I'm starting to plan a rebuild on my 1974 225 daily driver, and I'm looking for suggestions for modest upgrades. The rebuild will be done by a shop. The budget for "extras" will be say $500-$1000 over and above the cost of a stock rebuild, depending on how much benefit I can get for the extra cost.

Goals in priority order:
1. Good drivability including when cold, mainly in town at lower RPM
2. Minimal emissions (to the extent practical)
3. Decent mileage

Things I don't care about:
- making a lot of noise (I prefer quiet)
- horsepower numbers (or any numbers for that matter)

The car:
- 1974 Dart Swinger with 1974 emissions equipment (OSAC is already bypassed)
- factory electronic ignition
- Holley 1945
- 904 trans to 8.25" sure grip with 2.71 gear ratio
- stock exhaust recently replaced
- stock suspension, recently rebuilt with offset UCA bushings for increased caster--plan to add front sway bar eventually
- factory 1976 manual disk brakes, recently installed
- power steering--plan to replace steering gear with Firm Feel or similar

I've looked at the build sheet thread. Aggressive Ted's build in post #4 looks intriguing, but being a novice I'm not sure which of the items are the most important. Based on my goals:

A. Do I want a cam other than stock? If the original cam is OK I'm inclined to reuse it, but I expect it will be worn.
B. Should I increase compression? If so, how much and by what means?
C. Is it worth porting the head, and if so what/where should be cut?
D. Is it worth upgrading the exhaust? Noise turns me off but efficiency makes me drool.
E. If I have to increase the bore 0.030", should I go with factory pistons or something else?
F. Is it worth doing anything with the distributor vacuum advance (i.e. re-curve)?
G. Should I look at a different carburetor?
H. What else should I consider that's not mentioned here?

Thanks, here's some eye candy for your trouble.

I think the main limiting feature of my 1974 truck engine is most likely the camshaft. I'd be inclined to work with a different camshaft to gain some power and probably not suffer a huge MPG decrease. I am too new to these engines to give any recommendations on what specs you'd want, but I'm pretty sure the camshaft is most of the reason a 1974 engine made 95hp from the factory and the 1963 engine made much more.

If I find myself pulling the engine for any reason such as a rear main seal job, I plan on installing a different camshaft.

The 74 stock cam is actually OK. If your budget is limited to a normal rebuild plus $500-$1000, then the first thing I would do is increase the exhaust size to 2 1/4 inches to a free flowing muffler and 2 inch after the muffler, and then spend the rest of the money on the head. I also like quiet cars, and the Walker Quiet Flow muffler is a great choice. SlantSixDan has posted the specific model number of Walker muffler to get. You can find it with a search.

The head and exhaust are the biggest obstacles to the efficiency and performance on a slant six. If you can afford it, have the machine shop do the extra work to give you a true 8:1 DYNAMIC conmpression ratio with your cam.

Increasing exhaust flow, head flow, and achieving true 8:1 dynamic compression are the three best modfications that can be done to the slant six.

On the head, porting at least, bigger valves if you can afford them. If the valves get too big you may need to go to oversize pistons to avoid shrouding the valves..

The 1963 motor appears to make more HP on paper because the rating system for engines changed in 1972. The 1974 camshaft is actually a better performance camshaft than is the 1963 camshaft.

That's good to know. Thanks for the information! Other places I'd read that the 74 cam had a lot of overlap to attempt to burn as much fuel as possible to meet emissions standards of the time. I will say that my /6 is a smooth operator though. The engine runs fine but just won't win any races.

If you already have the engine down,,

I would:

1) mill the block - head to get to 8 to 8.25 static compression, that will be low enough that you will run regular gas with out issue. There are many online compression calculators,, here is one,,,

https://www.rbracing-rsr.com/compstaticcalc.html

before the engine is disassembled measure the existing piston recession and cc the heads, you will need that as a base line to know how much to have cut.

2) The cam is likely worn, have it reground to the Oregon Cam RV-10,, Oregon can also re weld the fuel pump lobe if needed

3) does your rebuild include a new timing chain and gears and having the cam properly degree'd, it needs to.

4) You certainly want to spring for a new water pump, belts and hoses. Have the oil pump checked for wear on the rotor and housing, replace if needed.

5) I disagree with Reeds comment on adding OS valves, for a street driver, keep the stock valves, have them reground or get new, either way get a nice three angle valve job and a back cut on the intake, that will you what you need.

