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

[craze1cars]

Hello,

Have a 1999 Volvo 5.0L GL PWTR. Vortec 305 rated at 220 hp. All stock, currently fitted with the factory Holley 2bbl 500 cfm. Runs excellent, and at WOT I'm sitting at 4,600 on digital tach. I would like to inch this figure up to 4,800 for absolute max thrust out of the hole for our primary use: Watersports.

#1) I'm certainly considering the obvious option...drop an inch of pitch. But for a replacement 20p for the 4 blade stainless 21p like I have now, I'm looking at $400-ish. Or I can have mine repitched for probably about half that. Or sell mine and recover at least half. So no matter how I slice it, for dropping an inch I figure on $200-ish.

#2) Considering a second option...try a 600 CFM Holley 4160 or 600 cfm Edelbrock 4109 4bbl marine carburetor. Should be direct bolt-on if I pull the adaptor off my manifold, correct?? I know how to rebuild them and I know how to tune them....so I could snag a used one all day long for $150-ish and rebuild it like new. ESPECIALLY the Holley...I have complete jet tuning kit, several gaskets and other parts for that in my shop already. So I'm figuring for the same $200-ish out of pocket I would gain a few ponies that might allow the motor push my current prop to the extra 200 or 300 RPM's up top that I'm seeking?

Option #2 sounds very appealing because price is about the same, my current stainless 4 blade prop is absolutely spotless so I don't need to replace, AND I'd have the bonus of having picked up a few extra HP. I don't care much about extra fuel consumption.

BUT, do you have any thoughts on whether #2 is a realistic expectation? I'm not expecting miracles, and I realize that a 305 wil only flow so much air at sub-5000 RPM no matter HOW big the carb is. But is 200-ish RPM a realistic gain to expect? Or do you think I'd see more, less, or no change? And before anyone suggests it, I fully realize a 350 would bolt right up, but that costs a bit more than the $200 options I'm listing, so no thanks...

So I guess my biggest questions are these: How many real HP, and/or how many RPM's, would you folks expect I might gain by installing a properly tuned 600cfm 4bbl over my currently well-tuned 500 cfm 2bbl? Anyone by chance have results to share after doing this to a 5.0 Vortec? Mercruiser or Volvo? Thanks in advance...

 

[John_S]

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

Based on the Merc MPI version of the 305 is 260hp, I'd say you would get about 20-25hp. Depends on hull, for how many additional wot rpms that is. I'd guess in the 100-150 range. You should notice a slight change in acceleration based on using the smaller primaries. Will it be the same as dropping the pitch an inch? Maybe. I would probably lean toward the reduced pitch vs 4brl, for seat of the pants, acceleration noticability, though.

PS: If you ran this thru the VE calculations, it probably says a 500cfm carb on a 305 is more than enough to get 5K rpms.

 

[bruceb58]

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

You forgot to figure in the cost of a new intake manifold.

 

[John_S]

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

You forgot to figure in the cost of a new intake manifold.

Bruce, I think most sbc volvos come with a 4brl manifold. It has a block-off plate for using a 2brl. It makes it much easier than a merc, to do the upgrade.

He does have to get a new flame arrester, and possible fuel line change. I'd also check to see if volvo changes anything for the timing curve.

 

[bruceb58]

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

Bruce, I think most sbc volvos come with a 4brl manifold.

Yes...looks like you are right!

 

[craze1cars]

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

Thanks for the input guys. Helpful.

Yes, it does appear that I have only to remove a simple 2bbl adapter plate from my current manifold, and then a 4 bbl would bolt right up. So I think no manifold needed unless I'm looking past something.

It's interesting John says I need a new flame arrestor. My current 2bbl Holley has a 5" diameter air horn. And I understand the replacement 4bbl carb is also a 5" diameter air horn? So it seems to me my flame arrestor would work? Or am I overlooking something there as well?

If it makes it any easier for you folks, this is pretty much what I currently have with specs:
http://www.holley.com/0-80402-1.asp

And this is what I would most likely consider replacing it with (however purchased used, then rebuilt by me):
http://www.holley.com/0-80551.asp

And with that swap I think my fuel line should be able to stay the same, especially if I swapped Holley to Holley. They appear to hook up in exactly the same location. But even if I need a line, that's easy...no biggie.

I never considered the possibility of needing to change the timing curve...can anyone confirm whether this would be needed? Not sure how to go about that, or how to figure out what I might need to do there. Additional input there is appreciated.

