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Old 10-10-2011, 06:50 PM
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stroker that has to run pump gas

need your help on this 350/383 eagle stroker kit flat top pistons pro comp heads 190 runners and 64 exhaust with 202 valve's.....im being told 10.40 cr and using a felpro 1010 and told that will be 10 1 sound ok to you? if i add a 12-210-2cam will i be ok on pump gas

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Old 10-10-2011, 07:14 PM
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First, are you running a 350 or 383? Next, 10.1 compression with an aluminum head should not ping Or detonate. I run a 10.7 406 with a 231/239@50 hydraulic roller. I don't have detonation problems. Aluminum heads are more forgiven when it comes to compression and pump gas. Your combo should b fine but if a 383, u might can get away with more compression.
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Old 10-11-2011, 07:02 AM
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yes a 383 and going nuts picking the right cam. i want a nasty idle but i need to run on pump gas. pulse its going in a 4x4 with stock converter but im thinking i may need to go with a 2000+ .im going to stay with stock gears i think there 273 any recondmadations for a cam?
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Old 10-11-2011, 07:22 AM
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Quote:
Originally Posted by yardman
yes a 383 and going nuts picking the right cam. i want a nasty idle but i need to run on pump gas. pulse its going in a 4x4 with stock converter but im thinking i may need to go with a 2000+ .im going to stay with stock gears i think there 273 any recondmadations for a cam?

You've already backed yourself into a hole and you didn't even get a cam!

Your compression is way too high for a 2,000 stall with that high of a running load.

You need to knock your compression down to 9:1, then the rest of your parts selection will work fine. To do that you'll need to swap pistons or somehow open your heads up to 76cc+ chambers, 12cc's is a lot to take out of a chamber, but it can be done.
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Old 10-11-2011, 09:05 AM
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yes i made bad choices right from the start and now im stuck with it.i know buying pro comp was not a good choice and i bought wrong size bummer im not going to pull new flat top pistons and don't dare open the pro comps. i never thought i had to be at 9.1 to run on pump gas of 93 octane
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Old 10-11-2011, 09:29 AM
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Quote:
Originally Posted by yardman
yes i made bad choices right from the start and now im stuck with it.i know buying pro comp was not a good choice and i bought wrong size bummer im not going to pull new flat top pistons and don't dare open the pro comps. i never thought i had to be at 9.1 to run on pump gas of 93 octane

A lot of people read internet stories of "street" cars running 10:1+ on an sbc on premium fuel. They can do that because of the ideal running conditions, yours are about the worst running conditions you can have on a street vehicle.

If you want to step up to a 3,000 stall and some 4.10 gears then you can run 10:1+ too... Pistons are probably your best way out at this point.

BTw even if you open your chambers to 76, you're still at about 9.% which can work
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Old 10-11-2011, 05:18 PM
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Quote:
Originally Posted by yardman
need your help on this 350/383 eagle stroker kit flat top pistons pro comp heads 190 runners and 64 exhaust with 202 valve's.....im being told 10.40 cr and using a felpro 1010 and told that will be 10 1 sound ok to you? if i add a 12-210-2cam will i be ok on pump gas
If these are 64cc chambers, with flat tops this shouldn't be too much of a problem.

You need to know something about the block and the pistons for that matter. The first thing is whether the block was zero decked or not. This makes a difference of .8 of a ratio. The second thing is the piston and what the distance from the pin to the crown is.

The next concern is the squish/quench clearance, this is the end result of adding the piston crown to cylinder deck distance to the gasket thickness. This should be .040 to not more than .060 inch. Tighter is more detonation resistant than larger, but getting under .040 for a street motor is parts collision risky and above .060 inch the effectiveness goes away pretty fast making the engine for any given compression ratio more ping prone.

The 268 cam is a well traveled path that does not require a high stall converter. For that cost a lower ratio rear end and if an automatic a 4 speed tranny like the 700R4 with its lower low and overdrive high would be money better spent.

Aluminum heads are goo for static compression ratios about one full ratio over cast iron. I figure if this engine has the nominal .025 inch crown to deck piston clearance common to SBCs and if we hold to .040 squish quench that makes a for a .015 gasket, use a rubber coated or multi layer if going this thin (I'll get to why later). figuring that into a 64 cc chamber with pistons having 6ccs of valve reliefs, my SCR calculator drives out 10.9, that's pretty stout but could be made livable with steeper gears. Opening up the squish quench to get .060 total makes for a .035 gasket which drops the SCR to 10.5, still pretty aggressive for this cam but getting there. The GM recommended gasket for aluminum heads is .053 thick. That with an .025 piston to deck clearance makes .078, this is getting weaker but no where as bad as GMs production, this would drop the SCR to 10.05. This is very livable with the set up you have.

If you don't need a high stall converter because of cam timing, don't use one. The point where it has the most slip isn't where you need it, that being the lower transmission gears. These keep the engine would up which gives it a lot of mechanical advantage which keeps the engine from pinging. It's low RPM cruise in high where the problem comes, but at this point the engine has lost a lot of mechanical advantage and no longer can force the converter to slip enough to unload it to where it isn't ping sensitive. Stiffer gears in the rear or smaller tires can be used to give the engine mechanical advantage that stays with it throughout the transmission's gear ranges. For a tranny the 700R4/4L60 (no E) offer a lower low by about a full ratio which will help get launched against those 2.7 rear gears. It also offers a 4th overdrive for high speed cruise.

Other ways to play with controlling too mush compression include cutting back and or slowing the ignition advance rates, lower engine operating temp, lower intake air temp, and richening the mixture a bit.

But overall I think if you go with a thicker head gasket you can drop the SCR to close to 10 to one and with a aluminum head this should work without having to carve the insides of the chambers of piston crown to get there.

The reason for a rubber coated head gasket at the minimum and preferably a multi-layered steel or even a thicker composition head gasket is that cast iron and aluminum have very different rates of thermal movement, aluminum expanding or contracting much more with temperature changes. This causes the aluminum part (heads in this case) to constantly scrub against the gasket. Since most thin gaskets steel and thicker gaskets use steel fire rings, this movement abrades, frets, or brinnels (your choice of words) the softer aluminum. The rubber coating provides a small amount of stress relief, but multi-layers and compositions provide much more to where the shear action is taken inside the gaskets layers instead of the gasket to head interface. This makes a much smaller wear problem for the head's gasket facing surface.

Hopefully, this gets you back on track with a minimum of cost and effort.

Bogie
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Old 10-11-2011, 05:29 PM
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I cannot comment on your gears or stall. I can, however, comment on your engine.

I am running a 383 with a CC XE274H cam (12-246-3). Duration @0.050 is 231-236*. TF 23* 64cc aluminum heads. Static CR is 10.30, dynamic CR is about 8.3. Mechanical timing is 34* all in @ 2500 rpm and vacuum advance adds another 15*. Quench, with a '0' deck block and 0.041 head gasket, is 0.041.

I run 89 octane BP gas without problems.
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Old 10-11-2011, 06:48 PM
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thanks i think i will be OK with this. as im pretty sure im 025 inch from crown and i did not have any deck work also my pistons have two valve and are 4 or 5cc and a felpro gasket 1010 is 039 and i have the 700r4 i don't have any tools to measure piston height. and i will have the heads ported and polished for added assurance. i guess i wont know till it all togather. thank you for all the info
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Old 10-12-2011, 11:03 AM
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Quote:
Originally Posted by yardman
thanks i think i will be OK with this. as im pretty sure im 025 inch from crown and i did not have any deck work also my pistons have two valve and are 4 or 5cc and a felpro gasket 1010 is 039 and i have the 700r4 i don't have any tools to measure piston height. and i will have the heads ported and polished for added assurance. i guess i wont know till it all togather. thank you for all the info
Whoa, dude; lets take it easy on porting and polishing. The effort to perform this enlarges the ports, this slows the mixture velocity within the ports at any and all RPMs. The good effect of this happens only in the upper RPM bands where the engine can use increased port flow against shorter valve open time (fractions of time not degrees of rotation get shorter as RPM goes up). But this causes problems at lower RPMs where your detonation issues will occur with the tall gearing. At lower RPMs the port velocity falls off which reduces the ram effect against the rising piston the 268 cam is closing the intake about 50 degrees After Bottom Dead Center (ABDC). This loss of mixture velocity also reduces mixing of fuel and air which leaves lean and rich pockets neither of which burn very fast nor well which then requires adding ignition advance which in turn increases the detonation sensitivity.

In many ways you lucked out with this engine as it now stands, I wouldn't recommend pushing it further without other changes to overall gearing first to get the revs up which invigorates all these intake flow issues that happen with enlarged ports.

Bogie
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Old 10-12-2011, 11:53 AM
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oh i thought that might help with my high cr I thought that woul help bring down my cr.once more i almost did what not to do. i sure do thank you for your help. today i started to think maby i will look around for a shop to finish this.before i buy /do more harm then good. i know i needed 76 cc heads not the 64 i have because i didn't know better.and didn't think about my cr thanks for the help
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Old 10-12-2011, 12:18 PM
How fast is fast enough?
 
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Originally Posted by yardman
oh i thought that might help with my high cr I thought that woul help bring down my cr.once more i almost did what not to do. i sure do thank you for your help. today i started to think maby i will look around for a shop to finish this.before i buy /do more harm then good. i know i needed 76 cc heads not the 64 i have because i didn't know better.and didn't think about my cr thanks for the help

"porting" or enlarging the chambers will help, and porting those heads can help power from idle on up if done properly.

The port velocity will only fall down if a bad port job is done.

If you want more power have them ported, if you can't afford that having the bowls and chambers done at the very least will pick up power AND will slightly lower your compression.

Also, a cam with more lift would be nice, for your gears the duration is pretty good (your gears are awful though) but more lift would help.
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Old 10-12-2011, 12:39 PM
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thanks. i was planing on having them done.but oldbogie said its not good to do. what cam do you think i need. and do you think port and polish will do good. i need all the help i can find thanks
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Old 10-12-2011, 12:49 PM
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Originally Posted by yardman
oh i thought that might help with my high cr I thought that woul help bring down my cr.once more i almost did what not to do. i sure do thank you for your help. today i started to think maby i will look around for a shop to finish this.before i buy /do more harm then good. i know i needed 76 cc heads not the 64 i have because i didn't know better.and didn't think about my cr thanks for the help
Actually the 64 cc chamber is preferable to the 76. The reason is it is more active having a greater portion devoted to the squish/quench step and having the spark plug located closer to the center of the chamber which reduces burn time because it goes outward from a central point instead of across from one side to the other. If you investigate NASCAR engines you will find very tight chambers on very large bores with quite short strokes. While a lot of this is to get a high winding engine, the tight chamber produces a huge amount of turbulence that extracts more energy from the mixture than one gets from a better breathing but poorer burning chamber. The effects of a high turbulence chamber are exactly what you want and what you've got.

The next thing is the piston crown shape. This is important from several standpoints:

1) is squish/quench where you want very close closure between the piston's crown surface and that of the S/Q deck of the head for an area of about 1/3 to 1/2 the chamber.

2) a flat top piston, again the flat top maximizes the effects of squish/quench with the additional benefit of minimizing interference with the burn's progress across the chamber as happens with a dome. All this said, there is a point where no matter how tricky you get with configurations there is a limit to how much compression a given octane fuel will support. So to adjust for this pistons often include dishes to add chamber volume which reduces the compression ratio. There are bad dish and good dish designs. The factory likes to use a round dish because it lets them use one piston on both sides of the engine (cost effective in the millions thye make and use). However, this reduces the effectiveness of the squish/quench and forces the end user to accept a less efficient engine or increase the used octane again spending more money for the power delivered. The compromise design that is used in the hot rod world is the D dish piston but these are side specific so you make half as many common to each other. With this the compression can be controlled with the dish volume all of which is under the valve pocket. At the same time a flat surface opposite the valve pocket maximizes the squish/quench function by keeping adequately large surfaces that close nearly together. So you get the engineering advantages of a flat top and a dish piston and pay the price in that the cost of development and tooling is spread across half the needed pistons instead of all.

Squish/quench is often referred to as mechanical octane. The close clearance as the piston crosses Top Dead Center (TDC) first ejects (squishes) the mixture from the far side of the chamber toward the spark plug. This is one last, and one hell of a, final stir to get fuel and oxygen molecules hugging each other before the spark is put to 'em. This also increases the density (number of molecules) in front of the spark plug which both makes it easier to set the mixture on fire and the higher density burns faster. This gets exceedingly important for long cammed or high ratio rocker armed engine. This is a description of squish; now for quench. The same parts have a second function that is taking the excess heat build up out of the mixture ahead of the flame front that otherwise causes the unburnt mixture on the far side of the chamber to explode before the fire gets there, this is classic detonation. The tight closure presents a zone that has a high surface area to volume ratio so it sinks the heat out as the unburnt mixture is compressed by the expanding burning gases on the other side of the chamber. This is mechanical octane at work, how close the closure, how much the surface area, the possible effects of Singh grooves are variables or tools you can use to tailor this function, within limits of course.

Of course there are limits to how small the camber cam be made before all this comes apart. Back in the late 1950's for an example Chevrolet came out with the 348, that morphed into the 409 and first BBC 427, at the same time the house of Ford released the Lincoln/Mercury (MEL) big block at 383, 410, 430 and 462 inches. The common denominator between these GM and Ford motors what the elimination of the valve pocket from the head entirely. The valves were close to flush with the deck, while the chamber shape was put into the piston. This just didn't work well for a lot of reasons some having to do with breathing and others being it made for a heavy and complex piston that was difficult to balance against on the crank's counterweights. No-one that has gone this route has had much success with it and many beside GM and Ford have tried it, so obviously there are some limits to how small the combustion chamber in the head can be reduced to.

Bogie
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Old 10-12-2011, 01:04 PM
How fast is fast enough?
 
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Originally Posted by yardman
thanks. i was planing on having them done.but oldbogie said its not good to do. what cam do you think i need. and do you think port and polish will do good. i need all the help i can find thanks
Old Bogie is VERY knowledgeable, and he has helped a lot of people, but sometimes he leaves out a few details. A bad port job can wreck havoc, but a good one is a win/win situation (other than cost). Just make sure who ever does the porting knows what they are doing. As for "polishing" no polish is needed, and if you do a decent job cleaning up the port work with a cartridge roll that is about as good as it gets. Some people like to polish the combustion chamber, but the difference is so small I doubt you could ever even notice it.

As far as cam goes what can you live with/afford? A hydraulic roller cam would be ideal but its not cheap, a good conversion kit can cost your $700+. If you stick with flat tappets, would a solid cam work or do you mind having to adjust lash? Also, 1.5 or 1.6 rockers? Are you willing to change valve springs?

A good off the shelf flat tappet cam from Comp would be 12-676-4 combine that with the proper springs, EDM'd lifters, and 1.6 rockers and you have a little lower cost than a hydraulic roller conversion with a good amount of lift that won't go flat (as long as you use good oil).
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