More HP

[Bondo]

Re: More HP

Vortecs wont work on the older 4 bolt blocks,

Hey Walt,.......... I Think you're Wrong on this point,.......<br />Matter of Fact,....... I Know you're wrong on this point.........<br />Vortec Heads will bolt onto Any of the SBCs,...Even the 400cid blocks(steam holes still need to be drilled)..... <br />The Difference is in the Intake Manifold,...Not the Head/Block area, or the Exhaust side.....<br /><br />The Only other point in your post that I'll take issue with is the quest for a 4 bolt Block,..........<br />SBCs have an Extremely Stout lower end,.... 4 bolt blocks Really Aren't Nessessary,... <br />Til you start Spinning in Excess of 6000rpms........<br />And, That's Not an Issue in a Marine Application........ <br />The Alphas start to Come Apart at anything over 5500rpms or so,.. Anyway.....<br /><br />Just How Many SBCs have you run across that Dumped the Crankshaft,.??...<br />Of them,.. How many were 2 bolt blocks, Vs. 4 bolt Blocks,.??....<br />And,.. How many were Blown because of torsional Flexing,.??.. Or more likely,.. Lack Of Oil,.??.....Or Excessive RPMs....<br /><br />Again,...... Not to start a Pi$$ing Match,......<br />Just to Clarify things.......<br /><br /><br />(Tony,.... Of Course I Don't Know for Sure,.. But I think he's talking about heads with Larger Valves,+ Big intake runners...Vortec heads Don't fall into this category..)

 

[Don S]

Re: More HP

Hey Walt, how about making that picture smaller so we don't have to use the scroll bar to get to the end of each line.<br />Nothing in that picture requiring that kind of size.<br />Plus, it's HeII on dialup waiting on it to load while the screen dances around.

 

[Weirdwalt]

Re: More HP

Your probably right Bondo, I'm not real familiar with what fits what. I believe the older 2.0 heads don't work on the newer blocks so I figured the newer heads wouldnt work on the older blocks. I always thought that created a deck height issue with intakes. Ah well aint the first time I've been wrong. <br />You're absolutely right on the 4 bolt mains. Most performance improvements dont need 4 bolts. However marine use is tough to begin with and adding in higher compression or building up a stroker puts even more stress on that block. No, cranks dont get thrown, I've never ever seen a broken main. However I have seen many many broken cranks and THAT is caused by torsional stress and support problems add to that. The purpose of the 4 bolt is to keep the flexing to a minimum and help keep the crank intact. I agree 100% with you that it's probably not necessary to have a 4 bolt setup, but my racing engines always have them. It's (relatively) cheap insurance. Broken cranks pretty much turn an entire engine into junk. I suppose it's really a matter of simple economics, I'd rather pay a few hundred and get 4 bolts than pay 3 thousand and build a new engine. Thanks for the clarification on the Vortec.

 

[Weirdwalt]

Re: More HP

Well Gee Don, A sucessful tech should be able to afford DSL dontchya think? Oh wait you're up there where it's dark most time now and the new technology is defined as a P1 and Win 98. I dunno I hear Alaska is beautiful but I doubt I could live there.

 

[FreeBeeTony]

Re: More HP

Bondo........glad to know you realize it's still me.......under my new name....... <br /><br />I thought the same thing regarding the block/heads/intake compatibility........really got an education during this last project!

 

[paulie0735]

Re: More HP

Babylonboater, Well despite a popular myth in the hot rod business… there is no such thing as a free lunch!!!! The Vortec heads will make more power than the stock heads but the extra power is really only noticeable at higher RPM, the stock heads will perform adequately from idle to 4500-4800 which is the usable rev range for this stock setup. The extra HP from the Vortec setup, (remembering that they require a special inlet manifold) comes at the higher RPM range that being 2500 – 6500, depending on cam, carb and exhaust fitted. Problem is that they require a cam and header exhaust together with the manifold and carb to get full use of the available power. The Mercruiser 260 has been put together to suit marine applications where off idle power and good flat torque is more desirable than midrange punch and top end power. I would be reluctant to fit such a setup on a ski boat as you need all the power you can find from idle to 4,000 which is the range it will spend 90% of its life at. This engine is likely to be getting tired and pushing the limits with bolt on HP will only lead to grief and heartache. Than there is the ‘not so small’ issue with the drive unit. In summary, the Vortec heads with all the related gear will yield 300hp at 6000rpm and might result in an additional 10 mph for a few minutes before the leg spews its guts all over the water, providing the engine holds together that long!!