I really appreciate the input from all of you, especially John's guestimate of HP and RPM. And yes John the VE calculations are very clear that I definitely would NOT exceed 500 CFM of flow for a 5.0L running 5K RPM. Curious if others have more input along these lines, as far as what I would notice in terms of actual gains, if any. The calculations are great, but I know that in real world tuning sometimes they don't follow seat-of-the-pants results. I've heard of many finding benefit fitting 4bbl to a 4.3L, so I would tend to assume I'd see a similar benefit bolting to my 5.0. But maybe not if those 4.3 carbs flow less than mine to start with...maybe they're smaller.

Has anyone out there actually fitted a 4bbl to a previously equipped 2bbl 5.0 Vortec? I would LOVE to hear a real-world result on this if anyone has done it.

No question the prop swap is easier and more direct, but this could be more fun!! I'm a tweaker...we'll see.

Thanks so much everyone.

 

[John_S]

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

It's interesting John says I need a new flame arrestor. My current 2bbl Holley has a 5" diameter air horn. And I understand the replacement 4bbl carb is also a 5" diameter air horn? So it seems to me my flame arrestor would work? Or am I overlooking something there as well?

John has expeirence only on mercruisers, where the 2brl carbs are not 5" diameter.

And if you go with the Holley instead of the Edelbrock, probably don't need fuel line. Volvo just makes it too easy. Lucky you.

BTW, the timing comment was based on mercruiser as well, and prior to vortec. Merc only had EFI and MPI with vortecs, no 4brls to compare. If you have access to a parts structure for volvo, like mercruiserparts.com, probably can figure out is there is a difference. Any timing difference would not be enough to hold me back from making the change.

I can't recall seeing anyone post on this for a 305 vortec volvo. Some 350 vortec volvos. But for how easy it is, you would think there would be more. Especially when it came time to rebuild or replace that 2brl.

 

[craze1cars]

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

Yeah I'm really struggling finding someone who has done this before. I guess Volvos are just in that fewer numbers out there? And I agree it totally looks like a slam dunk to do this conversion with no extra parts needed. Just a carb and gasket and nothing else as far as I can tell. This is why I'm giving it such serious consideration...I see very little to lose but my time...

And I can't find any Vortec 5.0's from Volvo that were ever fitted with a 4bbl. As much as I'd love to compare such notes between motors, they don't seem to exist. Best I can tell all their 96 and later 5.0's were either 2bbl or EFI.

I did find this antique post:
http://forums.iboats.com/showthread.php?t=209462

He had some challenges that appear to have never been resolved...you chimed in there at the time also. I later found a post where he was very satisfied with the upgrade. But I don't know what he did to fix the probs. So I sent him a PM and we'll see if he responds...I'm curious if he recalls how he resolved his tuning issues and might be willing to help me out.

I noticed he utilized a 4175 Holley (650cfm), instead of the 4160 (600cfm) I was considering. http://www.holley.com/0-80552.asp Do you or anyone have any input on this choice? Looks like that one WOULD need a fuel line reroute, so not sure why he's select that one. This whole spread-bore thing was talked about quite a bit in that thread, I'd be interested in learning more about that...I'm more of a high-rpm drag racing car guy, and I know my tuning experiences on those will not carry over effectively to these slow-spinning torque machines...so I'm just trying to educate myself fully before I choose to move forward...or if I bother at all. Maybe that 4160 is NOT spread bore like the 4175 is, and that's bad?

I might need to chat with Holley's tech support and see if they'll have some advice for me.

Thanks again.

 

[craze1cars]

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

Ok...after doing a little more looking, I'm quite certain my Volvo has a spread bore manifold, which explains why the other guy used a spread bore carburetor. The 4160 option appears to be square bore...

BUT, don't I just need to get a square bore to spread bore adaptor if I want to use a square bore carb?? Holley & Edelbrock sell them for $30-ish. Or for some performance reason should I be limiting myself to shopping for only spread bore design carbs? If the latter, I am limited to only the 4175 and Quadra-jets...even eliminates the Edelbrock 1409 option as that's square bore also.

Do those adaptors work fine for this sort of thing? Seems square bore carbs are far more numerous and easier to find...and it seems I'm more likely to find one that is closer to plug-n-play for my setup than having to switch carb types...

I'm just beginning to suffer from analysis-paralysis a bit here. LOL!

