What do you do to the head when you over-bore??? - Tuner-Junction

jadkar · #1 (**permalink**) November 17th, 2006, 10:50 AM

Even though my car is boosted I figure I will post this question here because boring and stroking is usually an "all-motor" technique.

My stock ITR block is getting bored and sleeved by ERL. So the question is I am going up to 86mm from the stock 84mm (I thin it's 84mm). Anyway, since the bore is being significantly enlarged do I need to do anything to the head?? In other words what the heck do I do about the head gasket and the combustion chambers on the head? They will be different sizes now.

It's strange whenever I hear someone talking about a large displacement block they never explain what they did to the head gasket and head.

Any info??? Please enlighten me

njn63 · #2 (**permalink**) November 17th, 2006, 12:07 PM

i know headgasket needs to be bigger. I forgot who did it but i know someone had OEM ones for an overbored motor or you can go Cometic... i'd rather stay with the OEM one though.

A_White_Gs-R · #3 (**permalink**) November 17th, 2006, 01:33 PM

cometic is good stuff. when i had my blocked overbored they didnt do anything to the head honestly. Ask the guys doing your block just to be on the safe side since you are boosting its a different animal. mine was only .20 over so i assume head was fine.

triniskill · #4 (**permalink**) November 19th, 2006, 01:30 PM

John..stock bore is 81mm..the only block that is 84 is the b20..
best bet is go with cometic..they have for any size or even custom if you want..

jadkar · #5 (**permalink**) November 19th, 2006, 02:44 PM

^^
Yeah, I got confused with the CRV block.

Anyway, I spoke to Josh at Endyn an he said the cometic gasket will work and that there was also a company out there that bores the OEM gasket. As for the head, the combustion chambers need to be opened up to the same bore as the block. So we are talking once again.....more money.

He also tried to talk me out of 86mm on the bore stating that it's not giving me enough room for re-boring later. At this point I don't care though. I'm building a brand new engine all the way from the blower to the block I'm not stopping short on my displacement goal. Especially since I wanted to go 92mm. Now that I'm stopping at 89mm I need to make some displacement up and I will on the bore size. My combination should leave me right at 2.1lt and the thing should be a beast!!.

I'm guessing with the increase in stroke, displacement, and slight psi. This car should be completely different to drive. It should be much faster.

scottigee · #6 (**permalink**) November 19th, 2006, 08:07 PM

Have you considered that changing the bore and stroke will limit the engine's ability to make power up high (reliably)?
I've always understood the rod / stroke ratio to affect the reliability of high revving engines because of the component forces resulting on the piston rods, crank and cylinder walls.

I like the big bore idea, I just don't want to see RIO blow up again

I guess that's what you're doing with this thread...research on how to do it well...so carry on

Transparent · #7 (**permalink**) November 19th, 2006, 08:14 PM

Quote:

Originally Posted by scottigee

Have you considered that changing the bore and stroke will limit the engine's ability to make power up high (reliably)?
I've always understood the rod / stroke ratio to affect the reliability of high revving engines because of the component forces resulting on the piston rods, crank and cylinder walls.

I like the big bore idea, I just don't want to see RIO blow up again

I guess that's what you're doing with this thread...research on how to do it well...so carry on

a longer stroke and bigger bore will make the motor less stable at high revs. but since its not a drastic change (like going to 92mm) the redline wont be effected too much. but also becasuse if the increasing displacement, there will be more tq at a lower rpm.

jadkar · #8 (**permalink**) November 19th, 2006, 09:44 PM

Quote:

Originally Posted by scottigee

Have you considered that changing the bore and stroke will limit the engine's ability to make power up high (reliably)?
I've always understood the rod / stroke ratio to affect the reliability of high revving engines because of the component forces resulting on the piston rods, crank and cylinder walls.

I like the big bore idea, I just don't want to see RIO blow up again

I guess that's what you're doing with this thread...research on how to do it well...so carry on

Yeah, I have had long talks with Jeff Evans, Larry from Endyn, John from LHT, and numerous others from Honda-Tech and here. As transparent said, I'm going with a 89mm stroke as opposed to my original 92mm idea. This along with Endyn's specially made rods and pistons will net me a rod ratio the same as a non-VTEC b series. This combined with the quality of the rods and the Darton sleeved block will still allow me to red line at 8600RPM.

Anyway, god forbid RIO's engine should blow again, I'll just have to do it all over

I plan on having this car for the rest of my life and I'm a driver, so sooner or later I'm sure I will have issues again. One day when I'm done having fun and I'm modding something else I'll probably toss a stock Type R engine in RIO and just park her. I won't drive it anymore, I'll just rub it with a diaper.