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onetrick56's 1964 Grand Prix

2020 September
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Hi everyone! Need some input, I’m close to getting my engine ready to install but wanted to add some power. My budget won’t allow me to get too crazy, e heads, rotating assembly etc. I have a 73 Pontiac 455 out of a grandville that runs like a top it was in the car when I bought it 4 years ago I pulled it and had been stored indoors since. Changing all gaskets and such oil pan, valve covers seals etc. I want to add some power to it without getting into heads and internals. The engine has big displacement but not much power and it has 2.41’s out back to boot. Does anyone have any input to gain power and torque with a stock bottom end and keeping the 6x-8 heads? I will be running an Edelbrock performer intake and Edelbrock 750 carb with 1 5/8 long tube headers. Thanks for any advise I might find here

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My recommendation would be to go with a mild performance street cam (like an RV cam) & lifters, a new timing chain, a high volume oil pump, new stamped steel roller rocker arms (perhaps up the ratio to 1.6:1). inspect your push rods and replace as necessary. Inspect and replace all your bearings as needed. Replace all or most of your engine bolts with ARP studs and bolts to hold the bottom and top ends together more reliably. If you have the cash, spring for cleaning up the heads with a triple angle valve job and some light porting. Inspect the valve guides to see if they are worn and need to be replaced. Port match the intake manifold/gaskets/heads. Lastly, replace the points in your distributor with a Petronix Ignitier III kit or replace the stock distributor with an aftermarket breakerless distributor. 

Talk to reputable engine builder in your area. Consider replacing the stock torque converter with one with a different stall speed that more closely matches your rebuilt engine's newer power band.

Also, did I understand you right? You have a 2.41 rear gear? If so, that is a great highway gear/MPH but not much for power. It's a little too tall. A 3.42 or 3.55 may be a better compromise. It will hurt fuel economy some (without an overdrive transmission) but it will put more power to the road. If you are opening up the diff case to change the ratio, you might want to install a positraction unit if you have a limited slip / open diff.

Finally, when you add power, are you doing anything to the braking system? I always advocate that when you are adding getty-up-and-go that you have to consider upgrading the whow! Better pads, drilled and slotted rotors, etc.?

Edited by Frosty
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17 hours ago, Foolinjected said:

Hi everyone! Need some input, I’m close to getting my engine ready to install but wanted to add some power. My budget won’t allow me to get too crazy, e heads, rotating assembly etc. I have a 73 Pontiac 455 out of a grandville that runs like a top it was in the car when I bought it 4 years ago I pulled it and had been stored indoors since. Changing all gaskets and such oil pan, valve covers seals etc. I want to add some power to it without getting into heads and internals. The engine has big displacement but not much power and it has 2.41’s out back to boot. Does anyone have any input to gain power and torque with a stock bottom end and keeping the 6x-8 heads? I will be running an Edelbrock performer intake and Edelbrock 750 carb with 1 5/8 long tube headers. Thanks for any advise I might find here

What Frosty says will do wonders, but you say you don’t want to get into heads & internals. And you say your budget is somewhat limited. So that said I’m not sure what you can or can’t afford?  The 455 has some oomph, but the biggest hold back would be the tranny & the 2:41 gears. So for what you have I would say the biggest bang for your buck would be do some tranny upgrade & go to 3:73 gears! The gears alone will make you feel like you added 100 hp. If you can change the distributor as Frosty suggests. A cam will do wonders, but you say no internals. Remember this car had a 301 smog engine  in it, so everything downstream reflex’s that!

7 hours ago, Frosty said:

My recommendation would be to go with a mild performance street cam (like an RV cam) & lifters, a new timing chain, a high volume oil pump, new stamped steel roller rocker arms (perhaps up the ratio to 1.6:1). inspect your push rods and replace as necessary. Inspect and replace all your bearings as needed. Replace all or most of your engine bolts with ARP studs and bolts to hold the bottom and top ends together more reliably. If you have the cash, spring for cleaning up the heads with a triple angle valve job and some light porting. Inspect the valve guides to see if they are worn and need to be replaced. Port match the intake manifold/gaskets/heads. Lastly, replace the points in your distributor with a Petronix Ignitier III kit or replace the stock distributor with an aftermarket breakerless distributor. 

Talk to reputable engine builder in your area. Consider replacing the stock torque converter with one with a different stall speed that more closely matches your rebuilt engine's newer power band.

