1993 502 Mag?? What would you do?
10-08-2003, 11:54 AM
#11
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Thanks Guy's!!! This is just what I was looking for!!
Dennis, I have your books, and they are great!! I think it is awesome that a guy like you is on here answering questions for guy's like me!!!
Usrus, When I bought it the surveyor did a leak down test and all cylinders had 130psi. I guess that sounds about right.
Later!
Dennis, I have your books, and they are great!! I think it is awesome that a guy like you is on here answering questions for guy's like me!!!
Usrus, When I bought it the surveyor did a leak down test and all cylinders had 130psi. I guess that sounds about right.
Later!
10-08-2003, 12:06 PM
#12
Charter Member # 55
Charter Member
Originally posted by Pure Energy
If you budget is tight, don't waste your money on exhaust!!! Stock Merc exhaust is good to about 600 hp. I had a procharged 454 and stock exhaust. It ran great. I switched to Imco Powerflow and still ran great. Absolutely no gain anywhere! Others may disagree, but your $3000+ could be better spent.
If you budget is tight, don't waste your money on exhaust!!! Stock Merc exhaust is good to about 600 hp. I had a procharged 454 and stock exhaust. It ran great. I switched to Imco Powerflow and still ran great. Absolutely no gain anywhere! Others may disagree, but your $3000+ could be better spent.
10-08-2003, 02:52 PM
#13
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I have the same year and 502 engines that you have, so I'm surprised that you didn't mention any problems with your carbs.
The following is what I did over the course of a few years, so the price of the exhaust wasn't so bad.
1. Added Stainless Marine exhaust. Picked up about 250 RPM, a couple MPH, and stopped the riser gasget leaks.
2. Added Stainless Marine "Pre- heat" Crossovers.
3. Added MSD Ignition box. (Kept old dist.)
4. Changed old Carter / Weber carb for an 800 Holley. Added a Phenolic open carb spacer and K&N Spark Arrester.
Outcome: Picked up 6-7 MPH. The engines looks great with the exhaust and crossovers. The engines sound great and they start right up after sitting for a week!
That may not be as "cheep" as adding a blower but, I don't have the headaches and didn't break into the engine yet either.
Good luck,
Bob
The following is what I did over the course of a few years, so the price of the exhaust wasn't so bad.
1. Added Stainless Marine exhaust. Picked up about 250 RPM, a couple MPH, and stopped the riser gasget leaks.
2. Added Stainless Marine "Pre- heat" Crossovers.
3. Added MSD Ignition box. (Kept old dist.)
4. Changed old Carter / Weber carb for an 800 Holley. Added a Phenolic open carb spacer and K&N Spark Arrester.
Outcome: Picked up 6-7 MPH. The engines looks great with the exhaust and crossovers. The engines sound great and they start right up after sitting for a week!
That may not be as "cheep" as adding a blower but, I don't have the headaches and didn't break into the engine yet either.
Good luck,
Bob
__________________
If it's not a thunder run.............than you're just burnen fuel!!!
If it's not a thunder run.............than you're just burnen fuel!!!
10-08-2003, 03:50 PM
#14
Charter Member #737
Charter Member
Originally posted by FunHome
Rich, We need to hook up for a beer, I have this Powerboat mag. for you and we can swap stories like we usually do!! Who has a flow bench??
Rich, We need to hook up for a beer, I have this Powerboat mag. for you and we can swap stories like we usually do!! Who has a flow bench??
10-08-2003, 07:22 PM
#15
~~~~
Charter Member
Hey Bob,
I had the dreadful Weber AFB on a stock 7.4 and it was a hard starter as you mentioned. It would also give me problems after going out for a run and then stopping for an hour. It would backfire 90% of the time when starting after that hour stop. Fuel must have been migrating into the intake. Sold the boat before I could and would have replaced it. I am surprised Dennis Moore likes it. Maybe he knows how to alleviate the starting problem.
Those "preheat crossovers" sound interesting. Can you enlighten us on their attributes?
Russ
I had the dreadful Weber AFB on a stock 7.4 and it was a hard starter as you mentioned. It would also give me problems after going out for a run and then stopping for an hour. It would backfire 90% of the time when starting after that hour stop. Fuel must have been migrating into the intake. Sold the boat before I could and would have replaced it. I am surprised Dennis Moore likes it. Maybe he knows how to alleviate the starting problem.
Those "preheat crossovers" sound interesting. Can you enlighten us on their attributes?
Russ
10-08-2003, 07:27 PM
#16
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Thread Starter
Bob, Now were talkin'!!! That sounds just about what I want to do!!
Dennis, What do you think? With those things Bob mentioned and the things you mentioned including the cam, It sounds like a good plan!?!?!????????
Rich (KCHOTBOAT), that is a heck of an idea!!! But, then I could get on here to get away from all the BS at work!!
Dennis, What do you think? With those things Bob mentioned and the things you mentioned including the cam, It sounds like a good plan!?!?!????????
Rich (KCHOTBOAT), that is a heck of an idea!!! But, then I could get on here to get away from all the BS at work!!
10-09-2003, 09:26 AM
#18
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Thread Starter
Originally posted by Dennis Moore
RLW
I really like the Edelbrock marine heads. I wrote a magazine article about them and did the research. The inconnel exhaust valves are great. Probably the best heads for a 500 horsepower naturally aspirated engine (they are the same as the 502/502 horsepower GM crate engine heads except hard anodized and inconnel exhaust valves).
Dennis Moore
RLW
I really like the Edelbrock marine heads. I wrote a magazine article about them and did the research. The inconnel exhaust valves are great. Probably the best heads for a 500 horsepower naturally aspirated engine (they are the same as the 502/502 horsepower GM crate engine heads except hard anodized and inconnel exhaust valves).
Dennis Moore
10-09-2003, 03:56 PM
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502'S
I disagree with not changing the exhaust system to aftermarket. That is particularly true if replacement is necessary. Although stock work OK on a mildly blown engine, the forced air motor doesn't depend on freeflowing exhaust nearly as much a a non blower motor. Also, most if not all on this site know the pitfalls of flowing water through the manifold/riser joint. I do agree that it's not the most bang for the buck, but I think that it's an important building block to a dependable, long term marine engine. Besides, there's plenty of high quality used exhaust for sale all over the place at very decent prices.
