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Old 05-05-2021, 12:04 PM
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Default 421 combination

Hopefully within the next 4/6 months I will start another engine combination for a future 64/65 Pontiac A body. What I have on hand is a 421 short block, #64 and 72cc Eheads. This will be a nice DQ cruiser, 320/330 rear, turbo 400 car. Since this isn't an all out performance build I'm leaning towards the #64s with the advertised 85cc chambers. Would like to run a HR cam in the 230/238@.050 and about. 520 lift. RA exhaust manifolds. I understand even with the #64s I may have to run a dish piston, but not as deep as the 72cc.
Does this sound like a decent combination, or what would you change?
If you have a different cam recommendation, please provide a part number.

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Old 05-05-2021, 01:48 PM
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61-63 61-63 is offline
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Sounds like a neat engine to me. You will get lots of input but my only comments would be to go with the eheads rather than the cast iron and mebby use a built turbo 350 trans rather than a 400 which would mean you wouldn't have to beat on your trans tunnel.

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Old 05-05-2021, 02:41 PM
65CatCoupe 65CatCoupe is offline
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If its really a DQ cruiser I wouldn't spend the xtra on the roller cam but that's just me. Don't forget you get away with more squeeze on the AL heads so the dish will probably end up about the same +/- a couple CCs.

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Old 05-05-2021, 02:59 PM
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mebby use a built turbo 350 trans rather than a 400 which would mean you wouldn't have to beat on your trans tunnel.[/QUOTE]

Wasn't aware of the tunnel modifications needed for the T400.
Really leaning towards hydraulic rollers. Thanks


Last edited by 68WarDog; 05-05-2021 at 03:22 PM.
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Old 05-05-2021, 03:07 PM
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Build it as a stock bore 428 ( 4.120” ) if you can ( if the bore cleans up at that) as that will get you in the 9 to 1 compression ball park with a 85 CC chambers and the 64 castings, also this will get you the needed valve notches in the piston to run either of those heads you have mentioned,

If you run the E heads then the 72 CC ones are less shrouded in the chambers for better flow, but you will need to go to a little bit of a dish piston, but not much because with the Aluminum heads you want a 10.5 to 1 compression due to the heat loss over a iron head.

I think your a tad too big in Cam duration for a drive anywhere DQ car with only about 9 to 1 compression and also in terms of maximum driveability and throttle response I hope your E heads are the D port version, not the 215 CC intake runner round exh port version!

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Last edited by steve25; 05-05-2021 at 03:22 PM.
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Old 05-05-2021, 03:27 PM
PontiacJim1959 PontiacJim1959 is offline
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Bore it .030" over and use 455 pistons and crank. Buy a rotating assembly from Butler if you can afford it, otherwise, piece meal it with the 455 crank, flat top pistons, prepped set of cast rods seeing you are looking for a cruiser.

Flat top pistons and a 96CC chamber will put you at 9:1 compression, or go lower compression with bigger CC heads and select a good cam to match the lower compression and run it on regular gas - more cubes means more TQ which will balance out instead of a higher RPM/HP build.

A TH-350 uses less HP to tun it and can be built to handle the power of a "cruiser." Better lower gearing to get the big car rolling - 2.75 1st versus TH400 - 2.48.

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Old 05-05-2021, 03:38 PM
grandam1979 grandam1979 is offline
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The Edelbrocks are going to flow better unless you are going to port the 64 heads. The Edelbrocks would let you run more compression without worry of knocking. I know you said it’s a cruiser but free power is hard to give away. Good luck with the build.

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Old 05-05-2021, 03:57 PM
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The TH400 fits without hammering the tunnel. The TH350 2.52 low isn’t much lower than the 2.48 TH400 low gear.

I built my 421 HO about as stock as I could including stock 421/389 heads and the 068 cam. Bore the block only as much as needed to clean up the bore would be my advice. I did lower the compression to 8.8:1 with Ross dished pistons.

