome I was expecting, either. I wasn't expecting allot, but 1-2 mph seemed reasonable. Maybe you will get a little from a good tuning. If you are not going to mess with it this summer, just keep a good eye on the plugs such that you are not running lean.

I'd do more research on what is different between the TBI and the 2brl carb. Given the intakes are close/same, there has to be another answer of how they are getting more hp. Cams, timing curve, something. One area to look at is rocker ratio. I believe I have seen some volvo owners state their engines were stock with 1.60 ratio.

I'd be VERY curious what you can dig up on that info. Please share if you find anything. I do have factory service manual for my GL, but it doesn't cover the TBI version. I just looked and it specs my rocker valve ratio is 1.50 to 1.

Rocker arms are always readily available for SBC's...and relatively easy and inexpensive to change. You may have uncovered my next experiment! LOL. I actually probably have access to some FREE (free to borrow at the very least) roller rocker arms that would bump ratio to 1.60 or maybe 1.65 for at least a test run...could be interesting. I'll have to call that buddy who has a bunch of extras laying in his garage.

The quest for more power is never-ending.