1974 360 horsepower rating

[moparlvr166]

I had a 74 Duster and I removed the F&R bumper shocks and bracing, I'm sure it was a 200 lbs. diet.

 

[Dan the man]

You sure you can’t run a custom cam? I thought there was a lift rule and that was it.

From what I've read and if I'm understanding things correctly, they check the cam specs at the rocker arm and it has to be no more than 1% of the stock lift and duration can't be more than 2%. The class is called pure stock muscle car drag racing and the rules are pretty strict. It's a class set up for factory performance cars. The car you run had to have a 4 barrel carburetor as a option from the factory or you can't compete.

 

[junkyardhero]

The actual cost isn't much more than doing a rebuild

AH-HAHAHAHAHHAHAHAHA
*deep breath*
HAHAHAHHAHAHAAAAA

looks like you're just going out there to have fun then, amigo. maybe they give participation ribbons or something.

 

[Dan the man]

AH-HAHAHAHAHHAHAHAHA
*deep breath*
HAHAHAHHAHAHAAAAA

looks like you're just going out there to have fun then, amigo. maybe they give participation ribbons or something.

There are cash prize money and trophies and like you said to have some fun.

 

[273]

From what I've read and if I'm understanding things correctly, they check the cam specs at the rocker arm and it has to be no more than 1% of the stock lift and duration can't be more than 2%. The class is called pure stock muscle car drag racing and the rules are pretty strict. It's a class set up for factory performance cars. The car you run had to have a 4 barrel carburetor as a option from the factory or you can't compete.

Where there's a will there's a way, I was watching how the f.a.s.t. class started was they were cheating so bad they started a class that was basically legal to cheat.

 

[Seth Jones]

There are no trophies or prize money at the PSMCDR. It is just for fun and it’s a blast.

 

[missing linc]

I've been doing research on the 1974 duster / dart sport with the 360. From what I've read the 360 in 1974 was rated at 245 horsepower at 4,400 rpm's, is this over rated or under rated or accurate? The reason for this is I've been looking at a 1974 duster with the possibly of rebuilding the 360 for pure stock muscle car drag racing. The engine has to be correct for the year / horsepower claimed, heads can not be ported, gasket matched, stock size valve's have to be run. I haven't been able to find out if a comp valve job is allowed but I doubt it. Compression ratio can be 1.5 points over stock and I have found two different ratios for the '74 360, 8.4:1 and 8.7:1. Cam has to have the stock lift and duration. Factory exhaust manifolds. Curve kit is allowed as is a high performance coil as long as it is the same shape and color as the original and has to be mounted in the factory location. What horsepower would be possible with only a increase in the compression ratio and somebody who has great tuning skills? Thanks everyone for any help and advice.

I ran almost exactly that engine in a 1970 Dart, a .040 over 360 out of a 1975 Dart Sport, stock heads and stroke, stock electronic ignition, backed by a 727 and 3.23 geared 8.75 rear with a Tru Trac differential, only changes were an Air Gap intake and 750 cfm Performer carb, TTi headers, and welded in subframe connectors. Car would run 13.80s all day long on drag radials, 14.0 on Cooper Cobra street tires, through 3 inch exhaust. I expect it could have been a little quicker with a well built 904 transmission. Car was 100% steel, with a full bucket and console interior, rear seat, spare and jack bolted in place, and usually 3/4 of a tank of fuel.
That class sounds like it would be a lot of fun to run in.

 

[Mattax]

E58 360 4 Bbl cam is reported to have the same specs as the ‘68 340 four speed cam.

360

4 barrel

Hydraulic

430/444

268/276

Similar specs to the standard 340 cam (68 Automatic).
If someone has the later FSMs could verify that.
It wouldn't surprise me if there were some changes to shape as Chrysler mentions cam changes related to emissions.

360 Stock Cam Spec's.?

Can anyone tell me what the lift & duration would be on a stock 74 Duster 360 cam?

www.forabodiesonly.com

340 cam specs?

gentleman anyone know the camshaft specs on a stock 72 340 lift/dur etc.? also was the 72 spec different than the early 70 models? cant seem to find it. thanks.

www.forabodiesonly.com

 

[Dave_J]

I bought a crashed 1974 Charger SE with a 360 4bbl that was rated at the 245 HP. It was a nice car, faster than many cars in the early 80's. But the trunk was like an AMC Gremlin, smashed flat and up by a Cab over Peterbuilt. It had 22,000 miles on it. We pulled everything and sent the body off to make 4 Toyotas. We put that 360 on a dyno and after doing some tuning, no AC belt, iron ex manifolds into the 2.5 dyno pipes... we had 335 gross HP at the flywheel. Dyno was done in Spanaways WA at Cope Brothers, ie Derik Cope of NASCAR fame. We put a 272 degree Luniti cam in and got 1 HP per cube, 362 HP Gross

