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I am going to be installing mac mid headers on my Lt1 soon. Should I go with these stainless studs for ease of holding the header in place during installation or shold I go with regular header bolts and lock washers? This is my first header install. Should I use gm stock manifold gaskets with copper gasket rtv or maybe Percy's aluminum seal 4 good gaskets? Can I use my stock o2 sensors with these mids?
I am going to be installing mac mid headers on my Lt1 soon. Should I go with these stainless studs for ease of holding the header in place during installation or shold I go with regular header bolts and lock washers? This is my first header install. Should I use gm stock manifold gaskets with copper gasket rtv or maybe Percy's aluminum seal 4 good gaskets? Can I use my stock o2 sensors with these mids?
Last edited by 350 groundpounder; 04-08-2015 at 11:02 PM.
Bolts work fine with a Fel Pro 1406 gasket. Make sure you re torque them after each of the first few heat cycles. Your stock oxygen sensors will work fine. As cheap as they are if they are high mileage I would replace them at the same time along with the spark plugs.
Don't use the studs. They do not allow for easily moving the header into place. I use the Percy gaskets and they work great. I used the ARP bolts with 3/8" bolt head. Don't put thread locker on the bolts. Just tighten the bolts after you drive it for the next couple of weeks.
What I've always done is bolt the header in place with one bolt, usually somewhere in the middle. That way the header is then suspended, then put in the very front and rear bolts and take the one used initially completely out. Now you can slip the header gasket into place and bolt accordingly.
Thanks for the info. Can you point me towards some good stainless bolts to use? 1 inch? Lock washers or not? Anyone use rtv with felpro gaskets? I need a really good seal with the mac mids because the primaries attach separately to the head ports if that makes sense? The headers dont go across the head laterally.
3/8" hex head at 3/4 or 1" in length will work. Go to Summit's site and do a search for ARP header bolts. Can probably search here too for specifics. No lockwashers needed. You will have to retorque the bolts after a few heat cycles because the gasket will shrink. After the gasket has done its business the bolts will remain tight if torqued properly.
The flanges are very think on the mac headers. Has anyone ever tried 1 1/4 length bolts for more bite? I can get the stock manifold gaskets for $30 for a pair from my Chevy dealer. I hear they work nice with macs. Why are arp stainless bolts better than a regular stainless bolt? Everyone seems to recommend then.
The flanges are very think on the mac headers. Has anyone ever tried 1 1/4 length bolts for more bite? I can get the stock manifold gaskets for $30 for a pair from my Chevy dealer. I hear they work nice with macs. Why are arp stainless bolts better than a regular stainless bolt? Everyone seems to recommend then.
When racing professionals in NHRA, IHRA, NASCAR, and Formula 1 competition need bullet-proof fasteners for their high-performance machines, they turn to one company: ARP. Since 1968, Automotive Racing Products has been engineering and perfecting bolts, studs, nuts, and other fasteners for engines, cylinder heads, headers, wheels, transmissions, and more. ARP uses only top-quality materials—far above the usual “aerospace quality” others settle for—in a highly exacting manufacturing process to create fasteners with the strength and durability to last race after race.
Well, I think I'm sold on the arp bolts in 1 inch. The 5/16 head has better fitment to get a wrench on I hear. Is there a certain bolt thread I have to look for too? Did you use washers with the arp bolts or just straight up bolts?
I think I'm sold on the stock oem gaskets also. I will put a thin layer of high temp rtv on both sides of the gasket. I'm sure that the mac flanges will have a few high and low points because of Murphy's law.
Hoping I don't need O2 extensions. Not sure on the ceramic coating because it is so freaking expensive.
04-08-2015, 10:48 PM
Header install help! 
