rich allen

Well, I think I made it past Stage 3 of Grieving process, which was depression. I almost threw in the towel for this season and was ready to move on to other projects. But I think I made it to stage 4, which is acceptance and hope.. I guess I am ready to give it a shot, and "hope" I can do this within reasonable budget.
-I'm tired of throwing good money after bad, so this will be it for those peanut heads. I would need to open them up for inspection, probably need to replace a valve or two that got smacked, rework some damaged seats, etc.. and I am not feelin it. It was a nice experiment, but these heads have their limits.

That being said, I would like to be in the water again this summer. I will fully disassemble to inspect bottom end. So far, I only pulled a couple of caps for a look,including the damaged piston, and bearings still look damn good, with most of surface coating still there, and no scratches.. Hopefully a good sign. Everything will get mic'd. I will still probably install a fresh set of bearings throughout lower end. Any opinions on this?

Beyond that, I am open to suggestions for this rebuild. i will replace:

-Heads (off the shelf variety from World products, etc..)
-Cam,rockers, pushrods
-pistons

I have performer intake, 750 edelbrock carb, EMI exhaust.
Block is decked .010, and bored .030, (assuming I won't see anything in the bores that forces me to go .060)

Looking to probably lower compression a bit to gain some margin of reliability, but would like to keep some nut as well. I love the mid range torque, and don't expect to go much over 5200 rpm

Let's here what you have for ideas/combo's, with consideration for quench, etc. without breaking my wallet and my marriage. This is a river runner, not an offshore poker runner. I am ready to get this going in the opposite direction.
Thanks guys

cubicinches

Personally, I wouldn't use a World Products head. Not that they won't perform, but their castings are terrible... at best. If you've got your heart set on an iron head, I'd use a Dart Iron Eagle... Much nicer piece than the World Products Merlin. If you're open to spending just a few more bucks, consider Edelbrock's Performer aluminum marine head... They're reasonably priced, and the aluminum head has several advantages over iron.

Also, as was stated earlier, I would ditch the Edelbrock carb in lieu of a Holley, or check out a Quick Fuel carb... Nice stuff for little more than a stock Holley. I use alot of their stuff.

rich allen

It was not lost on me when discussing fuel delivery issue as possible culprit. Let's see what we come up with for $$ when all is said and done. Perhaps there is some good used hardware out there to help get this project moving along within budget.

blue thunder

If I were you, I'd replace my piston, replace all rod bearings, get head gaskets that moves the fire ring away from the chamber (larger dia) and tighten the quench to no more than .040 with a thinner head gasket, and run alum heads with inconnel exh valves and severe duty intakes. Edelbrocks have treated me well and I agree with Cubes above. Also if your lifters have started too loose their crown that cam is junk. Time for a nice roller cam.

BillK

Keep in mind that if you replace the pistons with a different part number or brand, there will probably be a pretty big difference in weight and you should rebalance the crankshaft to compensate.

Ted G

iTrader: (1)

This is a picture of a detonated piston. Note all the little melted sections. There really is none of that on the parts you have posted. You have numerous hit marks from the ring and piston pieces bouncing around in there but there really is no detonation damage. Also note that detonation will almost always eat away at the sharp edges of the piston and do a fairly uniform job, once again none on your piston ledges or edges.

BAD ASS SCARAB

Have you ever check the full advance on your timming? For good fuel 10 degrees initial and about 38 Degrees total with your advance. If your going into 40 Degrees plus on pump gas then that would cause your detenation problem. If you was running race fuel then you can get away with 40 plus degree full advance. Timming would definatlly run cause this on low octain fuel. If the advance was too much. Just my two sents

cubicinches

No two detonated pistons are going to look the same. The damage varies and presents itself in different forms, typically dependent upon the severety of the detonation, and exactly what the conditions were that caused it. The pistons from an engine that was operated for a long period of time, while being continuously pushed just to, or just past, the point of detonation will look much different than pistons from an engine which experienced severe detonation for only a short period of time. An engine will typically make it's best power when tuned right at the ragged edge of detonating. That being said, many "perfectly tuned" engines are operated daily, over long periods of time, while being pushed just into short periods of detonation... every time this occurs, parts are fatigued... until the point in time that one or more conditions become unfavorable, and something fails. An engine whose tune-up is completely missed, due to fuel mixture, spark timing, etc. may be pushed into such a severe state of detonation that it only lasts one trip across the lake. The result is the same... broken parts. Yet the broken parts will likely look different from one engine to the other, due to the difference in conditions and the severety of them.

I've seen many engine failures (Valves, valve seats, pistons, head gaskets, rod bearings) that were dismissed as a simple part failure by the owner or builder, when the real cause was detonation to some extent. Especially in a marine application. A perfect example is your blanket statement that valve seats fall out of big block heads... which is innately untrue. There's millions of big block pickups and street cars running around out there with their valve seats intact. The truth is that the valve seats fall out of ANY engine which is experiencing cylinder temps high enough to cause the seats to lose their press fit in the cylinder head... cylinder temps which are either caused by, or contributing to... you guessed it... detonation.

stevesxm

correct. and if you look at the last pic he posted the under cutting of the burn thru area is the defining element. and it's all academic anyway at this point. he has to fix the hardware, put it on the dyno, confirm the egts and get on with it. if he thinks that some third party opinion is going to convince him that this is not detonation but some random failure so he can just put everything back the way it was then that's the typical amateur mistake that leads to the post 8 weeks from now that starts " two months ago i burned or broke a piston and don't know why so i put it back together just the way it was and now it has happened again... am i just unlucky ?

the motor burned a piston because of detonation. fix the motor with a correct combination of cr, afr ,cooling and set up, dyno it and get the egts correct and go home early.

that's the only answer here.

ThisIsLivin

I have a set of JE forged 4.560 flat top pistons on a set of GMPP 6.135" rods with ARP fasteners for sale. I have less than 100 hours on them and they are in mint condition. They gave me 9.01:1 compression with 117cc chambers. I bought the boat with 50 hours on it and it had been stored for years and the cylinders were rusted. Had to go .005" to clean it up. I can give you the number to the speed shop doing the work and you can get the straight scoop from them.