 

[FreeBeeTony]

Re: More HP

paulie.........as you can see from the pic of my boat I do not have a speed boat (or want one).<br /><br />I had a problem last year and it looked like either a blown head gasket or a cracked head. I opted to replace the heads and intake with the Vortec, looking for increased power and fuel effiency. I am hoping to be able to turn a bigger prop and keep the RPM's down. I do not plan on running this set up at WOT.<br /><br />I had a 15" pitch prop on it last season......hoping to run a 17". I don't go full throttle to get on plane.......my kids tell me I drive like an old man.........plan to cruise around 3500-3800 RPM's max.<br /><br />Don't think this type of "abuse" will kill my outdrive........

 

[Bondo]

Re: More HP

I always thought that created a deck height issue with intakes.

Ayuh,........ You're Exactly Right Walt,......<br /><br />The Intake Ports are .200ths" Higher on the side of the heads,..... <br />The Difference is made up using a matching Vortec Intake Manifold......<br />The Othersides of the Heads All have the Right Holes,.. In the Right Places......... <br /><br />Paulie,...... I don't know where You're getting your Info,..... But,... You're somewhat Wrong......<br />The Vortec Heads were originally designed as a Truck Application,.... They build Great Torque,.. Way Down Low,... <br />They're at their Best at Idle to 5500rpms,.....<br />With the Fast-Burn, Swirl combustion chambers,+ 170cc Intake ports,...<br />Makes them Perfect for Boats........<br /><br />Believe Me,.... BabylonBob,...errr,.. FreebeTony has More than done His Homework on these,......<br />I Think he's got it Really Close to Right,..... His Quench is alittle Fat,... But, I think it's going to Work, Just Fine.......

 

[jimmbo]

Re: More HP

Originally posted by Kopasetic:<br /> What the easiest way to increase HP, I've got an '87 Chris Craft Scorpion with 350/260 HP and Alpha 1 drive. Now that the boat is away, I'm trying to budget for spring, ideally looking for bolt-ons, any ideas, carbs, ignition, etc, where do I begin. Love this forum, thanks in advance

Bolt on supercharger

 

[paulie0735]

Re: More HP

Babylon, ok guess I was off track with your boat. I was still discussing the original topic of more HP from the 260 in the Chris Craft. At the end of the day if you need new heads than the Vortec are a good choice, but if you want max benefit from them than you need to tune the total package to get it! Either way they will do the job. I can't see you being able to go up 2" in pitch though with just a head and manifold swap unless your old heads were not sealing and really robbing you of HP. As for the economy question, I would do this - when your rig is back on the water, set up a vacuum gauge and run at the desired boat speed and note the vacuum reading. Change props and run at the same boat speed and again note the vacuum reading, in simple terms you’re looking for the highest vacuum reading while cruising at your desired boat speed. The vacuum reading will indicate to you how hard the engine is actually working, the less the vacuum the harder the engine is working and more fuel it will be using. Running a prop that’s to big can use more fuel than a smaller prop despite the higher RPM. You might also consider going to a 4 blade.<br /><br />Cheers and merry Christmas to all from downunder!

 

[jimmbo]

Re: More HP

Originally posted by paulie0735:<br /> The vacuum reading will indicate to you how hard the engine is actually working, the less the vacuum the harder the engine is working and more fuel it will be using. Running a prop that’s to big can use more fuel than a smaller prop despite the higher RPM. You might also consider going to a 4 blade.<br /><br />

If the higher rpm. lighter load raises the manifold vacuum above the point where the power enrichment curcuit is off economy might improve due to the leaner mix, but the engine is still pumping more cubic feet of air from the higher rpm. If vacuum remains below that point, then economy should be worse with the smaller prop

 

[paulie0735]

Re: More HP

I give up! Every suggestion can be turned around if you try hard enough. <br /><br />Bolt on supercharger?? <br />Step 1 Budget for new heads combustion chamber matched to the intended boost! New cam and valve gear, rebuild the bottom end, add forged pistons and steel rods, regraph the dissy add a bigger carb than get it tuned.<br />Step 2 Modify the cooling system and add an oil cooler. <br />Step 3 Reshape the engine hatch, prime and paint.<br />Step 4 Fit the bravo 3 and a new prop. <br />Step 4 Write to your insurance company and tell them that your engine is now supercharged. <br />Step 5 Take out an additional credit card for the fuel bills.<br />Step 6 Go out and blast past all the other like boats with a big cheesy grin……. But if that’s not what you want to do than forget steps 1 through 5 and proceed straight to step 6a<br /><br />Step 6a Enjoy your boat for what it is, by all means strive to get the best possible performance from it, but remember ‘no such thing as a free lunch’<br /><br />Oh…….and I can here it already, "supercharging can actually improve gas mileage" yes it can in a light weight car driven like a grandpa! Not in a boat such as pictured above powered by a SBC where the engine is going to be working at or around 4000 rpm = working hard all the time!! Than there is the argument that “supercharging can improve engine efficiency”, yes it can in the right application and they are mostly large Earth moving monsters or small Diesels that have been reduced in capacity with a turbo added to bring it back inline with the latest emissions standards. <br /><br />Its fun playing with other people’s money isn’t it!