Also, did I understand you right? You have a 2.41 rear gear? If so, that is a great highway gear/MPH but not much for power. It's a little too tall. A 3.42 or 3.55 may be a better compromise. It will hurt fuel economy some (without an overdrive transmission) but it will put more power to the road. If you are opening up the diff case to change the ratio, you might want to install a positraction unit if you have a limited slip / open diff.

Finally, when you add power, are you doing anything to the braking system? I always advocate that when you are adding getty-up-and-go that you have to consider upgrading the whow! Better pads, drilled and slotted rotors, etc.?

 

Edited by Last Indian
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Thanks guys, the car was originally a 400 car.its a 79 trans am, I see I didn’t mention that in the post,  Believe it or not I have the build sheet that came on the window, a little tattered but legible. The trans is b.o.p. t350, with shift kit. I have to agree the gears make it a slug of the line but about 60 and up its doing the dash and them some pretty quick but I think I want a little lower gear. I have the hei distributor installed, not performance brand, but how much difference would that make on my applications. As far as cams go hydraulic or flat? I was looking into the comp cams thumper kit with lifters, springs, timing chain it’s about $500 and plan on doing myself with the help of a friend. The cam part # is CL51-600-5 does this this seem reasonable with to do as far as still running the same heads with new springs and pushrods and lifters? And realistically what kind of gains are to be had from this on a 72 455 

In trying not to go over $2000, that’s including gaskets etc, 

2k just in the engine, trans is good but will be looking into gears

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Hi Foolinjected.

I think Last Indian and I were under the impression that you had a stock non-HEI distributor. The HEI distributor is fine for your street application. Just make sure that you've inspected it and replace anything that is worn or needs replacing, especially look at your cap, rotor, vacuum advance module, and coil module.

A lower gear will do you well off the line for sure, just know that it will hurt the MPG somewhat at some point. I have a 455 in my '72 Lemans, I run a 400TH and I have a 3.55 rear gear. I'm happy with it and the 12-14 MPG highway I get with it. The 3.73 gears that Last Indian recommends will definitely put some grunt to the pavement.

I am a fan of hydraulic roller cams over hydraulic flat tappets. Mainly because the beginning and end ramp profiles are significantly different over a flat tappet design and allow the valves to open a little sooner or close a little later. However, there is nothing wrong with a flat tappet design. Also, if you run a solid lifter cam, you would have to constantly check your valve lash , with a hydraulic you don't. I run a hydraulic flat tappet Melling cam in Lucy because that is what my engine builder recommended in 2004.

Two grand is not a bad budget. You just have to prioritize things.

I looked at your cam choice. My only question is between the High Energy and Thumpr cams. The High Energy cam has an RPM range of 1,500-5,500 while the Thumpr is going to be more happy between 2,000-5,500. What RPM range do you see your car spending the majority of it's time at - that you want to make power? I know 500 RPM is not a lot but if you want power down at the lower RPM range you have to have a slightly different profile. Just be honest with yourself. The Thumpr is a fine cam. I am just making you think about what you want your engine to do. Do you want it to get off the line or come alive at a slightly higher RPM?

Last question - is the rear end open or a positraction unit? I ask because if it is an open diff and you are going to change rear gears anyway, that would be the time to convert it to positraction too. If it is posi already, leave that part alone.

Edited by Frosty
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On 1/8/2020 at 9:26 PM, Foolinjected said:

Thanks guys, the car was originally a 400 car.its a 79 trans am, I see I didn’t mention that in the post,  Believe it or not I have the build sheet that came on the window, a little tattered but legible. The trans is b.o.p. t350, with shift kit. I have to agree the gears make it a slug of the line but about 60 and up its doing the dash and them some pretty quick but I think I want a little lower gear. I have the hei distributor installed, not performance brand, but how much difference would that make on my applications. As far as cams go hydraulic or flat? I was looking into the comp cams thumper kit with lifters, springs, timing chain it’s about $500 and plan on doing myself with the help of a friend. The cam part # is CL51-600-5 does this this seem reasonable with to do as far as still running the same heads with new springs and pushrods and lifters? And realistically what kind of gains are to be had from this on a 72 455 

In trying not to go over $2000, that’s including gaskets etc, 

2k just in the engine, trans is good but will be looking into gears

 

On 1/9/2020 at 8:38 AM, Frosty said:

Hi Foolinjected.

I think Last Indian and I were under the impression that you had a stock non-HEI distributor. The HEI distributor is fine for your street application. Just make sure that you've inspected it and replace anything that is worn or needs replacing, especially look at your cap, rotor, vacuum advance module, and coil module.

