Pontiac GTO Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
21 Posts
Discussion Starter #1
Hey there,

There is a good possibility the M20 in my 65 has a 10 spline input shaft. The Tremec is fitted out with a 26 spline design. Can the clutch discs (Centerforce dual) be modified for the configuration, or do I need to buy new discs?

TX
 

·
Registered
Joined
·
4,388 Posts
Are you sure the TKO500 uses the 26 spline input shaft? I see online the TKO500 is 10 and the TKO600 is 26. The hub of any clutch disc will need to be matched to the spline count on the input shaft of the transmission. So the answer is "no." You will need to purchase new clutch discs.
 

·
Registered
Joined
·
4,388 Posts
I will also add that you want the lightest clutch set-up that will give you the best clamping force. Reason being is the inertia factor of a heavy clutch on the TKO transmissions as the design of the synchros is such that they operate basically off of friction rather than the Muncie style brass synchros with teeth. The TKO synchros can be updated, unless they now come fitted with the carbon fiber blocker rings. Some seller upgrade these as part of what they offer. The TKO is not a high RPM shifting trans out of the box unless you go with this upgrade - as told to me several years ago when I purchased my TKO600. It is good to about 6,000 RPM's and will demonstrate shifting problems due to the design of the synchros unless you go the carbon fiber route. Again, this could have all been upgraded over the years, so keep this in mind.

Also, it is highly recommended to make sure you align the transmission input shaft to the crankshaft. The TKO uses a taper bearings whereas the Muncie uses ball bearings. The ball bearings allow for some misalignment. Taper bearings do not and you can have shifting issues or do trans damage. "Clutch Housing: The clutch housing must be properly installed and aligned using a dial indicator. The centerline of the transmission must match the crankshaft, or severe damage to the transmission will occur. The clutch housing must also be perpendicular to the rear of the engine block. A maximum run-out of .005” is allowable. Specific dial indicating instructions should be included with your clutch housing."

Just know what you are getting into as these are 2 different transmissions and what works with the Muncie may not work with the TKO.
 

·
Registered
Joined
·
21 Posts
Discussion Starter #4
I will also add that you want the lightest clutch set-up that will give you the best clamping force. Reason being is the inertia factor of a heavy clutch on the TKO transmissions as the design of the synchros is such that they operate basically off of friction rather than the Muncie style brass synchros with teeth. The TKO synchros can be updated, unless they now come fitted with the carbon fiber blocker rings. Some seller upgrade these as part of what they offer. The TKO is not a high RPM shifting trans out of the box unless you go with this upgrade - as told to me several years ago when I purchased my TKO600. It is good to about 6,000 RPM's and will demonstrate shifting problems due to the design of the synchros unless you go the carbon fiber route. Again, this could have all been upgraded over the years, so keep this in mind.

Also, it is highly recommended to make sure you align the transmission input shaft to the crankshaft. The TKO uses a taper bearings whereas the Muncie uses ball bearings. The ball bearings allow for some misalignment. Taper bearings do not and you can have shifting issues or do trans damage. "Clutch Housing: The clutch housing must be properly installed and aligned using a dial indicator. The centerline of the transmission must match the crankshaft, or severe damage to the transmission will occur. The clutch housing must also be perpendicular to the rear of the engine block. A maximum run-out of .005” is allowable. Specific dial indicating instructions should be included with your clutch housing."

Just know what you are getting into as these are 2 different transmissions and what works with the Muncie may not work with the TKO.
Jim, Thanks for the info. I will double check the spline number. Now that we have connected, here is a link to the car I own. If you don't mind could you look it over and give me your impression and thoughts. In addition to the transmission, I would like to change the rear to 3.55 and upgrade the heads to Aluminum. I have been told the fitted cam is a bit unusual for this set up and that a roller cam with a wider LSA would be a better fit. Here is the link if you are interested. 1965 Pontiac GTO - Subtle Yet Savage - High Performance Pontiac Magazine.

By the way, this will be primarily a street rod with a few shots at the track.

Ray
 

·
Registered
Joined
·
4,388 Posts
Jim, Thanks for the info. I will double check the spline number. Now that we have connected, here is a link to the car I own. If you don't mind could you look it over and give me your impression and thoughts. In addition to the transmission, I would like to change the rear to 3.55 and upgrade the heads to Aluminum. I have been told the fitted cam is a bit unusual for this set up and that a roller cam with a wider LSA would be a better fit. Here is the link if you are interested. 1965 Pontiac GTO - Subtle Yet Savage - High Performance Pontiac Magazine.

By the way, this will be primarily a street rod with a few shots at the track.

Ray
Very nice restomod, I like it.

OK, you asked so this in my opinion. Installation of the TKO generally requires cutting the floor at the trans tunnel to accommodate the larger size case. The 3.31 gears should be changed out and matched to the OD gear ratio of the TKO. Generally, I would suggest shooting for a gear ratio that would put your engine around 2,100 RPM's at 70 MPH. Others here will say you can go lower on the RPM, but for me, 1,800 - 1,900 RPM's is kinda lugging it if you have a cam that likes RPM's and even though your engine has plenty of torque to do so. I feel a little higher RPM has the oil pump working better and keeping a good oil flow/pressure to the engine. You also don't want to lug it and experience detonation when you hit a grade or push a little hard on the pedal. With my build and the TKO600 and the .64 OD, I went with a 3.89 gear in the Ford 9" I am using. 3.55's may be too low and you may want to step up to 3.73's. Figure out what trans you have and what your final OD is and then use one of the online RPM/Tire Size/MPH calculators to get you to where you want to be.

