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JR1967

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Discussion starter · #1 ·
I’m looking to get a better ET with my car. I’ll give you some specs and any info or help would be appreciated

Its a full weight 1967 Malibu so around 3600 with me in it
Engine is a SBC 383 and on a
Dyno at the wheels I got 300hp 400ftlbs of torque
Its running a 700r4
My axel ratio is 4.11
Running MT slicks that are 28in tall
The car has run a 12.8 as my best ET
Trap speed is 104mph

I know gutting the car would be easiest but its a nice driver and practical with kids to have a back seat
The transmission is getting weak, would I have a better ET with a different transmission or replace with another 700r4? TH400 maybe?
I dont want to go more radical than a 4.11, I wanted a 3.90 but its a 10 bolt so I was told its either a 3.73 or a 4.11, no 3.90 for a 10 bolt

Do you guys have any recommendations? Would fuel injection help? I have Edelbrock rpm heads, a 3200 stall, holly 750, timing gears, its a nice little ride but am looking for suggestions or recommendations?

If you have any ideas I would appreciate any info
 
#2 ·
I think you would benefit from a th400 from the gearing prospective, but you have to remember you won’t have overdrive anymore so 60mph is typical cruise speed of your fine with that.
 
#4 ·
Well, if you want to improve, you need to know where you’re starting and where you want to go.

Use the middle formula on this page to calculate your uncorrected flywheel hp (312) based on 3600 lbs and 104 mph.


Image


To see how well you’re using the power (mph is horsepower) use this handy formula.

1320’/104mph = optimum ET (12.69s)

Don’t fret, that’s what a well set up race car would run, you’re putting down the power reasonably OK.

To go quicker and faster, you need more sauce (since you don’t want to cut weight). You could pick up some by switching to TH350 to reduce wasted power but that’s of limited benefit.

In a reasonably streetable 383, 111+ mph and high 11s should be possible, at 3600 lbs with 4.11 gears.

What are the rest of the engine and transmission details?
 
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#5 ·
If the 60’ is decent and you like how the car drives now, everything’s in good working order, and you just want to go 11.s just put a very simple plate system on it. Stay around 150 shot and get your tune right you won’t even have to disassemble the motor.
 
#6 ·
A good 60 foot time is an indication of how well your chassis / tire combo is working, MPH tells you how strong the motor is (with gearing, converter and tire size taken into consideration). As asked above..what kind of 60 foot times are you consistently running ?
 
#7 ·
So you put it on a dyno. Did you tune it or just make some pulls? If you didn't tune it, I would start there and optimize your current engine. Also, give us some details on the engine like compression, heads, cam, intake, carb, headers, exhaust.
 
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#8 ·
If your 60 foot times are good you will need to upgrade for more horsepower. Honestly for a 383, 300 at the wheels seems low. Cheapest solution would to add a 125 shot of nitrous to get into the 11's. If you don't want that then you would be looking at better heads, roller camshaft and matching intake and carb.
Fuel injection won't improve your ET.
 
#10 ·
A 10:1 383 with good/decent Eddy RPM heads should be making more power than that, IMHO. 450/450 with a proper build and decent cam. (Gross HP...not at the wheels.)
See my signature. I made 361/360 at the rear wheels. On good days in cold weather, I do pretty much with DragginWagon mentions.
Something is wrong with the drivetrain, IMHO. The MPH is too low. Either the motor is hurt or the cam shaft is a bad match.
Or...if the OP is really lucky....the carb and distributor simply need work.
The ET and MPH more closely match a modest 350 than a healthy 383, using today's parts.
 
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#11 ·
Silly question: How does the OP know he has a 383 and not a 350? Did he actually build this motor....or is he going off what the prior owner told him when he bought the car?
Looking at chasis dyno numbers, ET, and MPH....I see a decent 350.....not a healthy, modern 383.
Now, as I mentioned above, if the carb and distributor aren't tuned/working right....that's a game changer.
 
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#12 · (Edited)
A Th350 or Th 400.

A better converter giving you a 1500 rpm drop. Send your chassis dyno chart to a converter company and tell them what you want.

Tune the combo more in depth. Locked out timing if needed and etc.

