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Big cubic inches small Chevy!
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320 Posts
Discussion Starter · #1 · (Edited)
I have a problem, and need an advice.

There is the spec of my Motor First; 468 big block chevy, with 353049 stage 3 porting oval port head, 2.19-1.88 Severy duty Manley Valve, Matching Valvetrain - Hydraulic Flat tappet Camshaft (11-214-4) 305 duration and 575 lift (253 duration at .050), 1.509 dual spring, chrome moly retainer and 10degrés lock.

0.60 bored Speed hypereuthetic with one valve relief and .100 dome. Everything is balanced and blueprinted.

I run a too hot Radical cam for my compression ration, this cam ask a 10.5 CR, and I have a 115 cc chamber and a 9.5 CR. When I was started my motor on headers, i never heard the noise on the head...when I put my 50 flowmaster muffler, I heard a little noise from the 2 head...last weekend, We pull out the motor and open hit...some valve was hitting the piston...I really dont understand why...A guy from a speed shop near from me said to put 4 degré advance on my timing chain to help my motor (Cause I have a CR too weak than the cam need) He tell me everything will be ok, you have enough clearance between your piston and valve ( He said that because I have a 115cc chamber and only .100 dome piston). I really dont understand what was my mistake...I have to rebuilt the motor and put the timing chain to zero, or put larger head gasket (I was puting steel head gasket at 19 thousand), make a bigger groove on my valve relief...

I really dont understant and need help...why this thing was happening to me (I have some shim under the exaust spring)..

Someone can help me, give me some advice or tricks.... PLZ

How calculate the clearance on a hydraulic valvetrain engine to be sure I have the right clearance, What is the minimum clearance?, What I have to do, keep the 4 degrees advance or start the engine at Zero...

I forgot 2 thing, I have the right Comp cam push rod and 1.7 full Roller Rocker with Valve lash at the end of valve.

Thanks in advance everybody
 

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Race it, Don't rice it!
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8,819 Posts
He told you to advance the cam from center to help lower ther RPM band. It sucks when you trust someone and they tell you wrong. Wether it was by mistake or otherwise. All you can do is check to see if the valves are bent. If they are you can get new ones and reinstall. If you are lucky and they didn't bend the heads, you will need to look for bet pushrods as well. You'll need to clay the piston for clearance(find out how in the search feature) and aim for .100 exhaust and .080 intake.
 

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Big cubic inches small Chevy!
Joined
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320 Posts
Discussion Starter · #3 ·
Yes, I thing some valves are really bad, Will be probably repair some valve seat....(I have 3 angle valve job on that head)...I dont understant what you want to mean by''Aim for .100 exaust and .080 intake..could you explain plz..I'm almost bilingual, I do my best...:welcome: Thanks. I have to put the head to a machine shop to be repair. And test if this head is still efficient.

I really dont know how much I have to spend again on those head.
 
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