eichhoma

iTrader: (1)

525 SC's.... 422 hours. Blower shop blowers, mild, 5-6 psi boost.

I have heard from a very reliable (and conservative) mechanic that very little needs to be done. Carbs, blowers gone through, change valve springs... that should be it... inspect valves, cam, lifters, etc.... and go from there....but then again I hear of people that go all out and do EVERYTHING. right down to pistons, rods, rings, main bearings etc... that just sounds way overboard to me. The boat spends most of its time in the midrange. Boat is not run hard or WOT very often at all.

So really... the motors are still strong. Compression test is excellent. (135-140 psi consistent across cylinders) Leak down is so so .... average leakage at about 24%. I hear up to 20% is still good and over 30% is trouble...

So, what really needs to be done here? I dont mind spending money at all, but have a real problem with wasting money.

Thanks!

StraightJacket

If they are out it wouldn't hurt to do a tear down at least to inspect. Even with low boost it is more strain on you rod bearings and can tapper the cylinders. Check the cross hatch pattern in the cylinders. Bare min. you'll just Hone, ring and bearing the short block , definitly put in an oil pump since your right there and thats the heart. Do the valve springs but have the seats and guides checked for wear. And a general inspection on everything else. If it has roller lifters ,check the tie bar , a friends had 300 hours on it and the 900 dollars lifters broke and took out the cam.
Just my opinion but if your going to do it , do it right and you won't end up doing it again.

Griff

Do you know how many hours are on the TBS 250 blowers since they are not the original ones????

Carbs should not need to be gone through unless there is an issue.

Where is the leak down showing the air is going???? That will determine what should be done. At a minumum, if you are going to tear into it, valve job and springs and inspect lifters.

Just for an FYI, I did the entire top ends on my 525sc at about 350hrs--exhaust valves, springs, locks, retainers, seals, switched to a 731 roller cam, timing chain set, head gaskets. Also, your comp check results are similar to what mine were around 135.

eichhoma

iTrader: (1)

Hey Griff...
The blowers at this point have about 175 hours on them...
Leakdown indicated loss of air from Valaves? or indication that it needs head work or a valve job? I will have to find the write up I got on them....

if you dont mind my asking... who did that work for you Griff?
I am curious what this is going to run.... thanks!

Knot 4 Me

I would definitely get rid of the flat tappet cams if you are tearing the motors down. Super Chillers would be a nice additon as well while everything is apart.

Griff

I did all the assembly myself and ordered most of the parts through Summit. This was on a single in my Pantera.

I had the the heads done at good local machine shop. I took them the springs and gave them the cam card specs to set spring height. Valve job, inconnel exhaust valves, seals and spring install was about $700.

Cam, lifters, timing chain set, valve springs, pushrods, head gaskets, head bolts, & misc. was about $1500.

I had a local dealer R & R the engine, but I disconnected and hooked everything back up. I also installed a new HD coupler and them do a gimble bearing. That was about a $1000.

Your blowers should not need to be gone through with 175hrs. Just change the lube at least every season. I'm not sure what lube TBS says to use.

Also, if your leakdown was done on cold engines, the % will be higher than if the engines were warm.

Griff

Keep in mind, the only real reason I tore into my engines and replaced the exhaust valves is because the original exhaust had leaked a slight amount of water onto 2 exhaast valves and pitted them. I figured when I had it out, I may as well try to add some HP with the cam.

eichhoma

iTrader: (1)

Ahhh... I see. Your definitley more talented than I am. haha.
The leakdown was done on cold engines.... crap. I should probably have done again then when its warm....

I will check on the oil to use from TBS....
Griff.... I owe you a few beers sometime pal for all the help!

QWKRN U

based on the numbers posted. Id do another leakdown test on the motors after they have been ran/still warm.In the past Ive treated anything below 20% leakdown as good and above that Id look into problems. The other thing to look at on the leak down is whats the difference between the highest and lowest?
If you tear it all the way down. at the minimum springs,valve job.
Id agree with putting in roller cams and ditching the flat tappet stuff.

Griff

If thats the case, I would think seriously about just leaving them alone for now and just running them next season. Do regular tune ups.
I would then budget for full rebuilds for next fall/winter. Figure 9-12k and bump the HP up to around 600-625. When doing the full rebuilds, it should be fairly easy increase the HP without costing much more than doing them stock.

Also, change the fuel pump/seapump lube every season. Mine would get pretty fuel diluted. Use Merc drive lube.