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08-25-2024, 01:01 PM | #1 |
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Cast Exhaust Manifolds (Approximately)
After 57 years my 2.5" stock exhaust manifold cracked. Wow what a shame, these things really woke up my 406 but looked stock. Oh well on to the fix. I ordered a set of 2.5" cast units from Summit. So here are the pics comparing them to what is left of the stock pieces. I have a saying that things made in the Pacific Rim are "approximations" of the real thing. Close but.....these new ones are not going on my truck. First pic is...well yea that happened. Second pic is the "new" high performance? Third pic is the old single exhaust port. One of these things is not like the other.....On this engine I need every square millimeter of flow (No I am not going with headers). Now I am looking at the TruRam set. Anybody have a set of those? I have AC so I think these will interfere with the new Alan Grove brackets I just put on.
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72 K20 Custom Camper, D60, 14BFF, full roller 406 TPI w custom built ECU and yes..it has tow hooks...and a 5 speed |
08-25-2024, 10:40 PM | #2 |
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Re: Cast Exhaust Manifolds (Approximately)
I got 2 sets of the Dorman ram horns from Summit, and they looked good. With just being rougher then factory versions, but no misaligned ports like yours.
If by true ram horns you mean the polished ones you can get from speedway that look rounded, and swoopy. I gave my dad a set of those, and they looked very nice to me |
08-26-2024, 12:56 PM | #3 |
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Re: Cast Exhaust Manifolds (Approximately)
Thanks for the input I'll have to call them about the port size/design. I was looking at these as a substitute for the original Corvette manifolds. The obstruction that can be seen in the port isn't misalignment it is how they are cast. The port on the other end is cast the same way and also the other manifold in the set is cast exactly the same. It seems odd that the manifold is a 2.5" high performance unit but with a complete face plant in the port design, again it is an approximation of the real functional high performance piece. The original Corvette manifolds can flow pretty well up to about 4000 rpm which is fine for the way I build my engine to tow. I have an RV cam that is "all in" at 5000 rpm, so there is no need to have big flow numbers above that as you get with headers.
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72 K20 Custom Camper, D60, 14BFF, full roller 406 TPI w custom built ECU and yes..it has tow hooks...and a 5 speed |
08-26-2024, 07:28 PM | #4 |
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Re: Cast Exhaust Manifolds (Approximately)
Wow, those are even worse than the ones I had. Mine had smaller ports than the o.e.m two inchers and they cracked pretty quickly anyhow. I only have a 283 now so I just want back to oem 2". But wow those....what a shame.
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08-28-2024, 12:12 PM | #5 | |
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Re: Cast Exhaust Manifolds (Approximately)
Quote:
Does your Dads truck have AC? Any pictures of the install on that truck?
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72 K20 Custom Camper, D60, 14BFF, full roller 406 TPI w custom built ECU and yes..it has tow hooks...and a 5 speed |
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08-28-2024, 08:03 PM | #6 |
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Re: Cast Exhaust Manifolds (Approximately)
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09-15-2024, 10:55 PM | #7 |
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Re: Cast Exhaust Manifolds (Approximately)
A slight update on this issue. I have searched and called just about every vendor of these "reproduction" manifolds and they all seem to have the very restrictive bolt support cast inside the ports EXCEPT one....I called Corvette Central and they have their own molds for the manifolds. But just like everyone else they have casting supply issues which basically means they don't have stock. I did talk to a guy there that actually had a set on his desk for his own car and he confirmed that the ports are correct and open. I'll have to wait until the end of the month for their restock to come in. I'll believe it when I see it.... I decided not to go with the manifolds in the picture above after finding out this info from CC.
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72 K20 Custom Camper, D60, 14BFF, full roller 406 TPI w custom built ECU and yes..it has tow hooks...and a 5 speed |
09-16-2024, 01:41 PM | #8 |
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Re: Cast Exhaust Manifolds (Approximately)
If it were me I would braze them up and continue....I have had great success with brazing and feel it would work well for you.
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09-16-2024, 03:23 PM | #9 |
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Re: Cast Exhaust Manifolds (Approximately)
Thanks but, the strength limits of brazing (especially at higher temps) is why I will stay away from that option.
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72 K20 Custom Camper, D60, 14BFF, full roller 406 TPI w custom built ECU and yes..it has tow hooks...and a 5 speed |
10-26-2024, 03:06 PM | #10 |
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Re: Cast Exhaust Manifolds (Approximately)
Ok, another update. I received the cast manifolds from CC and I am not impressed. These defects are in both of the manifolds I ordered and in the same place so I am guessing that the mold is the cause, maybe not? The concern is that the porosity will cause cracking during heat cycles. The pick is pointing to the deepest "pit". This area sees the highest temp and gas velocity so probably the absolute worst place for any kind of defects, pitting, porosity. I guess I could look for a foundry in the US that can cast these with better quality? This isn't high technology, casting iron is probably 1000 years old? Why can we not do this in this country anymore?
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10-26-2024, 08:32 PM | #11 |
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Re: Cast Exhaust Manifolds (Approximately)
Maybe send them back as defective and they could send you a better set? They can't all be low quality casting can they? I wouldn't be happy with those either. If CC only has low quality castings then I would look for good used ones on ebay and grind that hump out of them and maybe port them too.
