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As promised, here is a new thread to document the tuning process of my new hand built (by me) 383.
As a quick recap, its specs are: 388ci, 3.75 stroke. 6" rods. 10.8 CR, AFR 195 heads, Howards hyd roller cam .56/.56 237*, Z28/LT1 dual plane intake, Holley 4160 750 vac secondary. 2.5" rams horns 2.5" full undercar exhaust Off road mufflers.
3,73 gears, 27" tire, and 3.26 1st gear with the RS500.
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Please share your thoughts or follow along as I Science the hell out of this.
I ran a model for kicks. Full exhaust & 2 1/2 inch ramshorns. Your cam specs and compression, AFR 195 street heads, Z28 or Performer RPM with 750 vacuum carb.
The advance curve you have may be a little fast. You probably will not notice because the engine will seldom see the low rpm for a sustained load and duration. The take away is you can tune for a stable advance at idle without impacting power (stiffer springs & button tuning).
The cam's peak power is above 6000 rpm. The torque is also good, with 320lbft from 2500rpm up. You could run a shorter/smaller cam, but the dynamic compression is already at close to 8:1 so the inlet close event will need to stay nearly the same to avoid detonation. The gain with a smaller cam is less overlap, a cleaner idle and higher idle vacuum, but you would need to select carefully and widen the lobe center line (from 110 to 116 or more).
Open headers model over 460hp, and move the peak hp down about 600 rpm.
The power in the car models very close to my 357, near identical from 2000 to 4000 rpm. Your 383 model tq and hp however improve on my engine by about 10 below and 25 above that range (where the extra cubes help).
It should be able to cook off dry street tires accelerating from an off idle 1000 rpm rolling start in 1st or 2nd (with your gearing), when you accelerate past 2500 rpm with no clutch drama and no hesitation. Expect smiles when the break in and tuning is improved.
I think you are in SoCal so we may cross paths some day.
Very nice Ed and I have to ask, what would it take to get that analysis on my 406?
Don, this discussion just jogged my memory about a very similar problem I had but have since forgotten and it too involved the PCV system. I determined that the valve I was using was allowing too much air flow at idle and giving me a lean stumble as well. I believe I detailed it in a separate thread that I'll see if I can find. One I realized actual specs ares unavailable, I ended up buying a handfull of valves and testing each one till I found one with the desired characteristics.
It runs a little long as there were several back and forth posts clearing up differing semantics on PCV systems but most of the relevant info is on page 2.
Last edited by 65air_coupe; 07-17-2016 at 01:23 PM.
Good read on the PCV valves.... I had just assumed they were all relatively the same.... The one I have was selected based solely on the inlet/outlet fitting hose size to match my application. I will put the stock 63 PCV valve in and see what I get.
Note that the 64-65 365/375 cars didn't have a PCV but the restrictor fitting that I am also using currently. So, I'll see if my PCV matches the characteristics of the restrictor. (It should) as they went back to pcv valves on all motors in 66.
Who would have thunk such a small thing could be so undocumented, and yet have such a big impact on the engine!?
I ran a model for kicks. Full exhaust & 2 1/2 inch ramshorns. Your cam specs and compression, AFR 195 street heads, Z28 or Performer RPM with 750 vacuum carb.
The advance curve you have may be a little fast. You probably will not notice because the engine will seldom see the low rpm for a sustained load and duration. The take away is you can tune for a stable advance at idle without impacting power (stiffer springs & button tuning).
The cam's peak power is above 6000 rpm. The torque is also good, with 320lbft from 2500rpm up. You could run a shorter/smaller cam, but the dynamic compression is already at close to 8:1 so the inlet close event will need to stay nearly the same to avoid detonation. The gain with a smaller cam is less overlap, a cleaner idle and higher idle vacuum, but you would need to select carefully and widen the lobe center line (from 110 to 116 or more).
Open headers model over 460hp, and move the peak hp down about 600 rpm.
The power in the car models very close to my 357, near identical from 2000 to 4000 rpm. Your 383 model tq and hp however improve on my engine by about 10 below and 25 above that range (where the extra cubes help).
