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Discussion Starter · #1 ·
I'm very curious what you guys think this motor will make. I'll list all the parts in it and see what you guys think.
-4 bolt 350 standard bore
-Eagle I beam rods rates for 500 HP
-Spreedpro aluminum hypereutectic Flat top pistons
-906 vortec heads (no machine work)
-Summit cam (.480/.480 lift and 284/284 duration)
-Random headman shorty headers
-Dual 3 inch diameter 24inch length summit glass packs
-Summit stage 3 vortec intake
-650 Holley double pumper
-1.5 ratio pro-form extruded roller rockers
-1.250 inch comp cams springs 410 pound
-Ill be running a cowl induction hood too if that matters
I'm only 17 so if I wrote anything incorrectly forgive me.
 

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1949 Ford Coupe RESURRECTION
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939 Posts
you better plan on machine work on those valve guides they won't work with a .48 lift cam. Go to the Comp Cams website and look under their tools to see what I mean otherwise they're probably around 325 horse
 

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1949 Ford Coupe RESURRECTION
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939 Posts
Oh another thing get your cam, lifters, pushrods, rocker arms, Springs, retainers, and everything from the same vendor
 

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Wrench Turner
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A lot of IF's there on your parts lists.
I hope you have measured your retainer to seal clearance on those heads.If not & you don't have enough,you'll be making 0 HP. LOL. Some Vortecs can go .480" lift,while some can't take .450" & still provide an adequate safety margin.Using a beehive spring,or shorter retainers would get you the clearance you need for that cam without machine work.Also,with that much spring psi & lift,you are likely to have problems with the press in studs.Also very dangerous with a flat tappet cam.
If those flat tops are the common Speed Pro 345's,they will be sitting approx. .035" down the bore on an undecked block.Combine that with a thick headgasket & you could have your pistons sitting .076" from the head when assembled.This lowers your compression back down to approx. 9.2:1,lowers the power & the ability to tune for more power due to making the engine more prone to detonation.
You have the possibility of a strong 400 HP motor with better exhaust & carb,IF,it is set up,tuned properly & assembled properly.
 

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Wrench Turner
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With all the little details ironed out & assembled correctly such as having the quench(distance from piston top to head assembled) set in at approx. .040,long tube headers & well tuned exhaust,along with a 750 carb,this has the potential for 400 HP.The 650 carb would prolly get you there,but,the 750 would make it easier.
 

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I'm very curious what you guys think this motor will make. I'll list all the parts in it and see what you guys think.
-4 bolt 350 standard bore
-Eagle I beam rods rates for 500 HP
-Spreedpro aluminum hypereutectic Flat top pistons
-906 vortec heads (no machine work)
-Summit cam (.480/.480 lift and 284/284 duration)
-Random headman shorty headers
-Dual 3 inch diameter 24inch length summit glass packs
-Summit stage 3 vortec intake
-650 Holley double pumper
-1.5 ratio pro-form extruded roller rockers
-1.250 inch comp cams springs 410 pound
-Ill be running a cowl induction hood too if that matters
I'm only 17 so if I wrote anything incorrectly forgive me.

Is this planning or built? If built has it been fired up?


For an unmolested Vortec head lift at the valve of .480 is at or beyond what clearance these heads have between the top of the valve guide and stem seal to the bottom of the spring retainer unless you're using beehive springs and Comp 787 retainers.


The cam is very obsolete, it uses a lot of duration and not much lift to ease the valve train loading. The problem with these type cams is they are slow to close the valves, intake in particular is the issue. A late closing intake exposes the incoming charge to the forces of the rising piston working to blow mixture back into the intake track. This reduces the number of molecules inside the cylinder which in turn reduces the absolute pressure in the cylinder. Pressure is independent of compression ratio, it is a function of the amount of mixture by molecular weight being subjected to the compression ratio. The engine can be thought of as having 2 compression ratios, there is the Static Compression Ratio (SCR) that is based upon the dimensions of the piston sweep volume of bore and stroke; the volumes contained by the piston crown shape which if having a dish add to the volume and if a dome subtract from the volume; the clearance volumes of how far the piston resides from the deck when at TDC and the gasket volume which is usually a little larger than its bore because many gaskets are not round; and the combustion chamber volume. The SCR is the ratio of the sum of all the volumes divided by the volumes above and including the piston crown at TDC. There is another compression ratio that is called the Dynamic Compression Ratio (DCR) it is more complicated to get at as it is a recalculation of the total volume based on the piston's position as it rises up the bore at the point where the intake valve seats in crankshaft degrees. This is a complex trigonometric function that is involved to solve, fortunately there are many on line calculators to work this from some basic inputs. The DCR is somewhat a calculation that is approximately correct but absolutely wrong, but none the less a necessary step on the road to determining the best SCR that the cam timing needs for best power and thermal efficiency.


