400 engine rebuild | 2bbl -> 4bbl | more power | part questions

schwarzsurfer

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Hello together,

I plan to rebuild my '72 400 cui 2 bbl engine of my Newport in the future. But I don't just want to rebuild it, my thought was, if I already have this engine open I also can swap some parts to get little more hp out of it. I spend much time in reading and researching on what changes would make sense and what stuff would be not necessary or to expensive. This must not be a 500hp engine after it's done, I just want it to react quicker and more powerful than it is now.

I know, it is a low compression engine and most mods to get power out of this thing is raising the compression ratio. But I want as less machine work as possible. So my thought was to just take components from a 1972 400 cui 4 bbl HP engine, which makes 255 hp than 190 like mine at the moment. Maybe with some additional mods to rise it a little bit more.

I read the parts book and basically these are the changes:
- Crankshaft (forge instead of cast)
- Camshaft
- Valves/Springs (same size, but length or something was a little different)
- Intake Manifold (4 bbl instead of 2 bbl)
- Carb (4 bbl Thermoquad instead of 2 bbl Holley)
- Headers (different shape HP headers)

The block itself also has a different part number but I think they will interchange. Heads are the same. Pistons and rods are the same.

So I had to find out out that it is not thaaat easy to find all these parts from a 72 car... but I looked around a little bit and I could get:

- 73 4 bbl intake (with floor jets :( but they can be plugged)
- 452 Heads (could reuse my own, but these have hardened seats and are already ported)
- Forged Crank from a 383
- 9801 Thermoquad

So my questions are:

- Do plugged floor jets somehow influence the air flow negatively or is it like "you don't have a 600hp high end race engine - don't care about these floor jets"
- is the forged crank really necessary or will the cast one last? Would save me from changing the harmonic damper and the torque converter
- most questions are about the carb. I would like to go with a Thermoquad, because this was the original equipement. I read a lot and there are maaaaany versions of that thing. Originally 72 400 HP engine came with Thermoquad 6090s. This was a version with the large bore 1 1/2. The 9801 was the aftermarked version Carter offered in the late 70s or 80s, so would not be exactly the correct one, but I would be ok with it BUT it only has the smaller bore 1 3/8. Would it still work and perform good? Or should I look for another Thermoquad with the correct bore for BB application? Well, these engineers in the 70s might have had a reason why they had chosen the larger bore, hm? And the 9801 has an electric choke which would not fit the 73 intake manifold that has a hole for the thermo choke. Could I easily remove the electric choke and go with a thermo one with the correct linkage?

So you see I want to go mostly with stock components and I want to keep the original look of the engine. But I still might be ok with a Weiand 8008 or a Edelbrock performer intake or something like that. Some of them look nearly like a stock one.

I also think about adding KB240 pistons and a Hughes Whiplash Cam (maybe). I could mill the heads a bit, but I would not like to deck the block to raise compression. The engine has 7.5 or something in stock and with KB240 and milled heads maybe around 8.5 to 9 according to some internet sources. Still not high but it will be enough for my use case. This is a cruiser street car that just needs a little bit more punch while still looking stock.

Last question: Are these naive thoughts and you would rather suggest "stop buying old stuff, instead put on a 750 Edelbrock and so on and you are fine" or can my way be a way to go?

Thanks for reading and some input guys!

Marian

newport.jpg
 

70bigblockdodge

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A stock 4 bbl intake would be fine for what you want (I think), aluminum is lighter and runs cooler (more dense oxygen, thus more fuel to burn)
Cast crank will be okay to 500 hp and 6k rpm, no need to go look for forged crank, but if one were to happen by for free, sure why not.
Whiplash cam is okay might be a bit rough, but I do not know you taste, or tolerance.
2 bbl or 4 bbl pistons are about .120-.130 down in the bore. You need pistons at a minimum .080-.100 taller compression height, any KB pistons with as big as step/bump/dome you can get.
In the heads you need the bowl area cleaned out the guide profiled a bit and port match with intake manifold gasket, intake also. The valves should be backcut, remove ridge on port side of the valve head, or just buy aftermarket stainless one piece valves. Cheap insurance for a ~50 year old engine.
 

