SBC guru's, I could use a little advice/help!

[Buick From Hell]

I have a 350 in my 25' boat, and I'm looking for some "easy" extra power, and at the moment the "easiest" would be changing the rocker arms to some 1.6 rollers...

A few things I'm not sure of---what's with the "self-aligning" vs. not-self aligning rockers? The engine is a 1988 with the center-stud valve cover bolts, and 1987 seems to be the "cutoff" year, so will I need the self-aligning arms? (of course, they're more $$$)

I'm not sure of the cam specs, but I'm hoping the extra .030 or so lift is worth SOMETHING! I run this boat at fairly high altitudes, and ANY extra power will help! --as will any help and advice!

tia!

 

[Buick From Hell]

other info--

I put a new unilite distributor in it last spring, and I just pulled the holley 750 (WAY fat primary enrichment & secondaries) and put on a new Edelbrock 650 (which I'm still in the process of tuning)...not sure where the timing's at, but it was set at the "sweet spot" while running 2800 rpm at WOT...

So far, everything's about the same as before as far as power goes...

 

[Reaper]

NAWWWS AND A TYPE "R" badge should work well.


what model is the carb?
when i was messing around with my truck E brocks tech line was a huge Help ( long ass wait on hold) they suggested going "1 step" leaner, if you get the ebrock book out and look on pg 24 you'll see a graph. we used 1 (main jet #1426 , metering rod 1456). this really woke the truck up. i would since your so much higher then phoenix maybe go 2 steps leaner that would put you 8% leaner. i hope this helps. this is on a 1406 600 cfm E brock

i can copy this page for you and scan it if you like. this really helped me out.


Dathan

 

[slow87]

You can get some guides and ditch the self alligners if you want(basically go "old school".

Heres the difference beetween the two,
The non self alligning is the old school that uses pushrod guides to keep the rocker on the valve.

The self alligning(any production engine with center bolt (87& up) valve covers should have these)
Has walls(grooves,channel, whatever) on the rocker that allignes its self using the tip of the valve stem. And has no pushrod guides except the rocker itself.


If you really want some more power maybe you should just turbo it. Then you can "spool on the water".(sing it to the tune of smoke on the water )

 

[WakkoSS]

The 1.6 rockers won't do a whole lot, but they'll help. The Edelbrock/Carter carbs are great...right out of the box they work well. Do you have a standard type distributor? If there are weights inside for timing advance (be under the rotor) you can get heavier weights and different springs for under 10 bucks. Coils won't help much, the factory coil is 38k volts, the Accel coil is 40k. What headers? Smaller headers will give you more torque if that's where you're lacking. What RPM range are you running? Performer intake is good idle-5500, Performer RPM 1500-6500 (mild high rise).

The best suggestion so far is the Type R badge...guarenteed 15-20 horse from that alone!

 

[GNVAIR]

Best mod would be to add a set of 96-99 Vortec heads (062-906) and a mild cam. If the block is a roller cam block, you could get a factory LT1 cam for practically nothing.
The Vortec heads can be picked up on Ebay for approx $250. You do have to use a Vortec style intake.......get the Edelbrock Performer.
The Vortec heads are worth approx 40 horses over most other Chevrolet heads. They out flowed the iron Bowtie heads and all the mythical fuelie/camel hump heads right as they come.
I have the set up I described (restricted with TBI) on my truck and the thing flat out rips. Probably a 14 sec truck.

 

[Dusty Bradford]

Besides a set of Vortec heads and matching intake there isn't much to do short of a whole different motor. Do Not put a high performance cam for a car in a boat. It will kill it. The cam has to be ground for a boat to get the power range right.

 

[gofstbuick]

I don't know whether you require a lot of torque, but if not, I would look at a single plane intake, with a 1 or 2 inch spacer. Personnally, I like Holley carbs and DP repsond really nice on single plane intakes. Regarding timing, I usually set base timing at 20*btdc and disconnect the vacuum advance.

 

[stubbs]

Go here www.tpis.com

 

[Buick From Hell]

Thanks guys!

Here's the "operating specs"

Other than lacking power, it RUNS pretty decent. It currently holeshots at about 2400 rpm, and it won't plane out unless I can get above 2900. So, torque is definitely important in this range! At WOT my max RPM is 3800-3900, with about 38mph on the speedo...Mfg. specs say I should WOT between 4000-4400. Currently, I'm running props that are a bit steep, and I just bought a brand new pair with a smaller pitch, but I haven't even tried them yet. These SHOULD help the holeshot (which is REALLY where I need the power) by getting the initial RPM up to about 2600-2700, and hopefully get into the powerband sooner. The WOT rpm is also supposed to increase approx. 300-400 rpm.

Marine engines have "marine" cams, which are basically set up for midrange power since most "basic" marine engines never see higher than 5000 rpm (if THAT high) I DON'T want to change cams, since I'd have to yank the engine. However, changing heads & intake is definitely do-able!

