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

[John_S]

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

If there is a online parts breakdown, like what is available for Mercruiser, you can spend time identifing the part number differences to go investigate. I did that with Merc, and helped verify a number of things. I thought you found that the intake was used on the FI version, and just assumed you did it by the same part look-up method.

The rockers may not be so easy. If volvo is using the same gm cam as merc, and 1.6 rockers, then there was some change to standard vortec head to accomediate the lift. You would want to make sure yours was the same.

I think I have the timing curve for some SBC vortec volvo. Could already be what you have. I do remember there were two base settings. One for 87 octane, and one 89-91 octane? My bet yours is already set to latter. I'll see if I can find it and send to you.

 

[bruceb58]

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

Could also be that your 4 bladed prop has so much drag at higher RPMs that any extra few HP is going to not show much benefit. Might have been nice to compare 3 bladed prop before and after.

 

[craze1cars]

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

If there is a online parts breakdown, like what is available for Mercruiser, you can spend time identifing the part number differences to go investigate. I did that with Merc, and helped verify a number of things. I thought you found that the intake was used on the FI version, and just assumed you did it by the same part look-up method.

The rockers may not be so easy. If volvo is using the same gm cam as merc, and 1.6 rockers, then there was some change to standard vortec head to accomediate the lift. You would want to make sure yours was the same.

I think I have the timing curve for some SBC vortec volvo. Could already be what you have. I do remember there were two base settings. One for 87 octane, and one 89-91 octane? My bet yours is already set to latter. I'll see if I can find it and send to you.

You are correct on all accounts. I will spend time playing with parts lookup and comparing numbers someday when I have more time. And you are also correct that there are 2 base settings for Volvo, and mine is indeed already set for the more aggressive 89 octane min timing.

 

[ddbyrd3]

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

I will add to this post, I have a 2002 Glastron GX205 with the 5.0 liter GL motor. I have been wanting to do the exact same thing to my boat.

Thanks for sharing your experience..... Based on your outcome, I too will stick with my finely tuned 2bbl.

Maybe it's time to start looking for a 5.7liter and doing am engine swap..... Decisions, decisions!!!!

 

[craze1cars]

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

Boat hasn't been in the water since last test. Probably another 2 to 3 weeks before I will have time again. Kinda bummed, but my lack of time is for all good and fun reasons so not so bad...July thru September will be much more free for me, and I'll find plenty of time to boat this summer.

Anywho...

In the meantime I had another brainstorm. Carb spacer. When I pulled the factory 2bbl off, the 2bbl to 4bbl carb adapter ALSO came off. And that adapter served not only as an adapter, but also as a 1" 2-hole carb spacer, which increases plenum intake volume and generally changes the power curve of most any engine...

And I eliminated this feature. The new carb sits closer to the intake manifold now. I wonder if that hurt potential power output a bit.

Methinks I will be purchasing one of these:
http://www.summitracing.com/parts/MRG-3406/
to restore the height of the new carb back to where it was. Might give me a little extra juice.

OR....

Does anyone have an opinion on whether it might be worthy buying something better like this instead, that gets all swirley in the middle?
http://www.summitracing.com/parts/JET-62200/

Looks like a reasonably cheap experiment, especially the first one. And it will also take my PCV hose out of the very slight bind that the new lower carb mounting position has created.

I have pulled a spark plug. It looks safe, but quite a bit leaner than I expected it to be as the plug was absolutely spotless. And adding a spacer might lean it even a bit more. I'll do one change at a time, but I think for my first test-run with a carb spacer I'll also be going out on the water with a handful of larger jets to try.

Between adding a spacer and taking the time to do another jetting session, I might just find a little extra juice out of this new carb yet. We shall see.

After I feel I've obtained peak performance out of this carb, I may look into rocker arm experimentation and see if I can find even a touch more.

Will keep this updated if/when I find the time to play.

 

[ddbyrd3]

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

I certainly appreciate what you are doing, I sit back in anticipation to your findings..

Are you at all considering a cam swap. I know running the restricted 305 cylinder heads, I am not sure if any gain would be seen there either.. Just curious.

 

[craze1cars]

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

I certainly appreciate what you are doing, I sit back in anticipation to your findings..

Are you at all considering a cam swap. I know running the restricted 305 cylinder heads, I am not sure if any gain would be seen there either.. Just curious.

Not really. Mostly because it would mean a whole lot of extra work. It's much easier to change duration and lift by playing with rocker arm ratios in this boat than it is to swap out the cam. I don't need to pull the motor to swap rockers. But I would have to lift the motor to get access to the cam.