The Eh1 (almost exaclly a E58 spec) 360 in the Little Red Express is basically a 1972 up 340 with 20 more cubes. They factory rated them at 225 NET HP. ????
Same X head, 1.78" valve sizes, almost same cam spec, almost same compression ratios as the 72 340 with 240 HP NET. The LRT 360 would be, at a guess, around 255 HP NET

318 = Shetland Pony HP
340 = Quarter Horse HP
360 = Clydesdale HP

 

[Dan the man]

I ran almost exactly that engine in a 1970 Dart, a .040 over 360 out of a 1975 Dart Sport, stock heads and stroke, stock electronic ignition, backed by a 727 and 3.23 geared 8.75 rear with a Tru Trac differential, only changes were an Air Gap intake and 750 cfm Performer carb, TTi headers, and welded in subframe connectors. Car would run 13.80s all day long on drag radials, 14.0 on Cooper Cobra street tires, through 3 inch exhaust. I expect it could have been a little quicker with a well built 904 transmission. Car was 100% steel, with a full bucket and console interior, rear seat, spare and jack bolted in place, and usually 3/4 of a tank of fuel.
That class sounds like it would be a lot of fun to run in.

Question about the 3" exhaust, I've been told that anything over 2 1/2" hurts performance, but it sounds like it worked for you. Did you run the 340 cam and have a 3 angle valve job?

 

[Dan the man]

I've read on here that the 904 is better for performance than the 727. I don't know much about automatic transmission's what so ever. Why is the 904 a better transmission?

 

[Dan the man]

I bought a crashed 1974 Charger SE with a 360 4bbl that was rated at the 245 HP. It was a nice car, faster than many cars in the early 80's. But the trunk was like an AMC Gremlin, smashed flat and up by a Cab over Peterbuilt. It had 22,000 miles on it. We pulled everything and sent the body off to make 4 Toyotas. We put that 360 on a dyno and after doing some tuning, no AC belt, iron ex manifolds into the 2.5 dyno pipes... we had 335 gross HP at the flywheel. Dyno was done in Spanaways WA at Cope Brothers, ie Derik Cope of NASCAR fame. We put a 272 degree Luniti cam in and got 1 HP per cube, 362 HP Gross

The Eh1 (almost exaclly a E58 spec) 360 in the Little Red Express is basically a 1972 up 340 with 20 more cubes. They factory rated them at 225 NET HP. ????
Same X head, 1.78" valve sizes, almost same cam spec, almost same compression ratios as the 72 340 with 240 HP NET. The LRT 360 would be, at a guess, around 255 HP NET

318 = Shetland Pony HP
340 = Quarter Horse HP
360 = Clydesdale HP

What changes did you do with the carburetor and the ignition switch?

 

[273]

I've read on here that the 904 is better for performance than the 727. I don't know much about automatic transmission's what so ever. Why is the 904 a better transmission?

It's smaller and lighter duty, takes less power to turn it.

 

[Dan the man]

It's smaller and lighter duty, takes less power to turn it.

That makes sense.

 

[Rat Bastid]

Question about the 3" exhaust, I've been told that anything over 2 1/2" hurts performance, but it sounds like it worked for you. Did you run the 340 cam and have a 3 angle valve job?

Whoever told you that lied. Or they don’t know and they were repeating the lie. It can’t be they don’t know because it’s been proven many times it’s wrong.

You want to know what makes good headers and exhaust not make more power, or even lose power? I’ve been harping on this for decades.

When the LSA is too wide for the application the engine will be numb to any and all exhaust tuning. The wider you get from optimum the more numb the engine is.

So the defacto catalog 110 LSA is usually 3-4 degrees too wide. Usually. Some of the junk these guys are grinding is on a 112 and that’s HORRIBLE for the low (relatively) compression ratios most guys run. In fact, it makes the engine essentially numb to most tuning.

When you open the LSA wider than it should be, you kill overlap flow, and that kills power everywhere (IF your tune up is correct) and…think it through…it usually opens the exhaust valve LATER as you open the LSA.

If (its a HUGE IF) you have an incredibly efficient exhaust port you can delay EVO and get more work on the power loop and as long as you can get to atmosphere or close to it at BDC (and again, IF the port is efficient) you won’t lose anything on the pumping loop side.

If you’re running a crap exhaust port (most SBM exhaust ports are crap on a cracker) and you delay EVO you not only screw up the pumping side you kill blowdown.

So saying a 3 inch exhaust kills power over a 2.5 inch exhaust is at BEST based on poor engine building philosophy and worst case scenario it’s just nonsense.