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10-27-2024, 06:42 AM | #12 | |
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Re: Cast Exhaust Manifolds (Approximately)
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72 K20 Custom Camper, D60, 14BFF, full roller 406 TPI w custom built ECU and yes..it has tow hooks...and a 5 speed |
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10-27-2024, 10:35 AM | #13 |
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Re: Cast Exhaust Manifolds (Approximately)
A few things.
Almost all casting is done outside of the US given the looser regulations. Are you worried about the casting flaws ending up in failure of the part? I don't see anything in those flaws that would lead to a crack. I wouldn't be worried about anything like exhaust velocity or flow...anything other than a bone stock mild SBC is going to want more scavenging that even the best stock-type casting can deliver. There are "hot rod" style cast manifolds that are pretty and have better flow - Sanderson and I think Hooker make these. Finally, obviously there are a ton of these available used...and headers are obviously a choice |
10-27-2024, 04:55 PM | #14 | |
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Re: Cast Exhaust Manifolds (Approximately)
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72 K20 Custom Camper, D60, 14BFF, full roller 406 TPI w custom built ECU and yes..it has tow hooks...and a 5 speed |
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10-28-2024, 04:59 PM | #15 |
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Re: Cast Exhaust Manifolds (Approximately)
I put a set of these: https://www.holley.com/products/exha.../parts/8525HKR
on my mostly stock 350 when swapping away from headers. So far working fine about 18 months later. Don't know how well they compare performance wise to your former set of rams horns. They also come in ceramic coated but the recommended break in process was not friendly with a 30 mile drive home from the exhaust shop. |
10-28-2024, 08:00 PM | #16 | |
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Re: Cast Exhaust Manifolds (Approximately)
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72 K20 Custom Camper, D60, 14BFF, full roller 406 TPI w custom built ECU and yes..it has tow hooks...and a 5 speed |
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11-09-2024, 11:44 AM | #17 | |
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Re: Cast Exhaust Manifolds (Approximately)
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11-29-2024, 02:59 PM | #18 |
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Re: Cast Exhaust Manifolds (Approximately)
OK, so I changed my mind. I'm going to TIG braze the cracked piece. All this messing around with really really poor quality parts has put a bee in my bonnet! I still have the very expensive manifold on order, but it won't even be cast until the end of Dec. I need to get back to tuning my FI so I ordered brazing rods from Muggy Weld (https://www.muggyweld.com/product/72-electrode/). I did a bunch more reading on brazing and talked to their tech guy and it sounds like this might work? Anyhoo stay tuned for the next exciting chapter of " I can't believe people actually put that crap on their trucks" Seriously, who says " I don't care about quality or performance"? When I get the new piece I'll have a spare.
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72 K20 Custom Camper, D60, 14BFF, full roller 406 TPI w custom built ECU and yes..it has tow hooks...and a 5 speed |
11-29-2024, 04:13 PM | #19 |
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Re: Cast Exhaust Manifolds (Approximately)
Sounds like fun! Don't forget to post some pics!
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11-29-2024, 04:16 PM | #20 |
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Re: Cast Exhaust Manifolds (Approximately)
There are a lot of used ones around. GM even sold them for a long time. They were also installed on many Corvettes. And yes, with Air-conditioning. A 1965 365HP 327 could be had with AIR.
Search for 3797901 and 3797902 or your casting number. https://www.ebay.com/sch/i.html?_fro...7901&_osacat=0 |
11-29-2024, 05:35 PM | #21 |
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Re: Cast Exhaust Manifolds (Approximately)
Don't know if this would work for you but maybe better than brazing would stick welding with nickel rod?
On a few of my hod rod project with GM rear ends I have the axle tubes which are mild steel welded to the cast iron center section for added strength. I am far from a good welder so I take it to a local "pro" welding shop. As I understand to weld cast iron correctly the area to be welded has to be warmed up first. They use a torch. Then they weld using nickel rod and then wrap the welded area in insulation for a very slow cooling down. Looking at your cracked manifold I'm guessing they would drill holes at each end of the crack. Then "V" out the crack with a grinding disc. After pre heating weld. Just my .02. |
11-30-2024, 12:33 PM | #22 | |
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Re: Cast Exhaust Manifolds (Approximately)
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72 K20 Custom Camper, D60, 14BFF, full roller 406 TPI w custom built ECU and yes..it has tow hooks...and a 5 speed |
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12-04-2024, 07:37 AM | #23 |
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Re: Cast Exhaust Manifolds (Approximately)
I'm real close to buying this 350 with the rams on it , I don't know if they are aftermarket or not , do these give just as good of performance as headers ??
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12-04-2024, 04:08 PM | #24 | |
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Re: Cast Exhaust Manifolds (Approximately)
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So if the engine is making less than about .6 HP/CID then there's some impact; more than that then the impact increases significantly. If you've got a 1" y'd exhaust behind the headers, then again - not much gain. if you've got 2-1/2" duals behind it, then definitely more. TANSTAAFL |
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12-04-2024, 04:16 PM | #25 | |
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Re: Cast Exhaust Manifolds (Approximately)
Quote:
I have them with 2.5" pipes and mufflers, as the above poster notes, that helps. No restrictions from header to tailpipe.
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