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Need Info. On 428(?) Motor.
I stumbled across a motor today that I need help in identifying. Supposedly it is a 428, maybe a 1968. In the liter valley there is a #28, on front of block (passenger side) there is #0276415 & a YH under that, on rear of block there is #9792968, and of top of block(near the distributor hole) there is #K168.
The heads were off the motor & they are 6X. Tranny is a 375 Hydramatic. ALL of the motor parts are there except the intake, carb., and exhaust manifolds. PS pump, pulleys, starter, timing chain cover, etc. all there. The motor has already been bored .30 over & has forged pistons. Some minor surface rust in the cylinders but looks like another .30 bore will clean it up okay. Can you bore this motor safely .60 over & can pistons .60 over be found easily? Is this a 428 motor & what year & model car would it have come out of? Is it a decent motor to spend some money on and about what is it worth in present condition? The owner is an older guy & told me make him a reasonable offer. What would be a reasonable offer for this complete motor? Thanks for any help, advice, or info. you can provide about this motor. |
yes it's a 428 from 1969. date code is Oct 16, 1968 making it a 69 motor. probably from a big car. 6x heads are not from that motor. The original heads would probably be 62's, 46's or maybe 16's. 40 over would be safer than 60 over, but 60 over can be done. Pontiac called them 455's! The motor is probably worth 800-1200. Offer him $500 and bring her home. It's a very desirable motor with lots of potential.
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Thanks Limejudge69!
I appreciate the quick response & the good info. Am I correct that when you bore a 428 by .60 over that it becomes a 455, or did I misread your thread? I looked through some parts cataloges last night & found some .60 over Pontiac pistons for a 428 but didn't locate any .40 over pistons. Do you know where the best place to locate .40 overs would be? I called the seller of this motor last night to tell him I did have interest in buying it. He knows my 67' GTO and that I am a Pontiac fan. Said he knew the motor would be going to a "good home" and would take $300 for everything. I jumped on that and will be at his house to pick the motor up in about an hour. Thanks again.
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Get the block sonic checked before you bore. You may not get .060 out of it. If it will clean up at .035 over I would do that. SD Performance has Ross pistons at .035 that would work.
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With the aforementioned 4.21" stroke crank,as far as the bore is concerned,all a fella will need to make a 428 into 455 is a .030" overbore to match the 455's 4.150" bore size. :doh: 455 is 4.150" bore x 4.21" stroke. 428 is 4.120" bore x 4.0" stroke. A .060" over 428 with it's original 4" stroke crank is a 440. Also,the .040" over 4" stroke pistons will be an extremely difficult find,ask me the only pistons you'll find like that are custom order pistons,the .060" over pistons will be much easier to find. But I digress. I agree it sounds like an early '69 360hp 428,so it would have had the #46 heads on it likely,the YH code was used in both '68 and '69 so that does'nt tell us much,it's a big car code though,but that's a given now is'nt it. The late '68 date code (Nov. 16) hints to me it was built for '69 body production. The 360hp 428 for '69 was a 2 bolt main affair,where-as most the rest of the 428's were 4 bolt main engines,so that might be one way to absolutely pin down the original application. If it's a two bolt main block,for sure it went into a '69 body. HTH. |
I Got The Motor And A 375 Hydramatic Tranny.
Well, I'm now the proud owner of, and in possession of, the 428 motor I talked about. Just by "eye-balling" it, I think it will be necessary to do a .30 boring to clean the cylinders up. This will make it a total of .60 overbore. I will have it sonic checked to make sure the block is sound and can take this additional boring. Will this create potential problems for a street driven car? IE: overheating? I have no experience with a 428 and wonder if there are any common "weak", or "trouble-prone" characteristics with a 428 (bored to 440) that I need to be careful about, or be looking for.
What about the Hydramatic 375 transmission? Are they junk or is it a decent transmission? I'm familiar with a 350 & a 400 Hydramatic but not this 375. The prior owner said it drove & shifted great. Thanks again for everyone's input and pls. let me know if there's anything else I need to know about a 428 and a .60 overbore job. |
You don't have to stick to that 'OLD SCHOOL' .030/.060 stuff.
As long as there is a ring pac made in that or up size bore sizes I can have any piston set made. Such as 4.125/ 4.145/ 4.150/4.151/4.155 etc, etc. |
428
Killer motor, have to get custom made pistons, if you want forged.
Cast pistons, no problem. Get forged rods. If you ain't running NOS, cast pistons are great, keep it under 6000 rpm. Pontiac Gregg |
Any chance you can just hone the cylinders to clean up the rust Phil? Might be worth a try I'd say.
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GT182, excellent idea! I'm going to have a machinist (primarily builds Chevy motors but knowledgable of most GM motors, not much on Mopar or Ford stuff) check things out for me this weekend. I'm interested in what he finds and what suggestions he has about this motor. Thanx.
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great find!! |
#12 Heads.
I gave wrong info. in my original post. The seller told me he thought the heads were 6x heads. I pulled the valve covers and the number I see stamped in the middle of each head is #12. The heads have been cleaned up some with the "flash" removed & some polish & porting. What is the scoop on #12 heads? What yr. would they be & what motor would they have come off of? How do they flow & are they a decent head? Thanks again.
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Can anyone provide any info. on the #12 heads? I used the search function on this site but didn't really find any specific specs. for the Pontiac #12 head. I'm just trying to find out what motor they would have come off of, and is it a decent performance head. Thanks again.
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What is the number on the center exhaust ports? The complete number for #12 heads should be 9799612, 1970 400 Ram Air III heads. Let us know.
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All of Pontiac's big valve heads from '67 - '70 are basically the same in terms of performance potential. If they had 2.11" intake valves they were designed for 4bbl engines. There are minor differences in combustion chamber volumes & configurations in these years but that's pretty much it. In '71 the port configuration changed a little bit because of the larger combustion chambers but in stock form they're pretty much the same as far as flow and performance goes, just bigger chambers. In '73 the exhaust valve was downsized to 1.66" from 1.77" on all big valve heads but the intake ports remained relatively the same. In '75 the intake port design was slightly revised to restore the short turn radius under the valve that had been truncated by the larger combustion chambers. Again, in stock form, there's not a whole lot of difference.
When talking about porting for maximum performance the '67 - '70 and '75 - '78 large valve castings have the most potential due to their superior intake port designs. The later big valve heads can easily be upgraded to the earlier 1.77" exhaust valves. For a street-strip or basic street port job all years are basically good. Even the small valve heads (1.96" intake valves) have the same basic port design, just smaller dimensions to match the smaller valve. They can still be ported and have the larger valves installed to function just like the big valve castings, they just don't have as much ultimate potential when talking about maximum porting. The long and short of all this is - any large-valve D-port exhaust head is pretty much as good as any other with the only major difference being the size of the combustion chamber which will affect your compression ratio. The minor differences in the ports only come into play when considering porting for maximum performance, and these days most people just step up to an aluminum head rather than "race port" iron heads as the cost is close to the same at that point and the aluminum heads offer even more flow potential as well as other benefits. This picture shows the pertinent information for identifying a set of Pontiac heads: http://i114.photobucket.com/albums/n...cs/head_id.jpg |
This is what I think is stamped on the heads. It was late at night, & sort of dark in my garage, so I may have misread the #'s.
GM D N (arrow points to N) HO 79 3 6 (maybe an 8 & not a 6) Arrow points to 3. 12 5 Do these #'s make sense or do I need to get in better light & read them again? |
I'd say it's a 1970 12 code head.
Cast date H079 - Aug 7, 1969 |
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