need more power from 3.8 V6's

[Offshoreboat]

My engines are in good condition ,but have trouble with my 1982 270 Sea Ray Sundancer.Would changing from the 2 barrel to 4 bareel carbs help much?Can I put 4.3 4BBL intake manifolds on my 3.8's;Do You have more tune up tips for me?<br />thanks

 

[Walt T]

Re: need more power from 3.8 V6's

Changing from 2 to 4 bbl is the most cost effective way to get more power. HOWEVER, this power will ONLY be evident at WOT. Unless you use the secondaries, the power will not be available. Herein lies a catch 22 of more power. In order to use it, you must also burn large quantities of fuel. <br />Now, I have done the conversion to 4bbl on small single engine boats that performed well already with the 2bbl, and the results were good. Your boat is marginally powered to begin with, and adding the 4bbl will not help you unless you cruise at WOT all the time. If it were my boat, I would start planning to convert to 5.0's or 5.7's. Heck with that I'd go with twin 502's and BravoIII's. Then I'd convert the entire cabin to a giant fuel tank. Shower? who needs a shower?

 

[Offshoreboat]

Re: need more power from 3.8 V6's

 

[Offshoreboat]

Re: need more power from 3.8 V6's

thanks for reply Diesel Walt,know what You mean but money is all the word.As You said the 4bbl help at wot,so they must help me to get the boat in to planing.Would the 4.3 manifolds fit the 3.8?thanks

 

[Walt T]

Re: need more power from 3.8 V6's

No, they wont fit.<br />The 4 bbls will NOT get your boat on plane faster. They may even slow it down, as a matter of fact.<br /><br />4 barrel carbs are designed to allow extra fuel/air mixture in through the secondaries when the engine 'needs' it. The engine cannot take advantage of this extra air if it is running at a low rpm. Opening the secondaries at a low rpm as with mechanical secondaries will cause a 'bog' condition that will actually cause the engine to lose power. Once the engine speed increases, usually above 3200 rpm, then the engine will begin to take advantage of the extra fuel and air. This is why top end speeds tend to increase with the addition of 4bbl carbs, but low end pull and cruising speeds will usually stay the same. Most 4 bbl carbs are vacuum actuated secondaries, and those secondaries will not open until the thottle has been advanced to a certain point and engine vacuum is at a certain point. An engine at low rpm and a heavy load will not benefit from opening the secondaries at this point. An engine under a heavy load at high rpm will most certainly develop more power with the added fuel and air, so they will then open.<br />Yes, I know new (bigger) engines are expensive. But I speak the truth, even though it's probably not what you want to hear. <br />Your 270 is marginally powered to begin with, and adding 4 bbls to them will not make you any happier, only poorer. Twin 4.3's are marginal for that boat. That boat really needs twin 5.7's or 5.0's to get performance you would truly be happy with. <br />Find an owner that has done this and ask how happy they are. Thats about the only thing I can tell you.

 

[coupedeville]

Re: need more power from 3.8 V6's

Gotta disagree with you Walt; I think the 4.3 manifolds will fit the 3.8 [I'm assuming that the 3.8 we're talking about is the Chevy 229 cid V6].<br />The 3.8 is 3/4 of a 305 V8, the 4.3 is 3/4 of a 350 V8. That being said, it would be a waste of money to bother with the swap. 3.8's have very small bores, and really crappy cylinder heads.<br />Much more cost effective to swap out the 3.8's for 4.3's. 170hp x 2 = 340hp, the equivalent of a big block.

 

[Walt T]

Re: need more power from 3.8 V6's

Gee that makes sense, 3/4 of a 305, and 3/4 of a 350. Yes I know those old 5.0's and 5.7 you could interchange manifolds on some of them. The 3.8 is NOT in any way related to the 5.0, and nor is he 4.3 related to the 5.7. However we do agree that it's a waste of money to try to upgrade the 3.8's.

 

[coupedeville]

Re: need more power from 3.8 V6's

Sorry Walt, but you're wrong about the relationship between the 90 dgree Chevy V6's and V8's. Virtually all the dimensions are identical: Bore spacing, deck heights, pistons, valvetrain, oil pump, main bearings, cam bearings, externals like the water pump, etc.<br />The bore & stroke of a 4.3 are identical to that of a 5.7 - 4" x 3.48".<br />I'm assuming our Belgian friend has the 3.8 Chevrolet based engine, not the 3.8 Buick engine.

