All for .370 lift and under ........

[Dale Davies]

That's what we are going to try to get - low lift flow. However, no bench flow so this is a true "how I see it, hope it works" project ! LOL. We like surprises anyways, right ? !!!

Try looking at David Vizard Powertec 10 Youtube videos. Has a lifetime of racing and porting/engine building knowledge to pass on.

 

[318willrun]

Your gain is probably to the valves sealing again. Check my other post on camshafts. You could step up if you decide to upgrade the cam to a retrofit roller. The advantage is oil selection. With flat tappet cams now, the Zinc and Phosphorus content must be checked. Basically a 10W30 diesel oil.
I have my 289 Ford apart and the cam and lifters are showing signs of wear from using shelf oil before the removal of ZDDP was known about. I have the Engle cam from my 351 with low miles and in good shape I will put in. This is in a 1940 Ford Fordor, so probably not the most aerodynamic. I will be using diesel synthetic oil in it to protect the cam and lifters..

The problem trying to get a gain without really changing much was the engine actually ran really well prior to our change, valves were sealing. We did gain part throttle power that you can feel by the seat of your pants.

 

[318willrun]

Try looking at David Vizard Powertec 10 Youtube videos. Has a lifetime of racing and porting/engine building knowledge to pass on.

I am familiar with David's youtube channel. He does well.

 

[Dale Davies]

Yes, it is tough to repeat the conditions in a MPG test. However, I do believe the more miles and refills, the closer you are to the truth

MPG is very important, especially if you've been to the gas station lately... Ha! However, we want it to perform (as in have more zip) a little better as well.

I would be inclined to either change rockers to a higher ratio or swap the cam to a short duration high lift cam. 107 or 108 LCA for overall performance 210 to 215° 0.050 lift duration, 256 to 264 seat timing and 0.450 lift.
For that brick you need high torque at your cruise RPM which probably close to 2000.

 

[Dan the man]

I would be inclined to either change rockers to a higher ratio or swap the cam to a short duration high lift cam. 107 or 108 LCA for overall performance 210 to 215° 0.050 lift duration, 256 to 264 seat timing and 0.450 lift.
For that brick you need high torque at your cruise RPM which probably close to 2000.

What is seat timing? Or did you mean duration?

 

[Bewy]

Post #100. The Crower mileage cams were nothing really special & didn't close the intake valve late compared to a lot of mileage cams, which were ground on 112-114 LSA. The Crower cams were ground on 110 LSA. Isky economy cams were ground on 112 LSA, which closes the int later than 110.

 

[Dale Davies]

I would be inclined to either change rockers to a higher ratio or swap the cam to a short duration high lift cam. 107 or 108 LCA for overall performance 210 to 215° 0.050 lift duration, 256 to 264 seat timing and 0.450 lift.
For that brick you need high torque at your cruise RPM which probably close to 2000.

Sorry coach, duration. Basically an "RV" cam but today the shelf cams tend to be ground with either 110° or 112° LCA. According to David Vizard's 128 formula to calculate cam LCA and considering a 1.88" intake valve, optimum for the stock stroke 318 would be about 105° LCA. Idle may be a bit lumpy, so that is why I stated 107° or 108°. With a somewhat heavy and boxy van, low RPM torque is required, so giving up a bit of idle smoothness for better fuel mileage and torque between 2,000 and 4,000 RPM may be good to consider. Looking at Summit or Jegs for hydraulic flat tappet cams, the prices are fairly reasonable even with 16 lifters. Here in Canada we are adding about 30% to the cost plus shipping.
If the cam gives a mileage increase like I got in my 82 Blazer with the low compression 305 (+3US MPG) and todays fuel costs, that expense would be fairly quickly recouped.

 

[Dale Davies]

Post #100. The Crower mileage cams were nothing really special & didn't close the intake valve late compared to a lot of mileage cams, which were ground on 112-114 LSA. The Crower cams were ground on 110 LSA. Isky economy cams were ground on 112 LSA, which closes the int later than 110.

These were an Atkinson Cycle type cam, different than mileage cams. These apparently were not well received as they did not stick around for long. Problem was the tune also required modification and off idle torque suffered a bit. Now if building an engine for that cam, higher static compression could be used. At low RPM the dynamic compression bled of cylinder pressure but as the intake charge momentum picked up with RPM the static compression was more evident. I can not remember the intake duration and LCA specs but seem to recall a longer duration intake lobe, something along the lines of 10° to 15° more than the exhaust. Intake opening was close to the same as a regular cam but the closing was later.
Possibly Crane cams but I do not think so.

 

[Dan the man]

The problem trying to get a gain without really changing much was the engine actually ran really well prior to our change, valves were sealing. We did gain part throttle power that you can feel by the seat of your pants.

A friend of mine years ago, put a good dual exhaust system on his car and a good quality open air filter. We dialed it in the best we could with the tools and knowledge we had at the time and his car ran great for a 318 in a 1970 charger.

 

[Dan the man]

@318willrun, is it true that a smaller intake valve ( 1.88" ) with good port work flows better than a 2.02" intake valve and no port work. Would the smaller intake valve be good for port velocity.

 

[Dale Davies]

heads...

A friend of mine years ago, put a good dual exhaust system on his car and a good quality open air filter. We dialed it in the best we could with the tools and knowledge we had at the time and his car ran great for a 318 in a 1970 charger.

