Hello all
I know the majority of the discussions are related to big blocks with intercoolers/superchargers...etc. But, I'm hoping you may be able to provide some insight/recommendations...for a small block.
I have the following setup:
355 Small Block 4-bolt main
B&M 144 Blower (running max 5psi Boost)
750 Holley
COMP cam Part# 12-402-4
Gross Valve Lift .44 .444
Duration @.050 Intake 212 Exhaust 218
Lobe Lift Intake .2960 Exhaust .2960
Lobe Separation 114
Cast Pistons
Original Heads
Exhaust thru prop
Planned setup:
SuperChiller Intercooler for B&M 144 Blower with a separate water pickup, Sea Strainer and dump.
Changing the pulley's to overdrive the blower
Converting the boat to straight exhaust
Lightening Headers
MSD 6 Series Ignition
Heads/Forged Pistons
I'm not sure which type of heads/pistons to purchase. I've been looking at either the "World S/R Torquer or Sportsman-II" heads. They seem to be identical (2.02x1.60) other than the intake runner volume (170cc or 200cc, respectively). The Sportsman-II heads have optional angled vs. straight plugs, any thoughts which would be better? They also have a few options on the combustion chamber volume. Which leads me to the question of how low is to low for static compression.
The forged pistons I have been looking at are by SpeedPro with 21cc D-shaped - low compression. They state w/std stroke and rod:
64cc head - 8.35:1 compression ratio
76cc head - 7.55:1 compression ratio
I've always heard that a marine engine should be setup to make more torque than HP. So, wasn't sure if restricting the intake runner will help with this. Any suggestions would be greatly appreciated!!!
Thanks for all the other help (I read the board and have learned a great deal!)
Looks like you have it figured out to me.
Edelbrock aluminum heads are great and inexpensive. Do the bigger chambers with that piston for 7.5:1 compression.
World "SR" heads are "stock replacement"
Spin that 144 as fast as it will go with the intercooler and you are still pump gas friendly.
It will haul ass.
Oh Yea: Use the 6M2 ignition or at least the marine distrubutor. If not it will corrode out in 1 season.
Originally posted by Drakar
Hello all
I know the majority of the discussions are related to big blocks with intercoolers/superchargers...etc. But, I'm hoping you may be able to provide some insight/recommendations...for a small block.
I have the following setup:
355 Small Block 4-bolt main
B&M 144 Blower (running max 5psi Boost)
750 Holley
COMP cam Part# 12-402-4
Gross Valve Lift .44 .444
Duration @.050 Intake 212 Exhaust 218
Lobe Lift Intake .2960 Exhaust .2960
Lobe Separation 114
Cast Pistons
Original Heads
Exhaust thru prop
Planned setup:
SuperChiller Intercooler for B&M 144 Blower with a separate water pickup, Sea Strainer and dump.
Changing the pulley's to overdrive the blower
Converting the boat to straight exhaust
Lightening Headers
MSD 6 Series Ignition
Heads/Forged Pistons
I'm not sure which type of heads/pistons to purchase. I've been looking at either the "World S/R Torquer or Sportsman-II" heads. They seem to be identical (2.02x1.60) other than the intake runner volume (170cc or 200cc, respectively). The Sportsman-II heads have optional angled vs. straight plugs, any thoughts which would be better? They also have a few options on the combustion chamber volume. Which leads me to the question of how low is to low for static compression.
The forged pistons I have been looking at are by SpeedPro with 21cc D-shaped - low compression. They state w/std stroke and rod:
64cc head - 8.35:1 compression ratio
76cc head - 7.55:1 compression ratio
I've always heard that a marine engine should be setup to make more torque than HP. So, wasn't sure if restricting the intake runner will help with this. Any suggestions would be greatly appreciated!!!
Thanks for all the other help (I read the board and have learned a great deal!)
Some places you could save some money with little or no power loss would be: Crane HI-6M ignition with stock merc. distributor shaves off $300 and nicer setup too. Your stock exhaust manifolds are likely adequate, otherwise the Stainless marine hi-torque is an excellent manifold.Definitely thru-hull exhaust. Regarding angle plug or straight, not much if any power difference but angle plug could be difficult to access depending on which manifolds you run. I would do the strainer later, unless you boat in crappy water. If you do the low compression pistons and the 76cc chambers ypu're going to have to spin that blower fast!. I think the max. 144 rpm is 12,000? Pacific Power Boats has 2 or 3 of the 8-9 lb. pulleys laying around. Give them a call, you might be able to get one around $50 instead of $100. Here's a pic. of my old boat...
Infomaniac and HP350SC....thanks for the info!
Infomaniac: I'm running raw water cooling....is Aluminum ok to use? And do you have a recommended product from Edelbrock? I'm figuring the 2.02X1.60 should do fine...but, is a larger intake runner (200cc vs 170cc) better or does it hurt torque?
HP350SC: I'm going to check on the maximum RPM for the blower....that is a good point. I don't plan on running the engine RPM much over 5000. I believe this should keep the blower RPM in check. I have an email to Holley to confirm the max RPM.
