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Old 11-26-2021, 10:54 PM
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Default 428 in ‘70 TA (short or long term)?

I had another thread about the best heads for a 428 over on the Street forum. My original plan was to pull the RA III out of my TA for a refresh with good rods and pistons. The main reason for this was because the car pings a little bit when you open her up on warmer days. Engine was rebuilt by previous owner about 6000 miles ago (10 years). The rebuild was pretty low-performance. The cam is actually smaller than an 068, and also used the old-style 8-eyebrow pistons, which others have pointed out has probably contributed to my pinging problem.

I have a 428 (+.030) with 670 heads that I pulled out of my ‘67 GTO when it went through a frame off. That engine has the forged TRW pistons with the small 10cc dish. The ‘weak’ link in that engine is the early Pontiac forged rods.

My original plan was just to drop the 428 in the TA ‘as is’ and then do a rebuild on the 400. I was considering doing the stroker kit from Butler and finding a good shop (maybe Butler again) to massage the factory #12 heads. My ‘quandary’ now is, do I “risk” damaging my original WS 4-bolt block with a stroker kit, or do I just put that engine under the bench and go through the 428 with a good set of rods, aluminum heads and run it that way for a while. I kick myself a little bit because I was so intent on buying a number-matching car, but now I’m thinking about going away from that by swapping in the 428. I might even consider putting in one of the TKX 5-speed trans with the 428, just for fun.

And just to add more complexity to the mix, I’m on the process of possibly picking up a 455 block from a PY member.

So here are my questions/request for opinions. For argument’s sake, let’s say money is not an issue:

1. Would you just drop in the 428 ‘as is’ and do a stroker build on the original WS engine, or would you just put that engine away for now?

2. Rebuild the 400 (no stroker kit) with quality rods, pistons, HR cam, ported #12 heads? Just leave TA w/o engine for now (it’s winter in NJ anyway)

3. The 428 had already been bored .030 over, but probably has less than 10k miles on it. If I were going to rebuild it, with better rods/pistons, would I have to bore that again (.010?)? Is that more a machinist question?

4. I recently pulled the heads to check the pistons, and then reinstalled with new Fel-Pro head gaskets and torqued them down. If I pulled them again, perhaps to run the #12 heads, would I have to replace the head gaskets (again)?

5. If you were going to rebuild 428, would you run the #12 heads (pistons need to be properly dished) or go with aluminum heads? If you went with the #12 heads, who would you trust to clean them up (I want to run my stock shaker scoop so running stock intake is a necessity).

6. I know I would need an adapter to run the 428 in the 70 TA, are there certain ones that are better than others?

7. As I mentioned above, I have an ongoing conversation with a fellow PU member about a 455 block. If I wind up with that, would you just build that block and forget about the 428? Could you even to. #12 heads on a 455 (what size dish would that need?)

8. If I go with the 428 (or 455) what are your thoughts on the TKX 5-speed? Or would you just run the stock M21?

Appreciate any feedback. Thanks.


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  #2  
Old 11-26-2021, 11:14 PM
tom s tom s is online now
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Autotec will do custom pistons in 5s,don’t have to 10s

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Old 11-27-2021, 12:48 AM
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"...request for opinions. For argument’s sake, let’s say money is not an issue..."

(1) After market alum block, heads, intake, built with forged crank, H-beam rods, in the stroke & cam you want, at a safe pump gas CR. No GM parts needed.

(2) Same but with iron aftermarket block.

(3) 455 built with either a good stock crank, or forged aftermarket crank, alum heads, H-beam rods, pump gas friendly.

Most everybody agrees that saving the number matching engine is best, if you EVER plan to sell the car. Seems to make it worth lots more & interests more high dollar buyers.

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Old 11-27-2021, 07:57 AM
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Quote:
Originally Posted by tom s View Post
Autotec will do custom pistons in 5s,don’t have to 10s

Thanks Tom. No matter which option I go with (400 or 428 block) I’m assuming I can’t make any kind of piston decision until the engine is stripped down. I can’t just assume that because they are low mileage, they wont need any re-bore, correct?