6) For the head, new valve guides, new valve springs, invest in a light 'bowl buster' port job.

7) upgrade to a 2 bbl super six carb and intake.

I would go with a HEI conversion and get Duster Idiot to put a recurve and proper vacuum advance can on the distributor. A couple of dollars spent on a set NKG plugs, a nice set of sparkplug wires and a coil upgrade can be money well spent.

9) the exhaust as Reed mentioned would also be a good idea, unless, like you say is is new and you are happy with it,,If the current exhaust is a keeper,, spend the $ for an electric fan, getting rid of the stock always rotating manual fan, reduces low speed noise. Be sure to check your radiator to make sure it is still serviceable and won't strand you due to a leak..

10) You mentioned pistons,, stock style Silvolite pistons would be fine,
if you need an over bore to clean up the cylinders, I would go with .030 over and spend a few extra dollars to get the moly coated rings,, they break in easy and will give you long service. if you want to do something a little extra, have the MS weight balance the piston - rod assemblies, get them within a gram of each other,, makes a smooth idling motor.

and one more, take a good look at the damper,, Damper Dudes and there are other shops also, can rebuild the stock damper to like new.

I like Reeds suggestions. Your preference is minimal emissions,quiet,good mileage,basically a nice running stocker on a budget then it would be hard to beat that combo...
There is both power and emissions advantages in a better piston and ring package,but you'll need a set of longer slant 198 Ci rods which are hard to get,so money may be better spent,but in my opinion they make a significant improvement so if you find a set I'd go for it,but good luck in the search!
Ditch the Mopar ignition and go GM HEI,its old tech but is compact,reliable and available,and works well in your application,pretty hard to beat bang for buck!
Cams...well everyone has a preference,for you,I'd stick with a stocker and spend the money in the head,bigger intake valve and a nice bowl job will give you fresh seats at the right height,improved flow and less valve overlap running with a stock cam for better emissions and idle. If you got a mild stock type regrind with faster than stock opening rates and modest lifts I'd say go for it,otherwise just a stock cam is just fine. Put a 2bbl on it and call it a job.

interesting viewpoints. LOVE your car! now my 2 cents.

port the heads. this is something you're not going to want to do later, and if you are looking for better performance, this is the first place to look. the stock ignition will tide you over for now, and is an easy upgrade later (definitely worthwhile, just not urgent). service the oil pump to factory specs, as detailed in the factory service manual. i would not get an aftermarket pump, they are all but impossible to service without pulling the engine, and the pump bypass valve is a maintenance item, due every 25K miles. DEFINITELY get a new timing set and chain.

one of the most overlooked items would be the pulleys. make sure they are all in good shape; "extra" money for the build becomes "necessary" money today when the thing starts that incessant squalling. a brand new top of the line belt with a worn out pulley equals SCREECH.

my 75 came with a resonator after the muffler. if you decide to enlarge the exhaust pipe, be aware that this WILL increase noise. adding the second "muffler" helps keep things down to a more civilized noise level.

This has been very helpful. To clarify my driving intent, I do not ever plan to do anything more aggressive than merge onto the highway or make a left turn through a gap in oncoming traffic. And I'll rarely make a trip longer than 30 miles, so there won't be much extended highway driving.

I called the guy that will be doing the machine work, and he suggested to skip the porting; in his opinion it's expensive and really beneficial only above 3000 RPM. For my goals his only recommendations are to increase the compression (i.e. deck the block, mill the head) and do a "multi-angle" valve job (I'm not sure if that would include DadTruck's "back cut"). On the other hand, several of you have suggested variations on porting or bowl work. So I'm hearing mixed opinions.

Regarding the cam, I'll probably stick with stock unless someone makes a strong case for the Oregon RV-10. What's the difference in terms of combustion?

In addition to the rebuild, you've given me several complementary upgrades to consider:

• Ignition: it sounds liike the GM HEI will improve combustion, which aligns with my goals. I will add it to the list of future upgrades to complement the rebuild.
• Exhaust: will a larger pipe help if I don't also enlarge the ports or change the manifold? I currently have a 2" pipe all the way back (there's no catalytic converter, just to be clear).
• Vacuum advance: I will ask Duster Idiot to recurve it if he's still in that business.
• Carb/intake: I'm inclined to stick with the stock intake and carb unless a Super Six will really benefit my driving style.
• Differential: the machinist suggested raising the rear differential ratio to ~3.25 to improve drivability, which is a suggestion I've seen around here before. I'll add that to the future upgrade list too.