The current engine/blower ratio is 1:2 (5,000 engine : 10,000 blower). Modifying the lower/upper plies should give me (I'm trying to derive these numbers by charts on Holley's web site):
Blower ratios and est. boost:
A) 1:2.00 (5,000 : 10,000) - 5psi Boost
B) 1:2.33 (5,000 : 11,650) - 8.5psi Boost
C) 1:2.45 (5,000 : 12,250) - 10psi Boost
Static Compression Ratios to Effective CR (ECR):
B) 7.5:1 - 12.00:1
C) 7.5:1 - 12.60:1
B) 8.0:1 - 12.6:1
C) 8.0:1 - 13.4:1
Maybe I would be better off setting up the static compression at 8.0:1, since the blower can only spin so fast??? I think I've read that the ECR should not exceed 13:1...if true, does an intercooler raise that value (since the charge is less likely to detonate)?
Sorry, for all the questions. I'm no expert...but, I'm enjoying the learning experience and hoping to avoid some 'pitfalls' by asking questions.
Thanks!
I always use less than 8:1
You can always change boost. You cannot change pistons. (easily)
You are fixed up also when you step up to the bigger blower.
Any of the Edelbrock Performer RPM heads. Runners size and torque stuff is thrown away when you run boost in your application. It will make tons of torque. Cylinder filling is what you are looking for. The blower takes care of that.
If the Edelbrock Marine head is available for the small block go for it.
Good point on being easier to change boost than pistons!
Drakar, if you boat in freshwater alum. heads are fine. I don't think I'd run them in saltwater. Concentrate your cyl. head search on exhaust flow numbers instead of intake runner size.
How about some hull info. and drive type, etc.
Blower will be fine with 5000 motor rpm.
It is a 1987 SeaRay Sorrento24 cuddy. I purchased the hull a few years ago as a project... it had no moter, outdrive...etc., it was ready for the scrap yard.
The original outdrive was an Alpha....but, I decided to install a Bravo 1 to support my desire for more power. One of these days I want to get around and setup a website of the before and after pics. I attached a setup of the engine from this past summer.
Thanks for the help!
HP350SC: I was looking at your motor picture...did you have a water cross over? I have been debating whether or not to install one. I have read there can be hotspots in the engine if a circulating pump is not used?
What are your thoughts on them? (or anyone else?)
Thanks
Originally posted by Drakar
HP350SC: I was looking at your motor picture...did you have a water cross over? I have been debating whether or not to install one. I have read there can be hotspots in the engine if a circulating pump is not used?
What are your thoughts on them? (or anyone else?)
Thanks
Yes I had a water crossover. Water is pretty cold up here most of the time so I ran a bypass and t-stat. Originally went with crossover to pull some heat out of heads, ran the blower a year on stock heads and gaskets. Didn't have any hot spots or o/heat issues. Static c.r. was 9:3 @ 5lbs. so was pushing it. Head gaskets finally went(10 yrs. old anyway) so replaced cam and heads with Dart iron eagle 2.05 215cc runner and 72cc chamber to drop compression. Jacked boost to 7 lbs. at that time. Only gained about 4 mph as I recall, heads were a bit much for a 350, was going to go to 377 or 383 but sold boat.
Looks like you would benefit from MSD setup, 10deg. initial, 30 total all in by 2500-3000. You don't need vacuum advance on a marine application. Exhaust manifolds could be improved after all, I assumed you had the 350 mag. style.
Drakar,
I've run that setup(basically) .040 over 350 4bolt forged crank,crower rods, KB hyperutectic pistons,8.8:1 compression, edelbrock Rpm heads, Crower 242 flat hyd. cam and a 144 b&m with a nickerson carb 7# boost, 30 deg fixed timing. I bought Imco exhaust and didnt see any gain(I already had the thru hull exhaust). In a 3600# 1989 22 vee bottom Stingray. boat went from 55mph (stock 270hp) to 72 mph with an alpha drive. Id save the money on the intercooler and exhaust go for the alum. heads, bigger cam and the forged pistons. If you sell the boat then you can always sell the heads to a car guy. Id also keep your compression at about 8.25-8.5 or so. You shouldnt need a crossover either. Just run the 140 tstat Maybe drill a couple 3/16 holes in it. Keep it around 100-120. You have a heavy boat and if you stay in it for a long time it will get hot especially the oil. The aluminum heads will effectivly reduce your compression by 1 point and run cooler. I used to turn the motor to 6000 rpm for short periods. The shorter pitch prop reduced the load on the alpha and detonation as well. I did try the 9# boost pulley and didnt gain anything over the seven thats when I knew the blower was getting hot. It will run like a warmed up big block. The straight plug heads are a good recommendation. Have fun its a blast. I wanted to put that motor in a Bayliner or something just to blow some minds...oh well. FYI The motor has been in a chevy nova for 3 years with a single turbo and under 12 psi the car runs 10.60 in the 1/4 mil. Its never been apart. Greg
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