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Old 05-05-2021, 04:30 PM
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Having 3 running 421/428 Combo's. I am a advocate of the 4" stroke club.....
I would use either a 3.36 or 3.55 gear, depending in rear tire size.
Bore it .030 and use a stock bore 428 piston as Steve mentioned.
Is the crank in good shape or does it need to be ground? If it needs to be ground you can shrink it to a 2.200 journal and use a 6.700/6.800 rod and open up some piston options.
I lean towards E-heads. Grind the name off and paint them to look more stock.
Cam is decent for the combo. Stay in the 230+@ .050 range.
Definitely go for the TH400, no trans tunnel mods needed.

What type carb set up? I would look into the Bathtub intake Tom S is working on with a pair of AFB's or a used Offy intake with a pair.
Easy 475HP set up and drive anywhere.

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Old 05-05-2021, 04:30 PM
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[QUOTE=steve25;6247893]Build it as a stock bore 428 ( 4.120” ) if you can ( if the bore cleans up at that) as that will get you in the 9 to 1 compression ball park with a 85 CC chambers and the 64 castings, also this will get you the needed valve notches in the piston to run either of those heads you have mentioned,

Hopefully once I get the block to machine shop, will determine which direction to go. I wish the standard bore is salvageable. Going for that 64/65 HO GTO look with the #64s, although I'm aware these are 70 heads, and Pontiac never built a 421 HO GTO, and the eheads are round ports, wanting to stay D port. Betts Racing is using a 224/230@0.50..480 in my 70s NM engine, and I wanted something a little bigger with the extra cubes, maybe 228/236@.050 ?
If have to go .03 overbore, the Butler assembly becomes a viable option.

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Old 05-05-2021, 04:57 PM
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Quote:
Originally Posted by Mike Davis View Post
Having 3 running 421/428 Combo's. I am a advocate of the 4" stroke club.....
I would use either a 3.36 or 3.55 gear, depending in rear tire size.
Bore it .030 and use a stock bore 428 piston as Steve mentioned.
Is the crank in good shape or does it need to be ground? If it needs to be ground you can shrink it to a 2.200 journal and use a 6.700/6.800 rod and open up some piston options.
I lean towards E-heads. Grind the name off and paint them to look more stock.
Cam is decent for the combo. Stay in the 230+@ .050 range.
Definitely go for the TH400, no trans tunnel mods needed.

What type carb set up? I would look into the Bathtub intake Tom S is working on with a pair of AFB's or a used Offy intake with a pair.
Easy 475HP set up and drive anywhere.
Mike, the crank is in visibly good shape, but will know more once at shop. I have always like turning rod journals down to 2.20 and using shelf 6.8 BBC rods. Are those 6.7 custom ? Will be using one of the 66 after market tripower setups.
If the block has to go .03, Butler assembly kit becomes a better financial decision.
Since I have a T400 on hand, great to hear about no tunnel modifications needed.
If the eheads were D port, I would be leaning that direction and the #64 was recently rebuilt and setup for the same 224/230@0.50..480 cam going into another engine.

  #12  
Old 05-05-2021, 08:53 PM
PontiacJim1959 PontiacJim1959 is offline
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Quote:
Originally Posted by PontiacJim1959 View Post
Bore it .030" over and use 455 pistons and crank. Buy a rotating assembly from Butler if you can afford it, otherwise, piece meal it with the 455 crank, flat top pistons, prepped set of cast rods seeing you are looking for a cruiser.

Flat top pistons and a 96CC chamber will put you at 9:1 compression, or go lower compression with bigger CC heads and select a good cam to match the lower compression and run it on regular gas - more cubes means more TQ which will balance out instead of a higher RPM/HP build.

A TH-350 uses less HP to tun it and can be built to handle the power of a "cruiser." Better lower gearing to get the big car rolling - 2.75 1st versus TH400 - 2.48.
My bad, should say .060" over, not .030". But, looks like you have a good plan in mind regardless.

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Old 05-05-2021, 11:05 PM
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Just read in another thread that stock 428 pistons come with a 13cc dish. Do anyone have a part number? I see summit and others carry 428 pistons, but don't mention the dish.Thanks

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