1970 Dodge Dart 318 upgrades

[nm9stheham]

1968 Service Manual states 9.2:1 compression for my Coronet and I measured how far down in the hole they were (100% original car) and they were just about 0.028"/0.030" with a steel gasket. I think that would get you very close to 9.2. The Sealed Power Pistons put you a disgusting 0.090" in the hole.

If it really was that high in the hole, then you would indeed be up in that SCR range with 675 type heads. I have not ever heard of a stock piston at that height in the bore. Very interesting, and thanks for the data point; I'll see if I can find anything else that supports that. (I won't just run with the FSM CR numbers however... they have proved to be 'optimistic' over and over...)

For sure, it was/is an LA and not a Poly?

 

[Jim Kueneman]

If it really was that high in the hole, then you would indeed be up in that SCR range with 675 type heads. I have not ever heard of a stock piston at that height in the bore. Very interesting, and thanks for the data point; I'll see if I can find anything else that supports that. (I won't just run with the FSM CR numbers however... they have proved to be 'optimistic' over and over...)

For sure, it was/is an LA and not a Poly?

LA, I messed up and did not have the machine shop save the pistons!!

 

[Jim Kueneman]

Did the same thing but stroked the stock 318 with the cam and then my Duster build. My Coronet would be MUCH for fun to drive for sure.......

Remember this is with a stock restrictive exhaust/small valves and 2 barrel carb so the top end has more than these plots show if you let it breath better.

 

[Jim Kueneman]

I did notice the '73 318 I pulled down for the Duster had flat top pistons and were down in the hole a long way. My '68 Coronet pistons did have valve reliefs in them. The difference is OBVIOUS in the photos...

And the Coronet did (does) have 675 Heads.

 

[nm9stheham]

1968 Service Manual states 9.2:1 compression for my Coronet and I measured how far down in the hole they were (100% original car) and they were just about 0.028"/0.030" with a steel gasket. I think that would get you very close to 9.2. The Sealed Power Pistons put you a disgusting 0.090" in the hole.

BTW, I ran SCR with a .028" in the hole piston with 4 cc's of eyebrow volume, and a .023" thick head gasket, and typical 675 head chamber volume of 68 cc's; it comes up 8.9:1.

To support your info, I just looked up some piston info in the '69 and '73 FSM. They list 'piston length'.... top to bottom of skirt. For '69, it is 3.21" , and for '73, it is 3.47" . So, clearly there was a production change in the pistons within that time frame. Sadly, they don't list compression height, or give any reliable pix. Some of the 273 pistons tops were only a few thousandths in the hole at that time (I have a set), so your finding seems consistent with the very early engines being better set up for CR.

Thanks for the info... yeah, look at those pix! Very early 318 values just shot up LOL...

 

[Wyrmrider]

The early engines were but the head cc's you see are minimums as are the compression distances down the hole are for a minimum deck block
piston heights are usually correct but aftermarket builder pistons are "destroked" usually .015 to keep compression same with additional cu in form overbore- at least that's the excuse
bottom line you have to cc every head and measure every compression distance
BTW the other option for low end is a blower

 

[Wyrmrider]

I do not see any reason for a comp .842 Dual energy for a mopar The dual energy series cheaps out and uses the same lobes for intake and exhaust
the .842 XE series has separate intake and exhaust lobe profiles
example at another duration 275 than we are talking about in this thread 265 but same idea
.488/491 274/286 230/236 143/144 110lca/106icl 31 63 77 29 (60) 1800,6000 XE274H .842 not HL 2300 stall universal
.462/482 275/284 219/235 125/139 110lca/106icl 32 64 76 28 (60) 2000-6000 275DEH Dual Energy .842 universal one size fits all
if you do already have the DEH it looks like a candidate for 1.6 rockers on the intakes- but get your rocker geometry right first- spend the money there first

but IMHO there are better choices if you do not have a cam already and you are sure that 274-275 is the correct duration
.494/513 271/279 226/234 110/106 1800-6200 2400 stall Lunati Voodoo catalog grind shorter intake more dynamic compression
.518/543 271/281 224/234 112/108 Howard catalog grind
525 .350 273 226 147 HM226350 Howard intake master pick your exhaust and centerlines based on intake and exhaust and other build features
.525/525 275/287 231/237 149/ 110 comp XE275HL 2000-6000 smallest comp .904 HL grind unfortunately no 265 version
.477/477 275/275 225/225 108 2000-5500 2000 stall Lunati Street Master (SM) a budget cam
.529 0.353 275 228 148 HM2283525 Howard lobe for intake
.525 .350 275 231 149 Bullet HC 275/350 Bullet lobe for intake
.514/536 276/284 231/239 108/102 2800-6500 Lunati LA 9.5 3.90 Lunati catalog

 

[rumblefish360]

I do not see any reason for a comp .842 Dual energy for a mopar The dual energy series cheaps out

Cheap out! LMAO!
1: There is no reason to run a specific .904 lobe on a low performance intended cam. Ever.

