Am I an idiot for wanting to boost a high compression 318?

-
dusterbuster5621 said:
Hi All, I have a 318 in a 1975 Duster with the following specs: 10.3:1 static compression, 4 barrel dual plane air gap intake, Clevite hydraulic flat cam w/226 duration and 0.453 valve lift, headers, edelbrock carb, stock bottom end, some head work I did on my own, and at 5200 ft in elevation. I estimate I have around 320 hp at the crank based on those fun online engine hp calculators. Here's what I want: I want the engine to be more reliable (I have been getting vapor lock in the summer) and I want 400 hp at the wheels and I want to do it in the easiest way possible (not the cheapest) and I do not want to run NOS. I have been looking at Holley's Sniper EFI system along with their hyper spark set-up to increase the reliability. For those extra horses I am considering a Paxton super charger. Again, not cheap (around $10K in total for both EFI and charger) but easier than rebuilding an engine or so I think ha. A few questions I have below:
  • Is this really stupid? I was thinking I could keep the boost pretty low maybe less than 4 PSI if I opt for a bigger pulley on the charger?
  • If I was running 4 PSI of max boost, what octane level would I need for this set-up? I am okay with using 91 and then mixing in something like torco to increase the octane level.
  • The Paxton kit requires a hole be made in the oil pan. Does anyone have experience doing this? Curious to hear how you did it? Did it with the oil pan still on the car? Remove the oil pan and drill it?
I'll pay to have the car dynoed and tuned by someone with more experience than me after I get everything installed.

This engine is not the end goal for the car. I want to build a 360 set up to take on boost in the future (650 hp) but this is maybe 5 years down the line. I am hoping that the supercharger and holley EFI system will be transferable to that new engine. For now I just want the car to be more fun and not worry about breaking down. Not going to be a drag car. Just want to feel some punch driving it around :)
Click to expand...
Having had a warmed up 318 in my Barracuda when I lived in Colorado (over 20 years ago)....I can tell you that you are probably no where close to 320hp right now. If you think I'm wrong, take it to Bandimere Speedway and see what it runs.....if it runs 14's or better then I'm wrong. My guess is the number is probably closer to 200hp at elevation.

My little 318 did make it into the 13's with help from a little blue friend....way back when....
 
OLDSTYLE said:
4 pounds of boost at 10.3 static compression work out to 13.1 cr at sea level at 5000 feet is about 1 point less (12.1)
Click to expand...
Do you have a link to the calculator for that? I’ve heard an old general rule of thumb was every 4 pounds of boost is equal to one point in compression but always thought that was “out to lunch”.
 
Just thought it was worth pointing out. My daily driver is an 8.1 BBC in a 3500 dually with a remote mount garret gt55. I run 7 pound springs in the gate. It has over 560k miles on it. And using the link above, this is what I got.
A8A614BB-D33B-4548-A879-BB09F779275C.png

16 degrees of total timing on boost and has never run on anything but California pee pee gas 91 octane. And I don’t consider this a high compression engine.
 
flyfish said:
Having had a warmed up 318 in my Barracuda when I lived in Colorado (over 20 years ago)....I can tell you that you are probably no where close to 320hp right now. If you think I'm wrong, take it to Bandimere Speedway and see what it runs.....if it runs 14's or better then I'm wrong. My guess is the number is probably closer to 200hp at elevation.

My little 318 did make it into the 13's with help from a little blue friend....way back when....
Click to expand...

My 360 with ported Edelbrocks, .525" lift/222*@.050" hyd roller cam, RPM intake and shorty headers made 286 HP at the wheels on a chassis dyno at around 5000' elevation in Loveland, CO. So yeah 320 HP at the crank in Denver, ehhh idk about that...

The bored .060"-over part jumped out at me as a risk factor. My short block is a junkyard pullout high-mileage 5.9L Magnum with stock bores, pistons, rings with new rod bearings. I plan to put a Procharger on it some day but it has 9:1 static comp and Cometic MLS gaskets so it's already prepped for light boost, say 8-12 psi.

@TT5.9mag is right, times have changed a lot in the boosted engines world, high compression can and does work fine with boost if you know what you're doing. If using a turbo, making sure the hot-side plumbing flows well to keep the pressure ratio as close to 1:1 is key, if the hot-side pressure is higher you get hot exhaust gases pushed back into the chambers every cycle pre-heating the mixture which is why old-school (1980s) turbo engines had to be super low-compression to run safely on boost. Superchargers are simpler in that regard, just need to keep the charge air temps as cool as possible but also free-flowing exhaust with minimal backpressure.

When I briefly worked at a racing engines/hot rod shop I watched a 6.0 iron-block LS with over 11:1 compression and a big-*** turbo make multiple chassis dyno runs at I want to say 20 psi boost. However it was running E85 and the guys managing it were experienced pros. And it definitely had intercooling or at least water/meth injection.
 
