1975 360 bottom end power

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canadian duster

canadian duster

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hi everyone,

Im looking for some information on bottom end power for a 360 (1975). I find that it doesn't have much for low end "get up and go". I plan to go with a higher stall converter (currently has an edelbrock performer rpm carb) to help with this but what would better heads be then next best plan (try and get back some flow). These are the ones im looking at and they fit my budget. They are from aeroheads racing

ARO-CY-SB3401968-1987 340-360 A-Engine 1.88 x 1.60 SS valves (2.02 intake valve add $50.00) 67-70 CC open chamber design. .509" lift springs. 160CC intake port volume
 
You need to do some research on parts before you decide, the Edelbrock RPM is what it says, RPM, meaning it makes power in RPM's not bottom end power. Put that on a stock engine and you could actually make bottom end power worse. Read up, it's a complicated formula making power.
 
To get lower end torque, Compression, Timing, the Correct Cam, NOT too big, correct heads, NOT too much valve size, AND the right size Carb for all the above. Try not to stray too far from stock unless you are educated on the parts choice. And have a nice BR. [Bank Roll] Bigger valve size does not get you more low end torque. Smaller valves gives you a better vacuum signal, thus giving you a better low end throttle response.
 
I have learned this to be fact. Horse Power cost money, how fast do you want to go?
 
Bottom end power (torque) is hard to improve over stock there is room to be gained but most mods give you top end power. Gears is probably part of the problem, I see you have 4bbl, stock heads are good for high 300's horsepower wise. 1st step is compression test and tuning like carb and timing. Then Headers and Duals would be my next step, then something like comps xe262 cam, and head wise I go with EQ'S
 
Spend the money on gears, depending on what you have now.
Tune what you have up, it should have good torque.
 
If you can afford heads, then you can afford pistons.
Cylinder pressure picks up the bottom end. But do not confuse Static CR for Dynamic cr.
You can make a lot of Dcr with a small cam that has an early closing intake valve. And you will get a strong lowend.
Or you can install a cam with a little later closing intake, which will trade away some low-end, and get some power a little further up the rpm band, and it will strengthen the midrange. But for optimum results you would need to bring the Dcr back up; or go to what I call crutches. That would be gears N hi-stalls.
Here's how that works. If you can pump the engine torque up,at take-off by 10%, then you can give up 10% in the rear gear, which means you get to cruise at a 10% lower rpm.
The hi-flo heads won't help you a bunch off the line, unless you really shell out the coin. And to bolt them on to a soft short block, is to invite disappointment.
The cheapest way for your car to perform better off-the-line is gears, and/or a higher stall TC . No doubt about that. But sooner or later you get to high gear.A street 360 likes a starter gear of about 10 or 9, to one, with an M/T. Or up to 10% less with an auto. So if you have a 245low automatic, that would be 3.55s to 3.73s. If you go up in stall, you could go a little more conservative on the gearing.

So the number one thing to do is see what you are starting with. And that means a compression test and a leakdown test, as previously mentioned.Also do a stall test and find out exactly what your current gearing is.
 
273 said:
Bottom end power (torque) is hard to improve over stock there is room to be gained but most mods give you top end power.
Click to expand...

Do you do any real world tuning? This statement is so far off base it's not funny.

If he's looking in the book for timing, that's a HUGE mistake. More initial timing will boost power all over the low end and it's cheap to do.
 
Those Aero Racing heads are not much different than what you already have. If I was doing anything budget with the heads, I would:
- Get the ones you have upgraded with a good valve job with the ports opened up below the valve seat to help low lift flow.
- If you are so inclined, do a bit of cleanup porting yourself.

Mill the heads a bit to help the compression ratio a bit. Put in some better valve springs while in there, to be ready for other mods. Going beyond that, you're jumping up into the $1200-$1600 range for a pair of heads that will be a decent step up.

Then put in a torquey cam (the 256 or 262 durations would be good) and replace the timing chain and make sure it is properly advanced.

Then put it together and work hard on the ignition advance curve and carb tuning. DO you have a 4 bbl carb now?

Later on, headers and a good intake would help extend the top end RPM range some. Any 4 bbl carb I would use would be 670 cfm or less, vacuum secondary if mainly for street use.
 
crackedback said:
Do you do any real world tuning? This statement is so far off base it's not funny.

