10:1, Erson Hi Flow 1H, DCR, and Rhoads lifters?

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fshd4it

fshd4it

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So here I go with another "it's what I've got" cam query.

340, +.030 w/ speed pro L2316 pistons, stock X heads @ 68cc. According to both Wallace and UEM calculators, SCR will be 10.1 w/ a FelPro 1008 gasket, or 9.7 w/a 8553. I'm definitely leaning to the latter.

The cam I'd like to use is an old Erson Hi Flow 1H, .472/296 (228@.050), 108° C/L. The UEM calculator says DCR is 8.45 and 8.16, respectively. Again, I'm liking the lower number.

My concern, first- I used Rhoads lifters with this cam. Yes, Super Shops sold me on the whole package... Only a couple thousand miles on everything, they look great, but I'm wondering about the "bleed off" increasing my DCR. They state a reduction of 10°-15° and .020-.030 at idle, decreasing to none by 3,500 rpm.
Their example: 280°/.450" cam
265°/.425"@600
272°/.438"@2000
280°/.450@3500
91/92 Non-ethanol is all I use, but I'm worried about detonation under that 3500rpm point. I thought about reducing the intake closing point by their percentage and re-entering those numbers, but then I figure I'm really guessing.

My question, second- installing the cam advanced or retarded? I know it affects all of this, I just don't pretend to know how or why enough not to ask (yep, every single time).
Thanks all.
 
What is the advertised duration numbers and what does the cam card say for an ICL.

I’m not a fan of those lifters on a cam that small.

How far are the pistons out of the hole?
 
Advertised is 296°, I couldn't find a stated ICL. The pistons are above deck by .033 to .036, depending on the hole.

20260104_091518.jpg


20260104_091453.jpg
 
Ok, figure .034 out. His deep is the recess in the chamber. IIRC at 68cc’s you’ll still be .065-.070 deep.

Minus .034 gives you .031-.036 piston to head clearance.

Add .039 for the gasket and you are .073-.078 quench.

I damn sure wouldn’t use the thicker gasket.
 
If your cam is on a 108 LSA and you install it on a 108 ICL you will center the overlap triangle or you’ll be in split overlap or you’ll be in straight up.

Whatever term you want to use.

I certainly wouldn’t advance it.
 
fshd4it said:
So here I go with another "it's what I've got" cam query.

340, +.030 w/ speed pro L2316 pistons, stock X heads @ 68cc. According to both Wallace and UEM calculators, SCR will be 10.1 w/ a FelPro 1008 gasket, or 9.7 w/a 8553. I'm definitely leaning to the latter.

The cam I'd like to use is an old Erson Hi Flow 1H, .472/296 (228@.050), 108° C/L. The UEM calculator says DCR is 8.45 and 8.16, respectively. Again, I'm liking the lower number.

My concern, first- I used Rhoads lifters with this cam. Yes, Super Shops sold me on the whole package... Only a couple thousand miles on everything, they look great, but I'm wondering about the "bleed off" increasing my DCR. They state a reduction of 10°-15° and .020-.030 at idle, decreasing to none by 3,500 rpm.
Their example: 280°/.450" cam
265°/.425"@600
272°/.438"@2000
280°/.450@3500
91/92 Non-ethanol is all I use, but I'm worried about detonation under that 3500rpm point. I thought about reducing the intake closing point by their percentage and re-entering those numbers, but then I figure I'm really guessing.

My question, second- installing the cam advanced or retarded? I know it affects all of this, I just don't pretend to know how or why enough not to ask (yep, every single time).
Thanks all.
Click to expand...
Rhodes lifters.

I ran a set of Rhodes in my 340 about 30 years ago. You could hear them "come in" about mid 4000` range. They made a Fk'd up combo work. Isky 280 Mega with a 3.34:1 axle turning 275/60/15 was a poor set up.

Strong up top though!
 
Newbomb Turk said:
Ok, figure .034 out. His deep is the recess in the chamber. IIRC at 68cc’s you’ll still be .065-.070 deep.

Minus .034 gives you .031-.036 piston to head clearance.

Add .039 for the gasket and you are .073-.078 quench.

I damn sure wouldn’t use the thicker gasket.
Click to expand...
The pads are kinda all over the place, from .065" to .082", and not in a pattern that would suggest the heads are cut crooked.
I've thought about building a "quench motor", but only with a flat top piston and Magnum-type chambers. Figured that gives someone like me enough of a running start not to screw it up.
 
Is there a consensus for "safe" pump gas DCR? I've seen 8.4 or thereabouts, but as all things I trust that's application specific. Years back I degreed this cam (when it was in my other 340), hence the notes on that sheet. I entered both their 42°, then my 44° (plus 15°), and the DCR did drop slightly. So I think I get why advancing the cam is a no-no.
 
fshd4it said:
Is there a consensus for "safe" pump gas DCR? I've seen 8.4 or thereabouts, but as all things I trust that's application specific. Years back I degreed this cam (when it was in my other 340), hence the notes on that sheet. I entered both their 42°, then my 44° (plus 15°), and the DCR did drop slightly. So I think I get why advancing the cam is a no-no.
Click to expand...
Do you have 93 ethanol free available in your demographic.
 
Illahe said:
Do you have 93 ethanol free available in your demographic.
Click to expand...
Normally it's 91, there's one or 2 places I can get 92, but i haven't found 93 (yet). I've read our gas here in Washington isn't the greatest, but I don't know if that's true.
However, I'm moving (hence the rush to finish all these engines I've collected), and I'll be able to get 93-94 octane there.
 
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fshd4it said:
Normally it's 91, there's one or 2 places I can get 92, but i haven't found 93 (yet). I've read our gas here in Washington isn't the greatest, but I don't know if that's true.
However, I'm moving (hence the rush to finish all these engines I've collected), and I'll be able to get 93-94 octane there.
Click to expand...
You should be okay as long as you don’t load the motor with too tall of a gear.
 
fshd4it said:
I have a spare 3.91 chunk, still don't know what (if anything) this motor is going in for a while. I can keep them together as a set though.
Click to expand...
I run a 360 with 10cc dome pistons and iron heads on 93. 3.91 gear and 48* intake close at .050. [edit]@ 4700’da
 
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How close is the correlation between cylinder pressure and DCR? I suppose going with a cam that has more duration @ .050 will be a little safer? 3 motors, 2 cams, still gotta buy one ( as the Comp 275DEH is kinda off the table).
 
fshd4it said:
How close is the correlation between cylinder pressure and DCR? I suppose going with a cam that has more duration @ .050 will be a little safer? 3 motors, 2 cams, still gotta buy one ( as the Comp 275DEH is kinda off the table).
Click to expand...
Nb,T will have the best answer. We have a 72 Dart with a 360 that’s got mid 170psig at 4700da. 2.94 out back. It will run on anything at the pump. I’d speculate, 185-195 psig is the limit of 93 octane.
 
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The bleed down rate of Rhoads lifters will depend on oil viscosity & spring tension. The #s quoted are just a guide. DCR is about as useful as a sunroof in a submarine. It takes no account of how well the port flows &/or the actual weight of air that enters the cyl..
 
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