If you truly are just going to use it as a daily driver, then skip the porting and oversize valves. A "three-angle valve job" will help flow a bit.

Staying with the stock intake and carb will save money. If you have a new 2 inch exhaust and you are keeping he single barrel, I would leave the exhaust alone for now as well.

I second the HEI recommendations and a DusterIdiot recurve.

I guess in your situation the extra effort should be spent getting your machinist to calculate how much should be milled off the head or decked off the block to get you to 8:1 dynamic compression. This is different than static compression.

If you have money left over, spend it on the ignition system upgrades and on better headlights.

The HEI swap is the best bang for the buck mod I have ever done on a Mopar. Make sure you buy a genuine GM module and not the Chinese knock-offs. They can be had all day for a couple bucks at the local junkyard, and you can snip the wires and connections while you're there. Make darn sure to use the heat transfer paste with them or they'll overheat in no time. Follow this up with a good quality cap, rotor, plugs, and wires. That alone made mine like new.

_________________
If it was easy, everybody would be doing it.

the reason I would have the cam reground is that I am assuming your 74 cam has some miles on it,, maybe a 100 K ?? If the motor is a 30 or 40K mile motor, yea then the cam is probably like new,, but then why rebuild the motor, why not do just a gasket change?

so,,, the cam including the fuel pump lobe and the lifters have some wear,

and if you are trying to bring the other engine components up to like new, why not the cam? I would not allow Oregon to pick the grind for me, but they have some experience doing slant six regrinds, I have not heard any complaints about them, and its not much money,, 75.00 or so plus shipping,, you can have your lifters reground or buy new for little $.

The RV-10 is a basic well thought out small cam. Do a search on this forum for RV-10 cam,, you will find much info,,

and concerning back-cutting valves,

considering your street driving tendencies I recommended staying with stock valves. The small stock valves will increase port velocity and improve fuel - air mixing at low engine RPM's and that is perfect for what you plan to do,, however stock valves from the 60's and 70's are not very efficient. A back-cut on the intake will improve intake side port flow,
I did that on the slant six head that is in the D150, flowed before and after, picked up 10% at initial valve openings.

here is an article that explains back cutting further

http://www.hotrod.com/articles/valve-angle/

I wouldn't assume the cam is worn. I have pulled cams from high mile motors that look perfectly fine. Normally, I agree that if you are rebuilding why not put in a new cam. However, the parameters of your project are a daily driver with an emphasis on emissions and efficiency with only $500-$1000 ove the cost of a stock rebuild. A reground cam, even form Oregon Cam grinders is about $150 with shipping for the cam. Lifters are an additional expense, even if you go the cheap route and get reground ones. So say you are out $150-$250 for a reground cam. That is a significant portion of your $500-$1000 budget.

The stock 1974 cam really isn't that bad if you increase compression. Sure, a better cam helps, but if you are shooting for a mild build with minimal cost and modifications, I would spend money on increasing the compression before I spent the money on a new cam. Absolutely degree the cam and do the extra effort to calculate your true dynamic compression ratio and mill the block or head accordingly.

I guess you should find out how much your machinist will charge to calculate the dynamic compression ratio. The DCR changes based on cam timing and profile, so you should really pick your cam before you have the machine work done to achieve your desired DCR.

that is why cam measuring equipment measures to the thousands,
eyes are typically accurate to the 1/8 of an inch.

Hmmm. Well, I guess have your machinist measure the lobes to know for sure. If the lobes are worn to the point of needing replacement, then I agree that you should just go straight to the Oregon Cam regrind.

I'm not assuming the cam is worn, but I'm expecting it. The engine has 84K miles on it, but has been run for extended periods with worn out or contaminated oil or not enough oil. (I've been getting gas in the oil and the valve cover was coated with a thick layer of black grit when I got the car 5K miles and 3 years ago.)

Anyway, if the cam is OK I'll reuse it. In fact I'm probably getting ahead of myself here. If the cylinders don't need to be bored out I may not do much beyond replacing the rings. In fact I should ask what else to replace or inspect along with the rings. Any gotchas beyond what any mechanic would know to look for?