2nd bad 30.5cc motor

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Forist72

Forist72

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Well I am not to happy my 2nd 30.5cc head cracked in the same exact spot as the first one. I only have 2 tanks through it was not at full throttle and not running it hard and it is still on brake in settings. I was running it on flat ground it was running fine and then it went blaa. Has any one had this problem I don't want to spend more money on a replacement head if it is going to keep doing this. Anyone have any idea's thx.....
 
Why is it cracking? Ive never heard of one cracking from normal use, only from something else causing it. Have you found anyone else to have the same problem? Can you post pictures. You have me curious.
 
The first one they said it was prolly cuz I was using a .005" (0.15mm) Copper Cylinder Gasket. But the second one I used the paper gasket that came with the new head, and I don't see anything that could be causing it to happen. Here are some pics of them the new one has the carb and intake on it still.


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Sorry to hear that, hope someone knows exactly what it was...and you don't blow any more $


I'll be following as I'm looking to get one as well...
 
I'm using the DDM side dom and I cut it and put a coupler in case of flex from the pipe so I wont get stress on the motor.
 
Try a Zen topend man, ive seen a few of those CYs crack like that before on HBF. I think Rob64n had one do the same thing as well.
 
Going to see if they will cut me a deal on a zen head and piston. I have all the rest of the stuff to complete it. BTW any one know what is the difference between the Race Ported and Full Mod Zenoah 4 Bolt Long Blocks and reg zen 4 bolts?
 
The race ported motors are stout as all get out. A full mod motor is just asking for driveline issues ;)


Ever seen a 40lb Rampage do "cyclones" like monster trucks in grass? Thats what a full mod can do. My full mod was VERY much a pain to get tuned right, but Sean, Shreadhead and a few others helped me get the tune down. Im still running rich as hell up top (1 3/4 on the HSN and 1 on the LSN as per Shreadhead), at 90% throttle EPA and I still have more power than I know what to do with.
 
Thats odd how they cracked at the same spot on each head. Everyone puts different demands on their trucks. I cant imagine what did that. Have you searched the web for answers? I have been told before I should switch to 4 bolt especially when building an engine from the ground up but Im one of those people who has never had probs w/2 bolts. Maybe its my driving style but they work for me. Ive tried the 5t can, side dom, 5bss pipe, and sprint77 jetpro v3 rear exit with no problems putting stress on the head. What tires are you running? Are you running any form of chassis bracing?
 
Ive done a little reading on the root cause of the problem. The general consensus is that a headbolt came loose and the piston caught the lip of the jug on the upstroke cracking it. Bear in mind thats all general speculation, but alot of people say that could be the cause.
 
They want me to send the motor to them to see what the prob is but did not say if it will be replaced or not. He could not believe that it cracked in the same exact spot as the first one did.
 
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