Cam suggestions for 4.10 Gears - Impala Tech
Performance Our High Performance Area

 
LinkBack Thread Tools
post #1 of 11 (permalink) Old 06-17-2018, 07:05 PM Thread Starter
 
 
Join Date: Jun 2018
Location: Columbus, Ohio
Posts: 7
 
Cam suggestions for 4.10 Gears

New here but i am building( me helping my mechanic when its time) a 69 Impala Custom Coupe project. Got a 2 bolt 454 block that came out of a 72 Chevelle and it is bore 30 over. The block has been done up and freshened already from the machine shop i bought it from. But my question is that the cam have to match up with gears, heads and stall converter, correct? I got my eyes on a pair of 781 heads that have 2.19/188 valves and also been freshened up at a machine shop. If not those then i am going to go with brodix heads with the 2.250'' Intake / 1.880'' Exhaust Valves. What are thoughts on 4.10 combinations for the street. I will barely be on the freeway for more than 15 minutes if i do get on the freeway.
James Mullins is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old 06-17-2018, 09:06 PM
Moderator
 
Join Date: Jan 2006
Posts: 12,278
 
Welcome to the Team James!

Car is heavy so steeper rear gears will help get this big boat up on plane faster. However gas mileage will suffer; expect six to eight miles per gallon with 4.10 gears. I would suggest a 3.55 gear ratio is better suited to your needs as you won't be drag racing it.

As to a cam choice look for a RV cam. It will have more valve lift at lower duration for more bottom end torque to get her moving while still offering a little lope to the cam.

Big Dave
Big Dave is offline  
post #3 of 11 (permalink) Old 06-17-2018, 10:28 PM Thread Starter
 
 
Join Date: Jun 2018
Location: Columbus, Ohio
Posts: 7
 
Thanks Dave. Im not really big on the gas mileage because i have a heavy foot! But it would be nice to drive on the freeway without screaming rpms. I will like to occasionally take it to the drag strip when i get use to driving it. I also have a th400 as well. The rearend i have to put in there has i guess some people call it Thick Richmond gear. Also has a eaton posi. I believe it is original from 69. will the 3.55 gears be a straight swap do you think? Im hoping to get at least 550-600 hp.
James Mullins is offline  
 
post #4 of 11 (permalink) Old 06-18-2018, 09:47 AM
Moderator
 
Join Date: Jan 2006
Posts: 12,278
 
Depends upon the rear end you have now. If it has twelve bolts on the inspection cover it has three possible carrier (2, 3 or a 4 series gear carrier). A thick gear is one from a series below it that has been machined out of a thicker piece of metal to move the gear face closer to the center line of the pinion. this is because as the number goes up the pinion gets smaller in diameter so you have to move the face of the carrier or thicken the gear to allow the teeth to engage.

If you have a thick 4.10 now you have a three series carrier; so a 3.07 through a 3.73 will fit the carrier. If you have a thick 3.73 then some one bolted a three series gear on a two series carrier.

Your Eaton Posi can be rebuilt with new clutch discs if it is slipping.

Big Dave
Big Dave is offline  
post #5 of 11 (permalink) Old 06-18-2018, 01:55 PM
BA.
Moderator
 
Join Date: Aug 2008
Location: Miamisburg, Oh.
Posts: 3,108
Blog Entries: 15
 
Although I dont' have history with the BB, I agree that the 4.10 would be hard to bear even on that 15 minute journey. Depending upon your tire size, and I hope its meaty, I agree that 3.55 is a good fit, 3.73 would seem a limit.
On my car, a 3.42 gear was giving me 3000rpm at 70mph with a Nitto 275/50/17 tire. (not exactly a small tire)


Unfortunately, since I'm not a BB guy, those 781 heads aren't familiar to me.

HOW A NOVICE REBUILDS A 66 IMPALA CONVERTIBLE:
http://www.impalas.net/forums/blog.php?u=1432
BA. is offline  
post #6 of 11 (permalink) Old 06-18-2018, 03:10 PM
Moderator
 
Join Date: Jan 2006
Posts: 12,278
 
'781 (336781) is the same head as the '049 with the only difference being it had hardened valve seats for use with unleaded gas. It was the penultimate oval port head with an open combustion chamber (113 cc), that will support from 550 to 600 horsepower with bigger than stock valves and pocket porting.

Your 2.19"/1.88" valves are the same size as those used in the rectangular port HiPerf head as the stock oval port valve size was a punny 2.06"/1.72". You need to cc these heads (all heads that you buy actually) to verify combustion chamber volume as it will make a difference in your static compression ratio. This is not only because someone could have cut them but because in this time period combustion chambers were ballooning to lower static compression, and these open chamber heads had three different volumes ranging from 113 to 119 to 122cc.

Your choice of piston dome has to fill the void in the head to maintain power (usually a 25.7cc dome). With a flat top you will only get about 7.8:1 compression (great for a blower; poor for normally aspirated). With a 26 cc dome you will be about 9.4:1 which is the max you can run with a cast iron head and pump gas.

