John_S

Hi, I think this is my first post here, but have been reading and searching through the great engine upgrade info. I am doing a "mild" upgrade compared to most of what I see here.

I have '97 Bayliner (no comments please ) with a 5.7L 2brl (210hp) Alpha II. It is raw water cooled and boat only in fresh water. It is non-vortec, flat hyd lifters, and recessed (low-compression) stock flat-top pistons. Heads, intakes, and exhaust have been removed. My plans are:

- stock vortec heads
- 4brl intake and carb
- stock merc roller cam and components (slightly used)

My goals are 60mph top speed (52 now), very good idle quality (I have about 2 miles of no wake zone before getting to lake), good strong pulling torque for water sports, and the durabilty of a stock engine. My estimate of the above mods is 280hp. Max rpm 5K.

The cam and parts have already been agreed to, and will not increase hp, but should add durability. The heads are a go based on finding the recessed pistons. That puts me down to selecting intake and carb. After much reading (including Dennis's book), I think a Q-jet is the way to go. It should provide better idle quality than Edelbrock 1409 or Holley (600/650). It is also recommended highly by Dennis for stop and go boating, which is my primary use. Home lake is on the small side, so don't do much long distance running at or near top rpms.

Going with a Q-jet, basicly locks me into a Performer 2116 intake. I do see that Performer RPM is more popular here. Do any of you that run this, have any issues with extended running at idle to 1200rpms? Do you have any torque issues pulling slalom (sp) skiers up? If the Holley or 1409 have good enough idle circuits the weiand 8121P action plus might be an option.

While the RPM or other highrise dual plane will probably give me 10-15hp more in the 4-5k rpms, I am not sure I need it. I don't plan to run allot at WOT, just want to be able to hit the 60mph barrier, if I want to.

The exhaust plans are stay with the stock cast-iron and thru prop exhaust. Given my goals, don't think I need to change this. Possibly go to the tube style exhaust bellows.

I would appreciate any thoughts or comments on the above.


Assorted other questions:

- Does anyone have the GM part number for the throw away composite timing cover? I wasn't able to find it on GMPartsDirect.

- Does quench actually buy me anything with recessed pistons? It doesn't appear that Merc does given the thick stock gasket.

- The GM gasket set 12499223 looks like a decent buy, but would still want Merc exhaust gaskets. comments.

Wobble

Might want to consider strokin it to a 383 or bigger if you really want to see an 8mph gain. Their are some good deals to be had on SBC stroker rotating assy's

John_S

A stroker will not meet the "reliable" requirement when it comes to the alpha drive. Also, not looking in pulling engine at this point in time. I thought 6-7hp per mph was realistic. Not sure where I got that from, and will need to search. I don't think I can compromize the idle and low-end torque to try to hit the magic 60mph. It would have been nice, though!

Wobble

A fair rule of thumb in the 60 moh range is that it will take an extra 20hp for each added mph, the faster you go the less return you will see. I believe there are several board members pushing around 400 hp through an alpha setup.

John_S

Comments on intake and carb???

Full Force

iTrader: (5)

I am running a edelbrock rpm with holley 650 setup,I have dart heads and a mild cam also.
I went from stock 260 to my current combo and went from 46 mph to 50 on gps,I have a 245 limited so it is alot of boat for a small block,this winter I have a balanced/forged piston 350 short block coming that will get rid of my 8.5:1 compression,this is killing the boat right now but I ran it that way for this season.
I will have more compression now so I can have my custom cam done,I would change the cam if you want more gain,just make sure you do not overdo it.
I use Cam motion for my custom work and I have NEVER been let down.
I will help you out with anything I can answer,Tim

John_S

One of the "notes" I find about Holleys is "they won't idle in the same place twice" and other comments about poor idle quality. Are they true? The Holley I am most interested in is the 650cfm spreadbore, vac sec. I haven't had a Holley apart since the 70's.

The edelbrock 1409 seems to have a good reputation to be close to tuned out of the box for sbc, and be easy to tune if not. I have had a couple of these apart before, and they seem very simple. I have seen some comments on the idle quality but not to the same level of the holley. Does any one know at what rpm the air door starts to open? It is not adjustable as far as I can tell.

The q-jets seem to have the best idle circuits, and the good flexibility with adjustments. If anything, maybe too many adjustments. I have never had one of these apart, but the diagrams and rebuild procedures I've looked at haven't scared me.

Intake question: On many intakes there is a raised crosshatch pattern on the bottom of the runners, as viewed from carb opening. Not sure what this is for. I am guessing that it holds any raw fuel that dribbles out of carb so it has a chance to evaporate before just running into cylinders. Anyone know?

Not sure of the accuracy of this calculator Speed Calc but it would indicate I have a shot at 60. I used 4Klbs (on the heavy side with 1-2 people) + 210hp + 225 constant and got 52mph, which is what I'm seeing. Use 280hp and you get 60.

John_S

245Limited: I am not sure how Merc comes up with 9.1:1 static compression ratio on my stock engine. 76cc heads, head gasket, deck clearance, and subtracting for recessed pistons gets about the 8.5:1 as you reported. Thats using a -10cc for pistons. I think they are closer to -12cc, 9cc for dish + 3cc for valve reliefs. Anyone have the exact cc for these stock pistons?

Full Force

iTrader: (5)

I am not sure either,I have a merc manual that told me what it was,I have 64 cc heads and dish pistons,they also used a stainless head gasket that was 18 thousandths thick,1/2 of a regular gasket. I did the math with the flatops I have in the new engine with regular gaskets and 64 cc heads,it is 9.4:1

cuda

Are you going to try to change the cam without pulling the engine???