Tobias74

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thats what i did 400 block with stock pistons- 516 closed chamber heads but your better of with 440 source heads as it will be hard to find good 516 heads in Germany and i did use an Comp-cam 262 with new lifters and pushrods toped up with an edelbrock performer intake and 650 cfm AVS2 carb and C-Body HP exhaust manifolds that will wake your Newport up big time.
 

Davea Lux

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I would concur on going to the AVS carb, better performance and more reliable. Dual exhaust with the HP manifolds also a good idea, fuel in has to get back out. The forged steel crank is heavier and stronger, the cast crank is lighter but flexes more. Dampered valve springs will improve top end performance adding 2-4 degrees of cam advance will also help. The '69-'70 factory HP cam is also a good choice for a street engine. To get the advantage out of the engine upgrade, you also should use 3.23 gears if you do not already have them.

Dave
 
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CBODY67

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The main difference in the 2bbl and 4bbl 400s is in the camshaft, exhaust manifolds, and dual exhaust. The factory TQuad has way too much airflow potential for the stock engines, so something like an AVS would probably work better.

An inexpensive way to increase compression is to put on a set of closed chamber 1967 B/RB heads, with the exhausts upgraded to the 1.74 exhaust valves, if they didn't come with them. You'll need to bronze heilcoil the guides anyway, along with a valve job. Then use the Mopar Parf Porting Template kit to do the ports with.

A steel crank won't make any more power on the street, typically. Nor will the Clevite 77-style bearings the 400 4bbl came with, either. The factory roller chain timing set would bea good move for longevity and insurance (think well past 100K mile durability!! from my observations).

If you read about the 72 400 4bbl in the Dealer Order Guide, it becomes apparent that even with the low compression ratio, the other "guts" of the engine were still "Road Runner" in nature. Still the same HP engine the 383-400 HPs ever were, just with the lower compression ratio and other emissions-related changes.

Also plan on the 400 HO (looser) torque converter, too. Even with the stock 2.71 rear axle ratio. Although a 3.21 might work better at lower speeds.

Try not to "over-think" this deal, which can be easy to do. Just a normal, stock rebuild, with the earlier closed chamber heads (as mentioned), a comparable cam, HP exhaust manifolds and a good under-car exhaust system are the basics you'll need.

Enjoy!
CBODY67
 

Yeahrightgreer

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I just want it to react quicker and more powerful than it is now

If you want it to react “quicker” you should look into changing the converter while the motor is out. Find something that will match with your new cam. Along with potentially higher gears like another member said

Being in Germany I imagine you appreciate your highway driving so changing to 2.94 or maybe 3.23 would be good. Maybe even a custom gear ratio if you want

What’s the factory converter in these cars ? 11”?
 
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schwarzsurfer

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Hello all :)

Wow, thank you for your replies. Very good information for me so far. I will respond to some of the topics.

What’s the factory converter in these cars ? 11”?

According to the manual a 12" converter with 1875-2175 Stall RPM was installed in the factory. Would a smaller one be better? I think stall RPM should be little bit higher?

thats what i did 400 block with stock pistons- 516 closed chamber heads but your better of with 440 source heads as it will be hard to find good 516 heads in Germany and i did use an Comp-cam 262 with new lifters and pushrods toped up with an edelbrock performer intake and 650 cfm AVS2 carb and C-Body HP exhaust manifolds that will wake your Newport up big time.

I can only find 906 and the already ported 452 heads for sale at the moment. Cannot find some closed chamber heads. Should I save my money ont 452/906 and look for 915/516?

A stock 4 bbl intake would be fine for what you want (I think), aluminum is lighter and runs cooler (more dense oxygen, thus more fuel to burn)
Cast crank will be okay to 500 hp and 6k rpm, no need to go look for forged crank, but if one were to happen by for free, sure why not.
Whiplash cam is okay might be a bit rough, but I do not know you taste, or tolerance.
2 bbl or 4 bbl pistons are about .120-.130 down in the bore. You need pistons at a minimum .080-.100 taller compression height, any KB pistons with as big as step/bump/dome you can get.
In the heads you need the bowl area cleaned out the guide profiled a bit and port match with intake manifold gasket, intake also. The valves should be backcut, remove ridge on port side of the valve head, or just buy aftermarket stainless one piece valves. Cheap insurance for a ~50 year old engine.

