Interesting! Big injectors = more boost = Leaking Head Gasket!

[painmaster]

Something very interesting happened to me when I finally bought some 780cc injectors to replace my old 550's. Before the injectors I could only reach 25PSI on my 20g, max. I even have my external wastegate with enough washers in it so it NEVER opens. Now all I do is drop some 780cc injectors in and all of the sudden I'm hitting 30psi. Whats up with that? I never though that bigger injectors alone, would give me more boost!!!

I've been running pure 100 octane for a couple months on the street at 25PSI and now with one day of hitting 30PSI repeatedly it appears my coated mitsu metal head gasket is leaking causing my coolant system to pressurize up. I'm waiting for my HKS cams to come in so when they get here I'm thinking of pulling the head and inspecting and putting in a stock factory gasket. What do you guys think? It should be good for 30PSI, right? GRNDSM seems to be having luck with the stock gasket, at least I read that in one of his posts!

 

[CanadianTSi]

Simply changing Injectors should not change your boost settings...

 

[Coldandafraid]

maybe your old injectors didnt seal very good and air pressure was leaking out the bottom O-rings.

 

[PieTSI]

maybe your old injectors didnt seal very good and air pressure was leaking out the bottom O-rings.

This had to be the problem. The same thing happened on my car. Try doing a boost leak test sometime.

 

[awd4g63]

Way too much fuel would leak out before you'd lose 5 psi of boost.

Maybe you accidentally changed some settings on your boost controller?

 

[90AWDTalon]

Same thing happened to me when I went from 450's to 680's, went from 17psi to 20psi with no other changes.

 

[painmaster]

Simply changing Injectors should not change your boost settings...

Ya, thats what I thought!

 

[painmaster]

Way too much fuel would leak out before you'd lose 5 psi of boost.

Maybe you accidentally changed some settings on your boost controller?

I dont have any settings to mess with. I use a manual controller with the external wastegate that never opens. If it opens I would hear it!

 

[painmaster]

This had to be the problem. The same thing happened on my car. Try doing a boost leak test sometime.

I did one a while back at 25psi, and the seals around the injectors leaked a little and the bushing on the throttle body did too. But thats not enough for 5psi! Besides, now that I have more boost, I know I can't have any substantial leaks or my 20g wouldn't be able to put out 30PSI. I wonder if my boost will drop when I put the HKS cams in?

I'm thinking it has more to do with flow through the engine. Maybe more gas being shot in equals more burnt fuel coming out which equals more spool on the turbo. What do you think?

 

[cbellsondsm]

try the hks head gasket, i think they make one, i guess its kinda like welding the head to the block

 

[awd4g63]

Get the Cometic head gasket. It's basically a much cheaper, just as good HKS head gasket.

 

[painmaster]

Get the Cometic head gasket. It's basically a much cheaper, just as good HKS head gasket.

I think the general theory on the metal gaskets is that the head and block need to be ultra smooth. My head can't be milled any more, and I guess I would have to take my block out to a machine shop. I don't think I'm up for all of that, unless I'm missing something. What would I need to do to put a cometic in?

My head was rebuilt recently, and 95 pistons were dropped in without any machine work to the block. I am trying to stay away from having to do any rebuilding, unless I absolutely have to. That is why I'm leaning towards the stock gasket, because if there are any iregularities on my head or block surface I think it would be able to seal them better than the metal gasket without more machine work. Do you agree?

 

[boostedinwyo]

Many people have used the stock headgasket with no problems running 25 psi. And that is true if you do have any differences from the head to the block that the metal gasket will have a harder time sealing. Also if you do get the stock headgasket, alot of people will tell you not to use the felpro gasket, but a stock mitsu gasket. Well just to let you know, the gaskets are indentical and that there are only 2 or 3 companies that make headgaskets, they just have their name brand on it. So chances are whoever makes the felpro gaskets, are making the mitsu gasket too.

 

[1fast97gsx]

changing the injectors shouldn't raise the boost at all. Are you using arp headstuds? If you are using stock that might be your problem right there. If not then just check for boost leaks. Don't use any metal headgaskets without decking both the head and block ... it WILL leak if you don't do that. Just use the stock gasket with some ARPs and set the boost to 25 and you'll be fine