 

[jy118lfd]

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

Build a quadrajet. You will get better fuel economy (if you can stay out of the secondarys) and more power. I did this swap on a 5.0 vortec mercruiser, I used a volvo manifold and going from a 15 pitch aluminum spun at 4800 to a stainless 17 spun at 4900 I gained about 6 mph wot. I also gained speed at cruise along with economy. But I built my carb from scratch using what I know about quadrajets. You can build on with this book or send it to Cliff to get it done. http://www.cliffshighperformance.com/


I currently have this setup on the same boat but have repowered it with a 5.7. It now spins a 18 pitch stainless 4 blade and picked up about 4 mph. I think it would pick up more but the 4 blade cruises sooooo much better.

I have a 5000lb 24 foot walkaround. Alpha 1.62 drive.

From the beginning
2bbl 5.0l Cruised at 19 to 20 knots at around 11 gph 28 knots wot
4bbl 5.0l Cruised at 22 to 23 knots at 12 gph 33 knots wot
4bbl 5.7l 24 to 26 12.75 gph 37 knots wot


Email me if you need some specs for a carb. I will post them here but do not get on the site too much anymore.
jy118lfd@aol.com

 

[craze1cars]

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

Very interesting...thanks for the help. I'm not a total stranger to Quadrajets either...have worked on them in the past. I'll shoot you an email. Appreciate the tips.

 

[robjen1019]

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

If that 305 is rated at 220hp, that is probably all your going to get. The holley carb is rated for 500, I know on my aq225, my quadrajet secondaries only open when I really get on it. You might gain 5 to 10 hp which is probably 1mph or less. Also if you are looking for more grunt out of the hole, your only upgrade that is going to help is a 350 or change pitch on the prop. Dropping down a pitch on the prop will get you where you want. Maybe try a 4 blade and see if you like that better.

 

[John_S]

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

Ok...after doing a little more looking, I'm quite certain my Volvo has a spread bore manifold, which explains why the other guy used a spread bore carburetor. The 4160 option appears to be square bore...

Compare your manifold to the Edelbrock vortec performer. The performer can use either a spreadbore or squarebore. GM also has a similiar manifold. That is what I would expect volvo to use, but don't know for sure. Do you have a pic with carb removed?

 

[craze1cars]

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

Compare your manifold to the Edelbrock vortec performer. The performer can use either a spreadbore or squarebore. GM also has a similiar manifold. That is what I would expect volvo to use, but don't know for sure. Do you have a oic with carb removed?

I haven't lifted my carb off my manifold to look in there. I'm just internet-racing for now lol. What is "oic"? Are you asking about a bar splitting the 2 halves of the manifold??

Looks to me like spreadbore and squarebore carbs have 2 different bolt patterns...thus probably the availability of the adaptor. I'll have to pop it off sometime and sneak a peak under there unless somebody else here knows the answer. I've serached on line and can't find any pics of a 5.0L Vortec Volvo manifold...if anyone else finds one, please post a link.

Thanks.


Robjen, your AQ225 is pre-vortec. They're choked off by the limited flow capacity of their head design. The later Vortec heads (1996 and later I think?) are a totally different animal and have much more potential. The new Volvos that use my same Vortec motor are now rated at 270hp at 5,000 rpm (with EFI). I certainly do NOT expect to see that kind of HP by simply slapping on a 4 bbl, but all indications from those who have converted 2bbl vortec marine engines to 4bbl seem to think 240 to 245 hp is a realistic estimate of what they have reached...somewhere squarely in-between the 2bbl and EFI versions.

And as I posted in post #1, I alredy have a 4 blade stainless, and I fully realize that dropping pitch will get me my rpm and a hit of better hole-shot. Frnakly my boat performs excellent as-is...56 mph on GPS from a 20 ft runabout. And it pops outta the hole pretty quick. I'm certainly not disappointed. But I'm a bit of a hot-rodder in everything I own...cars, snowmobiles, boats, and I always would like to see if I can find a little more...I suppose this little project is more about fun and experimentation for me than any desire to get somewhere specific. If I gain little performance, I've still gained some great eductaion and enjoyable tuning experience. I do very much appreciate your input.

 

[mkast]

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

for absolute max thrust out of the hole for our primary use: Watersports.

For the biggest bang for the buck, if you want your hull to come out of the hole like it was shot out of a cannon, try this:

http://cgi.ebay.com/ebaymotors/ws/e...0066243668&viewitem=&sspagename=STRK:MEWAX:IT

 

[John_S]

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

I haven't lifted my carb off my manifold to look in there. I'm just internet-racing for now lol. What is "oic"? Are you asking about a bar splitting the 2 halves of the manifold??

