Player0

Looks like I'm doing a header gasket. Time for some resurfacing as well. Been reading a lot about whether to improve the intake airflow. Lindsey has their Stage II header which brings it to about 230 CFM. But that's a $1200 option and I'm not finding a lot of reviews on it.

Are there any dyno charts around with before and after with work like this? I know HP gains will vary depending on what else is in the system.

In my case, I have the MAF, I have the K27-8, I have the upgraded exhaust, but still the stock intercooler. Top end power has always been plenty but turbo lag is a bit rough. I'd like to flatten that curve a bit.

So what do you thing $700 over a normal valve job would buy me in terms of performance?

I'm also considering a spring upgrade. Reading all the advice here makes me think that sticking with the stock head gasket is the best bet. But does that mean sticking with 16PSI as well? Or do I need to try the cometic in order to hit 18+PSI?

Lindsey also offers head gaskets with "custom coolant modifications" which are supposed to improve cooling to the exhaust ports. Not really sure what that means. Are there coolant passages covered up by the gasket, or is the gasket the wrong size in spots? Doesn't make any sense to me.

V2Rocket

on a stock headgasket all the holes marked red here are blocked entirely. and the blue ones are holes maybe 3/16" wide. there is probably some good reason to limit where the coolant can circulate (flows through block to back then up into cylinder head towards front exit) but it seems silly to include that many passages in the head then. lindsey probably opens up a few of the holes.

Player0

Doesn't seem like very many people opt for the Lindsey header service. Do most people just go for a cheaper local valve job and maybe just do a little intake port cleanup on their own?

If this really picks up say 20HP, that's probably twice the gain I'd get from putting the same money in to an intercooler upgrade.

There's something convenient about sending it off to a place that is going to have all the valves and guides and any parts I might need to have replaced.

What about this pressure valve that's in the head? It seems to have an o-ring. Is it serviceable? Is it something I should clean or replace the seal on while it's off?

86 951 Driver

I would recommend putting a steam vent kit on the head. It makes bleeding the coolanr easier. It also is supposed to help reduce headgasket failure.

Player0

Yeah, I'm going to definitely do the steam vent kit. If it helps prevent head gasket failure then it's worth the very minimal amount of money and effort. I have no doubt that air gets trapped up in the top of the head even after a pressurized bleed. Others claim to see bubbles moving in the line all the time so it seems to work.

Then again, the original head gasket, as far as I know, went nearly 100K miles and 26 years without issue.

Black51

You can see a steady stream of coolant flowing through the line. And yes, if the system is not bled properly, you can see the bubbles. But it's more the sections where there is an air gap flowing through the line are what you have to bleed out of the system.