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Post Info TOPIC: 454 vs 468


- Ben #2 -

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454 vs 468
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Just curious if the extra cubes are really worth the cost in a street build? Been looking more into what’s needed for my bbc build and just wondering if the extra cost for boring is justified. My cylinders are stock and I’m told they look really good as is. If that’s the case, thinking just pistons, cam, etc and I’d be in business. 

Goal is pump gas, power curve 1800 up to 6000 rpm, street driven. Will run my iron heads, 2.19/1.88 with some porting/bowl blend, 750-800 ish carb, 8.5 ish comp and cam to match. 

I’ll likely still get the block decked for zero height, hyper flat tops, bigger rod bolts. 



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- Mike -
Olalla, Wa


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The true test is to check the cylinder bore taper and make sure it will “clean up” with a proper hone. If it will, stick with stock piston bore just to save the cost of machining.

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Ben


- RAMBO -Mill Creek, WASite Administrator

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What heads are you going to run? Flat tops kind of limit you. There is a kb hyper domed piston that isn't that much more $$than their flattops. I wish I had put that in mine.

Mine is a standard bore 454, just honed, not bored.
There was still a little trash in the boxes from water sitting for a while I'd guess, but not enough to affect the ring seal or blowby.





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Ben R.

1968 Chevelle 300 - 454 / 4spd



- Ben #2 -

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I have 781’s. I’m open to domes. I’ve been rereading your build lately. 

I’m kind of thinking if I can get by with a hone I can build it sooner. Not boring also leaves it open in the future if I wanted to build a bigger bore stroker and aluminum heads some day. 



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68 Malibu 307/PG. For now.....


- Durand -

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As long as the bores have no ring ridge, scaring, or taper like Mike said, you will gain little by boring other than getting straight cylinder walls at a moderate performance level.
The big gains from the bigger bore come in at higher performance levels when valve shrouding becomes an issue.

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'65 Pontiac Lemans 468 t400 4.10 12 bolt

Best ET  11.43 @ 117.7

Ben


- RAMBO -Mill Creek, WASite Administrator

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Bskredsvig wrote:

I have 781’s. I’m open to domes. I’ve been rereading your build lately. 

I’m kind of thinking if I can get by with a hone I can build it sooner. Not boring also leaves it open in the future if I wanted to build a bigger bore stroker and aluminum heads some day. 


 Those are like 118cc if I remember right... You'll be like 8:1 compression with flat tops. If you are on a budget build consider peanut port heads... Much smaller chamber size and will be fine for power under 5500.

Kettbo had a pretty potent setup running peanut ports if I remember right. I was going to run them on mine until the 67 closed chamber heads I have now popped up. I'm still only at 8.8:1 with the flattops. Popups would have had me in the high 9's or 10's compression wise.

 

Consider that the aftermarket pistons (the kb's anyway) sit farther in the hole than factory pistons. Be sure to consider the pin height in your calculations.

 



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Ben R.

1968 Chevelle 300 - 454 / 4spd



- Ben #2 -

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I was assuming I’d want 8.5-9 ish for a pump gas street build. Would more be better? I’m open to domes, just figured in my power level and intended use I’d stick with hypers. 

118cc sounds right from what I’ve read. I’m open to shaving the heads a little but don’t want to run into issues going too far. I Figured decking the block would get the compression up a little, but same with boring, if I can get by without it and use a dime or something, maybe that’s the route I’d go for now. Pretty sure my 307 is giving up on life so just debating on my options. 



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- Mike -
Puyallup, WA


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Some may eye roll at this but I'd consider the octane you intend to run/buy before making a decision...even buying 89 vs. 92 is a factor if you drive the car a lot and are getting basically the same mileage and similar power level. My Dakota required 89, my Sierra only needs 87...makes a small sacrifice in lower mileage negligeble due to the cost of the fuel.

