To dyno or not to dyno?

[Ant]

I have put together what I hope would be a nice 318(323) for what I wanna call the "the peppy grocery getter project", which is my four door 73 Dart. Awhile ago I wanted to dyno the motor to prove someone wrong, but they did not want to put up the money for the bet and backed off. So at that point I felt no reason to dyno the motor, but as time goes by, my curiosity keep growing. To break-in and tune the engine on the dyno it's gonna cost around $900 usd, but I have heard that it's good way to get the motor right before it goes in the car, and one guy has told me that he dynos pretty most motors he puts together for his customers. My engine is not going to be a HP monster, so should I do it for the curiosity and piece of mind?

Motor specs:
Block: 72-73 LA 318 bored .030 over (323 cu.in.).
Pistons: Cast replacement .030" overbore.(They should be)
CR Ratio: 8.6:1 just about when I measured. Asking the wrong calculator might be higher.
Crank: Stock cast.
Cam: Hughes SEH1620AL-12, which has been recommended a few times on the forums. The specs are 112°LSA, Lift: .330"(.495") intake, .335"(.503") exhaust, Duration @. 050" 216° in, 220° ext. Also installed with a double roller timing chain set.
Lifters: Whatever dlat tappet hydraulic Johnson lifters Hughes recommended.(I forgot)
Heads: 675 casting, ported with bowl blend, guide boss trimmed and narrowed, all casting slag and ugliness removed, throat cleaned up, sharp edges removed from short side, gasket matched to steel gasket and pushrod pinch is blended. It was so much work to get the intake ports nice at least the exhaust ports were quick and easy.
Valve springs: Hughes 1110P with dampers and installed at the recommended height, or at least close enough.
Rockers: Stock with some grinding for spring clearance.
Intake: Edelbrock Performer part# 2176. I did some touching up here and there just to reduce the factory ugliness.
Carb: Edelbrock AVS 650cfm
Headers: Duog's D453 long tube headers.
Ignition: Pretty much stock mopar electronic style with low resistance 8.5mm plug wires and an Accel 40,000v coil.

I did a little more work to the heads than shown, I wanted everything to to be as close to the same as possible and hopefully better optimized.

 

[GTX JOHN]

My son always does only in hsi Stock and Superstock
cars. It is a great way to break in our temperamental
proprietary ring combination.

For our Bracket and Street Strip car we do NOT,
as we can find better ways to spend or racing
money.

I would not myself with your combination. It will
be not that hard to break in and a trip to the Strip
will give you a pretty close idea of you HP by your
MPH after tuning and working with it.

 

[GTX JOHN]

My guess from racing 318 engines in stock for 50 years
and dyno work would be 330 to 340 HP. the compression
does not help (especially if they are down in the hole 50 or so)
and I do run much more duration. I am able to get 400 HP
plus on that size and compression engine in Stock Class,
but my camshafts are way bigger and I have a lot of
development time over the years.

 

[middleagecrisis]

I've never dyno'd any of the engines I've built. Not because I wouldn't want too, but because I'd rather spend the money on more parts. A dedicated race engine, such as the above-mentioned Stock and Superstock cars where every last horsepower matters, most definitely, but not any motor I've ever put together. If you have the extra funds though, go for it.

 

[rumblefish360]

I’m with GTX John on this. Nice combo to run 87 octane and a camshaft small enough to be a very pleasant driver with enough behind it to make that number he said.

Enjoy that “Peppy Grocery Getter.”
I would.

 

[33IMP]

MY opinion only:
It depends on budget, equipment, and goals for the combination.
If you can't afford it, or justify the expense, no
If your building a flat tappet engine for street/strip, and worried about cam breakin, then yes.
Just wanna check for oil leaks, on a factory roller motor? Nope.
Wanna tune a carbed or fuel injected engine for max power, proper a/f ratio, then yep.
Only you can make that decision, depending on your needs and abilities.
I didn't dyno my 406, I will dyno my 522, and 540.
It would have to be one WILD 318 for me to pay to dyno it!

 

[junkyardhero]

i made 330 on a 9.5:1 "328" and .450"/.455" 268/272 110LSA with a 750 topping it off and breathed on 302's

so i'd say you're in the ballpark of 330~350 depending on how high want to spin it.

unless it was going into something that was a bear to install and you wanted to 100% nail the cam break in and check for leaks i wouldn't bother putting it on the pump.

 

[Murray]

I plan to keep my car for a long, long time. And in that time someone will ask how much HP? To answer that question, and for my own curiosity, I dynoed mine. I hate amateurs wild estimates of their HP.

 

[Ant]

I think all of you are making some good points. Getting the engine dialed in with some numbers would be cool, but I will probably find out enough based on it's 1/4 mile times. I would like to get another radiator and AC hoses, I should just save the cash for that.

MY opinion only:
It depends on budget, equipment, and goals for the combination.
If you can't afford it, or justify the expense, no
If your building a flat tappet engine for street/strip, and worried about cam breakin, then yes.
Just wanna check for oil leaks, on a factory roller motor? Nope.
Wanna tune a carbed or fuel injected engine for max power, proper a/f ratio, then yep.
Only you can make that decision, depending on your needs and abilities.
I didn't dyno my 406, I will dyno my 522, and 540.
It would have to be one WILD 318 for me to pay to dyno it!