2: .842 lifters can handle very aggressive ramp rates.

3: You would never need to explore an aggressive .842 cam lift. There already are tens of thousands of logged dyno runs on every engine out there now.
[/QUOTE]

but get your rocker geometry right first- spend the money there

Good advice.

 

[waspaid]

Hey guys. In response to 318 hop ups. I can only speak from one I have drag racing. It's a 1985 Plymouth Gran Fury. I pulled the old 318 that had a rod knocking. Had a 1970 318 block that had been rebuilt a few years ago. Stock piston size (3.91). They were 8.8-1 compression pistons. Put a 474 lift Mopar Performance Cam with cleaned up 74 360 heads. .027 thickness head gaskets. Compression now at about 9.0-1. Nothing special to the heads. Plaining them and chambers cleaned and all the ports cleaned out. Air Gap intake, 650 double pump holley, Headers, 3 inch exhaust, MP Chrome box, MP distributer, Champion plugs. It has a 904 auto with 4500 stall. Running 4.56 gears with full spool. In the 1/8 mile she has a 1.88 sixty foot times and runs 8.76 in the 1/8 mile. Not too shabby for 1 3500 lb. car. Oh, it also has it's full interior as well. Bench front seat and all. I had accumulated these parts over the years and really only had to buy the cam, converter and gears and spool along with distributor, chrome box and plugs. I don't count plugs as you need 'em for everything anyway. Even the 8 3/4 rear I had came out of a B-body years ago. Thing is if new people to our hobby can make contacts they can get some really good stuff if they look hard enough. This engine runs with 5.0 Mustangs easy. People are surprised it's a 318.

 

[Jim Kueneman]

Hey guys. In response to 318 hop ups. I can only speak from one I have drag racing. It's a 1985 Plymouth Gran Fury. I pulled the old 318 that had a rod knocking. Had a 1970 318 block that had been rebuilt a few years ago. Stock piston size (3.91). They were 8.8-1 compression pistons. Put a 474 lift Mopar Performance Cam with cleaned up 74 360 heads. .027 thickness head gaskets. Compression now at about 9.0-1. Nothing special to the heads. Plaining them and chambers cleaned and all the ports cleaned out. Air Gap intake, 650 double pump holley, Headers, 3 inch exhaust, MP Chrome box, MP distributer, Champion plugs. It has a 904 auto with 4500 stall. Running 4.56 gears with full spool. In the 1/8 mile she has a 1.88 sixty foot times and runs 8.76 in the 1/8 mile. Not too shabby for 1 3500 lb. car. Oh, it also has it's full interior as well. Bench front seat and all. I had accumulated these parts over the years and really only had to buy the cam, converter and gears and spool along with distributor, chrome box and plugs. I don't count plugs as you need 'em for everything anyway. Even the 8 3/4 rear I had came out of a B-body years ago. Thing is if new people to our hobby can make contacts they can get some really good stuff if they look hard enough. This engine runs with 5.0 Mustangs easy. People are surprised it's a 318.

4.56 gears ..... I have to drive 30 miles at 75 mph to get to town... that would not work for me! That is the thing that can make a small engine feel fast, get the torque multiplication through the gearing! I have 2.91's in my Coronet so I can cruise the freeway at 75 mph at less than 3000 RPM... modern overdrive transmission has its advantages!

 

[AJ/FormS]

Bottom line here: Don't go too big with a cam. Stock 318 2 barrel cars can't stand too much of a increase without adding a 4 barrel, dual exhaust, converter, and rear gears. The cam you choose might not be that much bigger than the stock one and will be a lot of extra expense for not much gain. I have the same combination as you have. I already have duals and I switched the gears to a 3:23. It runs good and I get almost 20mpg/hwy. The next will be a 4 barrel and intake. I may stop there.

This is exactly right. The stock cam works because it keeps the DCr up, and starts making torque right off idle, so the 1850stall TC starts right into performance.

 

[Wyrmrider]

The Dual energy makes no sense for a mopar- I did say the XE was the better of less desirable choices the 268 is an old Harold Berkshire lobe ca 1977
".842 lifters can handle very aggressive ramp rates"- but the same ramp rate gives more acceleration with a .904 lifter- that's what comp says
the Comp Purple Plus has the same ramps as the .842 Nostalgia Plus series and the XE-HL Mopar grinds are very similar to the .842 HFI
but on the mopar lifter you can get more area or you can run one size shorter for increased Dynamic compression
"Never give a sucker an even break" applies to chevies
Actually on low compression motors a mopar makes the most sense- high rpm can hide a chevy cam
I do not like to leave torque on the table in a "low performance" build- that's wehre it's needed the most

 

[Richard Sweet]

Wyrmrider,
You may know what you're talking about but I wish what you say was easier to understand for us less knowledgeable folks.
Thanks for trying to share though.