To answer the OP's initial question, YES you would be Nuts to do that. Waste of money. Best complaint from OP: doesn't want to have to take the motor out ...:rofl:
 
TT5.9mag said:
Just thought it was worth pointing out. My daily driver is an 8.1 BBC in a 3500 dually with a remote mount garret gt55. I run 7 pound springs in the gate. It has over 560k miles on it. And using the link above, this is what I got.
View attachment 1715965128
16 degrees of total timing on boost and has never run on anything but California pee pee gas 91 octane. And I don’t consider this a high compression engine.
Click to expand...
You have over a half million miles on your bbc and it's NEVER been apart, that's very rare.
 
Dan the man said:
You have over a half million miles on your bbc and it's NEVER been apart, that's very rare.
Click to expand...
Owned since new. At 160k miles I tore it down to gap the rings and put a cam in it. Went back together with all the same original parts. The only thing I changed was the ring gap and the cam. Then built the remote mount turbo set up, and put a set of 100lb injectors in it. It’s been the best vehicle I’ve ever owned.
702DD385-A34D-468F-98B8-578B38247AA7.jpeg
 
TT5.9mag said:
Owned since new. At 160k miles I tore it down to gap the rings and put a cam in it. Went back together with all the same original parts. The only thing I changed was the ring gap and the cam. Then built the remote mount turbo set up, and put a set of 100lb injectors in it. It’s been the best vehicle I’ve ever owned.
View attachment 1715965516
Click to expand...
So you re gapped the old rings? I'm surprised that the rings sealed again.
 
dusterbuster5621 said:
Hi All, I have a 318 in a 1975 Duster with the following specs: 10.3:1 static compression, 4 barrel dual plane air gap intake, Clevite hydraulic flat cam w/226 duration and 0.453 valve lift, headers, edelbrock carb, stock bottom end, some head work I did on my own, and at 5200 ft in elevation. I estimate I have around 320 hp at the crank based on those fun online engine hp calculators. Here's what I want: I want the engine to be more reliable (I have been getting vapor lock in the summer) and I want 400 hp at the wheels and I want to do it in the easiest way possible (not the cheapest) and I do not want to run NOS. I have been looking at Holley's Sniper EFI system along with their hyper spark set-up to increase the reliability. For those extra horses I am considering a Paxton super charger. Again, not cheap (around $10K in total for both EFI and charger) but easier than rebuilding an engine or so I think ha. A few questions I have below:
  • Is this really stupid? I was thinking I could keep the boost pretty low maybe less than 4 PSI if I opt for a bigger pulley on the charger?
  • If I was running 4 PSI of max boost, what octane level would I need for this set-up? I am okay with using 91 and then mixing in something like torco to increase the octane level.
  • The Paxton kit requires a hole be made in the oil pan. Does anyone have experience doing this? Curious to hear how you did it? Did it with the oil pan still on the car? Remove the oil pan and drill it?
I'll pay to have the car dynoed and tuned by someone with more experience than me after I get everything installed.

This engine is not the end goal for the car. I want to build a 360 set up to take on boost in the future (650 hp) but this is maybe 5 years down the line. I am hoping that the supercharger and holley EFI system will be transferable to that new engine. For now I just want the car to be more fun and not worry about breaking down. Not going to be a drag car. Just want to feel some punch driving it around :)
Click to expand...
That compression is a bit high for boost. That said, the Bullet Mustang from a few years ago had I believe 11:1 CR and could be supercharged. Electronic engine control and careful tuning is the key. Holley Sniper would be good for fuel management. Now spark control is a ticklish point here. Setting up a conventional distributor would be difficult. I believe the company is Precision Distributors. They sell a programable distributor that you program using Blutooth from your phone. It has a MAP sensor in it to function as vaccum advance and also works on boosted engines for boost retard.
The low boost you describe should not give trouble with conservative tuning. When cruising and the intake manifold is under vaccum you can have more advance, but as soon as you get into the throttle and the manifold starts seeing positive pressure the advance needs to be dialed back and probably the mixture richened up a bit.
 
dusterbuster5621 said:
Oh I agree but then I have to pull an engine and I don't want to do that ha the parts I am dumping money into could (hopefully) be easily transferred to another engine. This 318 is definitely not a pristine block. Pretty sure it was 200K+ mile engine when I got it about 12 years ago. (my dad got it for me as engine to learn on when I was 13) After having the cylinders bored 60 over the number one piston still had a deep gash around the circumference of the cylinder about 0.5" from the deck. Because of this I don't really care about. Unless I should since its an LA?
Click to expand...
Regarding the "gash", I have a story for you. A farmer had a White tractor that broke a ring. This then wore vertically into the cylinder wall. I do not know who put rings in it, but the engine had a misfire or popping noise. On a NA diesel you can remove the exhaust and intake manifolds and listen at each port. If you remove the wire off the fuel solenoid, it will not start. You crank it over and can hear a leaking valve. When he did the rings he had a machine shop about an hour away, touch up the valves and seats. Seems they were off on one and it leaked. I took the heads off and took them down to them to check over. Their story was the wear in the cylinder. Two weeks later they called to get the heads. Said they found nothing wrong and the problem was the cylinder wall. So I installed the heads and still the popping out the same intake. Pulled the heads and took them to the Ford dealer in town as they have valve grinding equipement. They went through them and said ond seat was off a bit which they touched up. Put the tractor back together and it ran like a top. By then I think the rings and cylinder wall had conformed and it did not even burn oil. Kind of stopped using that machine shop after that.
 
