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Tips to get the best performance from the olds 455?

Tips to get the best performance from the olds 455?

Old May 16th, 2018, 09:00 PM
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Tips to get the best performance from the olds 455?

I have a 1971 olds 455 v8.
C heads.
Comp 268H cam.
2.5 inch dual exhaust.
Holley 750 cfm carb.
Edelbrock performer intake.
TH400 auto with kick downswitch connected.
Stock bottom end.
160'F thermostat.
K&N air filter on a drop pan top.

I was wondering if there was any easy low cost tricks to help my engine perform better and maybe sneak a few more hp out of it for the track. Preferably something that doesn't require major disassembly. lol

I read about an ice can for the fuel line to make the fuel cold. And a metal screen between the carb and intake to help the fuel atomize better. Anything else I can try that may help?
Should I remove the thermostat to keep my engine colder? (I would drive it to the track for the day)

I believe my carb is set right and my spark advance is right. Although I forgot my total advance as its been several months since I worked on it.

The car weighs like 4300-4500 lbs and has a 2.73 rear ratio, cant really fix that. lol

Last edited by GHOSTOWLGRID; May 16th, 2018 at 09:15 PM. Reason: Added
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Old May 17th, 2018, 06:11 AM
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If you really want to get more performance, you are going to have to address the rear gears. There is not much you can do to increase performances with those gears, that will notice. Go to even 3.08, will help. I like 3.23.
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Old May 17th, 2018, 12:17 PM
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3.42's! You'll think it's a different car.
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Old May 17th, 2018, 07:34 PM
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Is it possible that my 455 has good horsepower and my rear gears & weight are just hindering it that much?
But the big question is how hard is it to change the rear gears in a 1987 GM 10 bolt differential?
If I do this I'd want to buy a posi unit.

I still want to keep it streetable and I also do highway driving. I already get 11 mpg. lol

My tire OD is 27.7 inch. I think at 90 mph my engine turns 3000 rpm. (I dont have a tach).

Last edited by GHOSTOWLGRID; May 17th, 2018 at 07:50 PM. Reason: Added
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Old May 17th, 2018, 07:57 PM
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Originally Posted by GHOSTOWLGRID View Post
Is it possible that my 455 has good horsepower and my rear gears & weight are just hindering it that much?
But the big question is how hard is it to change the rear gears in a 1987 GM 10 bolt differential?
If I do this I'd want to buy a posi unit.

I still want to keep it streetable and I also do highway driving. I already get 11 mpg. lol

My tire OD is 27.7 inch. I think at 90 mph my engine turns 3000 rpm. (I dont have a teach).


At 4500 pounds, you are in a big car (heavy). Those gears are hindering performance, without a doubt. You'll want someone who is a experienced at changing gears and setting it up.
11 mpg is a little low, I would think.
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Old May 21st, 2018, 09:43 PM
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I like the idea of swapping the 3.08 gear into the car. It will take time for me to decide to swap them. lol

I'm open to other suggestions as well.
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Old May 22nd, 2018, 06:05 AM
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gears

Originally Posted by GHOSTOWLGRID View Post
I like the idea of swapping the 3.08 gear into the car. It will take time for me to decide to swap them. lol

I'm open to other suggestions as well.

3.08s from 2.73 is not a huge jump. I would go 3.23 gears and a free flowing exhaust. Tune what you have & enjoy.


If you were expecting a fast car you picked the wrong chassis to begin with.
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Old May 22nd, 2018, 09:31 AM
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My goal was to pick a large land yacht/luxury car and make it faster. lol


I'll look into the 3.23 gears.


Just out of curiosity, is there a directory that tells the factory bore size for the pistons?
Is it 4.185 inch?

