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Discussion Starter #1 (Edited)
Hi Folks,

I seen a discussion on the various Head choices for Porting and Tuning somewhere , but I can't find where that was. I know the usual top choices being the B20E and F Heads because of their larger Ex. Valves, CR etc. Is there a Thread showing where the B20 Carbie Head falls in the food chain for being reworked with the Larger Ex.Valve etc., Port sizes being small enough for optimizing and such. I'm not looking for a Race prepped and flowed Head with epoxy filled floors etc. I have 2 builds on the table, with both having .030" over Mahle Pistons. No Forged Pistons or Big Bore conversion. The primary Engine in progress now has parameters of just getting the most of a 9.75 to 10:1 CR and a D-Cam. I'd like to utilize my Carb Heads with as much work as I can do shy of Flow Bench time.
Cheers,
Wayne
67 220
69 P1800S
 

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My buddy and I have done extensive B18/20 head development on a flow bench, and we're getting very repeatable results. The surprise is that B18 intakes with 40mm valves and fat stems and guides, B20B heads with 42mm valves, and B20E/F heads with 44mm valves can all be made to flow exactly the same, right about 175 CFM at 28" H20.

The problem is that exhaust flow is terrible on any of the heads, and can only be improved about 15% by porting. Even then, it tops out at about .250 valve lift. The solution is to weld up the exhaust port floors and then grind on that:

 

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Discussion Starter #4
Very impressive Phil. For my purposes, I was trying to stay short of such extensive Headwork for this Engine. I have done simpler Porting and shaping of Combustion Chambers on past Lotus,' Alfa's, and the typical English Ford engines that have been used in Cars like my Formula Ford etc. How much would this extra Exhaust Flow benefit an Engine running under 7K rpm's and using an Exhaust system of not larger than 2"? I have seen that adding material to the floor of the exhaust port seems to be included in most of the thorough re-working of the Head's.
I'm a Die Casting Engineer and run the Moldmaking/Tool Room here at work and have pondered going this route on some of my past Triumph TR's. I was thinking of actually getting a clay impression of a successfully reshaped combustion chamber and 3D scanning it to cut electrode in graphite to burn in our die sinker EDM's. I would just mirror the shape on the opposite chambers. What kind of weld are you adding to the Ports? Is it a Cast Iron rod? (high nickel maintenance type). I was thinking these Ports could be EDM machined as well if so, but you haven't run into any issues over stressing and bowing the Heads much, which could lead to some cracking? I'm sure they are nicely welded, but Cast Iron is the worst to get right without having porosity or flux pockets. Have you seen them brazed up before? No special manifold mods or header needed either to carry that shorter runner height out further and have a transition to the larger opening ha? Thanks for the feedback
 

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I don't have any hard data to back it up, but subjectively the welded ports seem to extend and flatten the torque curve quite a bit compared to the engine I used to build with more conventional porting. I ship more engines than I install, so I've only gotten to drive one with this type of head work, but I was really pleased with how it pulled, considering it had SUs, a D cam and 10.0:1 CR. I'll be building some burlier ones this winter.

I'm not doing the welding myself, of course, so I'm not down into the details much. The first five heads we had done with iron rod of some specific sort (but I don't know what exactly), the last one used brass, which I think we'll use from now on. We had a fair number of voids in the first one, but not in areas that affected anything -- the only really critical part is the peak of the curve and just inside of the peak. It doesn't matter a bit what the port floor is shaped like outboard of that. It doesn't care if there's a manifold attached or not -- at least on a flow bench, which only tells you so much. We did get some warping on the first couple heads, but nothing that didn't machine out readily. The guy has gotten better with each head he's done.
 

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Discussion Starter #6
Very Interesting. Sounds like no compromise anywhere with your flattened torque curve, what's better than that. Let me ask one last question surrounding an Engine of this state of tune (10.0:1 CR + D Cam) because this is what I'll be working with,, What Intake Manifold would you advise using for SU's. I have a set of the older Individual Alloy ones without the cross tube I wanted to use. I only have one other candidate that's possible. A cast iron Intake with cross runner and a couple of those one piece Int/Ex units like on my 69 P1800S and another spare B20 from a 140. Exhaust Manifold or Header suggestion would be great to hear too!
I appreciate you replying to this thread.

