Since I need to use my factory exhaust for now, I'm about to drill/tap a bolt hole on my new Vortec head for the offset bolt hole for my factory dual exhaust for my L98. The bolt hole is at the firewall end of the head and is there on my L98 heads (they have an extra bolt hole- which I did not realize)

Anyone know if a bolt the depth of the other exhaust holes will interfere with anything in this particular head? (such as coolant passages)?

Scoggin Dickey said that no 350s used this hole and I must have a 305! (they must be wrong) I had to take everything apart after almost having everything done once I realized the hole wasn't there!

thanks in advance.

 

Do not attemp to drill that hole in a Vortec head. just run without that bolt or change the exhaust manifold.

 

This reminds me of the can I drill my doublehumps threads. Dont do it man, it surely isnt worth it to screw up a perfectly good head.

 

Believe me - I appreciate the advice - but I am wondering what the concern is exactly.

Is because there is a coolant passageway near the wall there or is it because I may mess up and ruin the head?

I'd love to pick up some headers but I won't have another $400 for the car for a while and I want to drive the car now! (ironically a vortec head is less than headers!) Also, I will need to cut/weld which will be a big project for me in itself (I have dual cats) Luckly my father-in-law is an experienced machinist and he offered to put the hole in.

Anyhow, if it will ruin the head, I won't do it. Do you think omitting that bolt would cause an exhaust leak?

thanks.

 

It will most definitely cause an exhaust leak.

 

Eyeball it and see where that hole goes. AFAIK it goes into a coolant passage for sure. You'll need to use sealant on the threads, that should stop it from puking coolant. Then use some sort of allen headed plug later once you get headers.

 

don't bother drilling that hole, if you can't afford $130 long tube headers, then I don't know what to tell you. Omit the bolt and it shouldn't leak, if it does, then double up on gaskets.

 

Where the heck do you find $130 long tubes?!?

EDIT - wait a minute, what do you mean "extra" exhaust bolt hole? On cyl #8, you mean there's the bolt hole BEHIND the last exhaust port.... Then the other hole after it right? I'm thinking about the drivers side heads I have (not Vortecs), and how they have that "extra" bolt hole at the front (which would be the same as the #8 rear.)
That bolt isn't needed. You already have a bolt after the exhaust port, so that one is decorative.

 

headmann long tubes are $130 and are what I am running, the 1 3/4 headers didn't pick up any power N/A at the strip so I went back to the cheapies.

 

Well i'll be damned, the 68460 long tubes are as cheap as the 68470 shorties... Well crap.
Kinda stuck when it comes to y-pipes though right? You pretty much have to run custom dual exhaust?

 

I checked, and since I have dual cats and I want to retain the air tubes, I can only get Edelbrock and Hedman, and you can't really get Hedman anymore since I was told from the guys at Hedman that they don't have demand for that model and they won't make a batch unless they have lots of orders. Also I think the Edelbrock was about $500, and I don't have a welder. Yeah, I know I can replace the cats, etc.. but basically it's a much larger project than I wanted to take on right now and I don't see where I can slap on something for less than about $475.

Anyhow... thanks for the info. I will think it over.

 

By the way, the normal bolt hole is not used for the #7 (I believe) exhaust port bolt toward the end of the head. On the L98s, the extra outer hole is used. So if I didn't use it there would only be 1 bolt for that port.

 

Trust me it will cause an exhaust leak. I've been there. I would drill it and take my chances.

 

My latest thought is to look at the manifold again and think about drilling the hole in that and just using the existing head exhaust bolt hole.

The reason I initially ruled it out is because I would probably just enter the exhaust opening but maybe that's better than dealing with a leak or ruining a good head. The bolt would probably just enter the inside of the exhaust but maybe it won't leak.

 

Good luck with that. I would say the options for not having something cobbled up on your brand new heads are: use a different manifold that lines up with your exisiting holes, or have the head (not the manifold) drilled and tapped. I know from experience how frustrating it is to have a fresh engine sound like junk because of a simple exhaust leak.

 

I personally wouldnt drill the head. Its too risky. Id run without it, or get headers. Its sort of foolish to do it just to get the car running for a bit while you decide what to do with the exhaust.

 

Would this work on a vortec?

-------Use early model heads in late model applications

Convert early model 6-bolt heads for use in late model, 7-bolt applications. Works with stock exhaust systems. Converts one cylinder head. Use the standard exhaust manifold gasket or seal with High-Temp Silicone (sold separately).-------

http://www.goodson.com/store/templat...l.php?IID=2902

Here's a link that says it can be used to adapt vortec heads to camaro exhaust manifold.

http://users.apex2000.net/whardie/engmod.html