335hp vs. HO motor - Pontiac GTO Forum
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post #1 of 10 (permalink) Old 01-09-2017, 01:08 PM Thread Starter
 
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335hp vs. HO motor

can someone please tell me if there were more differences between the standard 400 and the HO than the following:

'068' cam
ho manifolds
larger exhaust

any other internal differences?
thanks
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post #2 of 10 (permalink) Old 01-09-2017, 06:40 PM
 
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Originally Posted by linden_gto View Post
can someone please tell me if there were more differences between the standard 400 and the HO than the following:

'068' cam
ho manifolds
larger exhaust

any other internal differences?
thanks

Assume you are talking about the 1967 differences as you did not state what year. That looks about right. My book source says the Ram Air and HO engines both used the same exhaust manifolds, #9777641 (R) and #9777646 (L) with the #9777646 (L) being unique to the '67 GTO.

There may be other differences as well, such as radiator/fan, and carb numbers if you are going concours correct. The 4-speed cars got the factory upper/lower control arm braces.
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post #3 of 10 (permalink) Old 01-10-2017, 11:04 AM
 
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Original '67 400HO or RA GTO's had different front brake line routing on the line that runs across the crossmember. Also used a specific steering column with lower shaft that utilized a bolt on cast iron flange, same flange was used on '67 & 68 tilt columns. Back in the 80's, used to run across '67's that had picked up a set of factory RA manifolds & owners were often representing these '67's as factory "400 HO" cars, though they didn't have the correct engine block, brake line, or steering column. Thankfully, PHS came along & a lot of that nonsense ended.
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post #4 of 10 (permalink) Old 01-10-2017, 12:34 PM Thread Starter
 
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Originally Posted by PontiacJim View Post
Assume you are talking about the 1967 differences as you did not state what year. That looks about right. My book source says the Ram Air and HO engines both used the same exhaust manifolds, #9777641 (R) and #9777646 (L) with the #9777646 (L) being unique to the '67 GTO.

There may be other differences as well, such as radiator/fan, and carb numbers if you are going concours correct. The 4-speed cars got the factory upper/lower control arm braces.

thanks for that info. i wasn't aware of the CA braces.

from what i understand, the HO used a different cam than the 335hp motor and the RA motor used another cam beyond the '068' in the HOs. just trying to make sure i have all the differences covered. the RA also used stiffer valve springs than the 335hp and HO motors, as i understand it.
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Originally Posted by Pinion head View Post
Original '67 400HO or RA GTO's had different front brake line routing on the line that runs across the crossmember. Also used a specific steering column with lower shaft that utilized a bolt on cast iron flange, same flange was used on '67 & 68 tilt columns. Back in the 80's, used to run across '67's that had picked up a set of factory RA manifolds & owners were often representing these '67's as factory "400 HO" cars, though they didn't have the correct engine block, brake line, or steering column. Thankfully, PHS came along & a lot of that nonsense ended.
great info! thanks.
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post #6 of 10 (permalink) Old 01-10-2017, 07:27 PM
 
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I believe '67 HO motors used a single arm bracket for the alternator like all '66's, vs the 2 bracket assembly for the 335 hp cars. I also think the carb numbers were the same. Attached are some specs published in "The Legend" that may be useful to you.
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post #7 of 10 (permalink) Old 01-10-2017, 08:05 PM
 
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Originally Posted by linden_gto View Post
thanks for that info. i wasn't aware of the CA braces.

from what i understand, the HO used a different cam than the 335hp motor and the RA motor used another cam beyond the '068' in the HOs. just trying to make sure i have all the differences covered. the RA also used stiffer valve springs than the 335hp and HO motors, as i understand it.

The 335HP engine used the "067" while the RA used the "744" and was a carry-over from the 1966 "XS" engined Ram Air's. The valve springs were different for the "744" cam having a high load to match the cam. I have a number for the 1966 cam as being part #978570 .

A RA '67 was road/drag tested by Car Life. Here are some other specs that may be of interest. They listed the exhaust as dual exhaust, reverse-flow mufflers, and resonators. Pipes were 2" dia while tailpipes were 2 1/4" dia.. Rims were 14 x 6 JK, F-70 x 14 tires. Gas mileage under normal conditions (4.33 rear/4-speed) 8-12mpg.

PH points out some good info that few would be aware of.
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post #8 of 10 (permalink) Old 01-12-2017, 11:25 AM
 
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Originally Posted by pjw1967 View Post
I believe '67 HO motors used a single arm bracket for the alternator like all '66's, vs the 2 bracket assembly for the 335 hp cars. I also think the carb numbers were the same. Attached are some specs published in "The Legend" that may be useful to you.
Thanks! That is really good info from the Legend.
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post #9 of 10 (permalink) Old 01-12-2017, 11:44 AM
 
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Originally Posted by pjw1967 View Post
I believe '67 HO motors used a single arm bracket for the alternator like all '66's, vs the 2 bracket assembly for the 335 hp cars. I also think the carb numbers were the same. Attached are some specs published in "The Legend" that may be useful to you.
Both the front and rear strap type alternator brackets, large alum bracket, hockey stick bracket, & bolts & washer were used when a '67 Pontiac V8 engine was factory equipped with power steering.

When the car was not optioned with PS, & only a manual stag box, a long alt strap & small alum bracket aka "pivot block" were used, same as on the '66 Pontiac 8 4 bbl engines. Neither alt bracket setup was 400 HO specific.
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post #10 of 10 (permalink) Old 01-12-2017, 12:49 PM
 
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Originally Posted by Pinion head View Post
Both the front and rear strap type alternator brackets, large alum bracket, hockey stick bracket, & bolts & washer were used when a '67 Pontiac V8 engine was factory equipped with power steering.

When the car was not optioned with PS, & only a manual stag box, a long alt strap & small alum bracket aka "pivot block" were used, same as on the '66 Pontiac 8 4 bbl engines. Neither alt bracket setup was 400 HO specific.
Thanks, PH. I've only seen 3 '67 HO's and none had p/s.
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