Upgrading a 260hp 350
 

I know it's been beaten to death, but here's something I stumbled upon. I can pick up a set a 14096217 cylinder heads locally for cheap. They came off a running 270hp 350 Mag. I know these heads are the predecessor to the Vortec head. They are easily capable of making 285 to 300 horsepower, as they were on the 300 hp GM crate motors of the era. I know I need a new intake manifold with 27* center bolts and am wondering which intake to buy. Mind you, this is a budget build....because while the engine is out I will have to replace my wet transom.

Any recommendations on cam and intake would be great.

Thanks!!

Here's a cam I'm looking at.....

http://www.summitracing.com/parts/cc...make/chevrolet

I have to do more digging on the cam specs of that GM crate engine.

The 285hp engine had a cam lift of 447/447 with a 8.8-1 comp ratio

The 300hp engine had a cam lift of 435/460 with a 9.1-1 comp ratio

I really have no idea what pistons are in my engine and really won't know until I pull the heads. I'd be happy with 8.8-1, but of course the 9.1-1 would be best.

Buy that AFR composite intake manifold for the SB Chevy. It has been dynode by David Vizard and he swears by it. It made better HP and Torque # s right out of the box than any other intake manifold including the worked over intake manifolds. Plus you never ever have to worry about that intake manifold producing corrosion problems or dissimilar metals joining together.(dissimilar metals together produce corrosion over time especially in marine apps)

I would also look into bore & stroking the 350 into a 383.

The GM cast Iron Bowtie highrise intake was discontinued a few years ago. No stock left anywhere. I had sold 100's. GM's 86-95 part# is #14097494

So, a real good 86-95 application high rise Aluminum intake is Weiand's Speed Warrior:
http://www.summitracing.com/parts/wn...et?prefilter=1

the pre '86 260hp 350 heads are the same as the 270 horse 350mag post '86 except for the angle of the middle 2 intake bolt holes. You won't see any difference just switching those heads. They are the predecessor to the vortecs in that they came before them, but that is where the similarities end.

I think my heads are 76cc heads, not 64cc heads like the ones I'm looking at. I will pull a valve cover to be sure, but I'm 85% sure I have 76cc chambers on my engine.

Okay, the carbed '87-'95 350mag (and also the 5.7 260) had 76cc heads with center bolt valve covers and the more vertical center intake bolts. They were of the same performance as the pre 86 heads with perimeter valve covers and traditional intake pattern.

In '95 they had a TBI 350 mag, I assume these had the 64cc TBI heads, are these the ones you have? Aside from the compression bump I don't think you will gain much.

^^ The 64cc combustion chamber heads are what I will be picking up^^

They are an iron copy of the L-98 TPI heads that came on the Vettes and some Irocs.

http://www.gmpartsdirect.com/perform...CATID=671.html

Sorry wasn't trying to make it confusing.

If you don't have heads or an intake right now, go with 64cc VORTEC heads with a vortec style intake gm marine intake (or edelbrock rpm or rpm air gap). You will be much happier with the performance.

Found this......

http://www.chevrolet.com/content/dam...e-12499529.pdf

Still looking....

I can pick up a set of Vortec heads just a tad more money than the 217 heads. I still would need an intake anyways. Maybe that's the best way to go.

Heads:
http://www.summitracing.com/parts/nal-12558060

Marine intake (not really needed for fresh water, more pricey):
http://www.summitracing.com/parts/edl-2516

Non marine, okay for fresh:
http://www.summitracing.com/parts/edl-7516

http://www.summitracing.com/parts/edl-7116

For the cam, go roller if you can as you should have a roller block. The flat tappet you list would be okay, but not as good as a roller setup.

I wouldn't bother with those heads. They suck.

^^ I'm now leaning toward the Vortec heads. ^^

Now thinking clearly without a migraine, I would still have to buy an intake, so the money paid out would be similar.

Would the 262H cam be ok with Vortec heads?

Why?
Which are better in this price range?

Pass.

I have hands on experience with that motor and it's the biggest dog known to mankind. Whoever in GMPP stuck that hunk of schit camshaft in that engine should get one up his azz.