EVO is more critical than most people think. So IVC is most important and EVO is second in what matters. A close third is IVO and EVC is fourth, but three and four control overlap. It’s all critical.

So consider this. When someone advances their cam from straight up (where the overlap triangle is centered where it should be) and they gain power and driveability they think it’s from opening the intake sooner. I suggest it’s opening the exhaust sooner which gives more blowdown time and reduces pumping losses.

It’s not just a matter of bolting **** on and then saying it doesn’t work. It’s a system and every system affects the other.

 

[Dan the man]

dan, i'm *assuming* you've seen this: https://gmauthority.com/blog/2022/1...974-plymouth-duster-360-in-a-drag-race-video/

in the article they give the weight of the duster and if you run the ET/MPH/weight thru a drag calculator that maths out to 260 net horse

on back to back to back runs he averaged low 14's with a 13.8 at 99 break out.

so i'd say somebody who really knows their nuts and bolts could probably tune themselves to possibly 300 plus and probably mid 12's with some chassis work.

Awesome. I'd like to learn how to dial in a carburetor and ignition system for best performance. Does having the distributor phased help performance? Chassis work, what would be the best thing to do? The class that I'm looking into only allows spring clamps and pinion snubbers, I think that I read something about slapper bars too but I don't remember exactly.

 

[Dan the man]

Yes cause everyone follows the rules a 100%, depends how they check things ? Eg. I doubt they pull your cam a put it on Cam Analyzer.

They measure cam lift at the rocker arm, I don't know how they can check the duration.

 

[Dan the man]

There are no trophies or prize money at the PSMCDR. It is just for fun and it’s a blast.

Have you ran in PSMCDR? It sounds like a good time and not real expensive. I've done a little research on the cost of building a engine for that class and it's around 5k. The most expensive was having the cylinder heads reworked because you have to use the stock size valve's and chances are the valve seats are going to be in bad shape so that will mean having the seats replaced and new valves. Also, finding a machine shop that will do a good stock valve job, correct valve spring height and overall valve height. The pistons that I looked at were speed pro and cost around $400

 

[273]

Have you ran in PSMCDR? It sounds like a good time and not real expensive. I've done a little research on the cost of building a engine for that class and it's around 5k. The most expensive was having the cylinder heads reworked because you have to use the stock size valve's and chances are the valve seats are going to be in bad shape so that will mean having the seats replaced and new valves. Also, finding a machine shop that will do a good stock valve job, correct valve spring height and overall valve height. The pistons that I looked at were speed pro and cost around $400

is it's highly competitive racing ? if so doubt it's cheap to be competitive.

 

[Dan the man]

Whoever told you that lied. Or they don’t know and they were repeating the lie. It can’t be they don’t know because it’s been proven many times it’s wrong.

You want to know what makes good headers and exhaust not make more power, or even lose power? I’ve been harping on this for decades.

When the LSA is too wide for the application the engine will be numb to any and all exhaust tuning. The wider you get from optimum the more numb the engine is.

So the defacto catalog 110 LSA is usually 3-4 degrees too wide. Usually. Some of the junk these guys are grinding is on a 112 and that’s HORRIBLE for the low (relatively) compression ratios most guys run. In fact, it makes the engine essentially numb to most tuning.

When you open the LSA wider than it should be, you kill overlap flow, and that kills power everywhere (IF your tune up is correct) and…think it through…it usually opens the exhaust valve LATER as you open the LSA.

If (its a HUGE IF) you have an incredibly efficient exhaust port you can delay EVO and get more work on the power loop and as long as you can get to atmosphere or close to it at BDC (and again, IF the port is efficient) you won’t lose anything on the pumping loop side.

If you’re running a crap exhaust port (most SBM exhaust ports are crap on a cracker) and you delay EVO you not only screw up the pumping side you kill blowdown.

So saying a 3 inch exhaust kills power over a 2.5 inch exhaust is at BEST based on poor engine building philosophy and worst case scenario it’s just nonsense.

EVO is more critical than most people think. So IVC is most important and EVO is second in what matters. A close third is IVO and EVC is fourth, but three and four control overlap. It’s all critical.

So consider this. When someone advances their cam from straight up (where the overlap triangle is centered where it should be) and they gain power and driveability they think it’s from opening the intake sooner. I suggest it’s opening the exhaust sooner which gives more blowdown time and reduces pumping losses.

It’s not just a matter of bolting **** on and then saying it doesn’t work. It’s a system and every system affects the other.

With the 1974 360's having the 340 cam I figured that would be a fairly easy engine to get 300 horsepower out of. The cam has to have the same specs as the factory, no variations. Exhaust system can not be larger than 2 1/2" and stock exhaust manifolds are mandatory. How important is quench? The pistons can be ran at zero deck height to help with the compression ratio as a increase of 1.5 increase is allowed. I'm thinking about using a 0.039" thick head gasket but the heads are open chamber. I did some compression ratio calculations and I came up with 9.62:1. What's a bummer is that the class that I'm looking at only meets once a year.

