Some modifications?

Eclipse232 · 09-22-2009, 03:16 PM

Hey guys, I have a 97 454 Magnum. Everything is stock except for a pair of emi thunder exhaust manifolds. Im looking into replacing the carb, intake, and cam. Or maybe some other modifications you guys would suggest...

Here's what i was lookin at:
Carb. http://www.summitracing.com/parts/HLY-0-80537

Intake. http://www.summitracing.com/parts/WRL-063034/

Cam. http://www.summitracing.com/parts/CCA-K11-451-8/

What would you guys go with?

Alan454 · 09-22-2009, 05:50 PM

Was just talking to a guy at EMI, for their short Aluminum or Stainless risers they recommend a maximum of 230 deg duration (050) on the exhaust. That cam is 236 deg. I have been told on this forum that this is also the recommendation/rule of thumb for stock manifolds. Don't know if EMI is just being super conservative or not ...

Ghostrider · 09-22-2009, 08:37 PM

Not a bad combo but I'd go with the Edelbrock RPM Air Gap Manifold with that cam and exhaust. What heads do you have on? That World manifold (high rise, single plane) will limit your low end torque and performance will be limited at low speeds. You should get the EMI Stainless long tail risers to go with your manifolds unless you already have them?
That carb will do fine for your set up. The key to making that sort of motor work well though is the proper cam for what you want the boat to do. In your situation, I'd PM or call Bob M (RMBuilder on here) and ask for his advice on cams. He knows all. That and he can custom grind you a cam for around that price that'll suit your boat far better anyway.

Good luck and let us know how you get on!

Eclipse232 · 09-23-2009, 10:11 AM

No i dont have the long ss risers. I was trying to find out if id be able to do any kind of cam to the motor without changing the risers. The exhaust setup i have now just barely fits the boat, and thats with the standard aluminum risers. Im not lookin to go all out, i just want a little more power. A mild cam if possible...

Griff · 09-23-2009, 01:57 PM

If you don't have longer risers, you can't do much af a cam upgrade. With the cam, carb, intake combo, you'll be looking at about a 60hp gain. That will equal about 4 mph on the top end.

Eclipse232 · 09-23-2009, 03:20 PM

Well that kinda sucks about the cam. I have a 1990 wellcraft eclipse that I swapped out a 350 with a 454. I ran the exhaust out the sides because i didnt want an exhaust on top of my swim platform so I had to make custom exhaust tubes. The aluminum risers along with the exhaust tubes just make it past the inside of the swim platform. I may not even be able to use the long risers let alone the fact that I dont really feel like buying another set of risers.

Is there any cam that I can use that wont have any issues with the aluminum emi thunder risers? Another cam i was lookin at was this one http://www.summitracing.com/parts/CCA-K11-445-8/

This cam's exhaust duration is 224. Which fits under Alan454's suggestion. But honestly I dont quite understand it.
I apologize for my lack of knowledge about cams and the effects exhaust risers have on them.
I appreciate all the help guys. Thank you

Ghostrider · 09-23-2009, 10:43 PM

I run the Crane 731 cam with the aluminium (Aloominum to you yanks) risers but I modified them with a bit of SS pipe.

I bored the inside of the riser ends to fit 3" ID SS pipe then press fitted them in. I used epoxy and a couple of machine screws to hold the pipe on, but the press fit is tight anyway. I used 13.5" of SS pipe per riser, allowing for a 1.5" slip fit and 12" of extension. The end result is that the water can't mix with the exhaust until 12" further along in order to combat possible reversion. The water still exits the riser flange at the same point above the tube and keeps the pipe cool, then mixes with the exhause about 2" before the entance to the exhaust tip (4" Corsa spiral baffles).

I haven't had a chance to test it on the water yet, just on the hose but it seems to work so far. I'll adjust the inner pipe length to suit if I burn the outer hose at all. I forgot to take pics until after I had it all back together but that's my suggestion. Can anyone see any other possible problems I may face with that solution?

I figure my (cheap) solution has the same net effect as the EMI long SS risers in extending the tail length to allow for increased cam duration.

Any thoughts?

Good Luck!

Eclipse232 · 09-23-2009, 11:27 PM

Yea I dont even think i would have the room to make my own stainless risers. Coming straight out of the risers my exhaust tubes make a sharp angle so it misses the swim platform. What im hoping is finding a cam where i dont have to change anything on my exhaust setup. If possible i have no clue. Thanks

getrdunn · 09-23-2009, 11:43 PM

your cam choice should be fine. i would definately stay with a dual plane intake. your existing one should be aluminum correct? that's not a bad intake. also unless your stock carb is beyond rebuild i would consider sticking with it. your going to be limited to building much power unless you get into your heads and bump comp. as well. not trying to advise not to do your upgrades but just need to be realistic as to what your gains will be.

Eclipse232 · 09-24-2009, 12:06 AM

Thank you very much! Thats exactly what i wanted to hear! Yes my intake is aluminum, ive heard before that its not that bad of an intake, so i will probably just be replacing the cam and carb. Might just save the money from the intake. I dont want to get into the heads and mess with the comp, i like that the way it is. I was just lookin for a little extra. Thank You