 

[Jim Kueneman]

I do not see any reason for a comp .842 Dual energy for a mopar The dual energy series cheaps out and uses the same lobes for intake and exhaust
the .842 XE series has separate intake and exhaust lobe profiles
example at another duration 275 than we are talking about in this thread 265 but same idea
.488/491 274/286 230/236 143/144 110lca/106icl 31 63 77 29 (60) 1800,6000 XE274H .842 not HL 2300 stall universal
.462/482 275/284 219/235 125/139 110lca/106icl 32 64 76 28 (60) 2000-6000 275DEH Dual Energy .842 universal one size fits all
if you do already have the DEH it looks like a candidate for 1.6 rockers on the intakes- but get your rocker geometry right first- spend the money there first

but IMHO there are better choices if you do not have a cam already and you are sure that 274-275 is the correct duration
.494/513 271/279 226/234 110/106 1800-6200 2400 stall Lunati Voodoo catalog grind shorter intake more dynamic compression
.518/543 271/281 224/234 112/108 Howard catalog grind
525 .350 273 226 147 HM226350 Howard intake master pick your exhaust and centerlines based on intake and exhaust and other build features
.525/525 275/287 231/237 149/ 110 comp XE275HL 2000-6000 smallest comp .904 HL grind unfortunately no 265 version
.477/477 275/275 225/225 108 2000-5500 2000 stall Lunati Street Master (SM) a budget cam
.529 0.353 275 228 148 HM2283525 Howard lobe for intake
.525 .350 275 231 149 Bullet HC 275/350 Bullet lobe for intake
.514/536 276/284 231/239 108/102 2800-6500 Lunati LA 9.5 3.90 Lunati catalog

Put the Voodoo cam in the simulator and ran it on a stock 318 with the Comp Cam. It appears to be a better cam once you get some RPM (higher stall TC and lower gearing) but like we said it depends on what your plans for the car are. For me who rarely ever gets above 3500 RPM while driving I want all the torque I can make low for my high gearing. The Comp Cam still seems to be the better choice for that as the peak torque and peak HP occur within my normal band of driving RPM. If I had gearing such I was in the 4500 RPM band much of the time the Voodoo is better and the Comp Cam is running out of steam quickly after 4000 RPM

 

[AJ/FormS]

Methinks something is wrong with those curves. OOps nevermind, I had an idiot moment. OOps no, there is something not right about them.

Methinks the labels on the Comp and the oem have been switched

 

[Jim Kueneman]

Methinks something is wrong with those curves. OOps nevermind, I had an idiot moment. OOps no, there is something not right about them.

Methinks the labels on the Comp and the oem have been switched

The OEM is a guess, this is the only place I have found any information about the stock cam.....

318 Engine Specifications

 

[Wyrmrider]

Try a smaller voodoo with a 1.6 rocker on the intake
which would be best for a low compression build
351 181 318 stock

404 264 180 72 ABCD 318

458 264 202 120

459 268 212 127

356 269 194 68ABDC

420 270 204 edelbrock

455 272 216 Summit

441 276 218 Summit

410 278 203 stock 360

429 279 210 79 ABDC 340 Intake

430 284 212 Direct Connection 260

434 284 206 74 ABDC Stock 440 Intake

447 302 214

488 308 234

 

[nm9stheham]

The OEM is a guess, this is the only place I have found any information about the stock cam.....

318 Engine Specifications

Looks the same as in the '68 FSM for lift and overall durations. But what has been done (by you or the program) to simulate the slow ramps to .050" lift? It won't be nearly as fast as the Voodoo or XE lift rates. I'd expect the .050" lift durations to be shorter than the total durations by somewhere in the 60-65 degree range, if not a bit more.

BTW, if you enter the numbers in a different way, the stock LSA is 109, ICL is 110, and the stock cam's ground in advance is -1 degrees (1 degree retarded).... if I computed it right.

And yes, the 703 VooDoo is not where I would tend to go anyway for the stock 318. Try the 700 or 701 level. The Comp XE you shows is very much like the 701 VooDoo, but the Voodoo's 112 LSA will make it a bit different than the Comp.

It is indeed not intuitive that the Comp would have the big torque drop off compared to the stock cam... that is the source of questions. One difference that is readily apparent is the stock cam's mildly -1 degree retarded timing relative to the Comp's ground in advance of +4 degrees. That would indeed move the torque peak lower, but not drop the torque at high RPM like is shown. That leads to ask about the model of the 318 head+intake flow. That is a big deal here; if it flattens out at at .400" lift or lower, then the higher Comp and Voodoo lifts won't do anything. That needs to be examined/explored in the modeling.

