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TX H210SS · **Joined:** Thu May 27, 2010 9:10 am **Posts:** 1488

Ric, I guess your fine for putting around or cruising so the under power isn't much of an issue for your boat unless you are into water sports. Your boat is fine for the setup which is for cruising.

Towing skiers and tubes with 6 in the boat and one on the line will require some more horses for sure, but even with boosted power you would need to drop some of the added weight.

Surface Interval · **Posted:** Sun Jan 26, 2014 10:07 pm

Deafwish, I'm not sure that there is truly an rpm limit for these outdrives. You will typically see gear ratios on the data tag on the side of the outdrive. My old 190 Horizon had a 1.60:1 ratio. 1.6 revolutions of the engine to 1 on the prop. My 268 Vista has a 1.95:1, I think. Prop rpm might top out in the range of 2500 to 3500 rpm. The ratio has a lot to do with top speed of the boat, weight of the boat, engine horsepower, torque, and rpm, prop pitch, and several other factors. You will see prop pitch range any where from maybe 13" to 26" or more, but a lot of the boats we commonly see have 17 to 23 or maybe 25" pitch. Manufacturers will balance the specific details of the boat with prop diameter and pitch availability to come up with an outdrive ratio that delivers overall best performance. I believe a fairly new I/O engine (maybe a GM 6.0 liter) on the market has a redline of 6000rpm.

deafwish · **Posted:** Sun Jan 26, 2014 10:44 pm

My drive ratio is 1.66.
Given I may exceed the RPM range of the 5.7GL (4400 - 4600), might it pay to fit new valve springs while I'm getting the 4BBL upgrade done?

kd4pbs · **Joined:** Thu Sep 05, 2013 10:34 am **Posts:** 350

I'm pretty sure I never mentioned anything about 350HP being uber performance from a 400ci, Mr. Ric. 350 HP is indeed a large increase from a typical stock 400 though (obtained with only a cam change, 1.6:1 ratio roller-tipped rockers, tri-Y headers with 3" exhaust, electronic ignition, and this manifold with a quadrajet), and was used to illustrate how easily this manifold will more than fulfill deafwish's needs for his engine, as opposed to your inane idea that this high-flow cast iron OEM manifold is merely a low-flowing "smog" manifold. Then again, what do I know? I've only built 7 or 8 small block Chevrolet and 2 big block Chevrolet race and street/strip engines personally, and been involved in somewhere North of 30, so I indeed bow to your vast and superior knowledge of such, and even in my 30 years of wrenching hotrods and modifying gas and diesel engines in boats, cars, and motorcycles, I always welcome a chance to learn. Mainly because of course, I have never in those 30 years investigated the basic formula of how to make power over stock :roll:

. Please enlighten us as to your idea of how much horsepower a stock 400ci SBC would typically produce, and why 350 is "horrible" horsepower for a low compression 307ci engine made in the early 70s (as you say, ANY sized small block...) much less a 400ci one.

Deafwish, that plate should work perfectly. I've only ever seen one EGR baseplate profile for early SBC engines, regardless of manifold. You won't get a crazy increase in performance between a 2bbl and 4bbl, but you will likely see a noticeable increase in fuel economy and throttle response if you stick with a quadrajet, and probably 1-3 MPH more.
As for the valve springs, you'll likely be fine. Great find!

ric · **Posted:** Mon Jan 27, 2014 4:13 pm

kd4pbs wrote:

I'm pretty sure I never mentioned anything about 350HP being uber performance from a 400ci, Mr. Ric. 350 HP is indeed a large increase from a typical stock 400 though (obtained with only a cam change, 1.6:1 ratio roller-tipped rockers, tri-Y headers with 3" exhaust, electronic ignition, and this manifold with a quadrajet), and was used to illustrate how easily this manifold will more than fulfill deafwish's needs for his engine, as opposed to your inane idea that this high-flow cast iron OEM manifold is merely a low-flowing "smog" manifold. Then again, what do I know? I've only built 7 or 8 small block Chevrolet and 2 big block Chevrolet race and street/strip engines personally, and been involved in somewhere North of 30, so I indeed bow to your vast and superior knowledge of such, and even in my 30 years of wrenching hotrods and modifying gas and diesel engines in boats, cars, and motorcycles, I always welcome a chance to learn. Mainly because of course, I have never in those 30 years investigated the basic formula of how to make power over stock :roll:

. Please enlighten us as to your idea of how much horsepower a stock 400ci SBC would typically produce, and why 350 is "horrible" horsepower for a low compression 307ci engine made in the early 70s (as you say, ANY sized small block...) much less a 400ci one.

