nitrous build problems

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nitrous build problems

Post  10SHOTS on April 21st 2015, 7:34 pm

I been having some problems with Pistons cracking in the valve pocket , been doing a lot of reading on quench and rod length , some say a shorter rod will be better for heat because the piston don't stay at top dead center as long ,  this motor is 14.1 using a .045 head gasket , piston is .010 in the hole . I have also had problems with the head lifting and blowing water in the overflow bottle , it has 190 pounds cranking compression , so do I need to open the quench ? anyone ever heard of the shorter rod deal ?

more open quench suppose to make the chamber less  efficient making the motor less timing sensitive , if this is the case how much quench it recommended?
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Re: nitrous build problems

Post  dfree383 on April 21st 2015, 8:54 pm

You don't necessarily need quench if you have sufficient octane.

Also NO2 engines benefit from chamber softening.
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Re: nitrous build problems

Post  richter69 on April 21st 2015, 9:07 pm

what the nitrous tune? timing? fuel?

there is a good thread on quench right now in the nos section
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Re: nitrous build problems

Post  richter69 on April 21st 2015, 9:09 pm

also what heads, cam specs w valve events etc.
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nitrous

Post  10SHOTS on April 21st 2015, 10:32 pm

36n 26f  jet 5.5 pounds fuel psi , 116 sonoco max nos fuel
15 degrees total timing , #10 ngk plugs , 562 cid, TFS cnc 325 heads , Pistons .010 in the hole , .045 cometics
cam is a 284-298 on a 114 lobe sep , installed at 112 centerline , I'll have to get the timing events tomorrow,
ring land is down .350 with a .320 valve pocket ,  .117 thick at that point where there cracking .
6.800 steel rods


Last edited by 10SHOTS on April 21st 2015, 11:01 pm; edited 1 time in total
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Re: nitrous build problems

Post  dfree383 on April 21st 2015, 10:53 pm

Do you need all the valve relief? How much clearance you have?
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Re: nitrous build problems

Post  10SHOTS on April 21st 2015, 11:05 pm

dfree383 wrote:Do you need all the valve relief? How much clearance you have?
I might can get away with a .300 deep pocket , I clay checked it yesterday but I can't remember what exactly it was , I'll have to look for the clay or recheck it
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Re: nitrous build problems

Post  richter69 on April 21st 2015, 11:47 pm

What do all the plugs look like? Which holes are breaking pistons?


Id start with a thicker headgasket to open up the quench
and get some compression out.

Vacuum pump? Ring package?
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Re: nitrous build problems

Post  10SHOTS on April 22nd 2015, 7:48 am

plugs looked good , clean with a ring way at the bottom ,
1 1/6 ductile iron 1 1/6 cast 3 1/6 oil rings
don't have vacuum pump .
on the new Pistons I was thinking about putting them .020 in the hole , I don't know , how thick of a gasket ? Im buying 8 new Pistons and boring the block so I can do whatever with the Pistons , I can put less dome on to lower compression or put more quench and add dome to get 14.1 back or what ever needs to be done at this point , even a cam change
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Re: nitrous build problems

Post  10SHOTS on April 22nd 2015, 8:01 am

top ring land is .350. I was thinking about putting it at .400 and the second at .200 thick using a 1 1/6 ap steel .173 back cut top ring .043 Napier second and 3 1/6 oil ring , I just need it to last longer , I'll look at the Pistons and let you know the ones that are cracked , it's 4 or 5 of them
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Re: nitrous build problems

Post  dfree383 on April 22nd 2015, 9:35 am

IMO Talk with your piston mfg of choice and see about moving things around to add some thickness in the pocket area. Determine if you really need that much relief and placing the rings slightly lower may help too.

I'm not sure if hard anodizing them may help too?
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Re: nitrous build problems

Post  Lem Evans on April 22nd 2015, 9:58 am

I'd open up the piston to head distance.

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Re: nitrous build problems

Post  10SHOTS on April 22nd 2015, 10:56 am

Lem Evans wrote:I'd open up the piston to head distance.
so leave the compression and open the clearance ,
next question , how much ? thanks
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Re: nitrous build problems

Post  10SHOTS on April 22nd 2015, 11:02 am

[quote="richter69"]What do all the plugs look like? Which holes are breaking pistons?


Id start with a thicker headgasket to open up the quench
and get some compression out.

Vacuum pump? Ring package?[/quote
cam timing events @.050
in. opens 30 ,closes 74
ex. opens 85 ,closes 33

number 1-3-4-5-7-8
#3 is the worse then 4 , number 5 has a hair line crack Being the best
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Re: nitrous build problems

Post  Lem Evans on April 22nd 2015, 11:08 am

HeRo would better qualified to quote a #, but I will say that the party doesn't start until you get to .075"ish i.m.o.

Keep in mind that even after you open things up you could still have issues if the engine has 3 or 4 degrees more timing than it wants.

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