The distributor is pointless with centrifical advance, I *think* it has 24° total timing, all in at 3200, and I'm using an Accel 'standard' coil. The Edelbrock I have is the #1409 marine carb, the intake is actually a stock Q-jet that's been machined to accept ANY carb, and I'm using a 1/4" thick plex spacer. The carb came with .098 main and .101 secondary jets...I've already moved the .098's to the back, and installed .095's in front. Stock rods are 068/047, and the only rods I've found (so far) were 073/047's, which lean the cruise side TWO steps with NO change on the fat side...Only problem is, the only place I've had to test the boat is Strawberry reservoir, which is 8000' up, and I've NEVER got the boat on plane there! 2800 rpm at WOT while plowing thru the water is the best I've got so far. Without going into great detail, I CAN say I do have the carb "close".

As for headers, they're just stock water-cooled Volvo-Penta risers! I HAVE considered thru-transom exhaust, but the wifey likes her quiet boat! (and she has chronic headaches, so...)

Anyway, this thing is too big to ever be a hot rod boat, and I'm not too concerned with top speed, just looking for a little extra grunt to get the thing moving in the first place! I'm definitely going to give a head change some serious consideration!

 

[GNVAIR]

As an addendum to my previous post;
The Vortec heads will allow you to run more compression and/or more timing with their fast burn chambers. For approx $500 (between heads and intake and gaskets), you will see a big power difference. I know in a car you would. I am not sure how 40 horses would affect a boat, but I am sure it would do something.

 

[gofstbuick]

Originally posted by Buick From Hell
Thanks guys!

Here's the "operating specs"

The distributor is pointless with centrifical advance, I *think* it has 24° total timing, all in at 3200, and I'm using an Accel 'standard' coil.

Now armed with new information, IMHO you don't have enough timing. Please try my 20* base timing suggestion. A review in the Chevrolet power manual shows a timing trace, with base timing starting at 20* at idle (vacuum advance disconnected or mechanical advance only).

 

[Rollin]

BFH:

the intake is actually a stock Q-jet

Kevin, here is a little power for you. If you were to change to an Edlebrock RPM Intake and a smaller carb say a Holley 450 cfm you'll pick-up some low RPM grunt as well as some juicey mid range. Most stock SBC's usually pick-up around 10-15hp and 15 ftlbs of torque or more depending on combo just on the intake swap. Leave the rockers alone with a low rpm stock marine cam the .030 is not going to do much anyway and may do more harm than good. Why? Slowing velocity down by creating a larger pressure drop will kill the lowend. However, once it picks back-up the extra airflow would help but since your not taking it much over 4000 rpm were the extra flow would really shine,(damn marine cam ) nix that for now. Just to be safe, I'd also check fuel pressure it may be laying down on you. Something else to lay on ya, the secondaries may not be opening from lack of air signal. I think a smaller carb may be your best bet, this in conjunction with a good intake should wake it up. Course if you want to get Buck-Wild with your SBC we can conjure up somethin....

 

[John Larkin]

I used a 450cfm Holley Economaster (spreadbore) with a stock intake back in the late 70s/early 80s and it was all an Olds 350 needed on the street. I bet that spacer is raising your usable RPM band. I like the increased timing idea also, you need to get the advance curve way down though. Try to get it all in at 2400 (lighter springs?) Maybe increase the cam advance with an offset button. Match the combo!

 

[steve hughes]

If you do consider the vortec heads i believe they are small chamber . It may raise your compression . Don't know how much cocern it would be on a marine engine but something to think about. You can buy these heads new for about $460.00 . 24 degress timing isn't much on a sbc. Before you change parts and spend money play with the timing. You can probably run 32 - 34 with good gas.

 

[bruce]

Originally posted by GNVAIR
As an addendum to my previous post;
The Vortec heads will allow you to run more compression and/or more timing with their fast burn chambers. For approx $500 (between heads and intake and gaskets), you will see a big power difference. I know in a car you would. I am not sure how 40 horses would affect a boat, but I am sure it would do something.

With the fast burn heads, you don't have to run alot of timing, and in fact can do really well with 26-28d.

 

[bruce]

Originally posted by Buick From Hell

Marine engines have "marine" cams, which are basically set up for midrange power since most "basic" marine engines never see higher than 5000 rpm (if THAT high) I DON'T want to change cams, since I'd have to yank the engine. However, changing heads & intake is definitely do-able!

The distributor is pointless with centrifical advance, I *think* it has 24° total timing, all in at 3200, and I'm using an Accel 'standard' coil. I'm definitely going to give a head change some serious consideration!

Often the marine cams close the intake valve rather early to better trap the intake gases at lower speeds, and min reversion.

It's all about torque, IMO.

High turbulence, small chamber, low timing heads are the answer.

And if your keeping the revs down that 24d might be on the high side. getting the fuel curve right is critical, without having any gear changes, and torque multiplication, you have to make it all on grunt, as you've noticed.

Props are so critical, it's like the tranny and rear axle wrapped into one item. Guys around here, used to swap props around all the time to find out what worked best. Maybe you might try prop swaps with some guys.