In the write up, I did not see any mention of the upper & lower control arm braces. Your car may have them, it just was not mentioned in the article, but if not, I suggest you add these with the HP/Torque the engine has and for "spirited" driving and occasional trips down the track. These are bolt-on and simple to install. I went with the UMI brand, but there are others and at various prices. Pontiac installed their own version of these in 1967 on 4-speed cars and they are made aftermarket.

The aluminum heads will flow more than the #16 heads, of course, but you want to take advantage of them using a higher compression. Generally, the rule of thumb is to go 1 point higher in compression than iron heads with 9.0-9.3 compression typical of iron heads running pump gas. Reason being is that aluminum draws heat and cools faster, so a higher compression produces more pressure and more pressure equals more heat - so all things balance out. The intake ports are generally the larger RA IV size. The Performer RPM has the larger RA IV sized intake ports. Your RA exhaust manifolds on the #16 heads use the stock D-shaped ports so you want to also make sure you get an aluminum head with the D-ports and not the round-port exhaust shape. You may have to use a different length pushrod and I believe you also have to use matching head bolts with something like the Edelbrock. I am not sure if there is any special bolt set needed for something like the KRE heads. So make sure you know all the parts you will need to do the swap if you go that route.

The cam specs in the article is not one I would have chosen. The 108LSA is a "tight" lobe. The engine probably has "explosive" power by the seat of the pants feel, but runs out of RPM kinda quick and when it does, power falls off fast - BUTthis cam may match the flow of the heads as the #16 head flow will most likely be the limiting factor for the 461CI engine. For the street, you want a wider LSA so as to give you a nice broad power range - which may not feel as powerful as the 108, but it may actually beat a tighter LSA cam over a 1/4 mile race. My choice is a 112 LSA as kinda a compromise between the 110 and 114LSA cams. With the aluminum heads, you can go pretty big on lift, but you have to make sure you have the valve-to-piston clearance. Higher lifts mean more valve spring pressures which means parts wear a little faster. With the Pontiac, you build for torque, not HP - just like a Harley. A roller cam can be a benefit with high lifts because you can go high pressure on the springs and not be as concerned with wear, ie cam lobes/lifters. I am not a fan of roller cams due in part to costs, and due to the fact that if you do go roller, you want to use a high lift and that can now cause additional stresses applied to the lifter bores as the shape of the roller cam profile is more "square like" rather than egg shaped like a flat tappet. The fast lift of that square like lobe exerts additional pressure to the side of the lifter bore. It is possible to crack, or bust a lifter bore. An aftermarket lifter bore brace is available that is used to strengthen the lifter bores and make them more stable. Some will tell you that you do not need these on a low lift roller. Even a low lift roller lobe is somewhat square and is designed to loft the roller lifter up fast to open the valves quicker - still puts pressure on the sides of the lifter bore. My question is always, "Do you really want to take a chance on not using them and destroying your engine because you were told you didn't need them?" Pontiac did not design the lifter bores/lifter valley for roller cams/lifter - or someone would not have come up with an aftermarket lifter brace. But, the choice is yours. I am old school and still like/use a flat tappet cam, but prefer a solid flat tappet over hydraulic.

You don't need to go crazy with duration. The more duration you go, the higher in the RPM range your engine needs to spin and then you give up some bottom end TQ/HP which is what your really want for the street. With the larger cubed 461, the cam that is radical in a 400CI, will be milder in the 461CI. I would limit the engine to 6,000 RPM's reading the article and having all the forged bottom end. You could most likely go higher, but keep in mind what I said about the TKO, it may not like to shift very cleanly at higher RPM's unless you do some $work to it. Again, select a cam for tons of torque. I would keep duration at 280 degrees or slightly under UNLESS you were to use the Rhodes type lifters when going over 280. And if you ask 100 guys what the best cam is for your engine, you will get 100 answers. My cam choice for my 455CI ,060" over is the Crower 60310 solid cam and their corresponding lifters having the oil holes restricted to keep oil down in the bottom end rather than install restrictors in the lifter bores to limit oil to the lifter. 112LSA, .477/.501 lift, 284/288 advertised duration, 2,800-6000 RPM range (which may be lower with the bigger cubes) I am hoping to get around 5,600 - 5,800 RPM's out of my engine, but the larger cubes don't need to spin big numbers to produce big power.

I am using a set of 1972 Pontiac 7K3 heads which I did my own port work on and then had them rebuilt using the longer RA IV Ferrea stainless steel valves so I can go with a higher lift using the 1.65 ratio rocker arms if I choose to.

With all that said, I would first try using what you have rather than step up to aluminum heads and roller cam unless you just wanted to and were looking for big HP/TQ numbers. Aluminum heads will definitely flow better out of the box than the #16 heads and you can certainly get closer to 500HP or so with the aluminum heads/roller cam. The #16 heads are a good. Reading the article, I suspect they were prepped well. I would go with a different cam/lifters and see how you like it that way. Go with a wider LSA and drop the duration down a little or go with the Rhodes lifters to give you back some bottom end with a duration like the cam in the car now. Dial in a distributor advance curve to match the new cam.

But, its your build, so go with what you feel. (y)
 
1 - 5 of 5 Posts
Top