It should be able to cook off dry street tires accelerating from an off idle 1000 rpm rolling start in 1st or 2nd (with your gearing), when you accelerate past 2500 rpm with no clutch drama and no hesitation. Expect smiles when the break in and tuning is improved.
I think you are in SoCal so we may cross paths some day.
Hey, that looks like an Engine analyzer simulation. What version are you using? I have EA Pro 3.9, and I get slightly different results than what you show. The general difference is more power in the mid range and less power at the high end.
One reason may be the difference in the version of EA. I recall that when I changed from version 3.2 to 3.9, my results changed a bit.
The only other variable I can think of is the way you modeled the rams horn manifolds and the stock exhaust. What did you use for those?
For standard stock 2.5" mufflers, I use 400 CFM (total for two mufflers), and for the off-road mufflers I use 500 CFM total.
EA 3.9 forces me to use headers, but I can define them any way I want. So, I modeled the rams horns as "headers" that have 1.32" diameter primaries that are 6" long, with a 2.5" collector that is 25" long. The details probably don't matter much because the short primaries defeat any possible wave tuning effects and the mufflers probably dominate the flow limit.
I've had really great success with these adjustable PCV valves. They are expensive, but are extremely well made and will adjust to function perfectly with any high performance engine.
So, I swapped in the factory PCV valve....same chugging/ missing/ popping tailer hitch issue.
Put the restrictor in and it goes away. Runs pretty damn good once the cam settles in around 2200....... Runs strong and smooth.
New oil pan gasket still leaking, worse than before....gonna have to give it more attention <sigh>
Otherwise I'm getting close, and could likely just drive it, but the oil mess is so disheartening......
Don, Check the depth on your pan bolts, they may be bottoming out before torquing the gasket. It has happened to others so its worth a check.
I had an issue with an oil pan that would not seal, I came to the conclusion it was defective or bent. Fixed with The Right Stuff.
Dropped the pan in the front, cleaned everything totally dry, wiped with lacquer thinner as a last cleaner and put a thin layer of The Right Stuff on it.
It never leaked again. This went between a Fel-Pro Perma Dry Plus Gasket, rubberized silicone blue style, and the block and pan in the front at the timing cover. I know it is not correct but something was wrong causing it not to seal and this fixed it. The Right Stuff dries much faster than silicone and is much stronger than silicone so work quickly once you apply. It is expensive, about 4 times the cost of silicone but works and offers a stronger bond. Be sure to have a thin layer where the pan, timing cover and block meet on each side.
Don't go overboard on the application. The last thing you want is a chunk of this stuff in your oil pump some day because you left a glob inside your pan. When everything is bolted up tight wipe all the excess and the job will be invisible.
Good Luck
Mark
If it seals it is permanent, it won't let go in a couple years.
Last edited by Westlotorn; 07-22-2016 at 02:39 AM.
Thanks everyone. R7Red the pan, put some RTV in the leaky areas..and seemed dry this morning so I drove the car to work. But its stillleaking, maybe not as bad...so Ill cinch it up some more tonight and see if I can get it to seal. When I was messing with it last night before I pulled the pan off (at like 10 pm) I could push a feeler gauge between the block and the gasket in the front corners.... so that's definitely not right. Put RTV there and bolted it back up.
On the positive side I finally got 20 miles on the damn thing. Runs nice and cool, cooler than the 327 ran....
Idles at 750
I am running the restrictor in line with the PCV valve currently.... I will def try the adjustable PCV..looks perfect for me.
"I would try to up the idle feed restriction .003 and see if that makes it better."
Please explain how this is done..... Im not sure what you mean. Thanks
I've had really great success with these adjustable PCV valves. They are expensive, but are extremely well made and will adjust to function perfectly with any high performance engine.
With any sheet metal pan or valve cover, they must be peened true before installation. This is done by resting the flange against a straight hard surface (like the edge of a steel workbench top) and using the ball end of a ball peen hammer to hammer the pulled in holes back to flat. That way, you don't have gaps you are trying to fill with sealer. The gasket will do that job, provided the pan isn't bowed around each bolt hole.
07-17-2016, 12:37 PM
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