Deafwish, that plate should work perfectly. I've only ever seen one EGR baseplate profile for early SBC engines, regardless of manifold. You won't get a crazy increase in performance between a 2bbl and 4bbl, but you will likely see a noticeable increase in fuel economy and throttle response if you stick with a quadrajet, and probably 1-3 MPH more.
As for the valve springs, you'll likely be fine. Great find!

I don't care about the old stuff I'm talking about what's in his boat, the vortec head design is superior to anything GM made before. A stock vortec chevy 350 un-molested is 260hp off the assembly line with a 600cfm carb. That's what he has, just one that's detuned from Volvo further with a 2bbl carb. If you install the GM performance parts camshaft #14097395 which is also the camshaft used in the 5.7GXi and Mercruiser 350 MAG it brings it around the 350hp mark. The HP differences being the tune in the MEFI for marine engines.

His engine, a 5.7 Vortec with GM performance cam #14097395, a basic performance manifold like a simple edelbrock, and a 600cfm carb will bring him around the 350hp mark. My engine, a 5.0 Vortec with the same setup will be around 300-320hp. Currently with that cast iron manifold, 4bbl, and stock camshaft he's hovering exactly around the 260 mark.

deafwish · **Posted:** Tue Jan 28, 2014 12:34 am

Ric, this isn't a Vortec engine!
Kd4bps, thanks for your advice.

ric · **Posted:** Tue Jan 28, 2014 12:48 am

1997 and not a vortec? odd.

RotaryRacer · **Posted:** Tue Jan 28, 2014 9:01 am

96 was the first model year Vortec V8s were used in GM trucks. It is not odd at all that a boat built that or early the next year isn't a Vortec.

Remaining inventory on the shelf, GM not selling the newest engines to marinizers right away, a boat built in mid 1996 before there were any Vortecs in the supply chain. There are many reason why a boat with a 97 model year designation wouldn't be a Vortec.

ric · **Posted:** Tue Jan 28, 2014 10:29 am

RotaryRacer wrote:

96 was the first model year Vortec V8s were used in GM trucks. It is not odd at all that a boat built that or early the next year isn't a Vortec.

Remaining inventory on the shelf, GM not selling the newest engines to marinizers right away, a boat built in mid 1996 before there were any Vortecs in the supply chain. There are many reason why a boat with a 97 model year designation wouldn't be a Vortec.

Well, it's not the worst thing to happen. To convert is not expensive. Set of reman heads are in the $300 range.

kd4pbs · **Joined:** Thu Sep 05, 2013 10:34 am **Posts:** 350

Mr. Ric, I think something was lost along the way. The 400 I referred to was not a Vortec, and was modified long before Vortec parts were around. That being said, the thing to do back then was to use other HP parts. Vortec technology was far from the end-all-do-all-be-all in performance. Several heads in GM's arsenal that flow just as well if not better than the Vortec heads that came along later were available back then, as well as non-GM offerings such as Dart and AFE. One could easily reach close to 400HP with high-flowing heads, increased compression, and smartly matched induction and valve timing components. Getting 350 HP from an old 400 back in 1985 was indeed doing something. Getting 350HP from deafwish's engine without some stout mods would be spectacular, and unadvised -- longevity would be sacrificed. To start with, the restrictive through-the-drive exhaust would make it impossible.
Can't wait to see how well this simple upgrade adds to the boat!

ric · **Posted:** Tue Jan 28, 2014 12:17 pm

kd4pbs wrote:

Mr. Ric, I think something was lost along the way. The 400 I referred to was not a Vortec, and was modified long before Vortec parts were around. That being said, the thing to do back then was to use other HP parts. Vortec technology was far from the end-all-do-all-be-all in performance. Several heads in GM's arsenal that flow just as well if not better than the Vortec heads that came along later were available back then, as well as non-GM offerings such as Dart and AFE. One could easily reach close to 400HP with high-flowing heads, increased compression, and smartly matched induction and valve timing components. Getting 350 HP from an old 400 back in 1985 was indeed doing something. Getting 350HP from deafwish's engine without some stout mods would be spectacular, and unadvised -- longevity would be sacrificed. To start with, the restrictive through-the-drive exhaust would make it impossible.
Can't wait to see how well this simple upgrade adds to the boat!

