Pontiac GTO Forum banner

1 - 4 of 4 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
Hi all,

I am considering buying a GTO. It's a base 1970 Goat but a RAIII engine was supposedly added. The owner told me it had #16 heads. I am not knowledgeable but read somewhere that RA heads were #13 ?

Also, is it true some heads/cam were made for 4spds vs automatic. it has a TH400 and I would like to add a tremec 5spd

Thanks in advance!
Ivan
 

·
Registered
Joined
·
634 Posts
I think most of the '70 RA3 engines had #12 heads. But, lots of things came off the assembly line that were not supposed to be that way. If they had a RA3 car on the assembly line, that needed an engine, and they had #13 heads, but no #12 heads, they'd probably have used the #13 heads, to finish building the car. Don't think there is a lot of difference.

And, LOTS of auto trans engines got a one notch smaller cam than equivalent engines, which came with a manual trans.

Wallace shows the '70 RA3 came with #12 heads & 068 cam, with any trans.

Wallace Racing's Pontiac Engine Search
 

·
Registered
Joined
·
3,770 Posts
Hi all,

I am considering buying a GTO. It's a base 1970 Goat but a RAIII engine was supposedly added. The owner told me it had [URL=https://www.gtoforum.com/usertag.php?do=list&action=hash&hash=16]#16 [/URL] heads. I am not knowledgeable but read somewhere that RA heads were #13 ?

Also, is it true some heads/cam were made for 4spds vs automatic. it has a TH400 and I would like to add a tremec 5spd

Thanks in advance!
Ivan

1970 Ram Air III would have engine code WS for a manual trans and YZ for automatic. The correct heads will be #12 with both engines using the "068" cam.

In 1970, the GTO 330HP 400CI with automatic used the small valve #16 heads and the "066" cam if a GTO engine and the "066" and the smaller "254" cam if a big car engine. This head is not the same as the desirable 1968 & 1969 big valve heads with screw-in rocker arm studs. The small valve heads will also have press-n studs, so the small valve head is not a performance head - so don't be fooled.

You can verify the engine/heads as to the year they were made through the casting date codes found on the block and head. But seeing the seller made such a claim, and he is seemingly wrong, I would be suspect of the rest of the car and would want to verify the car as original and what engine/trans/rear end the car left the factory with. This can be confirmed through the purchase of the PHS documents for the car. Many clones and cobbled together cars out there just waiting to be purchased by the unknowing. PHS Historic Services

If going with the Tremec, know what you are getting into and the costs involved. You will have to cut the transmission tunnel/floor to make clearance for the large Tremec case and a some prefer not to cut up the floor. Other modifications will be needed as well, so not an inexpensive swap.

And, unlike a Muncie, The Tremec uses taper bearings versus roller bearings. Roller bearings are forgiving if you have a slight amount of bellhousing misalignment. Taper bearings are not forgiving, so you will want to ensure that you use a dial indicator to align your bellhousing so the transmission's input/mainshaft is in perfect alignment with the crankshaft or you will eventually damage the transmission and may experience shifting problems.

Next thing is the the RPM limits for shifting. I was told to keep shift points below 6,000 RPM's unless you spent the extra money to get the carbon fiber lined synchros - or the trans won't shift cleanly or until engine RPM's drop to where it will shift. I don't suspect this will be a problem as I doubt you plan on spinning the engine that high.

You will also have to change the rear-end gearing to match the gearing of the 5th gear OD, whichever ratio you get. Suspect you have 3.08 or 3.23 gearing in the present car? You can use one of the online calculators to see what the RPM & road speed is using trans gear ratio and rear axle ratio. You don't want to have to slip the trans into OD gear at 80 MPH to take advantage of it and anything less will have the engine lugging too low. I went with 3.90's using the .64 OD 5th gear ratio.

So with the necessary parts to install the TKO and a rear gear change, you may be looking at upwards of $5,500.

:thumbsup:
 

·
Registered
Joined
·
3 Posts
Discussion Starter #4
1970 Ram Air III would have engine code WS for a manual trans and YZ for automatic. The correct heads will be #12 with both engines using the "068" cam.

In 1970, the GTO 330HP 400CI with automatic used the small valve #16 heads and the "066" cam if a GTO engine and the "066" and the smaller "254" cam if a big car engine. This head is not the same as the desirable 1968 & 1969 big valve heads with screw-in rocker arm studs. The small valve heads will also have press-n studs, so the small valve head is not a performance head - so don't be fooled.

You can verify the engine/heads as to the year they were made through the casting date codes found on the block and head. But seeing the seller made such a claim, and he is seemingly wrong, I would be suspect of the rest of the car and would want to verify the car as original and what engine/trans/rear end the car left the factory with. This can be confirmed through the purchase of the PHS documents for the car. Many clones and cobbled together cars out there just waiting to be purchased by the unknowing. PHS Historic Services

If going with the Tremec, know what you are getting into and the costs involved. You will have to cut the transmission tunnel/floor to make clearance for the large Tremec case and a some prefer not to cut up the floor. Other modifications will be needed as well, so not an inexpensive swap.

And, unlike a Muncie, The Tremec uses taper bearings versus roller bearings. Roller bearings are forgiving if you have a slight amount of bellhousing misalignment. Taper bearings are not forgiving, so you will want to ensure that you use a dial indicator to align your bellhousing so the transmission's input/mainshaft is in perfect alignment with the crankshaft or you will eventually damage the transmission and may experience shifting problems.

Next thing is the the RPM limits for shifting. I was told to keep shift points below 6,000 RPM's unless you spent the extra money to get the carbon fiber lined synchros - or the trans won't shift cleanly or until engine RPM's drop to where it will shift. I don't suspect this will be a problem as I doubt you plan on spinning the engine that high.

You will also have to change the rear-end gearing to match the gearing of the 5th gear OD, whichever ratio you get. Suspect you have 3.08 or 3.23 gearing in the present car? You can use one of the online calculators to see what the RPM & road speed is using trans gear ratio and rear axle ratio. You don't want to have to slip the trans into OD gear at 80 MPH to take advantage of it and anything less will have the engine lugging too low. I went with 3.90's using the .64 OD 5th gear ratio.

So with the necessary parts to install the TKO and a rear gear change, you may be looking at upwards of $5,500.

:thumbsup:
that's what I was thinking...5k I will ask him for the engine code. w the smaller cam am I gonna have to change the cam too if I'm going to the tremec for low end torque? If so, I think I'll pass.
 
1 - 4 of 4 Posts
Top