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post #1 of 11 (permalink) Old 12-26-2016, 06:54 PM Thread Starter
 
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428 opinions?

I have a '67 400 I was doing a general rebuild on when I found the crank needed to be replaced,so now im getting a wild hair to go different.
I have #46 heads from a 350 that have screw in studs, 98cc chambers and 1.96 1.66 valves already completely rebuilt , and planned on using 5cc 2 valve relief pistons to get the compression up. Just because I like being different, what is the forums professional opinion on going with a 4" stroke 3" main 428 crank? This is just going to be a street motor, no racing whatsoever. That being said, I know big valve heads would be ideal for max hp, but that's not a concern. Does anyone have any thoughts on going with the crank that uses BBC rods over the Pontiac large journal? Pros and cons? Suggestions for a cam with this combo being backed by a Auto trans? When I was planning on the stock rebuild I was going to go with the comp xe262, is that enough cam for a 428 or should I go with something different? The heads will probably be my choking point, but should still see more power over staying 400
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post #2 of 11 (permalink) Old 12-26-2016, 07:27 PM
 
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I'd go with a forged 4.21 or 4.25 stroke crank. More cubes & low end torque. But, a 4" stroke is better than a 3.75, IMO.

http://butlerperformance.com/i-24591...tegory:1234863

http://butlerperformance.com/i-24453...tegory:1234863

http://butlerperformance.com/i-24591...tegory:1234863

It is said that the longer BBC rods produce slightly less piston side loading. But, I don't think there is enuff difference to be concerned about.

The #46 heads will be fine. But I'd go with one piece stainless valves. Broken stock valves have ruined lots of engines. But, on the other hand, lots of guys have not had any stock valve failures.

I would NOT go with an XE cam !

The cheapest decent cam is probably a Summit 2802. If you go with 4.0 stroke, the 2801 will be decent. A Crower 60243 will work with any of these strokes. A Crower 60242 or 60916 will also work.

https://www.summitracing.com/parts/sum-2802

No need to go any bigger than an 041 grind, such as the Crower 60919 & Melling SPC-8. If you go with one of these, I'd use Rhoads lifters, to smooth the idle & provide more vac.

http://www.ebay.com/itm/Engine-Camsh...ZXgN6J&vxp=mtr

https://www.summitracing.com/parts/r...w/make/pontiac

A Howards 410051-14 is the biggest I'd use without Rhoads lifters.

https://www.summitracing.com/parts/h...w/make/pontiac

http://www.jegs.com/i/Crower/258/66056X3-16/10002/-1

http://www.jegs.com/i/Crower/258/68404-16/10002/-1

If you want a dead smooth idle, and don't want to rev above 5000rpm, you can go with an 068 clone cam, such as the Melling SPC-7 or the Crane 968781.

http://www.ebay.com/itm/Engine-Camsh...FWcRb3&vxp=mtr

https://jet.com/product/detail/b976a...de=PLA15&ds_c=[*Campaign*]&ds_cid=[*CampagnID*]&ds_ag=[*Adgroup*]&product_id=b976ad4e0616440e97b1cd74094d8dba&produ ct_partition_id=61865531738&gclid=Cj0KEQiAnIPDBRC7 t5zJs4uQu5UBEiQA7u5NezkoIcYlFfpfW7cIVyfHolMLfzxCJM E-YfwZszm28cEaArfk8P8HAQ

http://www.ebay.com/itm/Pontiac-Ram-...1Uwp5F&vxp=mtr

Keep in mind that if you use the #46 heads, you'll need to use a '72-up intake, or an aftermarket alum. The '67-'71 factory intakes had a larger exhaust crossover hole on the passenger side. This will cause a leak with the '72 and later heads, because these heads have a blind hole, just above the exhaust heat crossover hole.

http://www.hotrod.com/articles/hppp-...-modification/

Last edited by bigD; 12-26-2016 at 08:24 PM.
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post #3 of 11 (permalink) Old 12-26-2016, 09:26 PM Thread Starter
 