dusterbuster5621 said:
Oh I agree but then I have to pull an engine and I don't want to do that ha the parts I am dumping money into could (hopefully) be easily transferred to another engine. This 318 is definitely not a pristine block. Pretty sure it was 200K+ mile engine when I got it about 12 years ago. (my dad got it for me as engine to learn on when I was 13) After having the cylinders bored 60 over the number one piston still had a deep gash around the circumference of the cylinder about 0.5" from the deck. Because of this I don't really care about. Unless I should since its an LA?
Click to expand...
 
I have experience with boosted applications, what you intend to do is not that crazy, since the boost level target is pretty low (4psi). As insurance or if you experience any pinging (you shouldn't, but if you do first try to take back the ignition timing 1 degree per psi of boost) you can take a couple of precautions: an easy one would be to add methanol injection (boost driven) to increase and another one is to get a set of thicker head gaskets so you can lower your compression easily 8.5 to 9.5 compression should be more than okay and then you can increase boost much more, 8-9 psi with the supercharger or even higher if you go turbo.

Take care,
 
OLDSTYLE said:
Boost Compression Ratio Calculator (rbracing-rsr.co
What you relate is in aviation called Density Altitude. High and/or hot reduces air density. A heavy loaded aircraft may not be able to sustain flight due to reduced engine power and reduced boyancy in the air.
A supercharger will increase power but suffers power loss at altitude. A turbocharger maintains power better in the thin air as it will spin faster to maintain manifold pressure.
The WW2 RR Merlin engine and some others had 2 stage or 2 speed superchargers that ran at a lower speed at lower altitude but changed up at higher altutude. This maintained power up to FL 300 or 350. Add 2 zeros for altitude.
Click to expand...
 
You’re static compression doesn’t matter. It’s the dynamic. And lots of new cars run higher compression with boost, just not too much and tuning needs to be right. It’s easily done with EFI because you can fine tune with sensors etc
 
Dale Davies said:
Electronic engine control and careful tuning is the key. Holley Sniper would be good for fuel management. Now spark control is a ticklish point here. Setting up a conventional distributor would be difficult. I believe the company is Precision Distributors. They sell a programable distributor that you program using Blutooth from your phone. It has a MAP sensor in it to function as vaccum advance and also works on boosted engines for boost retard.
Click to expand...

Progression Ignition

I looked them up and it sounds very intriguing. I might just go that route.

On my Procharged 408 I was running just an MSD distributor and MSD6AL with a timing dial under the dash. I don’t think it was working out.

Before I got my not my current D100 and Duster projects, about two years ago, I was buying parts to get the boosted Cuda back up and running.

After better research, learning, and new product development I purchased an MSD6 Programmable, 1 bar MAP sensor, EFI tank to replace my frame rail mounted Aeromotive A1000, and had my blow through carb rebuilt. I also locked out the distributor per the MSD6 Programmable instructions. This should suffice.

Now, with the plan to do the twin Chinese Cho Choo’s I am thinking about this Bluetooth distributor and selling the Procharger kit, complete with the new ignition and timing components. Hmm.
Chrysler
 
2F255AD6-271D-4F17-8B86-60C7349A06C7.jpeg
D8CFA360-D7AA-41FD-B923-65EF22F23523.jpeg
9916AD82-52C3-440C-AF6B-B868B43EF807.jpeg

  • Ignition timing is adjusted with your smartphone or tablet using the Progression Ignition Tuner App. There are NO mechanical adjustments inside the distributor.
  • Easy to use! The app will create a custom timing table for you by entering just a few basic numbers.
  • Tune with a modern style timing table interface. Powerful editing features for expert tuners but easy enough for a novice
  • Make timing adjustments in real time with the engine running or not
  • Store as many tables as you want on the smartphone or tablet. Change tables instantly using the app.
  • Theft prevention feature prevents the engine from starting using the app.
  • Wireless Bluetooth connection
  • The internal ignition module maximizes coil current to 8 amps up to 10,000 RPM
  • Built in Rev Limiter
  • 2.5 bar MAP sensor for turbo and supercharged applications
  • Timing range of 10 degrees BTDC to 50 degrees BTDC
  • Separate tachometer output wire
  • Sealed upper ball bearing for the shaft
  • Diameter of distributor is 4 1/8” not including the mounting lugs.
 
I would NEVER call a fellow FABO brother an idiot, but I think there are better ways to get blown than with a 318. See how I did that? Seriously, though, If I were going to blow a Mopar small block, it would be a 340 or 360 (or a stroked version of one of them). Don't get me wrong, I really like 318s, but if it were me, I'd go for a 340 or a 360.
 
You must log in or register to reply here.
-

Back
Top