blue thunder

In my experience, top ends are good for about 400hrs - run moderately. If you take care of the top end, and have no other devastating failures, 800hrs is reasonable overall for a mild engine in a perf boat. Sold a boat last year that had 1000 hrs on.. now it has 1100 and runs great. GM built a great bottom end/lube system.

BT

bobby daniels

I AGREE THE LOWER IS NO PROBLEM WITH GOOD OIL ECT. BUT VALVE SPRINGS USUALY GO AROUND 400 HRS WE USE COMP 929 COATED FOR REPLACEMENT THE COATING MAKES THEM LAST FOREVER ,NO SURE OF THE COATED NUMBER JUST TELL THEM YOU WAN A 929 COATED ITS IN THE CATALOG ,ALSO WATCH PLUG WIRES ,M S D BOXE ,,E TYPE COIL AND TAYLOR WIRES WILL HELP A TON EVEN A FEW HUNDRED R P M

Strip Poker 388

iTrader: (6)

I thought the 500 efi did nothave the prob with the valve springs. i heard it was the 500 hp carb versions?

What gas are yall running in your 500 efi,s ,is anything wrong with 93 rating gas?and why?

H2Xmark

Rob I am sure you are right, the 500hp carb had different springs than the EFI, some of the carb engines are breaking the inner valve spring at around 200 to 250 hours, they most of the time break the inner coil and you can not tell till you pull them down, so what happens is with only the outer still intact you float the valves at high rpm and either bend valves, or pushrods or something else, the bottom ends are great and hold up well, I have heard of a few rollers coming apart on the lifters but it is not real common, any one else hear of anything
Mark

SteveDavid

Rob,

Prior to adding the Whipples I ran 87 and 92-93 to determine which worked best. The 87 worked best, less exhaust residue and less oil consumption. I believe you will see a slight DECREASE in performance with the higher octane in these engines as they are programmed for 87-89.

The higher the octane number the slower the burn. This is good for reducing detonation in higher compression engines. However, in the 500 efi, the slower burn rate creates an incomplete fuel burn and thus the wasted fuel as evidenced by the transom exhaust residue and blow by.

Hope that helps,

Steve

Sydwayz

iTrader: (1)

ONLY 87 in mine. 1999 with about 160 hours.

Dean Ferry

Steve David,
Thanks for the insight. How's the BT running? What motors do you have in "Sabrina" now? That's interesting about the CMI's, I have KE headers on my HP500 w/ about a total of 250 hrs. on them and they are still going strong!! I think they are the best TRUE full 32" runner HEADER available! This boat I'm looking @ is a supposedly "Fresh Water" boat so hopefully the CMI still have some life in them.

Cord,
No I haven't changed out the Ex. valve springs yet, BUT I'm serious thinking about it this winter when I put the boat back on the trailer to do my yearly maintanance. How's the Firehawk coming along? Did you straighten out your 540?

Thanks again guys, I talked to HQ last night about the New boat and she just kinda "sighed". We are going to lump sum our kids College education this year, so maybe, just maybe after that is done, I'll get a new boat, maybe.
TGIF,
MD

SteveS

The only problem I've seen with the HP500 EFI and Carb are the valve springs. If you run hard I'd change the valve springs at about 150hrs. It's alot cheeper to get them before they let loose.

I've had good luck running 89.

jbrauer

I'm running 1995 HP500 carbs with about 200 hrs. They run perfect. I would expect even better results with the EFI motors.

Really depends on how they were cared for so far. What is the rest of the boat like?

More important - What is the current owner like? Would you trust him/her with your boat, because they've had it!!!

Wild Horses

Al little off topic... original '89 420's with 750 hrs. No issues other than one starter, one alt., one exhaust manifold gasket and minor front main seal leaks.

WH