Last edited by GHOSTOWLGRID; May 22nd, 2018 at 09:33 AM.
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Old May 22nd, 2018, 11:16 AM
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Originally Posted by GHOSTOWLGRID View Post
My goal was to pick a large land yacht/luxury car and make it faster. lol

Well, technically 2.73s will make it faster
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Old May 22nd, 2018, 05:22 PM
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Originally Posted by GHOSTOWLGRID View Post
Just out of curiosity, is there a directory that tells the factory bore size for the pistons?
Is it 4.185 inch?
Standard bore 455 is 4.125".
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Old May 22nd, 2018, 06:26 PM
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What model car do you have? A 1971 Delta Royale convertible?
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Old May 22nd, 2018, 08:19 PM
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Its a big old Cadillac. Its my sleeper. lol

Thanks for the bore info. I found torque specs for bolts and everything else but I couldn't seem to find that online.
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Old May 23rd, 2018, 10:11 AM
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Originally Posted by GHOSTOWLGRID View Post
I read about an ice can for the fuel line to make the fuel cold. And a metal screen between the carb and intake to help the fuel atomize better. Anything else I can try that may help?
Should I remove the thermostat to keep my engine colder? (I would drive it to the track for the day)
Save your money, save your money, and no.

By the time the fuel has made it through the carburetor it will make practically no difference whatever the temperature of it entering it.

The fuel screen has been peddled by snake oil salesmen every time the price of gas has gone up. If your engine is in good shape, with a well matched carb and manifold you would be hard pressed to make any improvements.

An overcooled engine will run like crap, if you are taking it down the strip a cooling system in good shape will be fine, I'm assuming you aren't taking round a circuit?.

Roger.
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Old May 23rd, 2018, 11:24 AM
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Quickest way to get that going will be rear gears, as people said. If you can swing it, an OD transmission would help to, since that would get you a lower effective gear as well.
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Old May 23rd, 2018, 11:45 AM
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4.11 gears and tailor rear tire diameter to intended use--in town/performance, or highway long distance cruising. Headers.
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Old May 23rd, 2018, 12:06 PM
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Why don't you just cruse around and look cool? With a 4500 lb car a kid with a supped up Honda will smoke you in the stoplight to stoplight world. Lots of options if your car weighed 3000 lbs not so much if you add 1500 lbs. Spend your money on making it a cool ride you will be many bucks ahead..... Just my thoughts.... Tedd
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Old May 23rd, 2018, 08:57 PM
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Originally Posted by Tedd Thompson View Post
Why don't you just cruse around and look cool? With a 4500 lb car a kid with a supped up Honda will smoke you in the stoplight to stoplight world. Lots of options if your car weighed 3000 lbs not so much if you add 1500 lbs. Spend your money on making it a cool ride you will be many bucks ahead..... Just my thoughts.... Tedd

I do cruse around with the v8 tone. Its fun. I'm not concerned with being the fastest drag car, just fast enough to win against my friends car on track day and have fun and get some attention at the track. lol

Its a fun "because I can" toy.

I've been looking up rear gears and posi units so it may be my summer goal this year.
It's an old car that also doubles as my winter daily so when this car rots out in maybe 5-10 years the engine will be overhauled and put in something else. By that time I'll do a proper build for decent hp and I'll makeit my summer only vehicle.

Last edited by GHOSTOWLGRID; May 23rd, 2018 at 09:04 PM. Reason: Added
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Old May 24th, 2018, 08:28 PM
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Originally Posted by GHOSTOWLGRID View Post
I have a 1971 olds 455 v8.
C heads.
Comp 268H cam.
2.5 inch dual exhaust.
Holley 750 cfm carb.
Edelbrock performer intake.
TH400 auto with kick downswitch connected.
Stock bottom end.
160'F thermostat.
K&N air filter on a drop pan top.