 

[Dan the man]

S

Whoever told you that lied. Or they don’t know and they were repeating the lie. It can’t be they don’t know because it’s been proven many times it’s wrong.

You want to know what makes good headers and exhaust not make more power, or even lose power? I’ve been harping on this for decades.

When the LSA is too wide for the application the engine will be numb to any and all exhaust tuning. The wider you get from optimum the more numb the engine is.

So the defacto catalog 110 LSA is usually 3-4 degrees too wide. Usually. Some of the junk these guys are grinding is on a 112 and that’s HORRIBLE for the low (relatively) compression ratios most guys run. In fact, it makes the engine essentially numb to most tuning.

When you open the LSA wider than it should be, you kill overlap flow, and that kills power everywhere (IF your tune up is correct) and…think it through…it usually opens the exhaust valve LATER as you open the LSA.

If (its a HUGE IF) you have an incredibly efficient exhaust port you can delay EVO and get more work on the power loop and as long as you can get to atmosphere or close to it at BDC (and again, IF the port is efficient) you won’t lose anything on the pumping loop side.

If you’re running a crap exhaust port (most SBM exhaust ports are crap on a cracker) and you delay EVO you not only screw up the pumping side you kill blowdown.

So saying a 3 inch exhaust kills power over a 2.5 inch exhaust is at BEST based on poor engine building philosophy and worst case scenario it’s just nonsense.

EVO is more critical than most people think. So IVC is most important and EVO is second in what matters. A close third is IVO and EVC is fourth, but three and four control overlap. It’s all critical.

So consider this. When someone advances their cam from straight up (where the overlap triangle is centered where it should be) and they gain power and driveability they think it’s from opening the intake sooner. I suggest it’s opening the exhaust sooner which gives more blowdown time and reduces pumping losses.

It’s not just a matter of bolting **** on and then saying it doesn’t work. It’s a system and every system affects the other.

Sounds like a custom ground cam would be the best way to go in order to get the best bang for the buck. Unfortunately I can't afford to buy good aftermarket heads, this is why I'm looking at PSMSDR. I know that a closed chamber head is better for performance but the magnum heads are know for cracking. If I was to build a engine for a daily driver with a little extra zip what would be a good choice for cylinder heads? Am I limited to speedmaster cylinder heads or something like that?

 

[junkyardhero]

Awesome. I'd like to learn how to dial in a carburetor and ignition system for best performance. Does having the distributor phased help performance? Chassis work, what would be the best thing to do? The class that I'm looking into only allows spring clamps and pinion snubbers, I think that I read something about slapper bars too but I don't remember exactly.

whatever gets you into a car, my dude!

 

[273]

S Sounds like a custom ground cam would be the best way to go in order to get the best bang for the buck. Unfortunately I can't afford to buy good aftermarket heads, this is why I'm looking at PSMSDR. I know that a closed chamber head is better for performance but the magnum heads are know for cracking. If I was to build a engine for a daily driver with a little extra zip what would be a good choice for cylinder heads? Am I limited to speedmaster cylinder heads or something like that?

why not do bracket racing ? rules are more open run what you want.

 

[missing linc]

Running 3 inch exhaust really helped pick up on the low end IMO, as for the heads, they were stock smogger era, nothing special done to them beyond a basic 3 angle grind. Cam was similar to a 1968 340 4 speed hydraulic flat tappet, but I don't recall what the LSA was, thinking it may have been 108*.
Pretty simple and basic package that worked well. I did spend a lot of time dialing in the carburetor and some on the ignition curve.
A 904 transmission is lighter duty, generally taking less power to make it work. I used what I had to work with and what I could afford at the time.
I went with 3 inch exhaust for 2 reasons, the first being that I was considering the possibility of going to a gen3 hemi in the future, and the second one was simply the cost was only a few dollars difference from 2.5 to 3 inch at the time.

 

[Seth Jones]

Have you ran in PSMCDR? It sounds like a good time and not real expensive. I've done a little research on the cost of building a engine for that class and it's around 5k. The most expensive was having the cylinder heads reworked because you have to use the stock size valve's and chances are the valve seats are going to be in bad shape so that will mean having the seats replaced and new valves. Also, finding a machine shop that will do a good stock valve job, correct valve spring height and overall valve height. The pistons that I looked at were speed pro and cost around $400

That's my duster in the video. The video is from last years PSMCDR. My 587 heads did not need seats. I shipped them to dwayne porter to be sure they were done properly since finding local guys that know what they are doing is tough.