I want torque and Mid-Range Power...screw top end.

[lowridin2g]

, diesel are obviously a different story

 

[beat90tsi]

Jesus. I remember 6-7 years ago when 550's were perfect for a 20g.

The overkilling gets worse and worse every year.

What kind of boost can you reliably support on a 20g w/550s?

 

[sweet97]

15-16 PSI with a 20G and 550cc inj's. Maybe more with a Walbro 255 and a higher base pressure. The guy I bought my '93 Talon from had a 20G powered Taln and he said Buschur recommended the 550's with the pump and probably a baseof 43 psi. I agree the size of injectors is always climbing, that's why I bought 720's for my 50 trim and I want to sell them!..... Mark

 

[leakyfaucet]

What kind of boost can you reliably support on a 20g w/550s?

Plenty, with race gas. :laugh:

 

[Talonman]

efficiancy is a factor to, I just replaced my 14b with a FP 18G and at 19 psi on pump I run lower hi-throttle safc settings on the 18G than I had to with the 14b at 19psi to keep knock in check. Im impressed with the 18g, I got a freshly rebuilt one by FP with 34mm flapper, turbine and compressor housings ported, for less than a ported EVO3 16g (no flapper mod). Together with pacesetter ceramic header, 122 perf 2.5" tubular 02 and full 3" exhaust I spool up by 3000-3100 rpm in 3rd gear. Today at about 45-50* I got no fuel cut at 19-20 psi and room to tune on my 550s, 19* advance and above with 0-4 knock. When summer comes and I may have to add fuel to avoid knock so I may get a set of FIC650s.

 

[High PSI]

...I'm looking for a head gasket. I've got it narrowed down to the mitsu metal head gasket and the HKS, either the 1.2mm or the 1.0 mm. Obviously lower thickeness = higher compression = better off boost power and quicker spool and low end power.

Most people have said to go with the mitsu just becuase it can hold craploads of boost and is less than half the price of the HKS. However, if I can get more compression out of the HKS, then it's worth it to me. Anyone have any experience with the HKS gaskets? Which would be best for what I'm shooting for?

Also, if anyone knows, what's the thickness of the stock gasket, and the metal mitsu?

 

[sweet97]

You wouldn't notice a .2mm difference. get the cheaper mitsu gasket. Mark

 

[espinelli]

You should also consider a Cometic HG. They offer various thicknesses and cost less then mitsu. I went with 30thou thickness and I believe standard is 40 or 50 thickness.

A good rule of thumb is that every 250thousandenths less is about a ~ .25 increase in your compression.

 

[High PSI]

You wouldn't notice a .2mm difference. get the cheaper mitsu gasket. Mark

As seen here

"The HKS head gasket is one of the best in the market for various reasons. First off it is made of several layers of steel and then coated with a special rubber compound to create a super strong seal. Secondly it is designed to accommodate over bored pistons and higher/lower compression. The are available in three configurations.

1mm-9.2 Comp Ratio
1.2mm:8.6 Comp Ratio
1.6mm-8.3 Comp Ratio"

.2mm could make the difference between a 9.2:1 compression ratio and a 8.6:1 compression ratio. I think that's a pretty noticable difference.

Anyone have any idea if these numbers are from a 1G or a 2G?

 

[High PSI]

You should also consider a Cometic HG. They offer various thicknesses and cost less then mitsu. I went with 30thou thickness and I believe standard is 40 or 50 thickness.

A good rule of thumb is that every 250thousandenths less is about a ~ .25 increase in your compression.

Reading through the posts, there were quite a few people that recommended against them, that's why I didn't mention the Cometic. I didn't hear anything bad about the mitsu multi-layer gasket, and I didn't hear anything at all about the HKS (besides the fact that it was expensive)...that's why I am asking about it.

 

[espinelli]

Reading through the posts, there were quite a few people that recommended against them, that's why I didn't mention the Cometic. I didn't hear anything bad about the mitsu multi-layer gasket, and I didn't hear anything at all about the HKS (besides the fact that it was expensive)...that's why I am asking about it.

No problem, I didn't have time to read the entire thread. However, I do know that cometic does not recommend the High Pressure version of that gasket as there seem to be a lot of problems with our application. It maybe possible that most of the people that have issues purchased the High Pressure version. I decided to go with the standard version and saved a few bucks as well. Just sharing some of the info I picked up along the way.

I can't say I heard anything bad about the Mitsu gasket and the only bad thing about HKS is the huge cost $$$. The only negative thing with Mitsu is that they do not offer various thickness's. I decided to go with Cometic as they have a .020 (which HKS doesn't) bigger bore as well as a good selection of heights.