Besides, what would I swap the cam to? What's available? I have no idea...

I have a few options with rocker arms that would mimic cam changes. Many SBC's respond well (in cars) to assymetrical ratio. I may try 1.6's on the intake and 1.5's on the exhaust. That worked really well on a 350 Chevy truck I owned years ago. Often that works better than running same ratio all around. But that was pre-vortec motor. I understand vortecs need self-centering rocker arms, but not sure how they'd respond to extra lift. But one of my buddies who did the 1.6 intake/1.5 exh thing in his newer vortec truck (350) saw notable gains in low-midrange pull and minor fuel economy gains, and he had no clearance problems. So I think they might work in this 305 also.

But I won't do ANYTHING of the sort until I finish dinking with this carb. One change at a time. As soon as 2 changes are made at once, you lose total control of what you are doing and where you are going. Every time. I've learned this the hard way in the past. Never again.

 

[Kainon]

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

My newphew has a 08 GLastron 205 with the 305ci 2bbl Holley Carbed, gets 4600 with a 4bld Piranha 24p Prop with 50 on his GPS and a could raise the drive, and get a 15 FOOT Rooster Tail with the RPMS @ 5200 and high 40's MPH.

 

[John_S]

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

I have a few options with rocker arms that would mimic cam changes. Many SBC's respond well (in cars) to assymetrical ratio. I may try 1.6's on the intake and 1.5's on the exhaust. That worked really well on a 350 Chevy truck I owned years ago. Often that works better than running same ratio all around. But that was pre-vortec motor. I understand vortecs need self-centering rocker arms, but not sure how they'd respond to extra lift. But one of my buddies who did the 1.6 intake/1.5 exh thing in his newer vortec truck (350) saw notable gains in low-midrange pull and minor fuel economy gains, and he had no clearance problems. So I think they might work in this 305 also.

While I don't expect any noticeable gain from the carb spacer, it is easy to try.


FWIW: The standard marine roller cam has higher lift and longer duration than intake side. ie it is a dual pattern, not a single pattern cam. This is to compensate for the more restrictive exhaust. Mixing rocker ratios, with favoring the intake side, doesn't seem to make sense. If you are going to do it, put it on both sides, just make sure you have the clearance. Standard vortec heads would be past safe, recommended lift limits. Volvos "might" have already of compensated for that, but don't know.

Good luck, and keep posting your progress.

 

[craze1cars]

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

FOUND SOME POWER!!

Got the cheapo carb spacer. Found it cheapest on Amazon for just under $24 shipped to my door. So now my total out of pocket expense is within pennies of $350 to do this conversion.

And the boat is now FASTER!

Carb spacer woke it up. Today's test netted me 58.2 mph at 4,700 RPM. Both numbers are the highest this boat has ever seen. Going back to my first baseline of 56.2 at 4,570, that's a gain of 2.0 mph and 130 RPM. I was in very similar conditions today in terms of weight, fuel level, and air temp as before. I also played with jetting, but I only had larger jets to play with. Pulled the 61's and put in 66's. Lost about 1.5 mph. Dropped to 64's and a little bit came back. Went back to the 61's and got just over 58 mph again. Even if I had smaller jets I don't think I'd try them anyway because the plugs look pretty lean, but not dangerously so. I'm now quite confident that the new carb is running peak, and with straight out of the box jetting.

So I have FINALLY answered my original question. "How much HP will be gained adding 4bbl to 5.0L GL Vortec?" Exactly FIFTEEN! (But ONLY if you also use a 1" spacer...just as the original 2bbl was factory equipped with one) How do I arrive at this 15 hp? Stingray's advertising.

I found some ads and specs for my boat on Stingray's website archives. They said my boat would do 56 mph top speed equipped with my 220 HP motor. It also said it would do 60 mph if equipped with the TBI version rated at 250 HP. My boat ran 56.2 in stock condition (how's THAT for truth in advertising?!) And now it runs 58.2. So I'm half way to the 60.2 mph I'd need to reach to say I'm making 250 hp. Halfway between 250 and 220 is 235hp. So clearly I now have a 235 hp motor. And if I get it to sqeek a 59 someday on smooth water I'm changing my claim to 240 hp...a 20 hp gain. But I don't have the facts to do that yet so I'm not gonna claim it yet.

Anyone disagree? All you gotta do is pay for my dyno time to prove me wrong. But until someone steps up to do that, I'm clinging to my poor-man-dyno calculations as ABSOLUTE FACT. LOL!