If he's looking in the book for timing, that's a HUGE mistake. More initial timing will boost power all over the low end and it's cheap to do.
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What I meant is a stock engine makes 80-90% of the torque it's ever gonna make.
 
I find on the street, my stock 1972 Satellite Sebring Plus 318 (auto) feels equal to or better than my parent's new 1971 Road Runner 383 (auto) I drove new back in high school.
 
273 said:
What I meant is a stock engine makes 80-90% of the torque it's ever gonna make.
Click to expand...

I Think I know what you are saying.
You can move the torque-peak up, or down, or make it swivel around a point in the rpm band. But to make the entire band move up, takes more airflow over that entire band; which would be either more cubes,or a special head,or supercharging. Or more Dcr. Depending on how far you want it to move, it could take deep pockets.
 
273 said:
What I meant is a stock engine makes 80-90% of the torque it's ever gonna make.
Click to expand...

Even THAT might not be true. A torque curve of an engine depends on MANY things, factors which are intertwined and affect each other. The "smog dogs" of the mid to late seventies and into the 80's are an example, and at least part of that problem, generally speaking, was cam design and cam timing. It absolutely was affected by ignition timing and the advance curve, or, LOL "lack of it."
 
67Dart273 said:
Even THAT might not be true. A torque curve of an engine depends on MANY things, factors which are intertwined and affect each other. The "smog dogs" of the mid to late seventies and into the 80's are an example, and at least part of that problem, generally speaking, was cam design and cam timing. It absolutely was affected by ignition timing and the advance curve, or, LOL "lack of it."
Click to expand...

I really don't get what your guys are saying you can build a 500-900 hp 360 try building more than 100 lbs-ft over stock 360 Natural Aspirated.
 
AJ/FormS said:
I Think I know what you are saying.
You can move the torque-peak up, or down, or make it swivel around a point in the rpm band. But to make the entire band move up, takes more airflow over that entire band; which would be either more cubes,or a special head,or supercharging. Or more Dcr. Depending on how far you want it to move, it could take deep pockets.
Click to expand...

Your correct but the OP is talking about building off idle torque and over stock is hard to improve.
 
well here's something;
Let's say that 360 has 8.5Scr,and the cylinder leakage is in good shape, and had a stock cam of 252* on a 114LDA.The Dcr would work out to 7.22 and the cylinder cranking pressure estimates at 139psi.
So then, say he pumps the Scr up to 10.0(whatever it takes). The Dcr hops up to a nice 8.5, and the pressure could rise to 171psi.
Thats a rise of 23%, in cylinder pressure.

But let's say his 360 is a little tired and only makes 120psi. So now the improvement in cylinder pressure could be over 50%!
I know how my 367 cuber performs at 165plus , and it's a HUGE improvement over stock, especially off-the-line..........Jus saying.

I also know how she performs at over 180psi, but that's another story!
 
AJ/FormS said:
well here's something;
Let's say that 360 has 8.5Scr,and the cylinder leakage is in good shape, and had a stock cam of 252* on a 114LDA.The Dcr would work out to 7.22 and the cylinder cranking pressure estimates at 139psi.
So then, say he pumps the Scr up to 10.0(whatever it takes). The Dcr hops up to a nice 8.5, and the pressure could rise to 171psi.
Thats a rise of 23%, in cylinder pressure.

But let's say his 360 is a little tired and only makes 120psi. So now the improvement in cylinder pressure could be over 50%!
I know how my 367 cuber performs at 165plus , and it's a HUGE improvement over stock, especially off-the-line..........Jus saying.

I also know how she performs at over 180psi, but that's another story!
Click to expand...

So how much of an improvement in ft-lbs is that ????
 
Like I said a couple of times it's hard to increase 100 lbs-ft over stock, or even half that?
 
To be honest there's got to be something wrong with the setup, my 5.9 in my jeep is fast and if a a body 360 is a dud for this guy there's something wrong, I know a guy that put a dead stock 360 in and sold it cause it scared the **** out of him lol
 
AJ/FormS said:
Yeah I'd like to know the answer to that too!
I have no data to translate cylinder pressure improvements to ftlbs, nor do I suppose there is one.
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I'm not trying to argue with you I appreciate your input
But honestly you can't say there huge improvements in torque over stock ??
 