The DCR calculation is variable to RPM which is what makes it a general not an absolute determination. But by test we know that the DCR should be an a range of 8 thru 9 to 1 depending on combustion chamber design and head material, older cast iron heads need to be about 8 to 1 where modern aluminum heads will work around 9 to 1. Modern chambered iron heads like the Vortec work well around 8.5 to 1. Aluminum heads will accept about half a ratio higher because aluminum moves combustion heat into the cooling system faster than aluminum. This in many ways is a measure of detonation resistance to pump fuels; if your racing on highly leaded, high octane fuels the compression ratios can be pushed higher. This also connects cam timing to compression ratio, where shorter cams need less ratio to avoid detonation while longer cams can tolerate more.


The last sentence becomes the essence of the DCR determination. The later the intake valve closes the more mixture is pushed back out of the cylinder and thus the lower the compression pressure. This happens under the torque peak at varying amounts based on RPM. RPM along with port and valve sizing establishes the velocity the mixture travels through the ports. Below the torque peak RPMs the mixture velocity doesn't develop enough energy in the flow to overcome the back pumping of the rising piston so some percent that varies with the RPM is pushed out of the cylinder and back into the intake often right out of the carburetor to be seen as a fuel cloud standing above the carb or TBI. Once at and over the torque peak there is sufficient velocity imparted to the inducted mixture to overcome the forces of the rising piston resulting in better cylinder filling, this can go to a point where the velocity can develop a small degree of super charge that is to fill the cylinder with a density higher than normal atmospheric pressure would alone be capable of doing. This in no small way can bring the conversation to long tube headers but that's a story by itself.


So the problem with a late closing intake valve as relates to long timing cams and in particular cams with long ramps is that to compensate for mixture being blown out of the cylinder by the rising piston is to increase the SCR until the DCR gets into the 8 through 9 to 1 range. The reason is that increasing the compression ratio (within boundaries) improves the actual in-cylinder pressure which increases thermodynamic efficiency and will provide some compensation in the off idle to torque peak RPM range that improves or fattens the power curve in this area. By test we've established that this range also avoids high RPM detonation; again subject to pump fuels, head material and combustion chamber design. The latter, also, worthy of its own discussion.


So welcome to the world of hot rodding engines; beneath the hot rodder generalizations is a lot of engineering and science. Get it right other people look at your tail lights.


Bogie
 

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Discussion Starter · #7 ·
Sorry to everyone that read that because by me saying no machine work on the heads I meant it's not ported or polished. I cut the valve guides with the cutter from comp cams. I also cut down the stud bosses with another comp cams cutter and put in ARP screw-in studs.
 

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Is this planning or built? If built has it been fired up?

Bogie
Sorry to everyone that read that because by me saying no machine work on the heads I meant it's not ported or polished. I cut the valve guides with the cutter from comp cams. I also cut down the stud bosses with another comp cams cutter and put in ARP screw-in studs.
My question is the same one Bogie has that is unanswered - is this built yet? If the answer is yes, then plan to upgrade those Proform rockers ASAP. And do you plan to dyno this at some point?
 

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Discussion Starter · #10 ·
I haven't fired it yet. I think what I will do is upgrade the cam after a while. Any suggestions on a cam while keeping my 2800 stall converter? Also do you think I will need to upgrade springs with it? After that is might turn it into a 383 later down the road.
 

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Discussion Starter · #11 ·
Not sure if I will dyno it. Not sure where there is a place around me but if I ever do I'll let you know.
 
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