Comp Cam might also be an idea or I look for a 383/400 HP cam. not sure yet. I do not really understand the part with "any KB pistons with as big as step/bump/dome you can get." So would the KB piston be good or not? As far as I read I thought it was taller than the stock one and so rise compression? Or did I get something wrong there?

The main difference in the 2bbl and 4bbl 400s is in the camshaft, exhaust manifolds, and dual exhaust. The factory TQuad has way too much airflow potential for the stock engines, so something like an AVS would probably work better.

An inexpensive way to increase compression is to put on a set of closed chamber 1967 B/RB heads, with the exhausts upgraded to the 1.74 exhaust valves, if they didn't come with them. You'll need to bronze heilcoil the guides anyway, along with a valve job. Then use the Mopar Parf Porting Template kit to do the ports with.

A steel crank won't make any more power on the street, typically. Nor will the Clevite 77-style bearings the 400 4bbl came with, either. The factory roller chain timing set would bea good move for longevity and insurance (think well past 100K mile durability!! from my observations).

If you read about the 72 400 4bbl in the Dealer Order Guide, it becomes apparent that even with the low compression ratio, the other "guts" of the engine were still "Road Runner" in nature. Still the same HP engine the 383-400 HPs ever were, just with the lower compression ratio and other emissions-related changes.

Also plan on the 400 HO (looser) torque converter, too. Even with the stock 2.71 rear axle ratio. Although a 3.21 might work better at lower speeds.

Try not to "over-think" this deal, which can be easy to do. Just a normal, stock rebuild, with the earlier closed chamber heads (as mentioned), a comparable cam, HP exhaust manifolds and a good under-car exhaust system are the basics you'll need.

Enjoy!
CBODY67

IF I would go for a Thermoquad it would even be better if it has the smaller bore? Because the large one has to much airflow? I might give it a try. Like the look of these things and read not to bad things about these carbs.

Did not think about the rear axle ratio. Not sure what I have at the moment. Need to check.

Dual exhaust already installed. Not a TTI or performance exhaust, but at least it shoud let through more exhaust gases than a stock exhaust.

Greetings
Marian

np2.jpg
 

fury fan

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On paper, I don't think the HP manifolds are really required for a mild 400 build.
The 365hp 426 wedge of '65 and 365hp 440 TNT of '66 both ran thru the standard log manifolds with 2" outlets (and the small-valve closed-chamber -516 heads).
Would those have breathed better with HP manifolds? Probably. But those manifolds were enough to support those power levels.

My point is - you appear to already have dual exh, which is the bigger part of that upgrade, unless the HPs are really cheap they probably aren't worth the $$ at your desired power level.

Main areas to improve a smog-era engine are, in order of increasing complexity/cost, are:
Ignition curve in the distributor, cam timing/valve timing events, and compression ratio.
 

CBODY67

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Back when I was in high school, an article appeared in CAR LIFE about how to determine rear wheel horsepower, via drag strip performance. With different correction factors for changes in weight, axle ratio, etc. So, I dug out all of my car magazine road tests and made note cards for the Chrysler Corp vehicles. All engines, all bodies, etc. Then, I'd correct those figures to "4000lbs, 3.23 rear axle ratio, H78-14 tires" (i.e., typical C-body items). This way, it gave me a constant reference point.

From that research, it became clear that the 413s and 426 Street Wedge motors were deficient in poiwer to the similar-power 440/350 engine. I looked at cam differences, but found no real defining items, there. Alwaya a mystery, UNTIL I happened to find a rh exhaust manifold for a 426 Street Wedge years later. When I saw the diameter of the manifold outlet, plus how it was built, THEN I came to the determination that the '66 440 manifold had a bigger outlet and better flow due to its shape.

With the 440/365 engine, the difference is the dual exhaust in concert with the dual snorkle air cleaner. With the same 256/260 cam. TWO normal C-body mufflers, nothing special in that area.

The smaller primaries of the spread-bore carbs are more about better fuel atomization (and lower exhaust emissions). The larger secondaries are the compensating factor to maintain WOT power. Having more even throttle bore sizes can make things easier for intake manifold configuration and getting more even flow to all cylinders. With the newer AVS2 carb, no real need for a spread-bore configuration as the annular discharge venturis do a better job of fuel atomization anyway.

IF you like the TQuad look, then opt for a Street Demon carb rather than a reman/rebuilt TQuad of undetermines history. Plus it will fit a normal intake, too.

