new head identification question - Pontiac GTO Forum
User Tag List

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 13 (permalink) Old 04-22-2006, 12:50 PM Thread Starter
 
Join Date: Mar 2006
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
new head identification question

I was able to find the head numbers. My best quess is 16. It is pretty worn with age. The only other number it could be is 18. I noticed that 16 did come on a 400 in 1968, and an 18 came on a 350 in 1968. I really think it is a 16, I had a few other people look. What I thought was strange is when I changed the spark plugs they were a 5/8 plug. The book said it should have been a 13/16 plug. From what the book said 71 and older use 13/16 and 72 and newer use 5/8. Also I did check the block and it is a 400. Would heads from a 350 fit on a 400?
Thank you to Randy and Lars for helping me locate the head numbers.
matt
matt68gto is offline  
Sponsored Links
Advertisement
 
post #2 of 13 (permalink) Old 04-22-2006, 02:34 PM
 
Join Date: Apr 2006
Location: Evans GA
Posts: 56
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Any head will bolt onto any block, at least for the 350's and 400's anyway. But that doesn't mean that the combination will work well. The same with the intake manifolds. And there has been a whole lot of mixing and matching out there so unless you are sure that the parts you have came on the block then I wouldn't assume that's the case.

And there are oddball heads out there with numbers that don't fit the list. I am running 061 heads on the 350 in my '69 LeMans conv. According to the chart they would be from a '67 2bbl 400, but I originally bought the engine they came on in back in 1982 from a guy who wrecked his GTO, and they have 2.11/1.77 valves so that makes no sense... (by the way to get big valve heads to work on a 350 with a high-lift cam you have to add chamfers at the top of the cylinders for valve relief.)

I have never seen a pre-'72 head that is supposed to use the smaller plugs so that seems suspect. Are you sure that someone just didn't have the right plugs in there?

Given the small plugs I don't think that there is a sure way of telling what you have without checking the valve size and cc's. If you are satisfied with the way that the engine runs then don't worry about it. If you plan on performance modifications then you should probably pull them and have them checked out anyway.

Walt
PontiacGuy is offline  
post #3 of 13 (permalink) Old 04-22-2006, 04:09 PM Thread Starter
 
Join Date: Mar 2006
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
walt
the plugs in there were r45ts ac delco. I just replaced them with the same.
i haven't had the car very long, and i am trying to figure out what heads i have. With the casting being 16 and the date code being e158 and the spark plugs being 5/8 I am confussed. Performance is o.k. but i plan on do mods this winter. I do know that the guy i bought it from replaced the motor in 1985. I was hoping that the heads were from the orignal motor. I know the block isn't. It is a 1977 block.
thanks
matt
matt68gto is offline  
 
post #4 of 13 (permalink) Old 04-22-2006, 09:57 PM
 
Join Date: Apr 2006
Location: Evans GA
Posts: 56
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Matt, I am no expert but I did build my share of Pontiac musclecars through the 80's and have done plenty of mixing and matching myself. With a 16 code on the exhaust ports the '68 heads sound right, but the small plugs really do bother me.

The '77 block is fine, although I always try to keep 60's parts in 60's cars just because. But 70's heads have a much lower compression ratio and definitely don't belong in a classic goat. The old heads sometimes disappear during engine swaps because they are valuable. The LeMans convertible that I have now is a rare "Sport" version and came with the 325 HP 350. The previous owner (clue-less) was very proud that he had put late 70's "Trans Am" heads on it when he had the engine rebuilt. I figure that the head swap was the shop's idea, and I am sure they made some good money on the old heads. Needless to say, the 350 with big-chambered 400 heads was a real dog and tossing them was one of the first things I did.

Which goes back to your situation. If you have the original heads on the car then the C/R will be very high for today's gas and it should want to ping and run-on especially if you try putting regular in it. This also puts quite a load on the starter motor when the engine is hot which is hard not to notice. The 70's compression is much lower which will make the engine much happier on pump gas, but this also kills power especially at higher RPMs. If you have the original heads and a reasonable cam it should pull strong through 5,000 RPM. If power quickly dies back over 4,000 RPM that's not a good sign. So how the engine actually runs should provide some clues.