I was wondering if there was any easy low cost tricks to help my engine perform better and maybe sneak a few more hp out of it for the track. Preferably something that doesn't require major disassembly. lol

I read about an ice can for the fuel line to make the fuel cold. And a metal screen between the carb and intake to help the fuel atomize better. Anything else I can try that may help?
Should I remove the thermostat to keep my engine colder? (I would drive it to the track for the day)

I believe my carb is set right and my spark advance is right. Although I forgot my total advance as its been several months since I worked on it.

The car weighs like 4300-4500 lbs and has a 2.73 rear ratio, cant really fix that. lol

You didn't say what part of the world you are in. The ice can "might" do some good if you are in a very hot ambient condition. The screen is also questionable. Keep in mind that it will reduce the CFM and in certain conditions can "ice" which really reduces performance. If it never ices it might be some advantage for MPG if that Holley isn't spraying very good from the venturis. If the engine is operating at 160F I wouldn't worry about removing the thermostat. If it's up around 230F (or more) you could take out the thermostat and plug the bypass to reduce the temperature some. If you haven't set up rear gears before don't experiment. It could be a disaster.
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Old May 24th, 2018, 08:32 PM
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Yah I want to set the whole summer aside for learning how to do the rear gears.

Since you mention the carb, I wanted to ask if my Holley 4160 mechanical double pumper is the right size for my engine/cam. Its a 750 cfm carb. Stock 1971 v8 and C heads no porting, 2.5 inch dual exhaust.
The cam is the comp 268H cam. Lift is 0.456 and duration is 0.050 219 and tappet lift is 268 and lobe seperation is 110.0
Intake/exhaust is both the same.
I never changed the jets or power valve on it, I did set the idle screws though. Its been running strong, maybe I can improve my afr?
My engine has a 160'F thermostat and doesnt get hot, at most 10-20 degrees more on a 90'F or so day. Typical tenps here are usually 70s to 80s.

Last edited by GHOSTOWLGRID; May 24th, 2018 at 08:44 PM.
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Old May 30th, 2018, 09:36 AM
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Update to my thread.


I finally had time to go over my engine and adjust it for this summer.
Outside temps here are already 95-105 degrees Fahrenheit. Good thing I have a 160'F thermostat. lol


I checked my holly carb, my idle was a bit rich from when I was winter driving so I leaned it out a bit, The Power enriching valves were also leaned out a very little bit because to much gas and had some stumbling when I floored it.


The spark is a mechanical and vacuum HEI unit, with vacuum off and locked it is sitting at 15 degrees advance at 900 rpm, and at 2800 rpm its about 26 degrees advance. (I'm afraid to rev it up to 3000). lol.
It runs strong, doesn't have issues, Idle drops to 600 rpm in drive with AC on, no issues there. Car runs strong and pulls very well at WOT. I read it should be 32 degrees total at 3000 rpm. With that, should I even try to get my total up to 32 degrees or should I leave it?
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Old May 30th, 2018, 11:42 AM
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32 minimum. I run mine at about 36 for best performance.
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Old May 30th, 2018, 04:10 PM
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Originally Posted by Fun71 View Post
32 minimum. I run mine at about 36 for best performance.

So my engine is actually de-tuned because I'm at 28 degrees. (I always thought 32 was the max, I didn't realize it was the minimum). I don't have time tonight, but tomorrow I want to turn it up some more and see what happens, hopefully it isn't raining.


What about my idle advance, will it hurt it to go more than 15 degrees mechanical?
The vacuum advance already moves the idle advance up to like 28 degrees by itself.
I'm not sure how to adjust my vacuum advance yet, I think its fixed.


What is your idle at? Do you have a vacuum advance on it?

Last edited by GHOSTOWLGRID; May 30th, 2018 at 04:15 PM. Reason: added
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Old May 30th, 2018, 04:56 PM
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I have an HEI distributor from a 77-79 403 engine. This particular distributor has ~16 mechanical advance so I set the initial to ~20 for a total of 36 mechanical advance.
When I was experimenting with settings several years ago, I set the total advance to 38 which put the initial at 22. I eventually turned the total down to 36 due to the summer heat here in Phoenix causing pinging. I currently have two medium springs from a Moroso HEI advance curve kit and the advance is all in by 2200 RPM.