A lower gear will do you well off the line for sure, just know that it will hurt the MPG somewhat at some point. I have a 455 in my '72 Lemans, I run a 400TH and I have a 3.55 rear gear. I'm happy with it and the 12-14 MPG highway I get with it. The 3.73 gears that Last Indian recommends will definitely put some grunt to the pavement.

I am a fan of hydraulic roller cams over hydraulic flat tappets. Mainly because the beginning and end ramp profiles are significantly different over a flat tappet design and allow the valves to open a little sooner or close a little later. However, there is nothing wrong with a flat tappet design. Also, if you run a solid lifter cam, you would have to constantly check your valve lash , with a hydraulic you don't. I run a hydraulic flat tappet Melling cam in Lucy because that is what my engine builder recommended in 2004.

Two grand is not a bad budget. You just have to prioritize things.

I looked at your cam choice. My only question is between the High Energy and Thumpr cams. The High Energy cam has an RPM range of 1,500-5,500 while the Thumpr is going to be more happy between 2,000-5,500. What RPM range do you see your car spending the majority of it's time at - that you want to make power? I know 500 RPM is not a lot but if you want power down at the lower RPM range you have to have a slightly different profile. Just be honest with yourself. The Thumpr is a fine cam. I am just making you think about what you want your engine to do. Do you want it to get off the line or come alive at a slightly higher RPM?

Last question - is the rear end open or a positraction unit? I ask because if it is an open diff and you are going to change rear gears anyway, that would be the time to convert it to positraction too. If it is posi already, leave that part alone.

Ok so you are willing to do internals! Of the two cams you mention I would use the high energy because of the rpm range. The 455 makes peak hp @ 4 grand and peak torque @ 2800, in stock form. So higher rpm gets you very little without changing the cam profile. Also if you’re willing to put in a cam, to me it makes no sense to not rework the heads! That work is pretty much free! You don’t need a fancy valve grind, just a good valve lapping, perfect circle valve seals & if necessary valve guides, plus port & polish! All stuff you can do at very little cost and the benefits will be greatly appreciate by your new cam! As far as the 350 turbo, who’s shift kit? Also the 350 can be a great tranny for a high torque motor, but only with some major internal mods since it does not have a full through shaft and I would guess that’s not something you would do. So in that sense Frosty’s turbo 400 is the preferred choice, but a better one would be a 700r4. The 3:73 gears are a optimal gear for that engine due to the low peak torque rpm. That engine stock is about a 6500 rpm motor, max! There is a calculation formula for engines and their piston speed at continuous operation. For automotive engines its 75% for aviation its 90%. There are a lot of other things that go into this whole discussion, but to much for here. So in the case of the 455 your continuous max rpm is around 4800 rpm and even that is a lot for any extended engine life. So the 3:73 gears coupled with either the 350 or the 400 will work. If you couple it with the 700r4 you will have the best of both worlds and a 700r4 will handle 500hp.

Edited by Last Indian
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  • 4 months later...
Posted (edited)

If your total budget is $2,000, a hyd roller will not be cost effective enough, although supeior in performance. A gear change/or transmission change is a must. So, realistically, your budget is main limiting factor. Rear gear, set up, gaskets, and fluid will run at least $500. 3:73 is too low for a non overdrive street driven 455 that sees 70 mph speeds for long distances. We use 3:55 with a 700R4 overdrive transmission. With no overdrive, the highest I would go is 3.08-3.23 if you do a lot of highway driving, or maybe 3.42-3.55 around town. Keep in mind, Pontiac ran 3.08 rear gears in their 455SD cars and they ran great!  

There is no need to change your intake, your factory iron 4 barrel intake will outperform any aftermarket intake at less than 500hp.

The lowest power to dollar hp increase that is available in the market is Nitros Oxide. A 125 hp kit, NOS Powershot Nitrous Oxide Systems is $550.  To safely run this kit, a fuel system upgrade will be in order. Expect to add an electric fuel pump, and either a larger fuel line or another fuel line, fuel pressure regulator, and filter.  You will have about $300-500 in the fuel system if you install it yourself.

When you start talking cam swap, you need a gasket set, oil, coolant, timing chain, lifters and cam at a minimum. If valve springs are not improved, gains will be small. Does the engine have adjustable valve train? If not, you are limited to around .420 lift. Everything considered, a cam change can make a 40 hp difference, but not a 125hp difference on an otherwise stock motor. 

Edited by Stripes
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