 

[lowridin2g]

You wouldn't notice a .2mm difference. get the cheaper mitsu gasket. Mark

you may not but your motor will

please!!! this is your compression ratio you are messing with here

 

[sweet97]

.2mm is .008" and I would surprised that would make a significant difference. I could be wrong but would like to see definifitive info to show me so. Thanks
PS: follow the rules regarding language, tanks again.

 

[92redman]

.2mm is .008" and I would surprised that would make a significant difference. I could be wrong but would like to see definifitive info to show me so. Thanks
PS: follow the rules regarding language, tanks again.

Not sure of the exact numbers so I will use imaginary ones that are hopefully close to give you an idea.

For a stock bore and stroke(8.5cmx8.7cm) the displacement is ((.5*8.5cm)^2)*3.14159*8.7mm= 493.68cc

Combustion chamber in head is about 45cc and the pistons have about 20cc between them and the deck surface.

(without a headgasket)
493.68cc + 65cc = 558.68cc for bdc volume.
65 cc = tdc volume
cr = 8.595


1.2 mm(stock????) headgasket adds 6.81cc

493.68cc + 65cc + 6.81cc = 565.49cc @ bdc
565.49cc/71.81cc = 7.875:1 cr

1mm headgasket adds only 5.675 to combustion chamber

493.68cc + 65cc + 5.675cc = 564.355 cc @ bdc
565.49cc/70.675cc = 8.00:1 cr

Feel free to check my math or supply the real figures if you happen to know them for sure.

 

[High PSI]

Not sure of the exact numbers so I will use imaginary ones that are hopefully close to give you an idea.

For a stock bore and stroke(8.5cmx8.7cm) the displacement is ((.5*8.5cm)^2)*3.14159*8.7mm= 493.68cc

Combustion chamber in head is about 45cc and the pistons have about 20cc between them and the deck surface.

493.68cc + 65cc = 558.68cc for bdc volume.
65 cc = tdc volume
cr = 8.595

1.2 mm headgasket adds 6.81cc

493.68cc + 65cc + 6.81cc = 565.49cc @ bdc
565.49cc/71.81cc = 7.875:1 cr

1mm headgasket adds only 5.675 to combustion chamber

493.68cc + 65cc + 5.675cc = 564.355 cc @ bdc
565.49cc/70.675cc = 8.00:1 cr

Feel free to check my math or supply the real figures if you happen to know them for sure.

The problem with your equations is that is assumes that the stock head gasket has no thickness. A 1.2mm thick HKS head gasket is not 1.2mm thicker than the stock unit, it's 1.2mm thick, period.

If the 1.2mm thick HKS head gasket dropped the compression ratio down to 7.857:1, imagine what the mitsu would do!

I think your math would be pretty accurate if someone knew the actual spec on the thickenss of the stock head gasket.

Anyone?

 

[92redman]

The problem with your equations is that is assumes that the stock head gasket has no thickness. A 1.2mm thick HKS head gasket is not 1.2mm thicker than the stock unit, it's 1.2mm thick, period.

If the 1.2mm thick HKS head gasket dropped the compression ratio down to 7.857:1, imagine what the mitsu would do!

I think your math would be pretty accurate if someone knew the actual spec on the thickenss of the stock head gasket.

Anyone?

Actually I was assuming the 1.2 was stock headgasket thickness. That fist equation was to get the numbers that I would then add the headgasket volume to. Sorry if that was confusing though.

Edit: searched and only found one person say that he thought the stock thickness was .040" or 1mm. Can anyone confirm or correct this?

 

[sweet97]

I am trying to get straight info and called them but did not follow all he said. 1-562-777-1522. Any more info would be appreciated as this IC is highly touted by them but why? Mark

 

[High PSI]

The problem with your equations is that is assumes that the stock head gasket has no thickness. A 1.2mm thick HKS head gasket is not 1.2mm thicker than the stock unit, it's 1.2mm thick, period.

If the 1.2mm thick HKS head gasket dropped the compression ratio down to 7.857:1, imagine what the mitsu would do!

I think your math would be pretty accurate if someone knew the actual spec on the thickenss of the stock head gasket.

Anyone?

Ahh ok, no that makes sense. I've got a 2g, so 7.XX:1 seems WAY low for the stock head gasket, but I forgot you had a 1G which was about 8:1.

 

[High PSI]

I am trying to get straight info and called them but did not follow all he said. 1-562-777-1522. Any more info would be appreciated as this IC is highly touted by them but why? Mark

Ummm...wrong thread bud.