In ANY engine air flow situation, there will be bottlenecks in the flow, somewhere. It could be a too-small carb, smaller ports in the intake manifold, smaller valves in the head, exhaust ports that "need work", exhaust manifolds, the under-car exhaust system, or any combination thereof. It's generally easier to free-up the post-cyl head items than those in front of the heads.

The other thing is that a bottleneck can depend upon the desired power level of the engine. Having a BIG carb on a BIG intake manifold might look good, but perform poorly if the rest of the system is not upgraded to use those things. Same with the cam, too.

ONE thing to remember, according to my machine shop operative is "Don't go to the bottom of the page to buy your parts." "Bottom of the page?" That's where the parts with the bigger numbers are. Best to air more toward the middle of the page! The parts which need other similar parts to make them work correctly.

CBODY67
 

fury fan

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From that research, it became clear that the 413s and 426 Street Wedge motors were deficient in poiwer to the similar-power 440/350 engine. I looked at cam differences, but found no real defining items, there. Alwaya a mystery, UNTIL I happened to find a rh exhaust manifold for a 426 Street Wedge years later. When I saw the diameter of the manifold outlet, plus how it was built, THEN I came to the determination that the '66 440 manifold had a bigger outlet and better flow due to its shape.
CBODY67
I'm in general agreement with most of what you said.

But according to the Govier code booklet I have, for C-body:
1965 - 2205535 is RH for 383, 413 Chrysler 383, 413 and 426 in Ply and Dodge C-body.
1966 - 2532464 is RH for '66-69 361, 383-2, and 440lp in a C-body.
(I do not see a specific listing for '66 440/365hp, so I've always believed it wore the same manifold as the 350hp engine of that year)

I just looked at a pair of them (the -535 and the -464), and the outlets are both 2", and both seem same cross-section and general shape, except the 440 manifold extends perhaps 2" closer to the ground (which doesn't seem to be much of an effect?).

Are the Govier #s wrong? Or are you maybe referring to the B-body 426SW manifolds, which are a rear-dump design?
 

schwarzsurfer

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If I take a Street demon can I put the linkage of my stock 2bbl holley on that carb? Or what Else do I need to make it compatible?
Greetings
Marian
 

lemondana

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I vote for putting your electric choke Thermoquad on the 73 stock intake, using the carbs electric choke. Most people on here have a dislike for Thermoquads, I don't know why-they are better than any Edelbrock carb. As far as those on here saying the large TQ has to much airflow for a 400. What are you thinking-Chrysler put these on the 400's when new, hell they even put the 850 on the early 360 4 barrel motors.
I guess the guys on here that don't like them have never had a good one. I have a NOS 1978 440 pickup Thermoquad on my 71 Polara in my avatar on the 440. I wouldn't trade it for any other carb! I've used many of them, with very few problems
 

CBODY67

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When I was doing my "power research" in the later '60s, it was well BEFORE anybody was concerned about casting numbers. You went by how things looked, PLUS the manifold-to-head pipe gasket diameters (in the Walkeer Exhaust paper catalog).

On that 426SW rear-exit rh-side exhaust manifold, the outlet diameter was not much bigger, if any, than a small block Chevy manifold. Yet the 426SW was ovefr 75cid larger. I also know that the manifolds on our '66 Newport 383 2bbl had a physically larger cross-section, too.

In the '65-era Imperial road tests, the acceleration numbers looked decent, but when the correction factors were applied, FEW of them were putting 200 horsepower to the ground. Which got me to thinking about "Why" that was. We knew that the new 440 was an advance in several areas, plus the then-new 256/260 cam. Which was termed "standard cam" when then 440/375 became the "HP Cam". When the 256/260 cam replaced the 252/252 cam, power output jumped with no other changes to the motor.

Perhaps the torque converters were a bit too tight? Which is possible. Seems like the exhaust systems were bent that well, as they were usually 2.0" pipes all the way to the back?

Consider, too, that the '65 C-body platform was the FIRST platform to have ample room under the hood for better service accessibility, with the Imperial moving to a version of it in '67. Those frame rail width issues influenced LOTS of things in powertrain designs!