The original vacuum canister gave 24 advance so I made a simple adjustable stop plate and limited it to 10 vacuum advance.

Last edited by Fun71; May 30th, 2018 at 05:02 PM.
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Old May 31st, 2018, 09:56 AM
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I turned my distributor clockwise some more, my total timing is up to 36 degrees (first try lol), still no pinging, outside temps are mid 80's Fahrenheit. I left my vacuum alone as well.
My idle is now up around 25-27 degrees advance with mechanical and vacuum both active.


My engine seems to like it, no pinging, no issues. I also have regular 87 octane gas. and its a 71 olds 455 with the stock dished pistons so I'm assuming that helps?
It does WOT just fine, and I can free rev it just fine as well. Loads more power, this thing didn't spin the RR wheel before when already moving at like 15 mph, now it did spin the RR on dry black top. So I'll have to be careful of that at the track for a better 1/4 time.


I do notice an improvement over the whole RPM range, before it was accelerating then like 3000 ish rpm it got better and acceleration increased a bit, now its increased a lot and consistently better from idle all the way up through max rpm.

I also have better throttle response from 0% throttle, I can hit the gas faster and now it jumps like a frog. No more stumbling off the line like it used to when I would hit the gas quickly, and same when already moving then flooring it 100%, it doesn't stumble there anymore, it just goes.

Thanks for the help with the timing, This whole time I misunderstood what I've been reading and your experience with your engine helped me with mine.


Also thanks everyone for the info for the rear gears, I'm not going to do them this summer, next time I will (Maybe next year), but now I have an idea what to go for.
This car looks like it will be plenty fast for winning against my friends/family at the track. lol. I can't wait to see my actual times on my time slip after I run it.

I also learned my rear differential is a 7.5 inch GM unit, so I'm thinking I will upgrade to the unit found in the 96 Impala SS (Now and then one shows up for parts because its been smashed), its a direct bolt in on my car, and I believe they already have posi and a lower rear gear (I think they were 3.11). Then I'll also have rear disk brakes too if I did that.


I didn't realize I was missing all this from a retarded spark curve, Its like a whole different car. lol

Last edited by GHOSTOWLGRID; May 31st, 2018 at 10:08 AM. Reason: added
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Old June 1st, 2018, 08:44 PM
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glad to hear you are figuring out a performance advance curve and power timing.


What year and model is your car exactly?

I had a 1980 Delta 88 2 dr. and it weighed 4500lbs with me in it. I ran a 1976 Monte Carlo 8.5 10 bolt with factory bolt in axles (no c-clips) with 3.42 gears and a factory posi.

Between those gears and a good torque converter in the 2,000-2,400 rpm stall range, you could easily drop the E.T. 1 second or more in the 1/4 mile and the car would be a whole different animal.

My car ran 12.7's @ 108mph in the 1/4 and I had a very mild built engine with about a 280 cam in it and 9.5:1 compression and headers.

You could get your car to be a whole different animal



You would be surprised, I used to get 14-16mpg with my car, so don't always think that lugging around with low numerical gears equals better mileage. It usually only means good mileage with a super low RPM stock engine with a super small cam.

Last edited by Battenrunner; June 1st, 2018 at 08:49 PM.
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Old June 3rd, 2018, 07:24 AM
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I had a very similar 455 build as yours. Mine was in my '77 Cutlass S, weighing in at 3960 with me in it. It was a '69 455 with C heads "small valve" all stock short block. I install a performer intake, comp cam 268he (218* .456") 650 holley dp, 1 3/4" headers 3" x-pipe exhaust, 4.10 gears, th350 shift lit 2400 stahl, 28"drag radial. Electric fan and manual steering. Never ran hot and drove on the street and ran 13.3's.
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