 

[Wyrmrider]

posted from 318 link from Jim- above
Mopar timing is by a unique method but close to @.008 similar to what Engle uses
the degrees I posted are at SAE Method- .006 at the valve or .004 at the lifter except I did not post the 318 seat timing just the .050
the seat timing can be 278 @.004 and has really long closing ramps which hurts dynamic compression
318 VALVE TIMING (in Degrees) about the only thing MOPAR duration and timing is good for is to compare with other Direct Connection and Factory cams
Intake Opens (BTC) 10
Intake Closes (ABC) 50
Exhaust Opens (BBC) 52
Exhaust Closes (ATC) 16
Valve Overlap 26
Intake Valve Duration 240
Exhaust Valve Duration 248
The third on the list looks good and is a CRANE but is their 3 series which may be too aggressive
The second cam is a max area asymetrical lobe and has 50% more duration @.275 lift than the Direct connection 260 which has much more seat timing
Note the 24 degrees difference between MOPAR (260) and SAE = 284 and the DC cam is quicker than the Factory instilled cam 240-278 38 degrees!
other contenders
459/480 268/272 212/220 127@200 112LCA Crane 693511
(measured @.006 at the lifter you have to convert)
Lunati Voodoo (s)
Custom order from Howard and Bullet

 

[Wyrmrider]

some more 318 cam data- there were several stock cams- her's two

373/399 240/248 10 50 58 10 (20) 1970 318

373/399 240/248 10 50 52 16 (26) 1971 looks like they changed the lobe centers moving the exhaust around same intake centerline, more overlap
72 -76 shows 373/400

.405 240/248 (26) 1500-5000 318 72-79 use MP 4451755 240-248-(24) as replacement

 

[waspaid]

4.56 gears ..... I have to drive 30 miles at 75 mph to get to town... that would not work for me! That is the thing that can make a small engine feel fast, get the torque multiplication through the gearing! I have 2.91's in my Coronet so I can cruise the freeway at 75 mph at less than 3000 RPM... modern overdrive transmission has its advantages!

Hey Jim. That's true. 4.56 gears aren't good for the road. But we drag race this car only. Actually, 3.23 or 3.55 would be as deep as you'd want to go. The 3.23's would keep the rev's down. Highway running with them would raise rpm's to about 300 to 500 rpms at the most. Car would have a really decent launch and provide both. No 4500 stall either. Something is about 2500 would work well. I've been fooling with MOPARS for years. I mean back in the early 70's. I also have a '71 340 Duster that I drag race. Full interior and all. .030 over 360 that runs 7.78's in the 1/8th mile. It's for drag racing only. 4.88's and all. I've got a '73 340 Duster that I bought new in October of '72. It has a 3.55 gear in it. Rev's at 70 mph at about 3200 rpms. I just love my MOPE's. A 318 though is often overlooked. They are strong motors.

 

[nm9stheham]

some more 318 cam data- there were several stock cams- her's two

373/399 240/248 10 50 58 10 (20) 1970 318

373/399 240/248 10 50 52 16 (26) 1971 looks like they changed the lobe centers moving the exhaust around same intake centerline, more overlap
72 -76 shows 373/400

.405 240/248 (26) 1500-5000 318 72-79 use MP 4451755 240-248-(24) as replacement

Thanks for the data; I'll guess that the latter were changes made for emissions... like the CR's being lowered.

And maybe more importantly, it important that the Mopar method was for duration at .008" tappet lift. Jim, if you re-do the graphs, I'd be putting in at least 10-15 degrees more on duration for that stock cam.

 

[Wyrmrider]

Jones cam 360 318 -------DC 260
[email protected] 278 264/275---- 284
[email protected] ------------------ 269
[email protected] 252 240 ------ 261
I can try and come up with intake close points if that would help
you can't tell where to go if you do not know where you started

 

[Wyrmrider]

all of the above cams take about the same number of degrees difference between .008 and .004 23-26 degrees
the gotcha is on the close side
The 440 cam takes 29 degrees to go from .004 to .050 (Crane's intensity) but takes 41 degrees to go from 50 to .004
The cams are asymetrical with the factory cams having long closing ramps- and really long closing ramps on the exhaust
hopes this helps on your dynamic compression efforts- which are appreciated and interesting

 

[nm9stheham]

Now THAT is interesting... that 23-26 degrees extra duration for the .004" vs .008" duration is pretty important. Which number is best for DCR - .004" or .006" lift at closing - is something that has to be guessed at... and it changes with RPM I am sure, being that we are wanting to know when the cylinder 'effectively' stops leaking any significant pressure.

I always wondered about the symmetry opening vs closing, and always assumed they were equal. I am a bit confused as to the reference to the '440 cam', with all that assymetrical closing vs opening ramp. Which cam is that?