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Small Block Tips?

J

JAnderson

New member
Any one with any low budget S/B tips? I have 93 218 Persuader w/ 350 Mag. 2 yrs ago when I got the boat I ran 63 on GPS. Then I added EMI Thunder Exhaust Manifolds and a K&N Filter. Now I run 61? I would like to get things back or tweak what needs to assist what I have already done. I do have shallow pockets, please be gentle. Any suggestions??
 
Any one with any low budget S/B tips? I have 93 218 Persuader w/ 350 Mag. 2 yrs ago when I got the boat I ran 63 on GPS. Then I added EMI Thunder Exhaust Manifolds and a K&N Filter. Now I run 61? I would like to get things back or tweak what needs to assist what I have already done. I do have shallow pockets, please be gentle. Any suggestions??
 
Can you be more specific? Is the rest of the motor stock? If not, what did you do? Did you change anyhting else before you noticed the decrease in speed?
 
It's a stock 350 Mag w/ the EMI Thunder and the 2 1/2 x 9 K&N. From what I have read and looked into the 350 Mag is set up pretty good. Stock has a high-rise intake, roller cam and Weber four barrel carb (same as Edelbrock performer).

Miss. River Rat
 
I don't know how limited your budget is but I believe a good set of big valve heads and a bigger carb would really wake that engine up.The difference between your mph runs could be something as simple as having a 1/4 tank of gas for one run and a full tank for the other.What kind of RPMs are you running now?Should be about 4800.What prop are you running?

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87 ENFORCER CUSTOM EDITION,454 MAGNUM SS ALPHA W/CUPPED 22 PROTESTOR PROP
 
First do you believe that the motor has good compression with no internal wear IE: cam lobes, valve springs, piston rings, etc..?? If the answer is yes, then we can look at some basics. First, plug check, are they rich, lean or good? Next, what is you total timing set at? It should be 34*-36*. Is there any chance that the carb bowl may have dirt in it?
If you do decide to do as Eriktheviking said, you have to allow enough in your budget to go for a cam swap as well. There is no sense in getting better flowing heads, if the valves are not open long and deep enough to let the air flow.
 
All things considered. Compression averaging 145. Timing played with several times, but nothing. Plugs are clean, but leaner than before. Going to check into re-jetting this spring. Prop selection limited, but have tried several. I run a 23 Mirage Plus @ 4400 and a 21 Laser II @ 4600. I get the best results with the Plus??? I need the characteristics of the Plus with a 14 ¼ dia with the small block. I would love to go with the heads and carb, but to much $$$. I have thought if a little more cam by it’s self would make a difference? I am not an engine builder, so I don’t want to get in to deep where its going to cost more to have some one make it right again than what it cost me for parts. Plus I am a boater not a mechanic, we do a lot of riding and I want to be able to just turn the key and go. So I may be stuck with a nice looking motor and 60 MPH, but all suggestions do help. Thanks, Justin

Miss. River Rat
 
I'd try a 22 Turbo prop.They're a 14 1/4 diameter.I ran a couple of them on boats that I've had over the years.Really liked their performance.
biggthumpup.gif
The larger diameter of the mirage is whats bringing your RPM's down.Whats nice about a small block chevy is they are about the cheapest engines to build.They're so many out there that parts are pretty reasonable.

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87 ENFORCER CUSTOM EDITION,454 MAGNUM SS ALPHA W/CUPPED 22 PROTESTOR PROP
 
You are right on the money with the re-jetting JAnderson. When I put straight out transom pipes on my 4.3 LX Persuader I lost about 5 mph because I didn't re-jet the carb. You improved the exhaust, now you get to add gas to that leaner running engine!! I'd try jets first, that's the cheapest way to go from here and you need to do it anyway. You may have to replace the carb to get one that is easy to change jets out.

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Checkmates owned: 1995 Pulsare 2100BR/1995 Mercury Promax 225 2.5 EFI. 1995 Persuader 183/4.3 LX V6. 1992 Pulse 171/1992 Mercury XR6 150 hp 2.5 liter.
 
Thanks, JW. This is something I should have done last spring, but I lost intrest when I opened the cooler. I just wanted to boat and not work on it. I am glad that somebody else seen this problem. I know alot of Edelbrock fans and Holley guys, so when it came to asking about carbs, I just got mixed opinions. I have heard good things about the weber carb, but what do you suggest?

Miss. River Rat
 
All I know about carbs is what I read recently in Family and Performance Boating. They put a new Holley carb on a motor because you can buy a great jet kit for it with several different sized jets. They put bigger and bigger jets in until the boat didn't go any faster, and then fine tuned with those.

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Checkmates owned: 1995 Pulsare 2100BR/1995 Mercury Promax 225 2.5 EFI. 1995 Persuader 183/4.3 LX V6. 1992 Pulse 171/1992 Mercury XR6 150 hp 2.5 liter.
 
You can use the Edelbrock tuning kit on that carb. It consists of metering rods, and jets are available as well, but probably not necessary. Metering rods are a 5 minute swap per pair, accessible from the top of the carb, no fuel leakage. I'd try that first.

Rickracer
http://www.rickracers.com
 
Thanks,guys.

Rickracer, I looked into the Edelbrock tunning kits. I emailed the tech guys at Edelbrock, they told me the Edelbrock kit wouldn't work that the venturi boosters were different. Have you tried this???

Miss. River Rat
 
You said <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> Weber four barrel carb (same as Edelbrock performer).<HR></BLOCKQUOTE>My point was that you don't necessarily need to re-jet. Much can be accomplished with simple metering rod and/or spring changes. (Assuming that the carb is <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>(same as Edelbrock performer).<HR></BLOCKQUOTE>Yes , I have done a considerable amount of tuning on Edelbrock, Holley, and Rochester carbs, as well as a variety of others. One of my specialities is carb rebuilding and tuniing, and I've done literally hundreds of all types, from leafblowers and weedeaters to race and roundy round cars to old military ground power units. If I can be of any assistance, let me know.

Rickracer
http://www.rickracers.com
rick@rickracers.com
 
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