Rpm 340 Cyl heads on a 318 !

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If 'twer me, I'd seriously look at some Chevy rods (made in a lot of lengths) and pistons, to push a 4.000" flat top piston .050" or .060" above deck for those heads. Or, mill the daylights out of the deck with a flat top 318 pistons to get it way up. That'll put you in the low-mid 11's SCR range and give you quench with that head. This assumes that SCR is adequate for your needs. I'd expect that to be a higher SCR than a milled 318 dome, simply because it fills that milled space in the 760179 head more completely. The SBC eyebrow position might be a bit off and require some work.

Milling the .060" 'open' chamber completely off of the Edelbrock head would do the same for SCR. Chamber volume would then be around 55 cc's. Not sure if that causes other issue with the valve area to drop it that close to the head; seems like that has been mentioned.
 
I have Edelbrock RPMs on my 318 and it runs great, 12.00 1/4 mile

I used both stock 273 cylinder heads and stock 340 cylinder heads on my .060 over 273 block bracket racer. With the 340 heads (2.02 intake) I notched the cylinder block for clearance.

Best time with 273 cylinder heads was 12.72, but with the 340 cylinder heads my best was low 13's. I believe using the same 273 domed pistons with both cylinder heads predicated a loss of compression (and performance decrease) with the 340 heads. At the time, I was young and ignorant and wasn't knowledgeable about CC'ing methods, etc.

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I used both stock 273 cylinder heads and stock 340 cylinder heads on my .060 over 273 block bracket racer. With the 340 heads (2.02 intake) I notched the cylinder block for clearance.

Best time with 273 cylinder heads was 12.72, but with the 340 cylinder heads my best was low 13's. I believe using the same 273 domed pistons with both cylinder heads predicated a loss of compression (and performance decrease) with the 340 heads. At the time, I was young and ignorant and wasn't knowledgeable about CC'ing methods, etc.

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Interesting story. This disproves the "flow out-powers compression" argument.
 
Interesting story. This disproves the "flow out-powers compression" argument.
Yes, I do believe one person who says that a lot also has said his car's "60 ft times are lacking"... not any wonder with the low compression loss of low RPM torque. In all fairness, I do believe that is with a stock TC; a high stall TC can somewhat cure that if you are drag racing. But that 'fix' just does not work in all applications.

And I have to wonder if dibbons' case also may have involved some flow blockage into the small bores, despite the notching. So that would not be a compression matter per se.
 
FWIW for the Chevy rod + pistons combo..... Here is one combination that might work with the 318 if you can bore to 4.00":
  • Icon forged 4.00" pistons IC792 with CH=1.678", Flat top with 2 valve reliefs
  • Then use a 6.300" long Chevy rod, with 2.100" rod bearing.
  • Grind down the SBM crank to that bearing size, and offset the center +.0125" higher.
  • Resulting piston to deck height would be +.045" (if I computed it right) and with a bit of block decking, you can adjust that for a .035' or .040" quench gap.
  • If you wanted even more CR, the the IC793 forged piston has a dome that can be massaged down a bit for whatever you might like.
 
FWIW for the Chevy rod + pistons combo..... Here is one combination that might work with the 318 if you can bore to 4.00":
  • Icon forged 4.00" pistons IC792 with CH=1.678", Flat top with 2 valve reliefs
  • Then use a 6.300" long Chevy rod, with 2.100" rod bearing.
  • Grind down the SBM crank to that bearing size, and offset the center +.0125" higher.
  • Resulting piston to deck height would be +.045" (if I computed it right) and with a bit of block decking, you can adjust that for a .035' or .040" quench gap.
  • If you wanted even more CR, the the IC793 forged piston has a dome that can be massaged down a bit for whatever you might like.
WOW - what a combination !!
The destroked crankshaft I purchased is Extremely unique to me because it is
new in the box and was one of Bob Gliddens crankshafts from when he run a Dodge .
The guy who sold it to me did note that crank could have GM rods installed on it with a little work so your RECIPE is inviting!
 
Well, hey it is a combination that works IF it works! E.g., I think the eyebrows are located a bit differently from the SBC versus the SBM. There are often a few niggling details that don't always show up on paper...
 
I overhauled a 318 years back and an older fella advised me against running 340 heads on a basically stock motor with mild cam. he mentioned compression ratio and cc of the chambers etc. I did listen to him and ran stock heads. the engine ran good.
 
Notch the cylinder wall. The bore is small enough that it becomes an issue with the 1.88 valve as far as flow goes but IIRC the 2.02 will hit the cylinder wall or be even closer than the 1.88 valve.
The 202 valve will not hit the cylinder wall. C'mon YR that's some bullshib
 
Trivia? I believe some big block Maximum wedge motors had bore notches. There were 2.14" intake valves available. Not sure if it was 413 (4.1875" bore), 426 (4.25" bore), or both versions that would have been notched.

From Mopar.com:
"The 426-III packages lasted only part-way through the 1964 model year—until the introduction of the 426 "Hemispherical Head" engine in the first months of the calendar year. However, these packages are still on the drag strips today, winning sportsman-class races year after year in tribute to the superiority of Chrysler engineering.

Parts for these desirable engines are still available from Mopar today. For example, two cylinder heads for the 1962–64 Max Wedge are available in the Mopar Performance catalogue: part no. P5007494 with 2.08" intake, 1.88" exhaust (the original dimensions); and P5249824 with 2.14" intake, 1.81" exhaust (the exhaust valve was made smaller to make room for the bigger intake)."
 
From racehemi.maxwedge.com which explains the clearance notch was for the 1.88" exhaust valves not the intake valves:
1962 Cylinder Head - part # 2402358 / casting # 2402286

"This was the first year for the new Maximum Performance big block Chrysler cylinder head. The new head has a noticeably taller and wider intake ports that provided much greater intake port volume over the current standard production head offering (approximately 25% more volume). Another change from the standard head was the removal of the intake manifold heat cross over. According to the 1962 Dodge salesman's "413 V-8 HIGH-PERFORMANCE ENGINE PACKAGE" booklet this removal was for "greater volumetric efficiency under competitive conditions." In a Chrysler internal paper it says this increased efficiency is due to less heat transfer due to the removal of the heat passage. This new ultra high performance head had a 2.08 intake valve and 1.88 exhaust valve which was 1/4 inch larger than current standard production heads. This larger exhaust valve required a machined clearance to be done to the top of the cylinder bore. These heads flowed like monsters and with the new crossram intake manifold with staggered two four barrel carbs made these powerful 413 engine nearly unapproachable on the strip. Like the current standard heads these Max Wedge heads featured a four bolt valve cover. The head casting does not have cast in stands for the rocker arm gear, rather it has machined pads for aluminum rocker shaft brackets to hold the rocker arm shafts. Here are some pictures of a proper unmolested original 1962 head..."
 
The 202 valve will not hit the cylinder wall. C'mon YR that's some bullshib
@yellowrose The 2.02 will not hit the wall.
@mini What he is saying is to open up the area to lessen the valve shrouding. This is most noticeable on a well prepped high HP engine (AKA race engine levels) and where you see big bore/short stroke combos zing out RPM. There HP curve up top just keeps going.
 
2.02’s clear a stock 318 bore. No “NEED” to notch the cylinder but it would help in a minor way.
Never heard of a 318 being punched out to 4.04. 4.00? Yes 4.04, no.

Build the 318 like a 340, don’t look back.

agree.
When Adney machined the 318 motor i have posted on here several times( 477 horse iron head 318) with 2.02 RT heads no bore notching done. And the motor was built for a dyno competition. If it would have mattered, he would have done it.
I had zero problems running the motor, made good power, good ET, beat on it for 4 seasons.
 
The 202 valve will not hit the cylinder wall. C'mon YR that's some bullshib


I said “IIRC” but in any case that 2.02 valve WILL benefit from notching the bore. It takes about 5 minutes on a flow bench to see that.

A 2.100 valve on a 4.080 bore picked up with a notch.
 
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I said “IIRC” but in any case that 2.02 valve WILL benefit from itching the bore. It takes about 5 minutes on a flow bench to see that.

A 2.100 valve on a 4.080 bore picked up with a notch.
This is true! Though I wouldn’t bother doing such work for a street or mild strip engine, these moves fall under the category of all the “Little Things” that add up in the search for HP and/or the edge in racing. Every little bit helps.
 
This is true! Though I wouldn’t bother doing such work for a street or mild strip engine, these moves fall under the category of all the “Little Things” that add up in the search for HP and/or the edge in racing. Every little bit helps.


IIRC (again...going off my memory here...) at about .500 lift the valve/bore can be an issue IF the valve is big enough that it’s within .060ish of the bore.

Never forget there is core shift in the blocks. I’ve seen OE stuff off almost .030 and I’ve seen some guys offset the boring bar to “clean up” a cylinder that has damage or wear for whatever reason.

Makes for a long day if you are trying to install Oring grooves in the block. BTDT.
 
I’ve seen that number (.060) for valve shrouding before. I haven’t been there myself. Just witnessed work being done. (For those who don’t know...) While making the clearance effort, the work done wasn’t a simple clearance cut but a reshaping of the cylinder heads chamber around the valve that has metal too close to the valve. It is a simple thing to do. The main two focus points are;

1: Removing material from the chamber around the parts closest to the valve to allow the air and fuel to get passed the valve with a path that will not allow the air and fuel to crash into the cylinder head.

2: When the material is removed, create a smooth pathway. Do not leave a wall anywhere. Reshape it smooth. It doesn’t have to be polished. Just lay it down. Remove only as much material as needed. There is no need to get wild or creative. The reason being is that once that valve opens up passed the angles of the valve job it is given, it no longer becomes a concern since all the air flow there on is no longer inhibited or facing any obstruction. The rest of the heads flow while the valve is being lifted passed that point of the valve job and the now missing obstruction of the wall in front of the valve that is now gone is the work of the bowl and ports.

The work I seen done was with a tiny flap wheel. IDK what cfm gain there is but the real gain is the quality of the air and fuel entering the chamber. If you could put a number on the cfm gain, lets just say is 8 cfm, your not going to see a rise in power directly related to the increased flow number but more since the (again!) QUALITY of the air and fuel mix is much better.

If anybody is faced with this, I’d recommend you give it a try. It’s of hard to do and I can be done in a short time.
 
My 318 is .60 over with Edelbrock heads, and they may have helped with how well the engine ran, best time with that combo was 11.71 at 113 in good air. 9.4-1 on the compression. a well built 318 will have good power.
 
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