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'67 Chevelle -- 383ci, Jerico DR4 4 speed -- 3.19 1st gearset, Gear Vendors Overdrive/Underdrive, Strange S60 w/3.54 gears

'70 Camaro -- In the works TT 6.0L, 4L80E, ??? rear end 



- Ben #2 -

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I am only marginally comcerned with mpgs. My biggest reason for pump gas requirement is so I can drive basically anywhere and get fuel; 89-92 is perfectly fine. Hell, my wife runs 92 in her Tahoe even though it only needs 89. 

I was also working on the assumption with iron heads and up to 92 octane, I’d be limited in compression. If not as limited as I thought, I’m all for 9.5-10 if it’ll work. 



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68 Malibu 307/PG. For now.....



- wondah whooooaman-
Colorado Springs


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What cam are you going to use?  I'm asking because compression will effect your cam choices.  Build the motor around your cylinder heads.



-- Edited by gotago on Friday 27th of April 2018 06:52:51 PM

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Mark
69 Chevelle SS
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Ben


- RAMBO -Mill Creek, WASite Administrator

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Need Doc or George to chime in... those guys know all the secrets to squeezing low budget HP out of a BBC.


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Ben R.

1968 Chevelle 300 - 454 / 4spd



- Ben #2 -

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Not sure on cam quite yet. Was looking at some of the lunati and clay smith ones under .600” but can’t remember the durations right now. Hyd flat tappet is my thinking. I don’t think this motor needs a roller cam but I could be convinced if the cost/benefit was enough. 



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- Durand -

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Cylinder head choice is dependent on, intended use, cid, transmission type/stall speed and rear gear ratio.

Open vs closed chamber?
Closed give you higher compression, and the open a better chamber design.

As for rpm range.
The peanut ports are superior up to about 4000 rpm and top out around 5000-5500 rpm as Ben said.
A little higher on a 396.
(They work well in daily drivers with automatic's and high gears, especially a Powerglide . )
Large ovals done right will go 6500 rpm on a 454 without issue and still have decent shift recovery on the street.
Rectangular ports, they are useless on a production size engine for the street.

Being you have 781's, I personally would use them with the 2.19/1.88's and minor bowl work for 6000-6500 on a 454.
781 castings are what I've been playing with lately, and are as above and on Pat's 87 octane flat top engine that is running 12.30's-12.40's in my car right now.
The set I massaged for my engine turn 7000 rpm on 468 cubes and 92 octane.

Don't get stuck on the static compression ratio numbers, they are less relevant then the dynamic compression.
Pick the piston that will get the dynamic compression right for the cam duration and the valve opening/closing event timing.



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'65 Pontiac Lemans 468 t400 4.10 12 bolt

Best ET  11.43 @ 117.7




- wondah whooooaman-
Colorado Springs


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Bskredsvig wrote:

Not sure on cam quite yet. Was looking at some of the lunati and clay smith ones under .600” but can’t remember the durations right now. Hyd flat tappet is my thinking. I don’t think this motor needs a roller cam but I could be convinced if the cost/benefit was enough. 


You can get incredible power from your 781s, Mark Jones does it all the time.  As Durand said don't fret too much on compression, you already have a good set of heads build the motor around them.  Heads are what make power.  If you're running a manual you can get a LITTLE aggressive with your cam choice since you don't have to worry about converters and such.  Chris Straub can set you up with a good cam based on your heads, either off the shelf or custom.  I still have a 402a3 SFT I could send you that would make a good thumper in a 454.        



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Mark
69 Chevelle SS
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- Ben #2 -

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Will be a 4 speed and I can match the rear gears to fit as its 3.08 now and 25” tires that need replaced. 

Here is some of what I had written down from my readings.

Was looking at the lunati bare bones 10110703. 

Hydraulic Flat Tappet. This high performance street cam likes 2400 RPM stall, 800 CFM carb, dual plane intake and headers. Makes unequaled power to 6200 RPM with proper valve springs. Very strong cam with great street manners for your crate motor. Factory EFI motors need custom chips/tuning.