 

[myclone]

I'll throw in my .02 since Im "another one of those SBC guys" or so I was told on here...

Anyway, the Vortec heads are a HUGE improvment over the old style stockers if you dont mind swapping heads. They have better combustion chambers (WAY BETTER!!), decent flow numbers that get even better with a VERY mild bowl clean up, and they can be had dirt cheap on ebay (for a few bucks more you can get them at your local GM parts dept).

Id hafta check but I believe edelbrock makes a dual plane intake just for the vortec heads unless you dont mind modding the intake to head bolt holes so the stock intake will bolt up. The vortecs intake to head bolt holes are drilled at diff angles is the reason you need a specific intake or need to mod the stockers' bolt holes.

As for the carb I personally liked the ease of tuning and drivability of the one edelbrock carb I messed with. I didnt own the car long after I put the carb on so I only tinkered with the metering rods a couple of times so Im not much help there other than giving edelbrock props for making a decent carb.

Lastly, I'd do a cam swap as a last resort myself as was mentioned and if you do decide to do the cam you will need to know if the engine is standard rotation or reverse rotation (some marine engines run the opposite direction than their automotive counter parts). Im guessing your engine is a standard rotation since you said that you recently swapped out the distributor but itd be best to check for sure before you plunk down the $ for a new cam.

HTH

 

[Carman83ss454]

Just thought I'd throw some info out:

The centerbolt valve covers are NOT a positive indication of self aligning rocker arms. Remember, GM was using centerbolt covers as early as '87, and self-aligning rockers appeared '89/'90ish, IIRC. The only way to know for sure is to pull off a valve cover.

The term "self-aligning" refers to the fact that the pushrod is held parallel to the lifter via small stamped-in "rails" on the rocker tip that cradle the valve tip, as opposed to non-self-aligning, which used the hole in the head that the pushrod passes thru as the alignment point.

To convert self-aligning type heads to non-self-aligning, you will need pushrod guideplates, which means you will need screw-in studs, which then also means removal of the head for milling the stud pads level, and drilling and tapping the holes. Would be cheaper to run the self aligning rockers.

If by chance you are interested in Vortec type heads, take a look at the Pro Topline Vortec replacement head. I has a lot of advantages over regular Vortecs, such as being ready for screw-in studs, milled down for guideplates, ready for better (bigger diameter) springs, cut-down valve giudes for an extra .100" valve lift (stock Vortecs are only capable of about .480" lift), and being a better (cleaner/smoother) casting in general.

The stock Vortecs also suffer from chronic failure of the casting at the upper water jacket passages that are adjacent to the row of center head bolt holes. There are a couple reasons: They handle heat about as well as Richard Simmons could handle a punch in the face from Mike Tyson, and the stock GM Vortec intaker gaskets are leak prone, allowing the engine to consume coolant, which lets the engine run hot. The GM Vortecs are also a very light casting, and are not very dense. In fact, one Pro Topline Vortec weighs almost 14 pounds more than a stock Vortec.

I have some comparison pics of my stock Vortecs and my Pro's if you're interested.

Scott

 

[Buick From Hell]

WOW, trust the buick community to come to the aid of a weakling 350 chebby!!

Some more "clarification"...

I should have stated the 24° advance is in addition to initial timing (fer instance, 34° total with 10° initial)...when we last timed it, it was while plowing water at WOT at about 2800 rpm, and we set the timing JUST at the point where, if you retarded it WHATSOEVER, you could notice it lose power, but if you ADVANCED it whatsover, you didn't notice anything...At this setting, it always fires instantly, doesn't knock...

Couple of reasons I changed the carb, first was because brand new spark plugs would be soaking wet with fuel after 5 hours of running. The first time we tore into the holley, we found 74 jets in front, with a 7.5" powervalve (that was blown). We changed to 71's, and put in a 6.5" powervalve. At 6300', this was the difference between NOT getting on plane and GETTING on plane! Another reason was the secondaries weren't opening! (as Rollin mentioned!) They would just BARELY open when the boat was at top speed, otherwise they didn't budge. The Diaphragm was okay when I tested it, but I didn't have a lighter spring at the time...Oddly, the BEST this boat ever ran was the day before I yanked the holley. BUT, just before that trip I'd pulled the 71 jets and put in 69's. The thing actually felt STRONG, and got on plane without even using the trim tabs (which were ALWAYS necessary before!) AND with banged-up props! I've have very limited tuning-time with the new carb after the jet change, but I HAVE found (at 8000' anyway) that while trying to get on plane, I'd pick UP a hundred or so rpm by backing off the throttle! Changing the rods (2 steps leaner cruise side) resulted in no help at all when backing off the throttle, so from THIS setting it seems that one step richer on the cruise side and one (or two) steps leaner on the fat side should be REAL close! Enrichment seems to come on about right, so I'm not gonna fool with rod springs just yet...


DAMN this is fun! The buick's been broke down for so long, I miss "talking shop"! (thanks everyone!)