A blower speed of 14,700rpm is going to be a problem sooner rather than latter as well. I spin mine 11,800rpm and feel they are close to the edge. 12500rpm is what I've known to be the max reliable rpm on a 525sc blower. Hopefully you plan for in boat setup to be more conservative. Also I have found 30-31* all in timing and 12:1 afr max to be good goals to achieve reasonable longevity with setup close to yours Ea.

The build mike Tkach did are utilizing my old blowers. They have 7" bottom and 3.25 top pulleys. I never put a smaller top pulley on because of what you said. I also never spun the engines past 5500 rpm. That setup put the blowers at 11,825rpm. I never hurt the blowers or the engines at that setup when I ran them. After a hard run those blowers would get pretty darn hot .

I remember when searching for replacement rear bearings for the blower, I had to double check that the bearings I was purchasing were rated for the rpm. Not all bearings are rated for that.

I don't recall where I got the 12,500 max rpm but its likely because when I sourced new bearings, that is the max rpm bearing I could find in the proper config.

Seems you compare apples to oranges here, if we compared the same boost level the difference would be about 20hp, as they saw 1psi more then what I did at the 650hp number, which from the data is 20hp and 25ft lbs. And I never made this into a competition and which one would make more on a sheet of paper, I believe you guys are doing more of that. This isn't a competition for me, Joe and I squashed all the bs from the last thread privately, but seems like it's popping back up again with his buddy, who obviously he sent the dyno sheet too.

As far as the intake goes, we checked out the mismatch of the rectangle port intake and what needed to be done. Ultimately with a 20 year old intake that needed a repair and then some time to match up the port it made sense to but the new oval port intake so that's what happened.

As far as the AFR's are concerned my builder has plenty of experience to make the right decisions when it comes to tuning the set up.

I never called mike or Joe a dummy, that's an assumption you made regarding a comment that I made saying I thought a 305 in a 4.25 bore is a little big. i never said it was a bad choice, or it was a junk set up. But why we keep coming back to this I don't know, it's over and done with let it go.

I have read and heard several different numbers regarding rpm and this blower. 12,500, 13,000, 13,500, 15,000+. I can say real world application I know of a 525sc that dyno'd at 688hp@6000 with almost 8psi of boost. It had a 2.8 pulley on it. Was built in 2008 and is still running the same set up to this date with the same blower with no issues. Now I'm not saying what's right and what's wrong cause I dont 100% know, but he has been spinning it up to 15000 rpms for 7 years.

You don`t seem to take advice well but I`m just going to throw it out there anyway; a builder that tells you a 177 likes to spin and they really shine @15, 000 rpm , then dynos your motor with a 13.5AFR on that little blower.. you may want to take what he says with a grain of salt.

I know.. I know , I`m a nobody. He builds motors everyday.. good luck man.




edit:

I found this a good read in the past :

http://www.offshoreonly.com/forums/g...ed-motors.html

well instead of making assumptions what experience do you have with the 177 and rpm's ? Have you ever had one? Did you ever test and see at what rpm it fails at? What data do you have to support what you are saying?

No intercooler, gotta be close to 100% over driven, max rated blower rpm, way too lean... Hmm I certainly have no experience running anything close to such combo .. you are 100% correct on that lol

You will thou, so please let me know how it works out.

Carry on.

You don't support what your saying with anything, you just say it. What makes what you are saying right over the next guy? This is the problem, I ask you a simple question cause I don't know you or most on here from Adam, You just come back with sarcastic smart ass comments, and really add nothing technical to the conversation. If you or anyone else want blind followers I'm not your guy, but it seems you have a hard time responding with anything productive when anyone asks you why you are saying what you are saying. The comment that I don't take advice well, well I didn't ask your advice, and the real question is why should i take it?

I know my builder will be doing final tuning in the boat. I also know he has extensive experience with building motors and running them in a boat at WOT for an entire race successfully, repeatedly, and in arguably the best deck to deck racing there is. So why should I doubt him who has proven himself time and time again cause of something a guy posts on the Internet and doesn't validate it at all? We are talking about an AFR that may may not even exist once in the boat.

As far as comparing the numbers on those builds, marks setup made 691HP at 6000, , and 666FT lbs , at 3800RPM. with 4.2psi. Ealeshs made 670HP at 6000, and 662FT lbs at 3800, with 5.6psi, and 636HP at 6000, with 3.5psi, and 617FT lbs, at 3800rpm. So, with 1psi less, ealesh's made 55HP less, and 47ft lbs less. With 1.5psi MORE than marks, it made 21HP less, and 4 ft lbs less at 3800.

Both engines had very similar cams from what I recall, very similar compression, same blower, main difference is one had 265 oval heads with oval intake, one had 305 heads, with rect ports. While this comparison isnt the most accurate information, I still have yet to see, where the small ovals did anything better, on a roots blower build, than a decently sized set of rectangles. The 40cc larger low velocity intake runner, surely didnt hurt torque output in the midrange. Heck marks was making 656ft lbs at 3500.

While , not a fair comparison, since they were on two different dynos, I do appreciate the info on the builds. For the longest time now, I've been "told", about the optimum port size for NA is optimium for blower, how much HP a certain head can support, how the larger heads would hurt low end and midrange, and all kinds of stuff without data. I've been told Im flat out wrong, stupid (yes, in pm's) and so forth regarding these small ci blower builds. Mike T and I are certainly no experts, but we arent also new to these types of builds.

Comparing numbers from dyno sheets are hard to do, when dealing with separate dyno's, different boost levels, air fuel ratios, etc. I think both of these engines made great power for what they are, so really, its a win for everyone, as long as the builds stay together.