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I did consider going 455, but seems like everyone's doing it, I like being different,lol. I have heard about having to go with an intake to match the different ports on the later heads, thanks for the reminder.
You say avoid the xe cams, why is that? Seems like they have a love em or hate em following. I don't know enough to have an onion either way, just trying to educate myself.
Idle quality isn't a concern, I kind of like a little lope!
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post #4 of 11 (permalink) Old 12-27-2016, 08:39 AM
 
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Harold Brookshire, a well known cam designer, especially for Ultradyne, also worked for Lunati and designed the Voodoo cams for Lunati. For the valve closing ramps he used the same ramp as GM did to save on the valve train. Comp's XE series has a rep of the closing ramps being so fast the valve bounces off the seat, hence a clicking noise.

Here's a thread on the PY (Pontiac Performance Years) Forum to give you some other thoughts on cams.

Voodoo cam choice - PY Online Forums

Keep us posted on your build. My GTO has a '69 Grand Prix 428.
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post #5 of 11 (permalink) Old 12-27-2016, 09:07 AM
 
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Besides the above mentioned problem with the XE cams, they were designed to increase cylinder pressure in low compression engines. Therefore, if you have anywhere near 9:1 CR, or more, an XE cam can easily put your engine in danger of detonation, with today's poor quality low octane pump gas.

The Lunati Voodoo cams are much better, but still increase pressure. The XE & Voodoo series cams are said to be "steep ramp" cams. They are not designed for higher compression street engines. If your engine has 9:1 CR or more, you need more adv duration, in order to relieve some of the pressure, and reduce the chances of detonation.

Just to show the difference in the advertised dur of a Voodoo cam, let's compare a Voodoo 276 with the popular Pontiac 041 grind. The 041 has an intake dur of 308 degrees. The Voodoo has an intake dur of 276 degrees. That's more than a 30 degree difference. So, it's easy to see that these 2 cams are nothing alike, even tho their dur @ .050 lift is similar.

http://www.lunatipower.com/Product.aspx?id=1777&gid=287

http://www.wallaceracing.com/camcode1.htm

https://www.summitracing.com/parts/lun-10511003

The Howards 410051-14 has the same dur @ .050 as the 041, but has 9 degrees more adv intake dur than the Voodoo.

https://www.summitracing.com/parts/h...w/make/pontiac

The Crower 60243 has 8 degrees more adv dur than the Voodoo, but slightly less dur @ .050, than the 041.

https://www.summitracing.com/parts/c...oAMaAjJS8P8HAQ

The Summit 2802 has 4 degrees less dur @ .050, than the 60243, but has 298 adv intake duration, which is 14 degrees more than the 60243. So, on paper, the 2802 looks like it would be less likely to produce detonation.

https://www.summitracing.com/parts/s...2DsaAqHJ8P8HAQ

So, what does all this mean ? It means that the XE cam is more likely to make noise & cause detonation, than any of the other cams mentioned, and that the Summit 2802 is less likely to cause detonation, than any of the other cams mentioned. IMO

Another thing that can help is to keep your quench distance down to around .040. You can do this with zero deck height & 1016 Fel-Pro head gaskets, which are .039 thick.

https://www.summitracing.com/parts/f...ohYaAkO98P8HAQ
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Last edited by bigD; 12-27-2016 at 10:02 AM.
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post #6 of 11 (permalink) Old 12-30-2016, 12:28 PM
 
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As you stated, heads will be the limiter in your combo. Using those heads, you are looking at about 8.5 compression or a tad bit more. I used the Wallace Compression Calculator using your numbers (400 bored .030" over 4" stroke), a typical Felpro head gasket, and with the pistons down in the bore .020" (deck height). Using a Cometic head gasket, .027" in thickness raises it up to 8.75.

The key here is Quench area above the piston. With the factory pistons .020" down in the hole, plus the Felpro gasket, you will have about a .060" quench distance. Not ideal, but of course works. The preferred Quench distance is .040-.045" in an effort to minimize any detonation. So the Cometic gasket does this without having to cut the deck on your block - keeping in kind that pistons expand when hot. Cometic's run about $100 each, so not inexpensive, but I don't know what decking costs AND it will change the geometry on the heads/intake/valley pan, etc., so this will have to be dealt with which could cost additional $$.

