1970 455 GTO Frankenengine help? - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 11-12-2017, 03:40 PM Thread Starter
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1970 455 GTO Frankenengine help?

New Pontiac owner, thanks for having me. I recently purchased 1970 GTO w 455cu in. The engine block number is a 485428 with YW stamped in front. The heads are stamped 64. I'm looking for advise to restore the motor to original 1970 performance as it appears I have mismatched block and heads from different years. Please advise. Thanks
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post #2 of 9 (permalink) Old 11-12-2017, 04:17 PM
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Welcome !

I would over haul what you have if the car is a driver ... but,,

I am fairly sure your heads are coded correct for your 70 the 64's .. only year made I think..
and probably the originals ... date codes on the heads and build date of your car
all come to mind as variables ...........
installed on a 72? low horse 455 ... thats ok too

this is a very hot topic and will certainly bring way more questions
than you may have ever imagined...

a few of a couple dozen questions that come to mind.... as

is it a 455 car
do you have other supporting parts to make it visually original.. intake? carb? distrib?
air cleaner exhaust manifolds etc for restoration

how original/stock is the rest of the car... tranny.. paint color.. interior color..

any history on the engine ? in or out of the car now? pictures

factory stick or auto

are you reselling? or

keeping it forever and build one the way you would have ordered it new ??

how deep are your pockets for rebuilding/restoring.....we all wanna save money ...but..

remember we are picture whores here and they help alot on comments...guidance ...opinions etc

is it a driver now ?

this post will never end ..... be ready ....... and enjoy your GTO

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post #3 of 9 (permalink) Old 11-12-2017, 06:07 PM
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AS pointed out, No. 64 heads are correct for the 1970 GTO 455 and also found on the 1970 Grand Prix 370 HP 455. 1970 engine had 4-bolt main caps. YW appears to be used on 455 engines for 1974 & 1975 - and most 455's were drilled for 4-bolt main caps but came with 2-bolt main caps.

Compression on a Pontiac is determined by the chamber size, or cc's, of the head. #64 heads had 87 cc's (10.25 compression) and screw-in rocker studs. The 1974 head had 114 cc's (8.0 compression) while the 1975 head had 124 cc's (7.6 compression).

Your YH 455 with the #64 heads should have the same compression as the factory engine. The cam used for the 1970 455/manual was the 068 cam and 455/auto got the 067 cam.
The cam for the 1974 & 1975 YW 455 used the 067 cam.

That said, the performance of your 455 as it is should be about right for a stock 1970 455/automatic. You can easily boost performance slightly with the 068 cam and Ram Air exhaust manifolds. Assume your car still has the Quadrajet carb.

I would suggest you purchase the PHS documents for your car. This will give you your car's build documents - engine/trans/rear/colors/options etc.. The documents I got for my 1968 Lemans included all the factory ASE engine specs - cam specs, valve spring heights/pressures, pistons/piston material, bore/stroke, etc.. This may be of help in selecting parts if you want to go as close to a factory stock rebuild on your engine as possible. However, I don't know if these engine specs are provided for all year cars/engines.
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post #4 of 9 (permalink) Old 11-12-2017, 06:37 PM Thread Starter
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Thanks for the reply. It is in great shape mostly all original 455 car with automatic turbo 400 trans from what i can tell. Intake and exhaust manifolds appear to be correct from the numbers. I bought it from a 2nd owner in British Columbia Canada. It is a canadian made car. The 1st owner had it for 45 years, it has absolutely no rust. It has 87000 original miles. The story I got is that the block was swapped out in the 1990's. The build sheet is on it's way from the Pontiac historical group. The car runs and drives pretty good ( i drove in back from B.C. to Seattle area). I do know it is not putting out 360 HP and I would like to get it to close to 400hp, stock looking nice idling. I'm 57 and this car will not be sold, I reliving my past LOL.
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post #5 of 9 (permalink) Old 11-12-2017, 08:21 PM
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Typically documentation wouwavyave to come from George Zapora as his company is the vendor for doc's from GM of Canada. This GTO may have been originally delivered into the states. Will be interesting to know more


Appears to be a fairly sharp nicely loaded '70 455 Auto.
From the original build sheet remnant:

75 Cardinal Red
A = black vinyl top

TR= 254, Red strato bucket seat interior

B33 = MATS, RR (both mat sets were red)
*F40 = Suspension (standard content '70-72 GTO suspension, 1.125" front swaybar, .875" rear swaybar, boxed lwr control arms)

(disc brakes were only avail on a '69-72 Pontiac A-body or GP as power disc brakes, in actuality, just one option)

L75 = 455 PERF ENG
M40 = TURB HYDRO 400
PX8 = G70 X 14 WW
U63 = RADIO-P/B (AM)
U76 = ??
W84 = ??
Y92 = LAMP
(originally Firm ride optioned A-body's set aprox 1" higher, stiffer springs, different part number spiral shocks)

Cool Car! seldom see really clean original red interior '70's. Recently, Ive been working on a red interior '70 GTO, & its near maroon from heavy sun exposure. In the Plains states, South, & Texas, nearly every '70 L75 M40 GTO I've ever ran across did not have G80 (posi).

Last edited by Pinion head; 11-12-2017 at 08:33 PM.
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post #6 of 9 (permalink) Old 11-12-2017, 08:32 PM Thread Starter
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Wow, thanks for the run down. It all appears to be there. I just finished installing the dome and trunk light. It also has a tissue holder in front LOL.
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post #7 of 9 (permalink) Old 11-12-2017, 08:37 PM
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No problem, the UPC codes were right in front of me. The tissue holder would have been a dealer accessory. Have one my Dad installed over 50 years ago & made it into half a dozen of our family's Pontiacs & one short bed Silverado. My Dad's affinity for adding reel out underhood lights & accessory tissue dispensers was not lost on me, as reel out under hood lights were one of the first trinkets I began pulling in the boneyards in the early '80's.
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post #8 of 9 (permalink) Old 12-09-2017, 01:45 AM Thread Starter
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Thanks for your help again. I have the paperwork now from Vintage vehicle services U76 is windshield antenna, W84 WAS ADDITIONAL FUEL FOR DELIVERY, LOL. Thanks for the advise. I found that it was the 7 millionth car produced in Oshawa Canada. It was drove off the assembly by the most senior employee in the plant and he was given the use for 2 weeks.
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post #9 of 9 (permalink) Old 12-31-2017, 11:39 PM
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Beautiful car. I always thought the 70 GTO was the 'classiest' looking muscle car ever made. I had one w/455 TH400 around 1974 - tan metallic with tan vinyl top and spoke hubcaps. It was fast but a guy with a 69 SS396 Chevelle 4-spd beat me. Surprised to see a 3.07 rear axle on yours - don't know what mine had but it was a highway cruiser - had it up to 132 mph... fastest I've ever gone in a car. I was 17 or 18 then. My dad bought it used to replace the Vega (would've been mom's grocery getter)... he liked cars. Curious what you'll find - check engine vacuum.
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