Wayne Lee
67 220
69 P1800S
 

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Unless you're talking about a manifold I don't know about, the separate aluminum one does have a balance tube. It just doesn't have a plenum between the intake runners.

If that's what you have, I would use it, and I would cut the intake portion off the iron unified manifold and use the exhaust section and the stock dual heap pipes that go with it. There are no headers on the market that beat that setup.
 

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Individual alloy sounds a bit like the straight-through Weber manifolds? No connection on those.

Agree with Phil on the exhaust section of the castiron ones. A few strategic cuts can remove the preheat box and intakes, then a light bead with cast iron stick weld (high nickel) on the cut lines to seal and reinforce the scar. I had great results with that on my B18.
 

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Discussion Starter #9
Thanks Guy's! The Aluminum Manifold I have does have the balance tube, I had seen another non Volvo manifold set in the garage that confused things. Turns out I have a fourth type of manifold with the internal butterflies from a late carbed engine too. I have a set of new 44mm intake valves on the shelf. Is there any advantage to installing them where the 42mm ones are now while I'm putting in the hardened seats? I understand the exhaust side is the weak side that needs more attention, but would it do more harm than good in the process. The larger Ex. Valves are a worthwhile upgrade I had assumed anyways, is that the case? Great idea cutting the exhaust portion of the manifold out.
 

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Do not put in larger intake valves. It'll flow worse. Going a bit larger on the exhaust valves may help a bit, I don't really know.
 

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With my B20F motor/head, can I just put the earlier/thinner head gasket in to bump up the compression? It seems too easy....
 

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Even running premium? The earlier models with the higher compression ping as well? Changing out the head gasket doesn't seem like that big of a deal with a pushrod motor. You should see some of my motorcycle engines I've torn down and rebuilt.
 

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Even running premium? The earlier models with the higher compression ping as well? Changing out the head gasket doesn't seem like that big of a deal with a pushrod motor. You should see some of my motorcycle engines I've torn down and rebuilt.
Go for it but you won't notice any performance gain.

George Dill
 

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Hi Folks,

I seen a discussion on the various Head choices for Porting and Tuning somewhere , but I can't find where that was. I know the usual top choices being the B20E and F Heads because of their larger Ex. Valves, CR etc. Is there a Thread showing where the B20 Carbie Head falls in the food chain for being reworked with the Larger Ex.Valve etc., Port sizes being small enough for optimizing and such. I'm not looking for a Race prepped and flowed Head with epoxy filled floors etc. I have 2 builds on the table, with both having .030" over Mahle Pistons. No Forged Pistons or Big Bore conversion. The primary Engine in progress now has parameters of just getting the most of a 9.75 to 10:1 CR and a D-Cam. I'd like to utilize my Carb Heads with as much work as I can do shy of Flow Bench time.
Cheers,
Wayne
67 220
69 P1800S
In keeping with the OPs question(?)...

When switching from a thick headgasket to a thinner headgasket on a B18/20 keep in mind the other changes needed for a successful install.

The two (new) water pump O-rings must have a thickness that will allow proper sealing when the (new?) head bolts are torqued.

The valves must be adjusted at least twice - once before the initial startup and after the final head bolt torque following a few hours of operation. Same for the ignition timing.

Consider new spark plugs with an application appropriate for higher compression. Coolant hoses ok? Radiator need cleaned/flushed? Heater core? New coolant?

When installing the new(?) water pump and new water pump seal kit consider a new thermostat.

Given that Cpt. Ron has demonstrated expert mechanical/engineering skill this swap should be an easy do on a weekend. He has two assistants and one supervisor (SWMBO) so Sunday evening should find all toodlin' along the Bay!

George Dill
 
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