if anyone can help me, it would be greatly appreciated. i have a 69 gto 400 ,i want to replace the water pump with a high volume pump,but i just learned my pump is the "short" pump used in early 69 all i can find is the long pump used in later 69,can the difference be made up in apulley change to get the belts to align correctly or am i just out of luck ...thanks to anyone who can help  

You don't have to toss the Short pump - just buy the adapters/spacers from Autopartswarehouse to move it out to align it with the LWP accessories. I did that a couple of years ago on a crate 502 and it works fine. The spacers are also aluminum and look like the finish on the pump.
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Autopartswarehouse.com the best!  

If he is talking about a 502 Chevrolet the spacers he is refering won't quite work on a PONTIAC. A company called Flow King will be able to fix you up with the high volume pump you need for your specific application. Hopefully your GTO is Pontiac powered.  

Here is some good info on timing covers, pumps and pulleys I ran across a while back....


All of the timing chain covers from 1964 to 1979 will bolt up and interchange with any motor from those years. However, you must use the matching water pump, pulley and crank pulley to avoid alignment problems with the alternator and/or power steering pump. All of the water pumps from ‘64-‘68 will interchange. These pumps have eight bolts and measure 3-5/8” long (from base to water pump pulley flange). The casting number for ‘64-‘65 is 9772716 and for ‘66-‘68 it is 4782482. The matching pulleys are 2” in height. From ‘64-‘67 Pontiac used a small diameter (5.25”) six bolt two-piece harmonic damper and from 68-79 a large diameter (6.75”), one piece four bolt damper was used. In ’69 Pontiac changed to an 11-bolt water pump but the early ’69 was different from late ’69-on. Many early ’69 Firebirds and GTO's used a pump that measured 4” long (casting# 9796351) and the pulley was 2-1/4” in height. From late ’69 to ’79 only one pump style was used, it measured 4-1/2” long and there are at least two different casting numbers used: 482138 and 488296. The matching pulley should measure 2-5/8” in height. Always use the correct diameter and style crank pulley to match the water pump pulley and also use the same series timing chain cover and balancer to properly line up your timing marks. The same timing chain cover was used for both ‘64 & ‘65 and had just a simple pointer. These were cast with number 9773371. The timing cover used on ’66 and ’67 employed a small timing scale marked -4, 0, and +6 and is otherwise identified as casting # 9783130. The ’68, ’69 and ’70 timing covers look very similar with timing marks of 0-6-12 degrees BTDC and accommodated the large diameter damper. The ’68 timing cover casting number is 9790347 and uses the 8-bolt water pump. The ’69-‘70 timing cover casting number is 9796346 and uses the improved 11-bolt pump. For ’71 and later the timing cover timing tab is marked from 4 degrees after to 12 degrees BTDC and is graduated all the way to 16 degrees BTDC. As compression ratios were lowered to 8:1 and lower there became a need for increased initial advance. Casting number for this cover is 482883. If you need to order a water pump the Federal Mogul part numbers are: ‘64-’68 is FP1388N, early ’69 is FP1409N and late ’69-on is FP1423.  

Wow! That's what I call a thorough answer! Thanks from all of us who new there was a difference, but didn't know what it was. I think this pretty much covers the whole ball field.
Steve  

Yeah, if every answer was that thorough, then there would not be any further discussion!  

I've saved that answer off to my PC since even I did not know every detail.  Thanks again!

Craig  

Too Much Information is sometimes a GOOD thing!