Since I see your question mark, I think we are sticking on the word huge, which is hugely subjective.lol
Consider this; a 360 is 13% bigger than a 318. And we all know the performance difference between those two. So to me that's huge. A 440 is 22% bigger than a 360. And the performance difference between those two is very huge. Let's try to keep things fair in your head, by imagining they are similarly equipped, and that we are just considering off-the-line performance here.
Next;a one-step gear change, from 3.23s to 3.55s is about a 10% improvement in this department,and you probably know how that feels. So 10% is not huge, but it is almost huge. So that I think puts huge somewhere around 12/15% .
Now let's go back to the OPs Duster. He's got an automatic. It probably stalls around 1800 with his 8.5 engine.How much torque does a stock 360 make down there and can it be improved 12/15% with a compression boost of 1.5Scr/1.3Dcr points. Maybe.Probably. But, I think increasing the pressure from 120 to 171, would be a close call.. Certainly 10% should be doable, and that is one rear gear size from 3.55 down, or 2 gear sizes from 3.55 up.Maybe huge was too strong a word.But maybe not.
I can tell you this; My 367 with aluminum Eddies and a 10.7Scr/8.6Dcr, (which would probably translate well to a 10.0/8.5 iron head), was a tire fryer with a 9.44 starter gear, and a 223* cam, and 295s.And I'm not saying rev it up and dump it. I am saying,slip it out just enough to not stall it and nail it! It had a "huge" bottom end.
 
canadian duster said:
hi everyone,

Im looking for some information on bottom end power for a 360 (1975). I find that it doesn't have much for low end "get up and go". I plan to go with a higher stall converter (currently has an edelbrock performer rpm carb) to help with this but what would better heads be then next best plan (try and get back some flow). These are the ones im looking at and they fit my budget. They are from aeroheads racing

ARO-CY-SB3401968-1987 340-360 A-Engine 1.88 x 1.60 SS valves (2.02 intake valve add $50.00) 67-70 CC open chamber design. .509" lift springs. 160CC intake port volume
Click to expand...

Here's a concept: list what you have , what's been done , & what you expect.. My advice: be patient, list what you actually may know( or need to learn..) : ( vehicle weight guesstimate/rear end gear ratio/transmission type/stock converter(?)/tire diameter/ current " from stock" modifications/ what you want out of it/ what you want to spend... As for lack of good performance from a low compression 360, no way.. Had a 77 Cordoba 360 long block 100+K ,on it.Stuffed it in a 67 Cuda ,with a 727. We ended up with 5901 budget Hooker headers,a basic 318/360 Performer manifold,a Crower " Baja Beast" cam (smaller than a stock 340 OEM can,pump that cylinder pressure up!). With a " road runner converter, a tweaked Thermoquad, and some tuning" it averaged 13:80's @ 101-103. Best was a 13.61 @ 102. 3:55's out back,street radials. It's there, you need to learn it...
 
273 said:
I'm not trying to argue with you I appreciate your input
But honestly you can't say there huge improvements in torque over stock ??
Click to expand...
I bumped the SCR in a 2.6L Mitsu 4 cylinder with mild cam, from a true 7.3 to a true 8.2, and the low end torque improvement fell into the HUGE category, not just per me, but per others who drove the car. (3150 lb car without driver BTW.) Before, it was "OK, I'll consider your request for acceleration as I feel like it" when you pressed the vertical pedal on the right; after, it said "WE'RE GOIN' NOW, NOW, NOW!" It really was a dramatic change. No other changes were made.

CR is way under-appreciated IMO, and a lot of this is due to the stupid calculators online that ESTIMATE the HP increase with CR at peak HP only. These are just a conglomeration of assumptions rolled into a % change estimator, and don't at all accurately reflect what goes on at low RPM versus CR.

Do some off-road races or rallies where you need a wide torque curve to produce good torque in all gears and at all sorts of engines speeds, and the effect of CR on producing a wide torque band becomes very obvious, very fast. The story of trying to slow down turbo rally cars is a classic: restrictors were mandated in the turbos, and the engines migrated to higher CR with better detonation management to make more low end torque to make up for the restriction of high end HP, and in about 2 years, the cars were faster than without the restrictors!
 
In post #3, I said first Compression. You need to get your Compression up. Just like every one has said. only engines I have seen built to hit a torque number is Diesels. And they have Huge compression numbers. We have all seen builds that sucked the lower end torque right out of a engine. BUT it roared at the top. Just dont get too ambitious with your build. UNLESS like I said you have lots of money. then it will be trial and error. Good luck
 
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