The Big Kaboom!!!

[WELTERRACER]

Well as predicted my engine finally gave up.. 10psi with stock rods and crank!

After a month of torture, i pulled out on the highway at about 3/4 throttle and KABOOM , must have broken a rod, and engine locked up tight..

Now the engine is coming out and new Forged rods, Forged crank and 8-9.1 compression forged pistons will need to be boughton and installed!

I guess stock crank and rods can handle 650+hp..LOL...

OOO well, not too worry, with new parts installed i should be able to pump up boost and go for 700+hp!....... SWEEEET!!

[Blown353]

Ouch, that sucks.

My hunch is you killed the thing from detonation, not from the RPMs or power you were making; you mentioned in a previous post you were running 36 degrees of timing on 93 octane with 10.3:1 compression. With no intercooler, uncoated pistons, that much compression/boost, and no timing retard my guess is detonation was the culprit. The pistons, rings, and plugs most likely show the telltale signs.

Did you ever pull plugs and check for signs of detonation? My guess is with a boost timing retard, you should have been pulling it down to 25-26 degrees TOPS under full boost, especially with 10.3:1 and uncoated pistons. I bet it was pinging all along but you didn't/couldn't hear it. Just because you can't hear anything doesn't mean it's not pinging, and it doesn't take much pinging to beat the snot out of a boosted engine.

Troy

[camcojb]

Ouch, that sucks.

My hunch is you killed the thing from detonation, not from the RPMs or power you were making; you mentioned in a previous post you were running 36 degrees of timing on 93 octane with 10.3:1 compression. With no intercooler, uncoated pistons, that much compression/boost, and no timing retard my guess is detonation was the culprit. The pistons, rings, and plugs most likely show the telltale signs.

Did you ever pull plugs and check for signs of detonation? My guess is with a boost timing retard, you should have been pulling it down to 25-26 degrees TOPS under full boost, especially with 10.3:1 and uncoated pistons. I bet it was pinging all along but you didn't/couldn't hear it. Just because you can't hear anything doesn't mean it's not pinging, and it doesn't take much pinging to beat the snot out of a boosted engine.

Troy

I 100% agree. Just can't run that compression and timing without higher octane, water/alky injection, or similar to protect against detonation.

Jody

[WELTERRACER]

Well, You guys might be right..

The top of the #7 piston broke just above the top piston ring.. ANd the cylinder lining broke letting antifreez into the cylinder and hydrolocking the engine.. engine was not lean but infact looked like the jetting was about dead on.. (plugs were tan to dark tan)... I also have about 3 valves that had bad oil seals. (explains the oil loss i was getting) Im really surprised it was the piston that broke and not the rods or crank.. (i guess ill keep them for another motor)

Atleast the heads are still good, All i need is to build my spare motor..

What do you guys recommend for compression... 8-1 or 9-1 compression??

[JLM]

That really depends. How much boost are you planning on running? Do you have iron heads or aluminum heads.

I would say a good place to be is around 8.5:1. You won't loose an incredible amount of low-end but you're still in a range that you can make some power still being on pump gas.

[PRO TC]

its ok brian you can ride with me the rest of the summer. that is if you trust my driving lol. ill say one thing it was scary fast when it was running.

pro tc/barry

[WELTERRACER]

Im running Dart Pro 1 heads with 2.05 intake and 1.60 exhaust valves with 64cc chambers and 215 intake runners..

I would like to bump up the boost to around 15lbs to make around 700hp on pump gas

[Fuelie Fan]

I'm not at all surprised that it was the pistons. Rods actually rarely break of their own accord, usually something else happens first, a bearing seizes or something, then the rod gets thrown out the side of the engine. Your combination was pretty much the THE recipe for popping a piston. Also, plug coloring can't reliably be used to judge mixture. It's a starting point, but not a fine tuning tool.

[shmoov69]

I would definately say (also!) that it was a rattle that killed it. It seems that cheper pistons will pop the top off before they burn a hole under detonation.
Granted, a blower is harder on cranks than a turbo is (because twist), but my stock junk crank, rods (and bolts!!), 2 bolt block and junk loose factory replacment hyper pistons lasted 2 1/2 years and 17,000 miles before it split thru the cyl walls (because of the skirts were gone!). It had 500 rwhp and was beat on regularly! But it did not rattle often and if it was not running right, I did not stay in it, usually!

[yody]

not that i know that much about centrifugal super chargers, but 650/700 horse out of a mild 350?? Don't know everything about your motor but i would guess it would make max NA about 450 horse, so the procharger adds 200-250 horse at only 15ilbs of boost? just wondering where the HP numbers are coming from, i always thought that 1 ilb of boost gave you about 10 horsepower. You better build one strong bottom end with 15 ilbs of boost with a supercharger and 700horse! what are the plans??

[Ralph LoGrasso]

not that i know that much about centrifugal super chargers, but 650/700 horse out of a mild 350?? Don't know everything about your motor but i would guess it would make max NA about 450 horse, so the procharger adds 200-250 horse at only 15ilbs of boost? just wondering where the HP numbers are coming from, i always thought that 1 ilb of boost gave you about 10 horsepower. You better build one strong bottom end with 15 ilbs of boost with a supercharger and 700horse! what are the plans??

The general rule in a "perfect world" is at 14.7 lbs of boost (1 atmosphere) NA HP doubles. But, this is in a perfect world...

[WELTERRACER]

not that i know that much about centrifugal super chargers, but 650/700 horse out of a mild 350?? Don't know everything about your motor but i would guess it would make max NA about 450 horse, so the procharger adds 200-250 horse at only 15ilbs of boost? just wondering where the HP numbers are coming from, i always thought that 1 ilb of boost gave you about 10 horsepower. You better build one strong bottom end with 15 ilbs of boost with a supercharger and 700horse! what are the plans??

I have purchased TRW forged pistons, CAT H beam 4340 rods, cat 4340 Crankshaft..

The rods and crank are good to 1000hp the stock block is supposidly good up to 900hp..

Acording to ATI... at 15PSI you take your N/A horsepower and times it by 1.7

So if im making 420 hp N/A..... at 15 psi it should make 714 HP

[BB69]

The 1.7 takes into account the losses in the system. As said before, if you ran 14.7PSI, your HP would be doubled if there were no losses. However, the blower is probably 80% efficient at max, and any intercooler you run also has some inefficiencies with it. The 10 HP per PSI doesn't take into account the size of the engine being blown, or how efficient the engine is NA. Doing some calculations on a 454, I get 35 HP per PSI. I did the same calcs on a 2.4L engine, and I come up with about 11 HP per PSI.

Ken

[gmachinz]

I'd say it's time to invets in a digital programmer with boost retard to begin with. I know a lot of people who cut corners in the ign. management dept. and they end up regretting it-or not knowing what they should have spent money on. -Jabin