Maybe on his pre-vortec engine without the upgraded rods/pisons it would be a stretch but on something vortec based it's not just heads. The whole engine is beefier. The first small block I ever built was a 350 when I was 15, older engines suck. Vortec is not end all be all, but you get PM rods, better pistons, better heads, roller cam, other upgrades. 350hp on a vortec 350 is something that will last the lifetime of a vessel, you can buy one with a warranty from GM for a couple grand. The "drive through" exhaust is good for around 400hp, and you can remove the exhaust bellow (what VP does on big blocks) to improve that situation.

There's plenty of write ups from GM Performance magazine/blog how to safely and reliably bring a 350 to 350+hp using off the shelf parts with longevity in mind. Starting with a base Vortec engine is 90% of the recipe. Intake, carb, cam. That's it.

http://www.hotrod.com/techarticles/engi ... evy_build/

Please note the article says (The L31 is the marine 5.7)
Also intriguing is a complete '96 to '02 L31 truck and van 350 Vortec engine (PN 12530282). This engine already has the right heads, plus it uses a hydraulic roller cam. Replace the mild cam with an aftermarket hydraulic roller and some stiffer springs (the roller lifters are reusable), along with the usual external performance pieces and you should make more power than the buildup covered here.

kd4pbs · **Joined:** Thu Sep 05, 2013 10:34 am **Posts:** 350

Dude... the bottom end on the Vortec engines were virtually unchanged from the original SBC. Non-vortec heads will even bolt straight up. The only changes were minor ones to the heads, and the addition of a roller valve train. We still got the junk cast pistons, the softer rods, and a cast crank. There still was no guarantee the Vortec engine had a 4-bolt main even. The Vortec mods to the original SBC required minor changes to the intake manifolds, and also to the timing chain cover. Vortec vs. non-Vortec is basically the difference between good flowing non-Vortec heads with basic bolt on mods such as heads, cam, and fuel injection versus a plain-jane smog engine. Heck, even the "Vortec" branded big blocks are still mostly based on common-sense mods to the original big block of the 60s. Again, give me good aftermarket parts on a non-Vortec engine over OEM Vortec any day of the week. I get to pick and choose my performance parts, and the availability is much larger than with the Vortec specific aftermarket parts. Still being a step in the right direction, the Vortec program was simply Chevrolet's attempt to squeeze extra life out of the Gen I platform until the next V8s rolled out with the introduction of the 5.3 Gen III by delivering from the factory all the "basic" mods the typical gearhead would add to a classic SBC. The 5.3 was a total redesign, and I'm glad to see the major marine manufacturers finally switching to that platform, albeit 10 years or so late.

ric · **Posted:** Thu Jan 30, 2014 1:36 pm

All vortec 350 engines have forged PM rods and hypereutectic pistons just for starters. Bunch of other changes. Not sure where you're getting that misinformation.

kd4pbs · **Joined:** Thu Sep 05, 2013 10:34 am **Posts:** 350

Empirical experience for building a few of them and finding cast aluminum pistons and standard rods. Not sure where you're getting yours, but my guess is that you're confusing the original Vortec SBC engine with the LT1 Vortec engine. The LT1 is by far a different animal than the engines we are referring to in this thread.

ric · **Posted:** Thu Jan 30, 2014 2:13 pm

kd4pbs wrote:

Empirical experience for building a few of them and finding cast aluminum pistons and standard rods. Not sure where you're getting yours, but my guess is that you're confusing the original Vortec SBC engine with the LT1 Vortec engine. The LT1 is by far a different animal than the engines we are referring to in this thread.

All 1996+ Vortec 350 engines have hyper pistons and PM rods. If it does not, it was not a vortec engine.

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