Anyhow. Adding 15 hp (or maybe a touch more) cost me $350. Anyone wanna copy? Buy the Holley 4175 carb AND buy the spacer (Mr Gasket part number 3406). Fabricate a fuel line and bolt it on. If the small gain is not worth it to ya, don't bother. Run quality is excellent, hole-shot is the same or maybe a hair better. Unsure of fuel usage since I don't track it very closely but doesn't seem any different.

And if you are currently running a questionable factory carb that maybe is pretty tired, needs a rebuild or some tuning work? No brainer...just do what I did and make the conversion. You'll probably REALLY notice a power gain if you're starting with an imperfect carb...

Maybe someday I'll play with rocker ratios, but probably not till fall. Too much skiing and boating to do, and I'm a bit tired of tuning for the moment...

 

[Mischief Managed]

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

you are pretty much spot on with the 15 HP gain. My calculations say 235.9.

 

[John_S]

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

Glad to hear you were successful. Curious, was it a open 1" spacer? or the 4 hole quadrajet style?

 

[Tail_Gunner]

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

http://www.volvopenta.com/VOLVOPENT..._ENGINES/Pages/out_of_production_engines.aspx


Std TB on a production 350 from gm is 1 11/16" bore about 480 cfm
Volvo puts a 2" bore on the 4.3 up allowing 680 cfm

It seems there main concern is air flow....you put a spacer on and picked up velocity.... or flow

If i were you id take a look at intakes...and your timing curves that are preprogrammed

Opps In the 4.3 GI they do use std lift ratios and its only a guess but i doubt they up in the v8...to 1.6

http://www.carcraft.com/techarticles/vortec_valve_spring_upgrade/index.html

 

[sethjon]

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

Its only a guess, but I think 25 HP max and not much in the way of RPM. You will use a lot more gas and then you have to ask yourself, why do it? You won't get much more of a hole shot and not much top end.

 

[craze1cars]

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

Glad to hear you were successful. Curious, was it a open 1" spacer? or the 4 hole quadrajet style?

4 hole quadrajet style. This exact product:
http://www.summitracing.com/parts/MRG-3406/

 

[mikeneal]

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

That is interesting about spacer, I had not thought of it but back when I did my swap I added a carb spacer to ensure that was not effecting my jetting. (VP uses a spacer, hence my thoughts). Sorta explains why I got moderate power increase and initially you didn't. I actually forgot about the spacer until you posted this.

 

[Tail_Gunner]

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

http://www.popularhotrodding.com/buyersguide/0601phr_best_carb_spacers_cheap_horsepower/index.html

 

[craze1cars]

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

This is old, but I'm bumping since it's my topic and a few people found it kinda fun.

I did some more experimenting and tuning recently. Found Volvo bulletin that said the exhaust flappers were not necessary and should be removed. I figured great! Remove an exhaust restriction at Volvo's recommendation! How can I go wrong? So I pulled them and did another run. No performance change.

But I did find a bit more power since I last wrote! As I had hoped, I was able to inch it up just a tiny hair more by a change to roller rocker arms. I bought 2 sets...1.5's and 1.6's, GM Performance brand, lightly used. Tried the 1.6's and stayed stagnant. Tried the 1.5's and gained only about 25 rpm over stock. Tried 1.5's on the intake and 1.6's on the exhaust...back to stock. Ended up with 1.5's on the exhaust and 1.6's on the intake...gained 75 rpm! And therefore reached a new all time high by just a TEENY TINY little bit. I decided to keep it like that and sold the leftover mixed set to another hot-rodder to get about half of my money back.

FWIW, that's 2 SBC's in a row that I have gone 1.6 intake/1.5 exhaust and gained a small amount of power...so it seems to be the happy combo for them, but I'm sure success with such a mix varies with cam choice.

And for anyone playing along at home and maybe trying to copy me? Remember these are VORTEC heads...and they require special roller rocker arms. They MUST be self-aligning (or you will seriously tear things up in there), and they MUST be narrow-body in order to clear the centerbolts. Standard SBC roller rockers DO NOT FIT. So be careful what you buy if you decide to try this...your choices are indeed rather limited.

And yes, there was plenty of clearance to run the 1.6's with factory cam on both sides...pushrod clearance a non-issue/geometry acceptable. No interference problems whatsoever, no mods needed. Just bolt 'em on and set the lash.

My new all time high top speed is now 58.7 mph at 4,775 rpm. Same prop, same load, and I always careful to do my testing on calm water in comparable air temp/humidity days as my baselines, as I know it makes a difference.