8.5-8.75 compression is not bad, but you will need to select the best cam for your compression. Here is where I like the Comp Cams line of 110 LSA offerings as you want a cam that builds pressure, ie higher dynamic compression due to intake valve closing and overlap. The wider LSA cams are generally best for higher compression engines, so you have to match your compression to the best cam for you application. Here is an excellent article on cam selection and cylinder pressure. This is for the Mopar guys, but it applies to any engine: #11--- Horsepressure Hughes Engines offers the "Whiplash" cams just for low compression engines based on the previous tech on cylinder pressure. Just listen to the video. #10---Whiplash Cams So you just want to get the right cam combo.

You already know the heads will be the killer in power. The smaller valves & unported heads will limit total air flow and RPM's. However, the velocity of the air intake should make the engine real responsive with the smaller valves and longer stroke. Don't be surprised if the engine drops off in power near the 5,000 RPM mark.

I assume you are looking at a rotating kit due in part to the Chevy rods. It probably won't matter either way, Chevy or Pontiac length rods at the lower street RPM's you will be turning. What you do want is forged rods in either case.

Use a stock iron Q-jet intake and factory Q-jet.

So, the combo will work, like any, you just have to match the components to maximize your efforts to achieve Horsepower & torque.
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post #7 of 11 (permalink) Old 12-30-2016, 03:05 PM
 
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I just ran these numbers thru the Wallace CR calculator.

428 +.030, 98cc heads, 3.8cc valve reliefs(Auto-Tec), .039 x 4.3 gaskets, .000 deck height

CR = 8.98:1.

Just a slight cut off the heads will put it over 9:1. That's plenty for a pump gas engine today.

Compression Ratio Calculator - Wallace Racing

You can also order the Auto-Tec pistons, with the pin location moved, at no charge, to give you zero deck height without cutting the deck down.

https://shanonsengineering.com/colle...at-top-pistons

But, for the same $$, I'd still go with a 4.21 or 4.25 stroke.
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post #8 of 11 (permalink) Old 12-30-2016, 05:58 PM
 
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I just ran these numbers thru the Wallace CR calculator.

428 +.030, 98cc heads, 3.8cc valve reliefs(Auto-Tec), .039 x 4.3 gaskets, .000 deck height

CR = 8.98:1.

Just a slight cut off the heads will put it over 9:1. That's plenty for a pump gas engine today.

Compression Ratio Calculator - Wallace Racing

You can also order the Auto-Tec pistons, with the pin location moved, at no charge, to give you zero deck height without cutting the deck down.

https://shanonsengineering.com/colle...at-top-pistons

But, for the same $$, I'd still go with a 4.21 or 4.25 stroke.

Another good suggestion using the pistons to both raise compression and move the pin height so you do not have to cut the deck.

However, the stumbling block is again the small heads. Using the Wallace calculator to estimate HP, and engine RPM, versus head flow: Estimate Horsepower from Intake Airflow shows a limited RPM range as would be expected.

The small valve heads will probably flow 180 CFM (at best) at 28" of water at a maximum lift of .500", so this number was used.

4.25" stroked (most common), .030" overbore, 400CI is 461 cubes. Setting the calculator specs on the Street/Strip mode, the calculator says 341HP at an RPM range between 2,570 and 4,070 RPM's. Choosing the Typical Race Engine mode produces more HP at 370HP, but the RPM numbers remain the same; 2,570 to 4,070 RPM's.

The 4.21" stroke yields a 455CI engine. Same 341HP, but the decrease in stroke yields higher RPM numbers; 2,624 to 4,124 RPM's in Street/Strip mode with the RPM's being the same in Race mode and HP increasing to the same 370HP above.