By the way if your 400 had the '68 350 heads then the C/R would end up at almost 12:1 which would create big problems, so this is highly unlikely.

Other things to look for- although the 70's heads will bolt up the heat crossover passages don't always match up correctly with the 60's intake manifolds. If you have the original 60's intake and an exhaust leak at the crossover that's also not a good sign. Let's see, another thing worth doing is pulling a valve cover to see if the heads have screw-in studs. To be honest I don't remember if the 16's came with them and there were plenty of excellent '60s heads that didn't, but its another thing to add to the ID list.

Walt
PontiacGuy is offline  
post #5 of 13 (permalink) Old 04-24-2006, 10:20 AM
 
lars's Avatar
 
Join Date: Sep 2004
Posts: 445
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 1 Post(s)
Matt -
Just because the heads had the new "peanut plugs" in them doesn't mean they are the correct plugs. Pull a plug out and check the spark plug seat. You can visually tell if the seat is for a flat gasket (large plug) or a taper seat (peanut plug) application. A pre-71 head does not use a peanut plug, but I see them installed all the time.
Lars
lars is offline  
post #6 of 13 (permalink) Old 04-24-2006, 07:43 PM Thread Starter
 
Join Date: Mar 2006
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Thanks again Walt and Lars!

Walt the car seems to run and start normal. When hot and I try to restart it, it seems to act like it is out of gas in the float bowl. (would the sound I should be listening for, sound like the timing is to far advanced or would it start like it was out of gas for about 5 seconds,if it had high compression) The guy I bought it from said he ran 87, since I bought it I have ran 91, not that it probably makes a difference. It has never pinged or ran on. Since it is a 77 block would the pistons lower the compression? Also is there a way to do a compression test and cross reference the number to tell the compression?

Last edited by matt68gto; 04-24-2006 at 08:55 PM.
matt68gto is offline  
post #7 of 13 (permalink) Old 04-24-2006, 08:54 PM Thread Starter
 
Join Date: Mar 2006
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Hey Lars,

I had a mechanic look at my head spark plug seat and he said that I did have the wrong spark plugs. That I needed the bigger plugs. he also said the casting number was 16.
thanks
happy matt
matt68gto is offline  
post #8 of 13 (permalink) Old 04-24-2006, 09:34 PM
 
Join Date: Apr 2006
Location: Evans GA
Posts: 56
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Man I have been out of this for a long time, except for playing around with my LeMans a bit during the past few years. So I am reaching back into memory. I just started watching this board when I decided to buy a new GTO. I'm glad Lars jumped in, maybe others with more recent experience can jump in.

But just for fun I'll give you my thoughts.

I agree with Lars that the small plugs should thread in. I can't imagine why anyone would do this but then the big plugs were still the "standard" when I was working on Pontiac engines. I suggest that you stop by a machine shop with some old-timers, they should be able to take a look at the seats and tell you right away which plugs are correct and answer your head question for good.

All of my 60's high-perf 400's didn't like pump gas much when they took the lead out, even the high-octane stuff. Unless something has changed in gas formulation I can't imagine running 87 octane in an old 10+ C/R engine. Also all of them really worked the starter motor especially when hot (sounds like too much timing advance). I installed high-torque starters and the biggest batteries I could find in order to keep them cranking through the summer months.

You can't tell compression ratio with a compression tester because the cam duration/timing affects the reading. And I never worked on a Pontiac engine with dished pistons and didn't even consider that your engine could have been rebuilt with them.

The bottom line is that you can probably resolve the head question by figuring out which plugs really belong. But the only way to tell what else you have is by pulling things apart.

Walt
PontiacGuy is offline  
post #9 of 13 (permalink) Old 04-24-2006, 09:35 PM
 
Join Date: Apr 2006
Location: Evans GA
Posts: 56
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I just saw that our posts crossed. Glad to hear that you have the good heads!

Walt
PontiacGuy is offline  
post #10 of 13 (permalink) Old 04-24-2006, 09:46 PM Thread Starter
 
Join Date: Mar 2006
Posts: 42
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Walt
Thanks for all your time
Look forward to talking to you in the future
matt68gto is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO General Discussion

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum 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











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



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