A 260hp motor will run better. Way better !

That cam was designed for high compression engines back in the 60's. Lots of seat duration. It wasn't even that good for those motors back then.

Totally assinine.

A 300hp 5.7 motor can be almost built by mistake and run so much better then that hunk of crap 290hp/5.7.

SB....so what do you recommend?

I've just been researching and trying to see what I can find.

Do you have a base motor to work with ? Or need to buy an engine ?

Are you looking for 300hp ? Or something else.

To be honest, I've been involved with some real brain draining diagnostics at work past few weeks, that I'm done with, so I'm in brainless cruise control right now............so I'm not quite sure what exactly you are up to.

I have a good running 260hp 350 right now. I have a pan leak, so the engine is coming out.....so why not upgrade??

I found this about springs...

http://www.alexsparts.com/valve-spri...rf-hyd-roller/

Those were the springs I used.

As far as looking for heads, find a dirt track guy that has blown up or replaced a 602 crate motor. you can get the heads and intake all in one shot, and those would be vortec heads.

Done this about 3 yrs ago. Ditch the gm heads and find a used set of dart iron eagles or sportsman 2 heads. U will be better in the long run. I used flat top pistons dart 200cc heads same 262h cam u are talking about with a dual plane high rise intake with a 750 holley. I picked up 6 mph with the rebuild and upgrades. I used a set of 1.6 rockers I had. 10.2 compression. Ran real good but as always it was replaced with a 396 small block in favor of more speed! !
In my opinion vortex heads are not much count. They need lots of work to make what I would call good power. Give me a set of old double humps over vortec any day!!!!

Vortec's are better than the double humps. Sorry.

They have a raised intake runner and very modern combustion chamber.

Off the Vortec's for a second....

I picked up just about 15 mph with reusing the stock million hr 1991 5.7/260hp short block. Pan never came off.
Decent heads - Bodix IK180's. They are nothing real special compared to AFR's. Vortec's in this application wouldn't be down more than 5-10hp.
Can run 87 octane.

So............

Double humps were great heads....In the 1960's.

You can see evidence in the timing. Vortec's only need 32 degrees, that is indicative of a faster, more complete combustion event.

The successful small bloc recipe used for seemingly forever is:
stock decent condition 5.7 260hp short block
Vortec heads (not ported, no bowl work. Yes on spring upgrades)
RPM intake or Air Gap
600-750 Holley
Comp 218/224 112LSA Marine HR (some have used GM Hot cam 218/228 112LSA)
GLM exh maniolds with 8-10" SS inner tube extensions (some have done this to stock exh manifolds)

Boom. Done. Even non performance hulled 20ft boats have picked up 10mph. Performace hulls 12+mph

You'll find a lot of small block builds and real world results here:
http://www.speedwake.com/forums/showthread.php?t=27967

Well my boat is a 20ft Cobia bowrider. I was planning on a RPM style intake, but I don't want to re-make the engine cover I just finished. I'm close now with the flame arrester, but I could come up with something.

Yeah take a walk threw your local dirt track pits and look for vortecs. Only place u will find them are in the crate class. They are junk. SB u are a bmfer. 15 mph with crummy brodix in heads wow. There just as sucky as vortecs. U are my hero. Think u can help me hit 200 mph in my 85 chevy dually with a 305 on 87?

Yeah if u wanted to put it in a dump truck! Let's see 10 hp equals about 1 mph. So 10 mph more would be about 100hp! Your flipping dreamin. I have been there don't that with vortecs. With that baby cam no way u can make 360 or so hp. Not going to happen!!

I never said they were the best thing since the string on a tampon, read my post:

I'm just telling him where he can find the parts.

I get it, you are a small block God and run race cars. Good for you. Keep trying to start a pissing match and we can have another potentially informative thread go right down the $hitter.

I'm personally new to the boat market, but have literally grown up with a wrench in my hand. I've been doing 12 volt wiring for 20 years. I wire limos, fire trucks, custom stereos and race cars. But my true passion is drag racing. I've helped build some pretty nasty street cars capable of running upper 6's in the 1/8th, that are driven to the track. I'm also building a 700hp BBC for my 79 Camaro that will also be a street legal car.