  • Advertised Duration (Int/Exh): 268/276
  • Duration @ .050 (Int/Exh): 227/233
  • Gross Valve Lift (Int/Exh): .542/.554
  • LSA/ICL: 110/106
  • Valve Lash (Int/Exh): Hyd/Hyd
  • RPM Range: 1800-6200

A domed piston like a UEM KB203 which says about 9.1 cr with 119 cc chamber. Have thumb rods, standard stroke cast crank. Probably get block decked to zero height but could use a shim gasket to keep from machining block for future reasons.

Holley 750-850, air gap, stealth, or similar intake. 781 heads with 2.19/1.88 valves, some port work. Full length headers 1-7/8-2“ into 3” exhaust. I’ll switch to hei distributor too.

 



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68 Malibu 307/PG. For now.....


- Durand -

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With that for a street engine, you will be in for a big surprise after your 307.
Just be careful with big blocks like that and 4 speeds, they will get loose on you real easy without a moments notice.
Only suggestions, would be to look into a set of rods,(By the time you buy bolts and have them machined, it is sometimes cheaper to just buy a set)and balance it.

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'65 Pontiac Lemans 468 t400 4.10 12 bolt

Best ET  11.43 @ 117.7



- Ben #2 -

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I will look into rods. 

More self restraint will definitely have to be used after the 307. I had a 383 in my chevelle in high school but it just had a th400 with a stock box truck converter. It had way more power up top but was a dog off the line So I’m sure a big block and 4 speed will be way different. 

I’d really like to do the motor right the first time and not skip stuff just to save a buck now but spend more later. I’m almost done building another bike to sell so I may just hold off on a motor until that is figured out and go from there. Just means I can’t drive the car in the meantime. 



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68 Malibu 307/PG. For now.....


- Beemer Brett - Redmond, WA

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I loved my 402a3 I put in when I refreshed the 468. For hydraulic my voodoo 60204? ran really good also both with manual trans.  Both had great street manners, nice lope, and strong but consistent power band for street/strip. 



-- Edited by Brettd85 on Saturday 28th of April 2018 09:29:23 AM

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- Ben #2 -

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I have the 60204 written down also. It’s a little more aggressive, says 10.1 comp or better and a little higher rpm range. 

But based on compression calc., if everything was it says on paper, that cam would give about 9.5 cr. Obviously it’d depend on deck height, actual head chamber cc, pin location, etc. But not too bad. 



-- Edited by Bskredsvig on Saturday 28th of April 2018 10:24:22 AM

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68 Malibu 307/PG. For now.....



- Mike -
Puyallup, WA


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Bskredsvig wrote:

I am only marginally comcerned with mpgs. My biggest reason for pump gas requirement is so I can drive basically anywhere and get fuel; 89-92 is perfectly fine. Hell, my wife runs 92 in her Tahoe even though it only needs 89. 

I was also working on the assumption with iron heads and up to 92 octane, I’d be limited in compression. If not as limited as I thought, I’m all for 9.5-10 if it’ll work. 


Understandable.  I am always concerned with MPGs, even with a hot rod, it allows more in life....be it driving the car more or money for other things.  My Chevelle gets 18-19mpg on the freeway but I'm not sacrificing anything with the power output or performance(lots of gearing here helps)...makes it easy for me to drive it anywhere.  I will say having to buy 89 octane made it so I never fueled at Costco...now I do.  However, if the engine only requires 89 all you're doing is wasting money, it doesn't help any to run 92 given the cost difference of the fuel.  Trying to keep your budget in mind here.

The dynamic compression based on what your cam timing events allow will determine how close to a fuel octane threshold you get.  Seems many people do well in the 9:1 compression range for power levels.



-- Edited by cobaltchev67 on Saturday 28th of April 2018 10:32:01 AM

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'67 Chevelle -- 383ci, Jerico DR4 4 speed -- 3.19 1st gearset, Gear Vendors Overdrive/Underdrive, Strange S60 w/3.54 gears

'70 Camaro -- In the works TT 6.0L, 4L80E, ??? rear end 

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