mcollinstn

Yep,

Leave the ignition alone. Replace the coil with a good performance coil (especially if it is the original 1992 coil) and leave the ignition alone. If you had some wild@ssed cam in it, the MSD would clean up the idle just a tad, but that's about all. If you were supercharged and running cold plugs and turning 6000rpm I'd advise differently.

If you don't have head money in your budget, at least have some cheap portwork done in the bowl area and top it off with a 3 angle valve job (leave the seat width a bit fatter than an automotive app (around .070).

AthORiTAH

I agree with jafo, it sounds like you've got the right stuff before and after the heads, but the air's got flow through the heads to make the hp. I would at minimum have those heads ported, but you are better off with a set of 202 160 world pro. sportsman......or vortech I suppose, but you have to redrill for intake and the chambers are smaller 62cc.

HippieCustoms

Ok, I am going allong with all this, and am not afraid to change my plans. I do have a question though. The thunderbolt IV ignition, what is the rev limit? I had a smaller prop on it once and was watching my tach close and it hit around 5,000 rpm. Is that right? Is there anyway for me to bump it up any? The only real reason I was going with the msd set up was so I could taylor the rev limit to 5,500. I am hoping to get the motor strong enough to push the engine to 5,000 with a good prop. I appreciate all the help. Keep the input coming....Hippie..

mcollinstn

Early 1990's had no rev limiter.
Yours may or may not. Do you feel that you "ran into" a limiter at 5000 or was that just all she'd pull?

With the cam you are looking at and stock heads, I don't think your power peak will be that high (5500).
5000 is more like it.

HippieCustoms

Definately felt like a limiter. It was running smooth and sweet and then fell flat on its face. I had not had the boat that long, and had just replaced th lower shift cable. So not being sure if I had made a mistake on something or not, as soon as it hit, I pulled back on the throttle. It has never done it again, but I have never run it that high either. I agree the cam should run out about 5000, I just want to make sure it does before the limiter kicks in. If it was a car or truck I would shoot for just a coulpe of hundred r's above the peak. Being a boat, I am still learning how these react.....lol. Hopefully this one will like the changes I make. Thanks again and keep them coming. You guys are schooling me and I like it.......Later, Hippie.

jafo

I don't think any of the IV ignitions were equipped with limiters, and your year should be a little early for a T-Bolt V? Hitting 5000 was just the limit the engine could turn that prop- normal ops range is listed as 4200-4600. You can definitely get away with 5000 or more if equipped with a roller valve train. After doing your mods, including maximizing your timing and jetting, prop it for around 5-5200. Your prop (and your quickness on the throttle if airborne ) are going to be your rev limiting factor with the stock ignition.

HippieCustoms

Thanks alot everyone....I am going to take all of your advice and change my plans alittle. I will hold off on the ignition, and get some head work done instead. I heard the suggestions for World products heads and did some searching. Is there a similar head that uses center bolt valve covers? If I goe vortech heads, I guess I have to include a new intake also. I have definatly led this thread in another direction than it's title......Thanks again. Hippie.

jafo

I believe the World Products heads are available with standard or center-bolt valve cover arrangement- both Torquer SR and Sportsman.
Check with Jegs, PAW, or Summit for info and best pricing.

jhnrckr

Check out Pro Topline heads, I got the best results from my SBC with these over Dart and World. Buy a new set of valve covers if you need to.