Paxton on a 408?

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MuuMuu101

MuuMuu101

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So, I am just seeing what the interweb has to say about this, but I have a Paxton supercharger I got as part of my engine when I bought it. Unfortunately, when we tore the engine apart (due to low compression in one cylinder) we found out it had a cracked piston. So, we ended up stroking it. Now I have this really cool 408 built by IMM and I'm just curious, could I put the Paxton on it in the future without possibly blowing it up? The Paxton (NOVI 1200SL) has just sitting in my garage for years.

This car is going to be a cruiser/race car. I originally built it for autocross, but I may transition over to road racing a couple times a year. I also do plan on just cruising it every weekend for a minimum of 10 miles, but may want to take it on some road trips.

It has a full 6-point cage, hotchkis suspension, 1.18 TB's, T56 Magnum transmission, and an 8 3/4 built with all Dr Diff parts (3.55's and Eaton True-Trac). So it's built for power. I don't really abuse it (hard launches). My limiting factor is tire as I'm only running a 300 TW 255/40/18. My next step is for a 200 TW 265/35/18, possibly a 275, if I can make it work.

Right now the 408 has the following parts:
Forged pistons
I-beam rods
Forged Scat crank
Engine Quest ported heads
LD4B port matched to the heads
Customer (aggressive) cam
9.6-10:1 compression

It made 523 hp and 522 ft-lbs of torque at the crank. I ran it at Willow Springs and I just want a little more power so I can keep up with the Hellcats.

If I do this, I'm going to install a Fitech on it first. I'm kind of tired of the rough start ups. Once I get that sorted, then I would move to the supercharger, but I won't run more than maybe 4-5 psi of boost as the trans is only rated for 700 ft-lbs of torque. We can only get 91 octane in CA and I'd rather not run water/meth injection, but it's an option. If anything, although it would be busy, I'd add a water-to-air or air-to-air intercooler.

What are your thoughts?
 
MuuMuu101 said:
So, I am just seeing what the interweb has to say about this, but I have a Paxton supercharger I got as part of my engine when I bought it. Unfortunately, when we tore the engine apart (due to low compression in one cylinder) we found out it had a cracked piston. So, we ended up stroking it. Now I have this really cool 408 built by IMM and I'm just curious, could I put the Paxton on it in the future without possibly blowing it up? The Paxton (NOVI 1200SL) has just sitting in my garage for years.

This car is going to be a cruiser/race car. I originally built it for autocross, but I may transition over to road racing a couple times a year. I also do plan on just cruising it every weekend for a minimum of 10 miles, but may want to take it on some road trips.

It has a full 6-point cage, hotchkis suspension, 1.18 TB's, T56 Magnum transmission, and an 8 3/4 built with all Dr Diff parts (3.55's and Eaton True-Trac). So it's built for power. I don't really abuse it (hard launches). My limiting factor is tire as I'm only running a 300 TW 255/40/18. My next step is for a 200 TW 265/35/18, possibly a 275, if I can make it work.

Right now the 408 has the following parts:
Forged pistons
I-beam rods
Forged Scat crank
Engine Quest ported heads
LD4B port matched to the heads
Customer (aggressive) cam
9.6-10:1 compression

It made 523 hp and 522 ft-lbs of torque at the crank. I ran it at Willow Springs and I just want a little more power so I can keep up with the Hellcats.

If I do this, I'm going to install a Fitech on it first. I'm kind of tired of the rough start ups. Once I get that sorted, then I would move to the supercharger, but I won't run more than maybe 4-5 psi of boost as the trans is only rated for 700 ft-lbs of torque. We can only get 91 octane in CA and I'd rather not run water/meth injection, but it's an option. If anything, although it would be busy, I'd add a water-to-air or air-to-air intercooler.

What are your thoughts?
Click to expand...

Short answer, of course you can safely run it without blowing the motor as that is what they were made for.
You might not like it much on longer trips, but there is not one reason it should damage the the motor unless you over boost, or don't have a good handle on your ignition timing and ring end gaps.
 
I had a acquaintance who put a Paxton on a 408 (he built the 360 to a 408 because he blew up the 360 ~ with too much boost). He then blew up the 408 with it too. You see as a general rule of thumb you get a point of compression for each three pounds of boost. His compression ratio started too high for a blower application (like yours may be) and then went through the roof (of the piston) once he dialed up the boost. However with that said if you are going to go mild boost like you quote you could be okay. But keep in mind that if you are making laps (& not just short acceleration bursts) your engine will build heat and basically self regulate that boost. I have had a lot of blower cars (still have one that I roadrace) and it can work for a long time if you have some restraint.
 
Boost is like drinking, Done in moderation, it can be safe and fun! LOL
 
Your stated compression ratio seems a bit high. You’d be safer with probably around 8:1 - 8.5:1.
 
toolmanmike said:
Boost is like drinking, Done in moderation, it can be safe and fun! LOL
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True but why run any huffer if you run it anemically underdriven and/or not get into it all the way? I think a dynamic comp ratio in the 8s would be a wiser route but since Brian (@ IMM) built it, ask him what he thinks. I think he'll say something similar to our discussion re: my 408/6-71.
 
That static compression may not be an issue. Whats the cranking compression? You may need a cam change with the SC. I'd call one of the shops that specialize in this. I know when I thought of running a procharger they told me I'd be fine with one, tuned properly of course. I have 10:1 static, 160cc.
 
What's the HP limit on a stock 360 block? 550, 600?
 
In my opinion with the power you are already making I would not use the the blower. A safe hp gain would only be 50-75 hp and even then with the high compression it is a gamble.
 
roccodart440 said:
That static compression may not be an issue. Whats the cranking compression? You may need a cam change with the SC. I'd call one of the shops that specialize in this. I know when I thought of running a procharger they told me I'd be fine with one, tuned properly of course. I have 10:1 static, 160cc.
Click to expand...
160cc what? Your at 10-1 now with a Paxton type blower?
WOW!

CUDA69 said:
What's the HP limit on a stock 360 block? 550, 600?
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Depends on how long you want it to live. IIRC, Crackedback did a thread in this topic.
doogievlg said:
You are pushing your luck when you get over 600.
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Even more so when your hopping on it a lot.
 
I forgot the horsepower capabilities of a 360 block. I'll save/sell the paxton for something else and just try to lighten up the Dart.
 
MuuMuu101 said:
I forgot the horsepower capabilities of a 360 block. I'll save/sell the paxton for something else and just try to lighten up the Dart.
Click to expand...

Throwing a small blower on a high performance NA engine probably won't be worth the trouble. Will your cam help build boost or work against it? Is your torque converter flash point set to get you into boost? Plus, if your 408 is putting down those numbers then it's breathing pretty good. That blower doesn't flow the cfm to support a well breathing engine with that kind of displacement. I have a Novi 2000 on a 408 with a 3" head unit pulley (second smallest they make) and am seeing 11psi.
 
MuuMuu101 said:
I forgot the horsepower capabilities of a 360 block. I'll save/sell the paxton for something else and just try to lighten up the Dart.
Click to expand...

Throwing a small blower on a high performance NA engine probably won't be worth the trouble. Will your cam help build boost or work against it? Is your torque converter flash point set to get you into boost? Plus, if your 408 is putting down those numbers then it's breathing pretty good. That blower doesn't flow the cfm to support a well breathing engine with that kind of displacement. I have a Novi 2000 on a 408 with a 3" head unit pulley (second smallest they make) and am seeing 11psi.
 
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