Just some thoughts,
CBODY67
 

CBODY67

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I started out to be a big fan ofd TQuads, especially when compareed to Rochester QJets! The whole deal with the smaller-primary venturi sizing was about getting a stronger signal through the venturi for better fual atomization, with more fuel being converted into power. The larger secondaries would only open as needed for the engine's needs.

In the orientation of "upgrade" with factory-oriented parts, I got a Torker 383 intake and the allegedly-matched 9801 TQuad for my '67 Newport 383 4bbl. Even if performance didn't improve by much, all of the atributes of the TQuad did not appear. Throttle response didn't really improve, nor did highway cruise economy. A very under-whelming situation.

The TQuad was Carter's "last stand", so to speak. The carbs were maligned for their differences, especially the phenolic fuel bowl that would crack/leak. As people took it in stride that in order to get the air horn off of a QJet, it took a hammer and punch!

Enjoy!
CBODY67
 

Gerald Morris

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I started out to be a big fan ofd TQuads, especially when compareed to Rochester QJets! ....

As people took it in stride that in order to get the air horn off of a QJet, it took a hammer and punch!

Enjoy!
CBODY67

I've got a TQuad from an old Moparian 3 yrs ago. No great stampede from folks to grab it off me. I'm glad I paid nothing for it. I'm happy with the rebuilt Stromberg Mathilda is running.

This thread interests me greatly, as I too have a 400 (77 vintage) and now have 3 915 heads to choose a pair out of for a good valve job. I have a forged crank from another 383, just to have the internally balanced quality 383s have. My aim always has been to rebuild that 400 as much like a mid 1960s 383 as possible, with some improvements consistent with an engine which will develop plenty low rpm torque and play well with my 2:76 rear end.

Having upgraded to the dual exhaust this summer gave Tilly about a +1 mpg improvement and a little more punch when rolling. God-willing, I'll be able to get the 400 going in the next 18 months.... I probably will use the 915s first on Tilly's current 383. the head gaskets are shot, and I hate removing heads without something better to put in their place as well as the gaskets!

I'll post folks when/if this project starts coming together. At least I've got a good deal of the iron I want for this project, though the cam/lifters will be a particularly interesting bit.

Happy Moparing All!
 

schwarzsurfer

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Hi again,

what type of exhaust manifold can I use? Do they have to be C-Body 383 manifolds or would also others work, e.g. from a B-Body? Are they shorter or have a different shape or something?

EXH73BB-PR-1.jpg


I think the C-Body things had this heat metal shield on it?

01111_dj7qtyifkfi_600x450-jpg.jpg


But if I don't care about it, could I use others as well? I tried to figure out which casting numbers fit a 400 C-Body, but it is not that easy to understand. Some of the manifolds fit 383/440, some only 383 or 440, don't know why.

Greetings
Marian
 

CBODY67

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In general, the LH heat stove models were for '70 and later and their hot-air snorkle air cleaners' emissions regulations.

LH sides will also have to have clearance for power brake boosters and steerimg linkages, which can vary from body platform to platform and model year.

Other than that, it's the exit angle, location, AND clocking of the pipe flange. Heat riser is a secondary consideration, possibly.

Each manifold should have both a casting number and casting date (related to model year use). Plus "RH" or "LH"?

Hope this might help,
CBODY67
 

schwarzsurfer

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In general, the LH heat stove models were for '70 and later and their hot-air snorkle air cleaners' emissions regulations.

LH sides will also have to have clearance for power brake boosters and steerimg linkages, which can vary from body platform to platform and model year.

Other than that, it's the exit angle, location, AND clocking of the pipe flange. Heat riser is a secondary consideration, possibly.

Each manifold should have both a casting number and casting date (related to model year use). Plus "RH" or "LH"?

Hope this might help,
CBODY67

Thanks, this helps. I did a little research and cross checked manuals and so on and there seem to be manifolds that were used on C and B bodys and some were B or C-Body only:

2951217 2951216 LH 1970-71 C 383-4 HP
2899968 2899879 RH 1970-71 BCS 383 440 HP

2863408 2863409 LH 1968-69 C 383-4 440 HP
2806896 2806900 RH 1968-69 BC 383 440 HP

2843991 2843992 LH 1968-69 B 383-4 440 HP

3751069 3751071 RH 1973 B 400 440 HP
3751067 3751068 LH 1973-74 B 400 440 HP

But I think these should work for me.

Marian
 
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