 

[Weirdwalt]

Re: More HP

You forgot the 3,000 dollars for the marine supercharger kit alone. Add in all the modifications and you up that to 4K. If you have to pay someone to do it then you may as well go to a big block/Bravo reman.

 

[John_S]

Re: More HP

You probably could get to 290-310HP, with the vortec head replacement (and associated components), without spending lots of money. Even that is probably not worth doing, unless your engine was been recently rebuilt or replaced. Doing all the top end work, would only accelerate the failure of a marginal bottom end. It may be easier and less costly to improve on it, when you do a planned engine replacement. As already stated, you will only gain 4-6 mph, from the additional HP.<br /><br />On the Vortec head replacement, a couple of items for further research: <br />- If you have flat-top pistons (unlike Tony's), your compression will be 10:1, or slightly higher. That will probably mean to burn 93 octane, or take a little off the advance timing.<br />- You may have standard hydraulic lifters in your engine. Should still work with Vortec heads (but check), but certainly consider moving to roller lifters and new cam. Could go to a slightly hotter than stock cam, for 10-15hp, while maintaining a good idle, and not sucking in water.<br />- Check your ignition curve on your Thunderbolt IV. If it is V8-22A, probaly OK. If V8-24S, you may need to change module. The Vortec heads like less total advance than your current heads.<br />- If you run in salt water (guessing not - from your location), and you have raw water cooling, verify you can get a cast iron intake for vortec heads, or add the expense of fresh water system to the list.<br />- Will need to recarb (square bore) or at least rejet and convert to electric or manual choke.<br /><br />If you really need help spending money, on upgrading your engine, stop over to OffShoreOnly forums. Those guys really know to do it up!

 

[jimmbo]

Re: More HP

I have a 2002 VP 5.7 260hp. It came with a 500cfm Holley 2bbl carb mounted on what looks like the old 350 LT-1 intake manifold. Last summer I pulled the 2bbl off and replaced it with a Holley 650 Spreadbore marine carb. Right out of the box it gave me 300 more rpm, which doesn't sound like much but with 1:1.5 gears means the prop is spinning 200 rpm more. It allowed me to increase the pitch 2 inches. The expected loss of low rpm torque wasn't there, perhaps due the new carb has very small primaires. It had better low end than it did when the 2 bbl was on. It is running too rich at WOT and with a jet change should pick up a few more rpms.

 

[mkast]

Re: More HP

Jimmbo,<br />I'm just wondering, how much did the carb, manifold,throttle linkage upgrade and prop cost?<br />What was the MPH increase?

 

[jimmbo]

Re: More HP

Volvo puts a 4 bbl manifold on their V8s and uses an adapter to mount the holley 2bbl, so there was no cost.<br />Holley carb was $450 Canadian in Jan 2004, has dropped since.<br />Linkage was adjustable enough by using other holes in bracket on motor and flipping fitting from 2bbl onto the 4bbl.<br />Prop was OMC Raker @ $475 Canadian in Jan2005, has dropped since.<br />difference was about 4 - 5 mph increase

 

[jimmbo]

Re: More HP

 

[LANCLJ]

Re: More HP

While OFFSHORE ONLY is a great site, they cater mostly to big block issues, since most big performance boats run 454's,496's, 502's, ect.<br /><br /> A better bet would be to get your hands on Dennis Moore's book Small Block Marine Performance.<br /><br /> With a small block, the Vortec is the way to go. Not just the heads, but the whole engine package. Available online from several sources anywhere from 2,500 to 3,500. Sell off your old setup to recover some of the cost. 300 horsepower should move your boat just fine.<br /><br /> If you keep up the condition of your Alpha Drive (gears, shafts, bearings, u-joints, ect.). it will be fine. Adding a drive shower is also a good idea. It keeps the upper gears from overheating.

 

[John_S]

Re: More HP

A better bet would be to get your hands on Dennis Moore's book Small Block Marine Performance

Agreed, It is getting harder and harder to get your hands on this out of print book, though. <br /><br /><br />

While OFFSHORE ONLY is a great site, they cater mostly to big block issues, since most big performance boats run 454's,496's, 502's, ect.<br />

Yes, but there is still allot of small block info. A number of those guys run a pair of small blocks. I haven't found any other site that has more info on small block marine performance improvements.