Big Dave
Big Dave is offline  
post #7 of 11 (permalink) Old 06-19-2018, 01:20 AM Thread Starter
 
 
Join Date: Jun 2018
Location: Columbus, Ohio
Posts: 7
 
Yeah I have hollow dome .250” 26ccIV Pistons to go with 6.135 scat rods and 4.000 scar crank which I just got all balanced with my scat damper. The rearmed that I have is a 12 bolt 4.10 and the posi was not slippin is what I was told when I got the rear end. It turns good tho. Haven’t put it under the car yet to test. I could still get the gears switched out no problem. But as for the 781 heads the guy said they are Pressure tested Cabinet glass bead blasted and washed. Valve pocket ported. 2.19/1.88 one piece forged SS raceflow valves. Guides cut down .020" more for higher lift cams! ERSON/PBM Hydraulic cam springs (.640 max lift) and Resurfaced.
James Mullins is offline  
post #8 of 11 (permalink) Old 06-19-2018, 01:24 AM Thread Starter
 
 
Join Date: Jun 2018
Location: Columbus, Ohio
Posts: 7
 
As for tires size is something I would info on as well. I want them meaty. That will probably get me the sticky I am looking for. I wonder if I can keep the driveshaft that I have with the 3.55 gears
James Mullins is offline  
post #9 of 11 (permalink) Old 06-19-2018, 12:20 PM
Moderator
 
Join Date: Jan 2006
Posts: 12,278
 
Changing gears doesn't change length of the drive shaft. Changing rear ends might as the ten bolt pinion could be shorter than the twelve bolt pinion, but I would try it first to see how well it fits.

Tires stickyness is determined by the wear number on the side. If the tire is guaranteed to last a hundred thousand miles (a number around 300) it will be as hard as iron and offer no traction (but they are great for burn out contests). The traction rating is a reflection of tread design, not how sticky the compound is. Slicks have a rotten traction rating because there is no tread to grip the road, but at a drag strip they are glued to the track with rubber cement. This is why they grip well there but not on the street.

Tire size has width (measured in milimeters) the aspect ratio which tells you the side wall thickness expressed as a ratio of width to the tire height and the wheel diameter Which has little to do with the size of the tire.

I say this because a 13 car tire and a 14 inch car tire are about the same size. The 14 inch and the 15 inch is the same size as are the 16, 17, 18, and 20 tires. By the time you get to 22 inch wheels the tire is a black rubber band stretched around the outside of the wheel and offers no ride quality at all. But it is still about the same size as the 13 inch wheel car tire. Wheel size (OD) basically determines how tall your side wall is, or expressed in terms of racing, how far the tread is from the metal wheel that holds the tread flat against the ground.

Now a 13 inch trailer tire is tiny by comparison to a car tire's height, and a 22 inch semi truck tire is very very tall. But basically unless it tells you differently on the tire carcass most car tires are 28 inches tall (or close to it).

Specialty tires like a Mickey Thompson Sportsman will not be 28 inches tall; it will tell you if it is 30 inches, 33 inches or 36 inches tall right on the sidewall. It will also tell you the tire's width and wheel size, (but not the aspect ratio). All racing tires work that way and will have on the sidewall "Not intended for highway use; for off road use only". This is because the tires are paper thin for use on a dry race track. They will have little to no tire tread and the tread that they have will not work on a wet road.

NASCAR uses special rain tires for a wet track (made by Goodyear and uses the same aqua-tread design as their street tire) but they won't hold on dry pavement; and have a thick tread area compared to a race tire with paper thin sidewalls that allow the tread to roll and move around if driven on the street (causing you to break away and skid suddenly when cornering).

Best street tire I have found is a Pirelli Trofeo R, and the second best is the Goodyear Eagle ZR Gatorback. They stick well and wear well considering I spent a lot of time going sideways or doing burn outs.

Big Dave
Big Dave is offline  
post #10 of 11 (permalink) Old 06-19-2018, 03:03 PM Thread Starter
 
 
Join Date: Jun 2018
Location: Columbus, Ohio
Posts: 7
 
I meant to say “stocky” look. But I i definitely want to go with 15 rally’s. It’s just the tire size I hear much about that can make a difference in rpms. Appreciate the info though, Dave. I usually have a co worker to help with this stuff but he’s been gon for a few months and I have gotten further in my build since he been on vacation. And I mentioned the driveshaft because under the impala now is a 10 bolt and it was hooked up to a PowerGlide. Didn’t know if thevdriveshft was different between 10 and 12 bolts.
James Mullins is offline  
post #11 of 11 (permalink) Old 06-19-2018, 03:38 PM
Moderator
 
Join Date: Jan 2006
Posts: 12,278
 
This is were a Chevrolet Parts manual comes in handy.

You can not buy parts for your car new except for those parts that are still in use on a new car (such as spark plugs); BUT a part number can be interchanged with a newer part number to see if it is still in use today (could be a drive shaft you could use could be under a Silverado or a SUV or whatever GM calls them now a days). Were the parts manual is useful is in verifying if the ten bolt drive shaft is the same as the twelve bolt. If it is the same part number it is the same part and it will fit.

Final gearing will be affected by the height of your tire. If you have a 27 inch tall tire and you are running a 4.10 your motor will be spinning 2,900 RPM at 55 mph: but if you have a 29 inch tall tire your motor will be spinning at 2,700 RPM. So you will see a decrease of 200 RPM on your tach in this case (you won't feel it or hear it which is why you need a tach). Most tires you buy for your car will be in the range of 27 to 29 inches tall centered on 28 inches tall. If you buy a specialty tire you can really increase the height of the tire but you may not actually be able to fit a bigger tire under the car without modifying the wheel well (tubing it) or body work to increase the size of the wheel arch.

This is a problem I ran into when I ran a Nova that I never had with a 1967-'68 Camaro (I never owned a 1969). The early Camaro body would swallow a 14 inch wide by 30 inch tall slick that could get me into the low ten-teens. It took a lot of work to run the same tire on a Nova even though it was 80% of a Camaro in terms of parts.

Big Dave
Big Dave is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Impala Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome