Thread: 454 build - what intake and cam ?

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Thanks for that wealth of advice and information techinspector1 !!!
All of your advice has been taken on board and I will follow your advice.

I am an automotive engineer my self and yes I do use lambda sensor based air/fuel ratio display units when checking on-road mixture of special tuned cars.

ignition timing is something I will have to play with once I get the car drivable.

The best fuel I can buy at a pump, here in Sri Lanka is 95 RON octane rating which is the same as 91 (R+M)/2 octane rating which is used in USA.

The car is not going to be a hot rod. It is going to be a fully fitted car with all bumpers etc intact and a power steering rack (way better than the box) and even air conditioning.

Ok now I have dismantled the engine and my build needs your expert advice again...

The current cubic capacity of the engine is 464 It has been fitted with 4.3" high compression pistons.
The compression ratio is 11.8:1

I need a camshaft that will allow this engine, to run on 91 R+M/2 octane (95 RON) fuel as that is the best fuel available here.

The bores and pistons are like new and this engine has not run much at all. Even the hone marks are still very clearly visible and all internal parts are very clean and like new.

I really would prefer not to have to spend money on a set of lower compression pistons.

What would be the cam that would give me a choppy idle, plenty of performance both low and mid range specially and reduce the effective compression to allow me to run this 11.8:1 compression engine on 91 octane fuel ?

289 block
781 heads (will install bigger valves)
Current intake Edelbrock Torker II (can change it)
Current carb Holley 650CFM double pumper

Car is 67 Impala sport sedan
Muncie M20 wide ratio 4 speed
12 bolt Positraction 4.10
will run 28" tall tires

OK, 11.8:1 isn't going to work with 91 octane fuel, particularly with iron heads, so the first thing we need to do is identify the pistons as to manufacturer and part number so we can decide if the domes are solid or not. If they're solid, we can begin to think about cutting the domes down to make a realistic static compression ratio. If the domes are hollow, you will have to bite the bullet and choose another type piston, as there is no way to bring the cylinder pressure down to the point that the motor can be operated on 91 without detonating itself to death. If you used enough cam to close the intake valve late enough to get it close to where it needs to be, the motor would have nothing below about 3500 rpm's and would probably still detonate. You would have to polish all rough edges off the pistons and chambers, use a very slow advance curve and a VERY tight squish. I personally would not even entertain the idea if it were mine.

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They are ARIAS Pistons. There is only the casting number on it. H-60-A no other markings.

I have contacted the manufacturer but they can't offer much info at all.

The piston has a slight indentation to the shape of the dome, on the under side. It was measured and there is 11mm material thickness on the dome.

I have to mill off 20cc worth of dome, to get a static compression ratio of 9.8:1

Do i mill it from the top with the cutter parallel to the crown or do I mill it on the large angled surface to the left on the dome, in the photo below ?

The latter will be better as it will remove more volume for the depth of cut. Since there is 11mm thickness, what would be a safe thickness to keep after milling ? 3mm ?

My first question would be: How do you know the volume of the dome to calculate the SCR? Did you pour the piston in the cylinder yourself with a burette? Do you have access to published data? How? Have you poured the combustion chambers? Are you just guessing at the chamber volume?

You see, personally, I have to have everything verified, either by the published data from the manufacturer or by verifying it myself with the proper instruments, like in this case, a 100 ml burette and some isopropyl alcohol tinted with food coloring.

As far as the angle of the cut on the piston crown, I'd cut it 90 degrees to the bore centerline to bring the crown height down as far as possible to allow maximum flame propogation across the chamber.

If I remember correctly, the piston crown thickness needs to be a minimum of 7% of the bore, so 7% of a 4.3" bore (109.22 mm) would be 0.301" (7.64 mm). You may want to run these figures past an automotive engineer at the Arias factory:
PH: (310) 532-9737
FAX: (310) 516-8203

For those of you who don't know how to find the volume of a pop-up piston crown:
Position the piston in a bore with the top of the pop-up just barely below the block deck. With the depth stick function of your dial caliper, measure from the deck to the flat spot on the piston crown just above the top ring. Seal the piston circumference to the bore with Vaseline so the alcohol will not leak down past the piston. Let's say the piston is down in the bore by 0.375" to clear the pop-up. Do the math:
.7854 x 4.3 x 4.3 x .375 x 16.387 = 89.2 cc's.
That's what the volume would pour if the dome were not in the way.
Now, pour the volume above the piston with a lexan or plexiglas cover over the bore. Let's say you pour the volume at 46.2 cc's. Now you would deduct the 46.2 from the 89.2 and find that the pop-up volume is 43 cc's.

With a chamber volume of 124 cc's, you would want a pop-up volume of ~23 cc's to make a 9.6:1 motor and you could then run the cam that I recommended to you, making the proper cylinder pressure to operate detonation-free on 91 octane pump gas and have the rough idle that you want. Don't guess at any of this. Measure everything. If the chambers cc out to less and you need help doing the figuring, do not hesitate to contact me and we'll do the math together.

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Many thanks for that very informative response techinspector1 ! your input is very much appreciated and is very important !

I am an automotive engineer so I know better than to guess at any of this and end up with money spent and something undrivable.
That is why I am taking the time to measure and calculate everything and get your expert advice before spending money.

I want to build this engine right.

All measurements were taken using the correct instruments.

Cylinder volume was obtained by measuring the bore with a bore micrometer and the stroke with a depth gauge.

Chamber volume was measured with a medical syringe.

Gasket volume same as above

Piston dome was measure by inserting the piston exactly 1" down the bore, sealing the crown to the cylinder and then measuring with the syringe and then calculating.

ring land volume was calculated from measurements.

These are the figures

Cylinder 958cc (109.38x102mm)
Chamber 115cc
Dome 41.6cc
Gasket 13cc
Ring land 1.1cc

If I take off 20cc worth of dome, I get 9.9:1 compression which is acceptable for 91 octane ?
I can use a thicker head gasket when I assemble so that will help.

I can start off by cutting the piston 90 degrees to center-line but I would be cutting from the sharp edge of the dome, thus removing very little material per depth of cut.
I would need to cut parallel to the flat angled surfaces to take off 20cc worth of material.

What do you say techinspector1 ? should I mill them first 90 degrees as far as possible and then along the angled plane to arrive at the required dome volume ?

Arias piston will be a forged material so that is a forging id not a casting number( yes I know---)

On cutting the top it will help if you can make a mold or exact measurement drawing of the hollow underneath the dome so as to determine exactly where the thin spot will be. The area above the boss that has wrist pin hole will be thickest area so you could cut quite a bit from exhaust valve area of that raised part.

I don't remember exactly the numbers but you can weigh the piston and determine how many CCs you have removed by aluminum weight to volume-2.7 grams per cc--20 cc equal 54 grams----------

As you machine the domes, keep in mind where the heat will be and don't get too thin near the spark plug area

I made up a set of 1 inch thick x 3 in plates for some soft jaws for mill to machine piston tops---machined to hold piston at straight up square and index piston depth with a ring (sometimes 2 or 3rd groove depending on cutter clearance needed)
index piston sideways with wrist pin. also machined a hole at combined valve angle.

Will try to post pic later today

This allows me to machine a set of pistons in mill with a base reference starting position.

I have also done soft jaws for lathe to size for any circular about the center line job.

Of course over the years I, ve also done it with a body grinder and a 60 grit disc!!!!!!


And Denny----I was rounding up to 2.7 from a weight of 2.699!!!!!!!!!!!!!!! Pretty close to one ounce per 10 CCs--------- so lets see---------20 cc equals 2 oz, 8 pistons equal 16 oz--/ONE POUND
Man, he's going to lighten up that thing so much it'll do wheel stands(maybe with some jack stands, trick lighting and right camera angle!!!!!!!!

Originally Posted by ceejay

If I take off 20cc worth of dome, I get 9.9:1 compression which is acceptable for 91 octane ?

If I were building it, I would shoot for 9.5:1. That will work best with the cam recommended, to make the best cylinder pressure and avoid detonation with iron heads.

Originally Posted by ceejay

I can use a thicker head gasket when I assemble so that will help.

BBZZZZZZT That's the sound of the wrong answer buzzer. It is not the function of the head gasket to set the static compression ratio. That's done with piston crown volume and combustion chamber volume. Block deck height and gasket thickness are used to set the squish/quench, possibly the most important aspect of building a pump gas motor. It's the distance from the flat crown of the piston to the underside of the cylinder head with the head gasket in place. Again, if this were my motor, I'd be shooting for a squish/quench of 0.040" (0.1016 mm) by first choosing the head gasket I wanted to use, then cutting the block decks to give me the squish/quench I wanted. I might even go a little tighter if the pistons were cast or cast hypereutectic, but with forged pistons, you have to run a little more piston to wall clearance, so the piston rocks a little more in the bore and it's possible, with part of a pop-up left on the crown, that it could rock enough to make contact with the head. A little kiss at max revs wouldn't necessarily be a really bad thing, but you wouldn't want a "thud". I have seen motors using flat-top pistons that left the imprint of the piston part number on the underside of the head. Now, that's gettin' 'er down pretty close.....