IMHO 318s get a bum rep. The cam was/is their problem, the same as the Chev 305 and Ford 302. Yes the 318 has smaller ports and valves than a 340, but they respond well to inexpensive mods and will run for a long time with a bit of TLC.

 

[Bewy]

Dale.
Post #108.
I have a lot of cam catalogs from the 70s to 90s. The only cams in them that have longer int duration are cams for turbo engines, none that I could find for NA use. I do not see anything 'special' about mileage cams, other than their parameters are chosen for optimum low speed efficiency.
Some cam companies preferred single pattern cams, some used dual pattern, some used both. This was reflected in their mileage cams which simply had less duration & very often wider LSA.

Post #107.
Agree 10000% with your DV comments & tight LSA. But you omitted an important part of DVs cam comments: if you do not want a rough idle, you reduce duration. You do not widen LSA.

 

[273]

@318willrun, is it true that a smaller intake valve ( 1.88" ) with good port work flows better than a 2.02" intake valve and no port work. Would the smaller intake valve be good for port velocity.

I never got that the valve and throat is the most restrictive part then the bowl but also shortest part of the intake tract, wouldn't the mouth of the port and intake runner be the major contributor to velocity? Wouldn't make sense to make the valve and bowl to be able to keep up with the rest of the intake tract.

 

[Dan the man]

I never got that the valve and throat is the most restrictive part then the bowl but also shortest part of the intake tract, wouldn't the mouth of the port and intake runner be the major contributor to velocity? Wouldn't make sense to make the valve and bowl to be able to keep up with the rest of the intake tract.

Makes sense to me. I don't know much about cylinder heads, trying to make the most out of what I've learned

 

[Dale Davies]

@318willrun, is it true that a smaller intake valve ( 1.88" ) with good port work flows better than a 2.02" intake valve and no port work. Would the smaller intake valve be good for port velocity.

A lot to look at there. Flow will tend to be higher with the 2.02 intake valve and the generally associated larger port volume.
With judicious porting in the right spots to remove obstacles and enlarge where the flow naturally wants to go, the small port will tend to have higher port energy. This is basically flow speed and the mass moving to fill the cylinder more after the piston starts up the compression stroke and before the valve fully closes.
Now to your question concerning the valve, with a good 3 angle valve job and discretionary grinding to unshroud the valve, the 1.88" can work well. Besides the seat shaping, a 25° back cut on the intake vastly improves low lift flow as the intake valve just opens. The valve to seat form is the limitation on flow up to about 0.35" on most engines. With most of the older engines we are looking at probably having valve lift topping out at 0.53" even with an aftermarket cam, flow below 0.35" has a big effect on engine performance. What that back cut does is open up the valve to seat curtain area sooner. You want the flow to stay attached to the valve form so turbulence is not introduced.
So the answer is yes, a 1.88 valve and port can be modified to perform as well as or better than an untouched 2.02 valve and port.
To learn and get a better understanding, get David Vizard's Porting and Flow Testing book. Also good are his Powertec 10 Youtube videos. He discusses a lot of different topics that in his presentation may be directed at Ford or Chev, but a person can pick up tips or pointers that can be applied to other engines.

 

[Dale Davies]

Dale.
Post #108.
I have a lot of cam catalogs from the 70s to 90s. The only cams in them that have longer int duration are cams for turbo engines, none that I could find for NA use. I do not see anything 'special' about mileage cams, other than their parameters are chosen for optimum low speed efficiency.
Some cam companies preferred single pattern cams, some used dual pattern, some used both. This was reflected in their mileage cams which simply had less duration & very often wider LSA.

Post #107.
Agree 10000% with your DV comments & tight LSA. But you omitted an important part of DVs cam comments: if you do not want a rough idle, you reduce duration. You do not widen LSA.

Regarding your comment on post #107, I agree. Only when you are looking at an already short duration cam, you might have to open up the LCA a degree or two. Performance will be reduced a bit. As DV states, you are better with LCA a degree or two tight than a degree or two wider.

 

[Dale Davies]

I never got that the valve and throat is the most restrictive part then the bowl but also shortest part of the intake tract, wouldn't the mouth of the port and intake runner be the major contributor to velocity? Wouldn't make sense to make the valve and bowl to be able to keep up with the rest of the intake tract.

The port cross sectional areas are fixed while the valve curtain area is constantly changing as the valve opens and closes.
SBF heads have challenging shaping with a fairly large intrusion into the port for the pushrods. But that area is still large compared to the valve curtain area, especially at low lift. DV teaches if you have a flow bench, look for the low hanging fruit first. That is the curtain area. When you get that flowing well you look to other areas in the bowl and then in the port.
In his book he describes his DV really cheap flow bench. It does not read in CFM but will show improvements. With pitot tubes, flow balls and thread strands in a tube you can see where the flow wants to go and turbulent areas. A pitot moved in the port senses pressure drop. A flow ball moved in the port will cause a flow reduction when moved to a high flow area but have minimal effect where the air is not going. The threads glued into a tube will flap around in the wind like a flag. If flow gets turbulent their motion will be caotic.

 

[318willrun]

@318willrun, is it true that a smaller intake valve ( 1.88" ) with good port work flows better than a 2.02" intake valve and no port work. Would the smaller intake valve be good for port velocity.

1st statement is true. 2nd statement can be true, but lots of variables leading up to the valve.