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240 valve size?

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68Flareside240
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240 valve size?

Post #1 by 68Flareside240 » Tue Jun 11, 2019 5:06 pm

I appreciate the loads of information given, and looking back into the pages and pages of posts, I am sure you all get tired of answering the same questions over and over. But I would appreciate an opinion on my motor build. I have read about putting bigger valves in the head, and now would be the time to do it with the head apart and at the machine shop. What kind of expense should I expect in this, and is it really worth doing with the 240?. Bottom end will be stock, Offy C and headers, and currently undecided on cam ( will need much guidance here). From what I have gathered, it won't be needed for a mild build with decent flowing exhaust.

In other news, I had the radiator disassembled and cleaned. The guy told me it was one of the worst he had seen in 30 years. Ha. That explains me heat issue.

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Re: 240 valve size?

Post #2 by THE FRENCHTOWN FLYER » Tue Jun 11, 2019 5:37 pm

Any time you go with an intake manifold upgrade - and cam - I recommend increasing the valve size(s) to leverage the gains possible with the manifold or cam alone.
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Re: 240 valve size?

Post #3 by pmuller9 » Tue Jun 11, 2019 9:37 pm

SI valves have the 1.94/1.60 valves in the stock 240/300 length which is 4.810"
The Chevy valves are longer at 4.910"

The last few 300 builds have been using cams with the .050" duration around 220 degrees .
The 240 would work well with .050" durations in the 210 to 214 degree range.

The engine will need around an 8.8 compression ratio to stay with 87 to 89 octane pump gas with those camshaft profiles.

The Speed Pro H273CP piston would provide a compression ratio very close to 8.8 at zero deck and a 68cc combustion chamber.

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68Flareside240
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Re: 240 valve size?

Post #4 by 68Flareside240 » Fri Jun 21, 2019 6:25 pm

Well, machine work is almost complete. Waiting on pistons so they can bore. I ordered a master rebuild kit (minus cam and lifters) from Internal Engine Parts group who has a warehouse close to me, Birmingham Piston Warehouse. Pistons are Sealed Power stockers for 289/302, 0.040" over. I assume it is the Sealed Power 1109P 40. Got everything except the cam for 278.82 drop shipped to the machine shop. As for the head, I decided to stay stock. Machine shop said that the head was overall in good shape and will clean up nicely. Said that the valves looked like they were replaced when the head was worked before and should be fine. I assume I should go ahead and get new springs, retainers, etc. Seem cheap enough.

Knowing now what the bottom end will be like, do you still suggest a cam in the 0.050" 210-214 degree range? Is there any concern using the Chevy rockers with these cams? Would I need to get a stiffer valve spring if running these rockers?

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Re: 240 valve size?

Post #5 by pmuller9 » Fri Jun 21, 2019 9:13 pm

68Flareside240 wrote:Knowing now what the bottom end will be like, do you still suggest a cam in the 0.050" 210-214 degree range? Is there any concern using the Chevy rockers with these cams? Would I need to get a stiffer valve spring if running these rockers?

Yes, still suggest a cam in the .050" 210-214 range.
viewtopic.php?p=613117#p613117

The concern with the 1.75 ratio Chevy rockers is the extra open valve spring pressure can pull out the stock pressed in rocker studs.
Use a new set of stock 1.6 ratio rockers.

The stock spring replacement is the Comp 903-12.
They fit the stock intake valve retainer.
I prefer not to use the stock rotator exhaust retainer.

A little stiffer spring for the higher rpm 240 is the Crane 96803 with the Comp 768 retainer but then there is concern for the press in studs.

I would have your machinist drill and tap the head for screw in studs and eliminate the problem.

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Re: 240 valve size?

Post #6 by 68Flareside240 » Fri Jun 21, 2019 10:00 pm

I apologize. Yes, the 7 remaining press in studs are being pulled and screw ins installed.

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Re: 240 valve size?

Post #7 by pmuller9 » Fri Jun 21, 2019 10:24 pm

68Flareside240 wrote:I apologize. Yes, the 7 remaining press in studs are being pulled and screw ins installed.

No problem
That being the case you can stay with the 1.75 ratio Chevy rockers.
I'm assuming you have them already?

Before suggesting a cam it would be good to review
Offy "C" intake and Headers.

Which Carburetor?
What do you want for the RPM power range and what type of driving?

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Re: 240 valve size?

Post #8 by 68Flareside240 » Fri Jun 21, 2019 10:37 pm

Yes I ran the chevys probably the last 300 miles I put on the truck. They were subtle, but I could tell a difference, especially in exhaust note.

