I have some time to kill before my rebuilt engine goes in my A100. I'd like to port out the stock manifold to 2.25 inches and had a few questions.
1. Is there a 2.25 inch gasket that is sold that I can use as a guide? I don't want to just start grinding and end up lop sided.

2. Can I do this with the manifold still on the block? I assume i'll need to shove a rag up by the heat riser flat to block shavings?

3. Couldn't a cylinder hone with aggressive stones be used to open the port?

4. I have decided to go with 2.25 inch exhaust and would love to have dual exhaust. (single to dual pipes). Will I be hurting the performance much by going with a single to dual pipes? This will be a daily driver for my son with minimal highway driving.

Thanks for reading

1. Sure, Remflex, Felpro, etc....all make 2.25" gaskets. I used a spare 2.25" metal flange as a guide.
2. Sure.
3. That would take forever but might be nice for a final cut. Use a die grinder and carbide cutters.
4. Not if you keep the pipe small, no larger than 2".

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Just a reminder.......

2.25" exhaust pipe has an ID of 2.125"

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Ted: thanks for the response. Can you elaborate on the pipe size. I assume you mean 2.25" down from manifold, through muffler, then split into two pipes that are 2" and no larger. Let me know if i'm understanding you right.

emsvitil: Thanks for the info; I was thinking this whole time the pipe sizes i've been reading about were all internal. So, does this mean I only need to bore the hole to 2.125", or move up to a 2.5" ID pipe and bore the hole to 2.25"?

The exhaust pipe material is measured on the outside, So a 2.25" pipe will have an inside diameter of 2.125". You will have to make sure the hole is at least as big as the inside diameter of the pipe.

Richard

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Part of Tyrde-Browne Racing

You can do it that way if you like, or run two muffler and tail pipe systems. Some folks run twin Dutra manifolds or one Dutra and one modified stock manifold and use 2"" for each bank all that way back.

I started with 2.25" at the head pipe then run 2.5" into a Flow Master HP2 muffler then 2.5" into a Flow Master 70 with a 2.5 " tail pipe. It is super quiet and very free flowing. Click on the red link below my name to view pictures. This is the first really nice exhaust system I have had on a Slant Six. Very free flowing and extremely quiet at all rpms.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Thanks Ted. I want to keep the stock manifold for now. My main focus is getting the van on the road so my son can start enjoying it. He can decide what upgrades he wants down the road. (dutra duals, etc).
I'll do the single exhaust if I have to, but if it's only a few bucks more, I'll have it split into two 2" pipes before the rear wheels.

edit: Very, very nice car and engine bay, Ted.

The exhaust pipe should always be larger than the manifold outlet. Having that step up in size improves performance. This is true at the manifold-to-head junction too.

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Joshua

I can see this point for a single exhaust. Is this also the case when splitting the single into duals? Does 2.25" into muffler and dual 2" coming out be the same or similar to a single pipe with 2.25" into muffler with a 4" coming out?

No, the step principle applies where pulse pressure is strong. If you're spitting the pipe further downstream and not seriously decreasing the overall pipe cross section you should be fine. You're still adding weight, expense and complexity though. With adequate muffler flow capacity single exhaust makes just as much power as duals and since it weighs less the vehicle performance increases.

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Joshua

Thanks Joshua. I'm getting it now. I appreciate it.

PS: I've been in telecom for 14 years. Nice to talk to a telecom brother. :0)