Also very valid, I do want the cam and lifters to break in fine, but it's not a wild enough enough that may justify the cost. I do want to put together something wild someday, but it's not gonna be in the 318 cubic inch range.

Nice combo to run 87 octane and a camshaft small enough to be a very pleasant driver with enough behind it to make that number he said.

That was pretty much the goal, when I saw the price of gas go up, lol. Also, at around 3200lbs the car should feel plenty quick for a go anywhere driver.

 

[TT5.9mag]

Dyno just for a number? Not only no but hell no.
Dyno for tuning and break in? Absolutely yes and well worth it. That goes for race engines, street engines, and everything in between.

 

[TT5.9mag]

Go to a car show and see how many of those cars run like absolute garbage. Tuning is a severely lacking aspect of our community. If you know how to tune a carb (any carb) and are confident in your ability to set a curve in the distributor, AND are willing to take the time to do comparative runs to quantify the results, then the money could be spent other places. If you want the reassurance that it’s broken in, runs good, doesn’t leak, and has a spot on tune up (depending on who’s dyno you take it to, results may vary) and you’re not confident in your abilities then the $900 is chump change, dyno it.

 

[TT5.9mag]

And I think I’ll have to disagree with some of the above comments, a 323 with 8.6:1 comp and a 216@050 cam with cleaned up heads is not a 1hp/cu in engine. I don’t think it’ll break 300, and honestly I think it’ll be down pretty far below that. But I’m a cynical bastard. Doesn’t mean it won’t run good though.

 

[rumblefish360]

And I think I’ll have to disagree with some of the above comments, a 323 with 8.6:1 comp and a 216@050 cam with cleaned up heads is not a 1hp/cu in engine. I don’t think it’ll break 300, and honestly I think it’ll be down pretty far below that. But I’m a cynical bastard. Doesn’t mean it won’t run good though.

Cynical bastard? LMAO! Better than overly optimistic!
It’ll make 300+, IMO. I think @Ant has a nice daily driver with a little umph to be a little fun.

Ant, if you have the future funds for any upgrade, do an OD trans. The deeper first gear will help that get up and go while the OD will have it nice and relaxed rpm wise at Hwy speeds.
3.55’s would be about optimal.

 

[TT5.9mag]

Cynical bastard? LMAO! Better than overly optimistic!
It’ll make 300+, IMO. I think @Ant has a nice daily driver with a little umph to be a little fun.

Ant, if you have the future funds for any upgrade, do an OD trans. The deeper first gear will help that get up and go while the OD will have it nice and relaxed rpm wise at Hwy speeds.
3.55’s would be about optimal.

Glad you laughed at that.

 

[273]

The final hp would depend on how well the port job turned out, I'd say 300 hp at least, 350 hp if they got the flow.

 

[Ant]

I think I can get away with tuning on the road.

Ant, if you have the future funds for any upgrade, do an OD trans. The deeper first gear will help that get up and go while the OD will have it nice and relaxed rpm wise at Hwy speeds.
3.55’s would be about optimal.

The future upgrade funds might go to a new rear axle if my limit slip diff experiment fails with the 7.25 axle lol.

 

[Newbomb Turk]

I would care what the final number is, but if the dyno operator is worth a crap you’ll get off the dyno with the correct timing curve.

That’s at minimum.

 

[Bewy]

You have spent a lot of money getting this far. I would dyno the engine to ensure jetting, timing etc is correct, & if not you can correct it, to get the max out of the engine parts.

 

[Ant]

The final hp would depend on how well the port job turned out, I'd say 300 hp at least, 350 hp if they got the flow.

I don't know if the heads will support past 350 hp with a decent porting job. Also, is it me, or does it seem like the Hughes cams trade duration with more lift to "take advantage of chryslers larger .904" dia lifter" or something like that?

 

[273]

I don't know if the heads will support past 350 hp with a decent porting job. Also, is it me, or does it seem like the Hughes cams trade duration with more lift to "take advantage of chryslers larger .904" dia lifter" or something like that?

I wouldn't say trades duration for lift, but I get your point, yes it's a fast ramp cam that takes advantage of the .904" lifter should work very well.

 

[crackedback]

With 500ish lift, it should make 300+

 

[TT5.9mag]

With 500ish lift, it should make 300+

Maybe if you and I argue about how much power it could make we can get @Ant to actually dyno it.

 

[TT5.9mag]

Awhile ago I wanted to dyno the motor to prove someone wrong, but they did not want to put up the money for the bet and backed off.

Can’t believe we all looked passed this. What was the original bet?

 

[PRH]

My curiosity would be about how high the engine would rev with the fast rate Hyd cam.
Would it easily go higher than the natural peak of the combo, or would the rpm peak be limited by some unhappiness in the valve train?

35 years ago I threw together a 318 with some parts that were laying around the shop I was working at.
I don’t recall which heads, but some generic open chamber 318 heads(probably 675’s) that I went thru and did some cursory whittling on, used 340 cam, performer, 1-5/8” headers, tested a few carbs.
It didn’t quite make 300hp, but got close.
The stock 340 cam easily went past 6000 without protest though.

I’m sure with a “better” cam and some head milling there was another 20hp up for grabs.

 

[496 polara]

IF you are worried about cam break in and don mind the cost then go for it. HP numbers are a double edged sword,if you like them they are bragging rights. If not it can leave a bitter taste.
Tuning can be done later on a chassis dyno a lot cheaper.