So if we go ALL THEY WAY BACK to my post #1...I've essentially reached my goal. I have reached ALMOST 4,800 rpms on the same prop, for reasonable cash and unreasonable (but fun) amount of time and wrenching. Brief summary: 4bbl Holley, 1" carb spacer, exhuast flappers pulled, 1.5 exhaust roller rockers, 1.6 intake roller rockers. Yippee! I'd say I've added about 20 to 25 hp over stock doing that...With smart Ebay buying/selling over time I'm probably out of pocket in the $550 range, and I still have a leftover 2 bbl carb I could sell to offset that a bit if I choose. Not bad IMO....

Worth it? For me yes. For many others no. You decide...just thought I'd share where I have ended up.

Am I done? No tuner is ever done...I'm so close to 60 mph I just hafta do it...so for the moment I'm playing with props. Got to thinking maybe I have changed the peak HP curve of this motor with my mods. Maybe it makes more power at a higher rpm? Maybe it'll get deeper into the secondary's of the 4bbl if I let it rev a bit more? Only 1 way to find out...I bought exact same prop I had (21 Solas HR Titan Stainless 4 blade) in a 19 pitch. Ran it. 5,200 rpm at 57.5mph...a slight drop. But holeshot was STUNNING. On plane in 2.5 seconds...zero to 30 in less than 4 seconds. Absolute BLAST!

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. And I don't think the Volvo SX drive should be pushed past 5,000 too often for longevity. So I wanna bring it down partway and try again. So I just had one of my props repitched to a 20, and we'll try that soon. I'm striving for maybe 5000 rpm and hoping for a top speed just over 59???? Will test soon...some of my theories pan out...some do not. Only testing can answer for sure.

Yes I'm aware my 4 blade props are probably not ideal for top speed and I could probably hit my new 60 mph goal easily with a 3 blade...but I refuse to give up my stunning holeshot of this 4 blade. I gotta remember this tuning hobby of mine is secondary to my wakeboarding lifestyle all summer...it's kinda cool having the absolute FASTEST Wakeboard tower/PerfectPass equipped machine on the lake...so I can beat all those silly slow Mastercrafts and Moombas to the best smooth water and claim THE best place on the lake to go boardin' before they get there LOL....

Stay tuned!!

 

[ramster]

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

I did the four barrel switch last year on my glastron 195SX, same 5.0 GL. I used a Quadrajet not a holley, and picked up about 2-3 MPH and better holeshot. The best prop so far for me is the Apollo four blade 20, great holeshot and no loss of topend. After toying with 5.0, I've made the plunge and bought a GM Performance L-31 Vortech short block, added ProComp Al heads milled to 60cc for 9.9 comp. and a Howards Cams 214/218 duration .488/.495 lift with 1.5 roller rockers, and a Q-jet. Sounds good but havent done the test run yet, hopefully tommorow.

 

[craze1cars]

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

Sounds good! Please report your improvement! Should be fairly noticable going from the 305 to a semi-built 350...I expect you to blow that prop WAY past your RPM comfort zone...suspect you'll be needing more pitch.

I've considered a 350 upgrade myself, ESPECIALLY since this particular mill is actually freeze-cracked and I'm on year #3 of JB weld patch LOL. But frankly I don't really want to spend that kinda cash on my 12 year old low-line boat that I picked up at a pawn shop for pennies on the dollar and patched up. I've always prioritized keeping to a fairly tight budget with this project. Plus this cracked block runs positively PERFECT LOL! And I don't honestly know that my particular boat could handle much more...these Stingrays are not known for beefy build quality. Frankly I find it to be downright cheap. And my hull is so light it's already quite a bit of a handful and wakeboard tower raises my CG a bit. Nearly 60 mph real speed in a lightweight 20 ft runabout with high CG is not something to take lightly...the slightest twitch of the steering wheel is amplfied 10-fold. Careful trim usage is critical to get thru the 30 to 45 porpoise zone without initiating big hops, and then after that if the trim is too low at high speed it REALLY causes the bow to dig...there's a very narrow sweet spot between bow steering and chinewalking that I have to find...and both are pretty dangerous at 55+. Without perfect trim & steering application thru the speed range a flipover is a realisitic possibility no doubt. So it has to be a special/perfect day for me to even approach the limit, with glass water and NOBODY else in the vicinity to create a potential quick maneuver problem. I'm usually alone, but I do have a one friend who is a fellow speed freak/auto racer who fully understands the danger aspect and loves it as much as I do...so he's been on board a couple times.