I always wanted a boat and bought my current one cheap. I like to go fast, but is also like fishing and cruising with family and friends. I'm trying to build a nice, all purpose boat with a healthy, reliable engine. I will be adding side exit captains call exhaust on my boat.

I'm going to be using the Vortec heads on this build. I appreciate all the input and never meant to stir the pot on this forum. I truly value all your input and take it all into consideration.

Thanks

It doesn't take any type of magic to get 350-375 horse from a 350 small block. In fact you have to purposely mismatch parts and retard the timing to 20 total not to make it. Are vortecs the best, not by far, but OP has stated he is on a budget.

nce the string on a tampon, read my post:

I wish i was a small block god!! I have done very well with them. Not trying to start a pissing match at all. I just have been threw this many of times and there are much better heads for about the same $$ The vortecs will work tho. After yrs of racing engine very similar to this u tend to get a idea of what works best.
GM put them in the trucks and not the hot rod cars for a reason!!

No to sound like I am putting down the OP but the fact of matter is he has a Cobia Family Runabout. I know by some of his post that he has a lot of time in & ???? money as this was a problem child of boat / motor to take on. Anyways this boat is only going to be so fast and controllable up to certain point. After that certain point, the boat could be undrivable.

Just saying maybe take a look at older used Checkmates - late 80's early 90's or even something like a 1995 - 225 Crownline with a carb 454 bravo app for reasonable money Both for production boats were well built and did not see the normal wood rot and dry rot that most of the other production boats seen during that timeframe. Both brands / model here could handle low 70's without problems.

I have been in the Cobia brand of boats before and down the road, Yamaha bought them out but they did away with all sterndrive power apps and went to Cobia CC boats with all outboards. FWIW.

No offense again IMO hot rodding your current boat with the time and money might not be the route to go. I would find a deal on a more sport type style boat app. I think older Checkmates might be worth a look for you and really seem like the boat you are trying to make currently. Good luck.

BMFER ?

Don't know what that means.

Anyway, go ahead, doubt me. I don't care.

And yeh, that boat I mentioned will change 1mph with 10mph. In fact, with a stock everything motor, it gained almost 3mph going from the normal quadrajet intake to the High Bowtie one.

Most 21ft boats and under will probably gain 8-10mph with the recipe I've given....yes, on a good health stock Merc 5.7 bottom end. Edit in: Unless the boat plows thru the water like a ski boat.

Call me a liar. i don't care. You'll just lose out on good info. No sweat off my back.

I do agree with you, but I currently love the boat as it is. Granted, it will never be an open bow power boat....but I want a nice all around boat that will boogie whe I want it to. It currently runs about 50, but I know i want a tad more. I am more than mechanically capable to handle the work and am not afraid to do so.

I did my research and knew about Cobia/ Robalo and how they were bought by Yamaha. I like the lines of the boat and it rides well too.

My nxt boat will most likely be a 225BR with a BBC, but right now my pocket book is restricting me. I know I have done a TON to this boat already, but I knew what I was getting myself into also. Since I have aa oil pan leak I was going to do a mild upgrade while the engine was out.

Thanks for looking out though, I truly appreciate it.

Thanks for your feedback. Just sometimes hitting a brick wall with boats can be so frustrating and wasted money out of pocket. Glad you did not take my post to heart as I was not beating you up.

I have tried to help you out as well in a few of your posts getting things in order. Good luck. I have to run now to go work on boats because that's what I do for a living and I have to pay the bills every month. Thank god I have a great wife and earns a decent living.

I've come a LONG way with this boat. It runs near perfect as it is, but I can't leave well enough alone!! LOL

2fastforvortecheads has bigger issues than we thought.
Grab some popcorn and read all this:
http://www.offshoreonly.com/forums/g...please-17.html

And then some searches and you'll see him asking for aluminum prop advice, and then Holley carb tuning advice,,,,,,,,,,but yet, he says he's the exspurt.

LMAOF.