Looks to me like spreadbore and squarebore carbs have 2 different bolt patterns...thus probably the availability of the adaptor. I'll have to pop it off sometime and sneak a peak under there unless somebody else here knows the answer. I've serached on line and can't find any pics of a 5.0L Vortec Volvo manifold...if anyone else finds one, please post a link.

Thanks.

The "o" key is right next to the "p" key.

Yes, it should have a dual bolt pattern if it can mount both type of carbs.

I used an Edelbrock 2116 w/Q-jet.

I suspect that volvo uses the GM intake #12496820 :

Or maybe a bronzed water passage version of, but don't know for sure. They may have it made just for them.

 

[thumbdoctor]

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

If you would like to stay with the Holley family of carburetors (bolt on replacement for the 500 CFM 2 BBL). Holley has an 0-80555C (4175) spread bore Quadrajet replacement. I have never seen this carb used in marine applications but it offers the same tune-ability as regular square hole Holleys and is offered in a 650 CFM vacuum secondary. If your Vortec intake manifold is the stock cast iron unit that's found on some Mercruiser, Yamaha & OMC, you will be limited on which flange pattern to bolt up to and the spread bore to square bore might lead to some clearance / linkage geometry problems.

 

[ECVCHAMP]

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

I have a 08 220hp and I am thinking of doing the same thing (when my factory war. runs out). I hope you can figure this out so I can do the same. Please keep us posted.

 

[83Evinrude]

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

craze1cars: I'm following this thread with interest for my own 5.0L 220hp as well.

My 2004 VP 5.0L also appears to have a 4bbl manifold factory installed. I'm not sure if its square or spread or universal as I haven't had the carb off.

 

[craze1cars]

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

Well...now I have a mini fan club on this topic...that's cool. I hate to disappoint you guys but I am truly in the research only mode right now. And with wakeboarding season about 3 full days away, and the fact that we do watersports at least 2 to 3 days per week all summer long on THIS boat, I probably will NOT interrupt good watersports session with a long testing/tuning session trying to dial in a new carb for this boat. There's too much risk that I won't get it dialed in well very quickly, which means we'd lose ride time!! That's bad.

My honest plan for this entire project is to research now, collect the parts I decide on over the summer, and wait until the water becomes cold enough to pucker our sphincters (usually late September) and THEN finish out the fall testing/tuning on whatever carb I pick out to do this. So y'all MIGHT have to follow this thread until Octoberish if you really want to see my results. But maybe I'll surprise myself and get brave sometime mid-summer and give it a shot...we shall see. I can always revert back to my current setup easy enough I suppose if it doesn't work out.

Thanks for all the input again John. Your thoughts have been most valuable...I do fully understand now what you were asking, I just don't know the answer quite yet.

"oic" LOL! And to think I acually did a quick Google search for "manifold oic" to figure out if I was missing some terminology here!! Obviously I can see now you were looking for a PIC!!! I feel like a complete moron now...

Anyhow. Guess I'll have to pop this carb off and have a look-see under there. This I can do quick & easy without loss of ride time. Maybe sometime in the next few days I'll be able to report back, with a "PIC", showing my manifold and bolt pattern so it will help in my shopping expedition and decision making.

As always, still looking for SOMEONE who has done this mod to a 5.0L Vortec Volvo. The closest so far is jy118lfd, who reports gaining 100 RPM even after adding 2 inches of pitch! That is a SUBSTANTIAL increase...and frankly more than I would anticipate. But not really apples-to-apples since he also reports changing from a Mercruiser manifold to a Volvo manifold. And I already have a Volvo manifold. And maybe his stock carb was way out of tune to start with. BUT his post it is my only clue thusfar of something that may possibly represent potential real-world performance results. So just MAYBE I can push my current prop 200 or 300 RPMS faster than my rig currently does, with a simple 4bbl install...as far as I'm concerned the jury is still out on that idea.

And before I forget and lose my little scratch pad of tuning notes, I'm putting it here right now as a baseline since this is exactly what this boat ran as a best after dialing in my stock 2bbl just last week:

56.2 mph gps, 4,570 rpms, 21p 4 blade stainless Solas Titan HR-4. Perfectly jetted factory 2bbl, full fresh ignition tune-up with all new parts and timing set. 502 hours. Speed & RPMS obtained from Perfectpass Stargazer gauge.

And in case anyone is wondering, the boat in question is a 1999 Stingray 200LX bowrider.

Stay tuned. And keep brainstorming if anyone has something of value to add....