Took the boat out yesterday to run it unloaded for the first time after installing the heads. I was hitting the Rev limiter right out of the gate and couldn't get much more than 25mph. I was getting 27 before the heads so I knew something wasn't right.

I used my GD trim wheel to drop the motor, but the motor wouldn't run any deeper so I was beginning to think I out of luck. Then i remembered the trim tabs. Got it in shallow water and for some reason my tabs had no curve to them, just pointed straight out. After bending up 1/4 to 1/2 inch the motor ran right.

I was able to trim down a good ways so I could stay off the limiter. No rooster tail, water line at the cav plate and I was running 28 at 4150 rpms. Really felt like a whole different motor. Before the heads, I had to trim up and throw a tail to get the motor to wind out.

Got a trip tonight with 2 other adults and 2 kids. Expecting 750#'s of body weight and another 200 in gear.

So the real tests on these heads begin at dark.

Sounds like you need more prop!

Almost feels like an extra motor on back.

This means you need to mod your avatar pic now - LOL

I was wondering if just the mikuni, and performance exhaust paired with a set of IM heads would make much of a difference on my 35 GDSD. I already have the mikuni kit from BPS and a 2 into 1 exhaust I made with a harley 2 into 1 pipe and that combo squeeked out 120 rpms. I would think a set of free flowing heads that seal well on the power stroke would be a solid combo and you just answered my question. I just want a reliable solid strong running motor and a good set of heads may just be the ticket. And maybe a fairly tame cam somewhere down the road.
In your opinion were the IM heads worth the money?

Just wait till you throw exhaust, mikuni, and a cam in there.

Ran today with my son, 65# and a friend 100#s and I was still all over the rev limiter. Motor still trimmed down and throwing no tail. Running 25.5-26.

I noticed on the mud buddy website that they said you have to install their roller rockers and pushrods with those heads which would bring the upgrade up to around $1000 which is a bit out of my price range. I'll have to call them and see if I can just use the stock valve springs and rockers in those heads as that would save me alot of money. I could justify swinging $580 just not that much more for the other stuff. Those stainless valves should also give you peice of mind that the exhaust valve won't drop off into the chamber and and wreak havoc on the top end! It does sound like you did feel a "seat of the pants" change with changing the heads and no cam. Supposebly those heads are decked just a wee bit to still allow you to use pump gas without detonating the chamber and piston to death. I'm glad to hear that under a load the motor still pulled strong and in my opinion those are some good speeds your acheiving with that motor. Have you noticed any flat spots or does it pull strong from idle to wide open throttle? Did you increase the main jet size or did you leave it stock? Is the idle smooth? thanks!

Keep a eye out for used heads, I scored some this past spring with rollers/ rods and a nice port and polish................EVT did the work.. paid way under $500.......

cb5331 thanks for the info as that pretty much made my decision for me since I won't have to use their pushrods or RR's. thanks again!

bbb thanks for the follow up as it's good to hear that the heads are still holding their own. Those are some seriously impressive gains as far as I'm concerned with just a head upgrade. Did you by any chance upgrade to their roller rockers and pushrods or did you use the stock RR's and pushrods? I think you will even increase the lift of the valves with their roller rockers as they have an increased ratio on them. I've had quite a few people tell me not to expect anything without a cam added to the heads and from what your experiencing with just the heads my thoughts towards just a head upgrade have changed. Mud buddy has always been very helpful and accommodating with me and I beleive that they have experiemented with various changes to the heads to find the most effective combo. For the price they charge (which I beleive is very reasonable) and the quality work they are doing to the heads it has turned into a no brainer for me! I just need to save a little more money. thanks

Running the stock rods and rockers. Wasn't ready for that $400 upgrade.

I wasn't going to buy the IM heads if I had to buy the rods and rockers either.

Glad to hear that the heads gave you a gain with the stock RR's and pushrods as that will save me alot of money. Just to let you know I appreciate all the info. you handed me as I like to hear from people who have actually done what I'm looking for and you fit that description to a T. Thanks again!

bbb,
Glad your liking the heads. They are a great upgrade for the money.
as far as how they do with no cam, It really depends on the motor you put them on. They will make a noticeable improvement in any motor, but how noticeable depends on what you started with. We see a big disparity from stock motor to stock motor in how well the valves seal. Every now and then somebody gets a motor that is perfect and we call it a "hot" motor. But most aren't quite that good. If you've got a motor that's not sealing perfectly then you will see a big increase in performance when you add the heads. That the category most people fit in.

either way, I've never had anybody dissappointed with them.

I upgraded a stock cdi 35 mudbuddy on a 1750 Huntdeck Gatortrax and got this:

35 sport CDI
Iron mountain heads
48 lower gear
Stock everything else

1750 mudbuddy edition (flotation) huntdeck
drivers box
extended front deck with hatch
bow rails, trolling motor bracket
trolling motor, one battery in the back.
One person (200ish lbs)

First thing i noticed is that she idles very smooth and at about 750-800 rpm in gear. The holeshot is a LOT stronger than my stock 35. I would say a little stronger than my old 35 mini with a mikuni and crossover. All my stock (except one real runner) 35's have run 25 on this hull (25.6, 25.4). My 35 mini ran 25.4 stock and 26.8 with a mikuni on it on this same hull. That will give you some real world comparison numbers.

I made one pass down the lake so I didn't really get to play with it much. It ran 28 both ways at just over 4100 rpms. I could easily trim up and hit the rev limiter.