Big Prob W/ 426 Now!!!!

[03pissedoff426]

alright well for some reason my piston is hitting my spark plug just a tad and closing the gap. and it also hit my exhuast valves about a hair, i can see the marks on the piston, but it isnt hitting my intake side. im using steel type head gasket, a namura tech i believe. designed for bigger bore engine with high comp. i put a new gasket below the jug also. so it's not like i didn't put in that gasket to get higher comp. cuase it's in there. 13:1 is high enough. what can i do now? the head wasn't shaved or decked or anything. still all the original surfaces, just cleaned. and when i say it is barley touching it, i mean you know the gap on the spark plug. its tiny, well when the piston hits it, it just pushes it shut, doesn't destroy the spark plug or anything, no chips no nothing. do they make thicker gaskets for this reason? anyone know of any? or using them? thanks guys

[wilkin250r]

This is a first. Is this on a 400EX? Generally they have a huge deck height, so people generally have a problem the OTHER way, the piston is too far down and they're not getting the advertised compression ratios.

Many companies make different thickness gaskets. What brand head gasket are you using right now?

I would advise you to contact some gasket companies and see what options are available. If possible, I would change the BASE gasket, rather than the head gasket. A thicker head gasket is more likely to blow or spring a leak, but the base gasket doesn't see combustion pressures, so going thicker on the base won't make it more likely to blow.

[03pissedoff426]

yea, thats what i was kinda thinking about. im using the namura tech metal type gaskets. supposed to be pretty good. i think i will buy a paper gasket for between the jug and motor, and maybe keep the metal one i have there now also. the mark on the top of the piston from the plug looks like somebody took a pen and tapped on it with there hand a few times, so it's almost nothing, but it's enough. and yea this is the first time with this motor. but im using a new type of gasket, but they are supposed to be better. but im guessing they are a little thinner though. that sucks. it's ashame my honda dealer bends you over when you order parts there, even when you take in service honda's price for the item.

[K_Fulk]

My 426 would do that, with the stock spark plug. Pick up a DR8EA NGK plug.

[prepracing]

check the simplest thing 1st...... the sparkplug, did you gap it ? is it the right plug ?

[03pissedoff426]

yea the plug was gapped right, but it seems like the plug is too long. im prob gonna go with the plug the person above mentioned, Thnaks

still have the bigger issue of the exaust valves hitting the piston????

[03pissedoff426]

yea, they hit, but just a tad, im not concerned with it though, since it didn't bend anything. just curious as to why it did it. maybe alot of pistons arent designed for bigger exhuast valves. since hardley anyone does it. but your almost stupid if you don't. if your sucking in more air, you need to get rid of more.

[400exrider707]

Theres the problem, you have oversized valves. The piston needs to be machined to accept the larger valves!!!

[tater_kamik]

ummm, no offense, but you arent worried about the piston hitting the valves??

[SHADETREE101]

mine did that too. the problem wasn't the piston hitting the sparkplug, it was the heat and compression closing the gap. as for the valves if you hit them then it is your rocker adjustment. you have plenty of stock clearence and should nevercome close unless you adjusted them wrong. i have been rinnung the 13:1 for two seasons. running the colder plug will solve the issue of the gap closing but you are defeating your purpose of the piston if you do. give it more fuel. you can deck around 75 thou out of the cylinder and head giving you 15:1 with the piston and still have enough clearence.

[mikeboone]

I had talked with a friend who built a Hot 426 for drag racing with mod like you and totaled the topend with rod stretched.

I asked him what warning signs to look for and he said the plug would start closing up. Many times a rod in bult motors wont break but stretch enough to do damage.

I would ensure correct plug and have shop check squish with solder. It doesnt take a hard hit to bend a valve and it will NOT seat fully losing a huge amount of HP. Have shop do leakdown test on cylinder as well. You can get a PSI tester yourself at any auto parts supply

[03pissedoff426]

the rod strecthing sounds like a possibility. i know how to adjust valves and what not, and have done so a few time just to make sure i was right. i hope my service manual has a center to center lenght on the connecting rod. that sux. what would make this happen. i didn't even get to break it in this time. so could i go with a stroker crank and rod now? i only saw kits for the 87mm and 89mm but no 88mm kits? has anyone done a switch from stock to stroker themselves? any special tool needed? i have access to pretty much anything/ let me know guys. winter is around the corner then spring and summer so the sooner i can get her together again the better!!!!

oh yea. when i take the head of, my piston is like an 1/8" away from the top of the sleeve, i kinda forget if that is normal or not. i think the wear marks were like 5/8" down on my old sleeve. but i forget stuff, i have a bad brain

[03pissedoff426]

so could i get a stroker for 426 or would i have to step upto a 440? cuase im trying to stay away from them. my friend has one, and was smoking him all the time with my 426, but not anymore till i get this piece fixed. i figured i might as well go with a stroker crank since it's gonna be in pieces anyways. might as well do right the first time.