As a matter of interest, it has been found that a motor that has used a thicker head gasket to lower static compression ratio will be more detonation-prone than a motor with a thinner head gasket and slightly higher static compression ratio, due to the wider squish/quench measurement with the thicker gasket.

Originally Posted by ceejay

I can start off by cutting the piston 90 degrees to center-line but I would be cutting from the sharp edge of the dome, thus removing very little material per depth of cut.

Personally, I would want to get the dome height out of the way first, to help with propogation of the flame front across the chamber. Having to navigate around that tall dome isn't the best way to light the fire completely across the chamber in my opinion. Once you've done all you can with height, twist the piston around and begin cutting on other angles, all the while keeping the 7.64 mm minimum thickness in mind. Cut and measure, cut and measure. You'll likely end up at around 21-22 cc's for the pop-up, to achieve 9.5:1. Don't forget that the motor will have to be rebalanced for the lighter pistons.

Originally Posted by ceejay

What do you say techinspector1 ? should I mill them first 90 degrees as far as possible and then along the angled plane to arrive at the required dome volume ?

That would be my plan if I were doing it for you, paying attention to the minimum 7.64 mm crown thickness.

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Originally Posted by DennyW

((I am an automotive engineer so I know better than to guess at any of this and end up with money spent and something undrivable.
That is why I am taking the time to measure and calculate everything and get your expert advice before spending money.))

I hope you are also figuring in the spark plugs you plan to run also. It's those little things that will bite you.

You are correct Denny, that's why I gave him a pretty good lesson on plugs in post #15.

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trying to upload piston fixture pics from my phone---------https://a.gfx.ms//photo_57.png

C:\Users\Gerald\AppData\Local\Temp\Temp1_Piston fixtures.zip\IMG_20160430_131624660.jpg

Denny I emailed the pic to you so could you please post it-Its out of my phone as my camera is too big and shows more details than most people on here want to see----

Thanks Denny-

this is drawer full of fixtures for pistons and some for holding cylinder headers for work in the mill (as compared to just normal resurfacing, valve work etc/etc)

The two longer pieces with the two cut outs are for working valve notch angles, the two short ones are for holding piston straight for square to bore work. On the long ones you can see how its machined down so a ring can be installed and used as reference point that's repeatable for several pistons. The shorter straight ones the ring would just set on top of the piece.

Place is full of special fixtures for doing STUFF--------that's what happens when you are doing things in some of those undefined areas-----------

Thank you every one for all your input and photos !! I really appreciate all the input !!

Every thing said about milling the pistons is taken on board. I will keep you guys posted on how it goes.

techinspector1, can I bounce another cam option off you (and anyone else too) please.

We agreed that the Edelbrock "performer RPM" intake was suitable for my application.

I have been researching and found that Eddelbrock offers a "Top end kit" their part number 2095, which includes 2 aluminum heads, the performer RPM intake and their 7162 camshaft.

They say this complete kit has been tested on a 9.6:1 compression 454 and produces 540HP and 539 ft/lbs which are great figures for my application.

I was wondering about using their camshaft in place of the comp cams 11-600-8.
Edelbrock states that this camshaft is matched to perform with their RPM intake, which I will be using anyway.

I would use those with my existing 781 heads and later on, once the car is running if I feel I want more performance out of it, I could install their RPM heads which would then make up their top end kit.

I have looked at their power and torque graph for the top end kit on the 9.6:1 454 and compared it with the graph obtained from Comp Cams online cam quest software. I plugged in all the numbers and looked at the graph for their 11-600-8 cam

The Edelbrock cam seems to be more suitable for me because it provides more power and torque even at the lower revs.

I have watched a video of a Chevelle online, which is running the top end kit on a 60 over 454 and it sounds great too.

Your valuable input please

Does your gas over there have lead in it? if not, besides the roller/flat tappet issues today are ones about exhaust seats on the earlier cyl heads that won't survive unleaded fuels. And with your piston issues---I'd have to suggest that you take a serious look at using new pistons( removing the amount of material you need to do will cause a severe balance issue ) and sell off your hi compression ones, also consider the usage of the Edel heads for the new type seats, plus tremendous weight saving.
also maybe with the new heads (open chamber?) your compression could be low enough not to have to deal with the piston domes ( closed chamber pistons will clear open chamber heads but not vice vs)