 

[geriksen]

Re: need more power from 3.8 V6's

a pair of late model used 4.3's would fix him up nicely. 3.8? It think they only did that for one year<br />I agree with both of you that putting 4bbls on them would be a waste of time and money. You would also end up with a frankenstien of bracketry

 

[Walt T]

Re: need more power from 3.8 V6's

You are partially right. In 1978 when the first ones were built, those were in effect V-8's with the last two cylinders lopped off. However, the bore was 3.50". From 1980 on the bore was changed to 3.74" upping the cid to 229. Many other items wer changed making the engines no longer interchangeable with V-8's. Valve train, valves, con rods, crank and cam are all different. Blocks have also been changed. Basically they are the same, but hell so are Fords and Chevy's.

 

[coupedeville]

Re: need more power from 3.8 V6's

Well obviously the block, heads, crank, cam, intake and exhaust manifolds are different between V6 and V8 - after all, it's 6 cylinders versus 8. All the rest of the bits will fit [except the con rods in the 4.3].<br />And it's actually #'s 5 & 6 cylinders that are missing. Check the valve arrangement.<br />By the way, the original small 6 with the 3.5" bore was a 200 incher - 3/4 of a 262 V8. Remember the 262?

 

[coupedeville]

Re: need more power from 3.8 V6's

Offshoreboat: Have a look at this site http://www.edelbrock.com/automotive/man_sbchev.html They have the listing for 4 barrel intakes for the 3.8 & 4.3 90degree V6.

 

[Offshoreboat]

Re: need more power from 3.8 V6's

Thanks for Your replys folks<br />One more thing,I know from my manual that OMC produced the 3.8 with 4 barrel Q jet manifold for 2 Years rated at 185 HP versus 170 HP for the 2 barrel.I dont expect the performance of 2 Big Blocks in my boat,but since after opening them both up and they are looking hardly run in i only would like to make the most of them before putting the pair back in the boat.<br />I think thats we are here on the forum ,to help make things as cheap and good as possible.<br />The 3;8's where also produced with Turbo Chargers in some GM car Models(They still are now rated at more HP with EFI and NO turbo)so I think that we must not underestimate them.<br />Thanks for more info<br />

 

[sony2001]

Re: need more power from 3.8 V6's

If I was underpowered and wanting to avoid a major reworking of the powerplants I would seriously think of giving up an inch or more on the props and accepting a lower WOT speed and gaining everything below that.

 

[coupedeville]

Re: need more power from 3.8 V6's

Offshoreboat, I'm still not sure what we're talking about: Do you have the Chevrolet based 3.8 engine, or the Buick based 3.8? It makes a BIG difference. The Buick based engine has a lot more parts available for it.<br />Fastest way to tell is the location of the distributor: Chev has distributor mounted at rear of engine, Buick is mounted at the front, angled off to the right side.

 

[Offshoreboat]

Re: need more power from 3.8 V6's

Hi again,I have the 229 Chevy engines.<br />WOT Top speed is not the prime problem,but I would like to go over the hump more quikly.

 

[Offshoreboat]

Re: need more power from 3.8 V6's

Currently running 14,5X19 props Like to keep those and hoping on 4bbl carbs ?<br />Thanks for reply<br />offshoreboat

 

[coupedeville]

Re: need more power from 3.8 V6's

What horsepower are they rated at? In a car, they only managed to wheeze out 115, marine maybe 130 or 140? Either way, for a 27 footer, at a good 3 tons, they're working hard.

 

[geronimo]

Re: need more power from 3.8 V6's

hi offshore men , i have read the replies to your queston and it seems that indeed the only way is to replace the v6 by a pair of 350 with bravo drives just dont forget to study and calculate the position of the engines and drives due to added weight in the stern .<br />maybe you better try it out how these original engines will do and perform and take a good bottle of champagne with you instead of spending lots of money to gain 5 KNOTS MAYBE

 

[geriksen]

Re: need more power from 3.8 V6's

I agree with JOS. You really have two viable options. Replace the entire packages and spend over $20,000 on this boat. (What is the whole boat worth?) Or you could take and inch of pitch out of the props, or go hog wild and buy new ones. $300.00 Your comment earlier was that you were o.k with the top end you just wanted it to come out of the hole better. If I were you I would tune up those engines, keep them totally stock and reliable and replace the props. You will be happier.