The 4.00" stroke, .030" over yields a 433CI engine. Same 341HP, but the decrease in stroke again yields higher RPM numbers; 2,833 to 4,333 RPM's. In Race mode, same 370HP with the higher RPM numbers.

What can be seen is that the stroke affects the RPM power band range. It does not mean you won't spin the engine to higher RPM's, it just shows that the larger the stroke (and cubic inches), the lower the power range drops using the smaller heads - and Pontiac engineers knew this as the 455 used torque over HP to move the big cars.

Just for fun, lets use an Edelbrock D-port head that flows 251 CFM's at .500" lift at 28" of water for comparison using the 4.25" stroked 461 engine. WOW! In the Street/Strip mode, you get 476HP in an RPM range of 4,176 to 5,676 RPM's. The increase in airflow boosts power up 135 horsepower and raises the power band into the mid-upper RPM's. Race mode simply increases the HP to 516HP with same RPM band.

What is not given of course is compression ratio,cam selection, intake/carb, or exhaust as this is taken into consideration through the selection of choosing which calculator mode you want the engine use to fall into - so this is a generalization at best, but it works for our example.

The point of this exercise is to simply show how head flow affects HP as stroke affects the powerband at which HP is made. The key ingredient in maximizing HP, no matter what size your engine is, is air flow, or CFM's. Knowing what the heads/intake/carb will flow can then be matched to the cam selection and desired use of the engine. You can also have too much air flow just as you can have too much cam or carb.
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post #9 of 11 (permalink) Old 12-30-2016, 06:45 PM Thread Starter
 
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Well, after talking to one of the techs from Butler, I have decided to go with the 4.25" stroke instead of the 4". So now my 428 build had gone to a 461. Im ordering the balanced rotating assembly from them with the eagle crank and rods with the Mahle pistons with 6cc dish, this should put me in the approx 9.3 compression range with a zero deck. Im thinking the Lunati 10510703 from Butler and the Crower 68404 Valve springs. Im highly disappointed in the dyno numbers Pontiac Jim posted, I was really hoping to be at least 400hp, I really can't afford to upgrade the heads unfortunately. Any thoughts on the cam im looking at for this combo? I like what the voodoo cams do with their ramps to ease valve closing. Do you think I could break the cam in with the crower springs or would I have to remove the inner spring for cam break in?
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post #10 of 11 (permalink) Old 12-30-2016, 08:10 PM
 
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Good choice. Don't be disappointed in the HP numbers as you want to build a Pontiac engine for torque - its not a high winding Chevy. The 1970 455 with the smaller valves as yours, but 10 to 1 compression, factory "067" cam, made 360HP @ 4300 and 500 ft lbs of torque @ 2700 RPM. The '71 455, 8.2 compression, "067" cam, dropped to 325HP @ 4400 RPM and 455 ft lbs of torque @ 3200 RPM. So if we split the difference and theoretically applied it to your engine having the 9.3 compression, you'd be near 345HP and 480 ft lbs of torque. Again, stump puller.

With the 9.3 compression, (my opinion on this) you probably don't want the 110 LSA Comp Cams selection. I built my 455CI to have 9.2 compression. I have the 7K3 heads which are large valve and I did a lot of port work on them myself. They should flow fairly well. I selected the Crower 60310 solid cam for my build. I like a solid cam. This cam has the 112 LSA which I feel will work well with the cubic inches and a 5,800 - 6,000 RPM limit (although the engine is built for more, I feel the heads are my limiting factor). It should produce a ton of torque, and coupled to the 5-speed OD and 3.89 gearing, should move pretty good. But, it would be too big for your combo, but I think a cam with a 112 LSA might do you better, but I am no expert on cams.

Since you purchased your assembly from Butler, why not fill out their cam spec sheet and let them select a cam to go with the rest of your build? There are a ton of cams you can choose, any of the ones bigD suggested look good as well. You just don't want a cam that will be too big and put your power band too high in the upper RPM range where you might not be able to utilize it. You want to maximize the low-end to mid range RPM spread due in part to the heads. So get a suggestion from Butler and see what they suggest to maximize your build.
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