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Old 11-27-2021, 08:04 AM
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Quote:
Originally Posted by ponyakr View Post
"...request for opinions. For argument’s sake, let’s say money is not an issue..."

(1) After market alum block, heads, intake, built with forged crank, H-beam rods, in the stroke & cam you want, at a safe pump gas CR. No GM parts needed.

(2) Same but with iron aftermarket block.

(3) 455 built with either a good stock crank, or forged aftermarket crank, alum heads, H-beam rods, pump gas friendly.

Most everybody agrees that saving the number matching engine is best, if you EVER plan to sell the car. Seems to make it worth lots more & interests more high dollar buyers.

Thanks Ponyakr. I guess I should have qualified the budget by saying I could probably get a set of aluminum heads, and a rotating assembly, but I don’t think I could swing the additional $3500+ for an aftermarket block.

In option 3, it seems you would suggest building a 455. Any reason to not build the 428, perhaps using one of the Butler stroker kits? Just curious.


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Old 11-27-2021, 08:29 AM
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Quote:
1. Would you just drop in the 428 ‘as is’ and do a stroker build on the original WS engine, or would you just put that engine away for now?
This will not be a 'just drop in' project?
The 428 uses the old 2 bolt engine mounts. You would have to use adapter mounts or change the frame mounts. The adapters can be a problem lots of times because the geometry is off compared to original.

The better deal would be the 455. (or at least a 70 and up engine block)


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Old 11-27-2021, 11:59 AM
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A long time ago I was mentally kicking around a 428 crank 455 block set up.

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Old 11-27-2021, 12:14 PM
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"...Any reason to not build the 428..."

As others have said, the 428 only has 2 motor mount bolt holes on each side.

BUT, if you are a good fabricator & don't mind doing whatever it takes to bolt the 428 block in the car, go for it.

IF you REALLY wanna use the 428 block, it might be a good idea to do the mounting BEFORE you spend any money on rebuilding it. Install it "as is", so that after it's rebuilt you can just bolt it right in.

The previous mention of a 428 crank in a 455 block sounds good. That way, you'd have the 428 stroke & the 455 block that should bolt right in. AND, you'd still have the 428 block, which you could sell for several hundred bucks.

You have options.

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Old 11-27-2021, 01:17 PM
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Has anyone used the Butler adapter plates?Im planning on putting a 301 block in a first gen bird.I have the adapter plates.Tom

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Old 11-27-2021, 01:44 PM
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Back in the day a buddy and I autocrossed a 70 4 speed formula L78. For the Michiganders we ran at Waterford Hills, MIS and Milan Dragway. We spun a rod bearing due to the dreaded RH turn oil starvation at WH, so we built a 428 short block to stuff under the #12 heads and stock intake and q-jet. The rebuild also included a 744 cam and 1.65 rockers. Of course motor mounts were a problem and the only solution at the time was solid mount adapters. We had a little more engine vibration translated into the passenger compartment but that combination of 428, M20 and 3:55 axle was a great runner!

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Old 11-27-2021, 08:40 PM
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I used a 1970 455 4-bolt block with a 428 crank and Ram IV top end in a 1970 T/A I owned in the early 1980s It was an extremely powerful motor, but didn't perform well with on pump gas. Luckily you could still buy Sunoco racing fuel straight from the pump in a number of places. I really liked that combination. I was running one of the HO Specialties camshafts in it.

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Old 11-27-2021, 09:08 PM
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I knew that I would have to go with the adapters to run the 428 in the TA, but I did not know those adapters are not always a ‘bolt in’ option. Maybe I should consider that 455 that I was talking to a fellow member about. It’s a bare 2-bolt block (no crank). If I went that route, would you recommend turning it into a 4-bolt block, or would the 2-bolt be fine?


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Old 11-29-2021, 02:38 PM
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You didn't mention what you were planning to do with the car? The black hole of more horsepower usually leads to other modifications to the vehicle and you expressed concern over the car losing it's numbers matching status. How far are you willing to go. Or in other words how much storage space do you have for all the original parts you have removed?
Another option might be trading the car for one that is more to your current desires.

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