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Swap 502ci for 540ci ?

3K views 47 replies 10 participants last post by  blown1500 
#1 ·
Looking at swapping my hp500efi for a na 540 block over 600hp. My question is will my engine mounts line up? Will my headers blot up? Drive alignment? Anything else I might not be thinking of?
 
#2 ·
CJ,,,are you talking about a 540 stroker motor?? or Merlin block? I don't see any reason why it won't fit unless you went from a standard deck to a tall deck,or vice versa.
Do yourself a favor and just buy the Whipple. It will be alot less hassle ,and can always un-bolted it if selling the boat. This way you can recoup some of the dollars back.
just my .02
 
#4 ·
What got me thinking was I saw Hawk motors advertising a 600 hp motor with 3 year warranty and an efi option. I also learned it was a 540ci block. So this brings me to this question. Will every thing bolt up? I like the idea of a bigger block working less than a supercharged block working harder. Of course with a whipple I'm closer to 700hp. But then there are drive issues. The final decision is far away, this is just some initial research. I welcome any opinions!
 
#5 ·
You should be able to get 600 HP from you motor by doing a cam change and some minor injection mods. Larger injectors, and throttle body, reprogrammed ECU and use the Crane 731 cam. Arizona Speed and Marine has been a tremendous help to me during the construction of my motor.

Then you could install a 4.25" stroke crank with longer rods and new pistons to increase your displacement.

Todd
 
#8 ·
Pachanga..... I know there is room for engine mods. I just really like the reliability of something stock. If it was a simple enhancement with my engine, I think Merc would have done it. Instead they went with a supercharged engine with low boost( hp575sci). I run my engine hard, So I really want to be sure its going to hold together. But for conversation purposes, what did you spend on your engine? Are you sure its 600hp? Was it a complete package, or did you and ASM combine parts?
 
#10 ·
CJ,
You might want to consider going to a set of aftermarket Aluminum Heads, a little bigger cam profile, and a custom ECU re-map. I've talked with Dustin many times about the potential of the 500EFI and his money is on a set of aftermarket Aluminum heads every time. Of course, he is working primarily with blower applications, but I would tend to think that it would still do something on an N/A setup. Also, the new heads would be a good base for any other further engine upgrades. Dustin claims he was seeing 800 - 850 hp on a 500EFI with Aluminum heads at 11 - 12 psi of boost. Something to consider, you know I am going to be a little biased towards the blower side of things. Bang (literally) for the buck, add on blowers can't be beat! All said and done, you could upgrade your 500 EFI to at least 800 hp (still retaining the EFI) for around $8,000 (Yankee).

-B
 
#11 ·
CJ, am I sure it is 600? No it is not. After I solved my intake gasket problem and water pressure problem, we did some more tuning and some minor program mods on the ECU and dynoed the motor @ 647hp @5400rpm.
This is a bored and stroked 454 so final displacement is 496.

How much did this cost? Well everything was new, this motor was built completely from scratch. Not including my labor, I have less than 20k in it and the biggest expense was the injection.

Todd
 
#12 ·
Boatnut, when I say stock, I mean tested and proven. 600hp I believe is easier for a 540ci block than a 502ci. Unless I'm wrong. And yes 600hp is still pushing it for a bravo. But I can always upgrade the top gears easier and cheaper than a different drive. Andrew, It looks like $13000.00 for me and that is with no drive replacement, which I believe is essential. So I guess it comes to what this new engine is worth and cost to install. Also what I may get for mine. Ideally, a Whipple with a Imco would be real nice. I think a Imco is over $20000.00 for me. So put it all together and I guess I'm looking at $33000.00 before a new prop. Yah, this is looking farther and farther away! Hey Andrew did you get my PM earlier this week?
 
#13 ·
I dont know CJ,,, if it was me I would run my stock Bravo ,,, with a 28 foot boat, your still pretty light.

well,,, let me start over,, I say I would run the stock Bravo because I am VERY easy on my boat at the holeshot. if you are one of those guys who hammers it from a dead stop, and is constantly wave hoping ,,,, yes,,, upgrade your drive.
 
#14 ·
Obnoxus, I'm not one of those fools that holeshots! I don't even now why they test boats that way. In all the mags I read there is always a time to plain. Who cares how long it takes to plain, were not drag racing!. I said I was hard on the engine. And I don't exactly baby the drive, I have learned! But at wot for extended amounts of time, I consider that to be hard.
 
#15 · (Edited)
Assuming that the 540 you are talking about is the tall-deck Merlin block, you can reasonably expect the following should you swap:

1. You'll need different exhaust manifolds, at least on the inboard side of each engine.
2. The outboard side of the engines may require some fiberglass modification if you choose not to put on new exhaust manifolds on the outboard side.
3. Depending on the intake/carb set-up on the 540, you may need hatch modifications to clear for the air cleaner. Look at what sort of clearance you have now, and figure at a minimum that you'll lose an inch and a half using a standard manifold. High rise manifolds will be more.
4. The front engine mounts should not be a problem, rears ???

We ran into all of the above when we put in new 509's after coming from standard GM 454 big block. Takes some contortions when the second engine goes in if your engine bay opening isn't wide enough, but it can be done.

We had Stainless Marine exhaust manifolds on the old engines; when we found they wouldn't work on the inboard sides of the new 509's, we nmde the phone call and got new ones. I would assume most other manifold manufacturers have similar solutions. We did not have a probelm with enginemounts at all, but we're running TRS/tranny set-up. I did require some re-shimming in the rear to get the alignment correct, but that's no big deal.
 
#17 ·
O.K. Just got off the phone (can you tell I'm bored today?) with Hawk. They build to suit. If I were to order for a replacement of a hp500efi, they build with the proper heads to use with my cmi's! They utilze the same electrical plug as my engine. The engine is efi. Comes with KE dual scavage water pump, Aero motive fuel pump, preluber and water flush! With my engine in trade they are asking $15000.00! 3 year warranty! And they ship to me. How does that sound?
 
#25 ·
Hello, Guys,
You can make 600-630 from the 502EFI. I just did it on the dyno. I don't recommend the 731 Crane for this application. I changed cams and used slightly modified Merlin 310 heads, Arizona Speed and Marine computer mods. This is a 91 octane engine, but is dead reliiable, good idle, very good performance and economy. Max rpm was 5450rpm.
540 will beat the 502, but there are many things to consider. The motor mounts front and rear are identical as are the exhaust mount, depending on tall or short deck and if the exhaust flange is moved on the heads you use. Most of the time, this is not a factor.
 
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