Suspension set up such as springs, shocks, anti roll bar and etc.

Don't touch the engine, unless you want to spend a thousand on better heads or a port job.

Remember street/strip cars are a compromise to your comfort. You can only answer that.
 
#13 · (Edited)
One more question…what’s the elevation, and more directly, what was the barometer during testing and racing?

Where are you and what day is the data from?
 
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#14 ·
blue_69_malibu said:
Silly question: How does the OP know he has a 383 and not a 350? Did he actually build this motor....or is he going off what the prior owner told him when he bought the car?
Looking at chasis dyno numbers, ET, and MPH....I see a decent 350.....not a healthy, modern 383.
Now, as I mentioned above, if the carb and distributor aren't tuned/working right....that's a game changer.
Click to expand...

He could look at the balancer.

Lower power levels could be external balanced.

Could be internally balanced.
 
#15 ·
Agreed that power seems low.

Since it's a Edelbrock headed engine. I would think it would be low.

However, he will have to tell us specs and tune stuff.
 
#16 ·
As mentioned above, need more info.
With 4.11's and a 3.0 1st, you could probably use the 3.73's. Possibly running out of breath if you use 3rd like I have to with the 80E.
That's what happened to me with the IROC long block at the track with 4.30's for old combo.
 
#17 ·
Heads are small for one….I had the same heads on my 383. Made 335 hp at the wheels and ran 11.80’s

Buddy has a similar 383 in a similar weight camaro...he has AFR 210’s and runs about a half sec faster.
 
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#18 ·
JR1967 said:
I’m looking to get a better ET with my car. I’ll give you some specs and any info or help would be appreciated
Its a full weight 1967 Malibu so around 3600 with me in it
Engine is a SBC 383 and on a
Dyno at the wheels I got 300hp 400ftlbs of torque
Its running a 700r4
My axel ratio is 4.11
Running MT slicks that are 28in tall
The car has run a 12.8 as my best ET
Trap speed is 104mph
I know gutting the car would be easiest but its a nice driver and practical with kids to have a back seat
The transmission is getting weak, would I have a better ET with a different transmission or replace with another 700r4? TH400 maybe?
I dont want to go more radical than a 4.11, I wanted a 3.90 but its a 10 bolt so I was told its either a 3.73 or a 4.11, no 3.90 for a 10 bolt
Do you guys have any recommendations? Would fuel injection help? I have Edelbrock rpm heads, a 3200 stall, holly 750, timing gears, its a nice little ride but am looking for suggestions or recommendations?
If you have any ideas I would appreciate any info
Click to expand...
See my Signature for my 67 BBC Times etc.
I agree with the above Posts #ed 6 / 7 / 10 / 11 / 12
and what are your ET #s for 60 Foot / 330' / 1/8th Mile / 1/4 Mile

I have a Stock Weight 67 with Full Interior / Hooker Headers / 2.5" Exhaust / TH400 Trans / 3.70 Gears
Make sure the 750 Holly is running Right & that the Engine is Tuned Right

That 700r4 with the First Gear Ratio and the 4.11 RearEnd Gears does not help/work to good for the Launch

Suspension SetUp is very Important as you want to get the FrontEnd to Go Up on Launch
and the RearEnd Tires to be Pushed down into the Pavement on Launch
the Right Tires also help / I run Street / Strip Tires on mine and get pretty good 60' Times

If you want details on what my Cheap Suspension SetUp that is on my 67
that I drive on the Hwy for 100 Mile oneway trips and in City Traffic plus at the Track let me know
I drive 40-50 Miles from Home to the Track, then Race all Day then Drive Back Home 40-50 Miles

Image

Image

Image
 
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#20 ·
For reference, my old 10.3:1 - 383 SBC made 365 RWHP and ran 11.60's @ 114 with low 1.60 - 60's. 3610 lbs race weight '71 Chevelle. 28x10.5 bias slick, 4.56 gears, and TH350.

With cam, induction, and exhaust updates it made 395 RWHP, but never ran it again in the 1/4. Ran a best of 7.32 in the 1/8th, but converter was about 1000+ RPM too tight to fully take advantage of the new power. 60' times were still in the low 1.60's.
 
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