I plan on the offy c and I am looking at the edelbrock 500. From what I read it’s a good carb for adjustability and mild performance. I do plan on putting headers on it, probably gonna try those eBay headers posted earlier. Upgrade from points to pertronix ignitor and coil.

Overall looking for mild performance but wanting to be reliable and drivable. Very little, if any towing. Other than a light jon boat. Just a cruiser.

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Re: 240 valve size?

Post #9 by pmuller9 » Sat Jun 22, 2019 11:55 am

I'm going to recommend the Crower 266HDP (19213) .456”/.461” 210/213 266/274 112deg cam for the following reasons.

I don't like running stamped or cast rockers over .500" lift.
The clearance between the slot in the rocker and the rocker stud needs to be checked at full lift to make sure the stud is not running into the end of the slot.
The pattern on the top of the valve stem will also need to be checked to make sure the rocker is not running close to the edge.
The Crower 266HDP exhaust valve lift with the 1.75 ratio rocker is right at .500" lift.

The 266HDP has a wider 112 degree LSA which decreases valve overlap for a better idle and higher engine vacuum.

Normally your engine has around an 8.4 compression ratio but with a .040" over piston and possibly some block decking for cleanup I'm not sure what the final ratio will be.
In order to keep the engine running on 87 octane pump gas the new cam should not have much less then the stock cams 268 degree advertised duration.
The 266HDP has an advertised intake duration of 266 degrees.

Before ordering springs and retainers it would be good to know what the stock retainer height is from the spring seats on the head after the valve job.
Normal installed spring height is 1.700".
If it ends up being more the Crane 96803-12 with the Comp 768-12 retainers will work. You may have to order Comp 768-16 retainers to get them faster.

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Re: 240 valve size?

Post #10 by Max_Effort » Sat Jun 22, 2019 12:44 pm

This Erson camshaft from the Pmuller list looks good for a mild build.
ERSON CAMS
E270101 (RV10H) .448"/.448" 208/208 280/280 110deg

Erson has good quality, it’s priced right and in stock.

Comments?

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Re: 240 valve size?

Post #11 by pmuller9 » Sat Jun 22, 2019 1:39 pm

The Erson cam looks good especially with the lower lift and long advertised duration.
Thanks Max

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Re: 240 valve size?

Post #12 by 68Flareside240 » Sun Jun 23, 2019 5:33 pm

Thank you for the recommendations. I am not sure what the deck will be. I plan on running over there this week to check on things and talk about it. Gonna look into those cams this week and hopefully get one ordered. Trying to buy what I need as I can and stockpile it. Once I get everything I need I’ll start the build. Looking like I’m gonna have about $2100k in it when I finished. I don’t think that’s too bad for machine work and all the aftermarket stuff I’m putting on it.

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Re: 240 valve size?

Post #13 by pmuller9 » Sun Jun 23, 2019 5:39 pm

The Erson cam will give you a little better off idle response and it has the same overlap as the Crower cam.
Also the Erson cam has 280 degrees advertised duration which will allow a higher compression ratio and still be able to run 87 octane gas.

Will you be installing the cam?

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Re: 240 valve size?

Post #14 by 68Flareside240 » Sun Jun 23, 2019 5:59 pm

Yes I will be building the entire engine. Shop will be fitting pistons to rods. I do plan on degreeing the cam.

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Re: 240 valve size?

Post #15 by pmuller9 » Mon Jun 24, 2019 10:49 am

68Flareside240 wrote:Yes I will be building the entire engine. Shop will be fitting pistons to rods. I do plan on degreeing the cam.

When you degree the cam would you mind recording both the .006" and .050" durations of the intake and exhaust cam lobes.
I would appreciate it.
I like to sample what each cam company is using for advertised durations as well as their accuracy to specs.

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Re: 240 valve size?

Post #16 by 68Flareside240 » Mon Jun 24, 2019 11:00 am

I would be happy to. If you wouldn't mind, please explain the reasoning on the measurement at 0.006". Also, I was looking at the Erson cams, and saw the 292 duration they have, still at 0.478" lift. Would this cam be too much for me?

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Re: 240 valve size?

Post #17 by pmuller9 » Mon Jun 24, 2019 11:57 am

68Flareside240 wrote:I would be happy to. If you wouldn't mind, please explain the reasoning on the measurement at 0.006". Also, I was looking at the Erson cams, and saw the 292 duration they have, still at 0.478" lift. Would this cam be too much for me?

The SAE standard for measuring advertised duration is at .006" lobe lift from zero lash.
Most cam companies hold to that but some use less lobe lift to increase the advertised duration and there are others that are more.
The only reason we care is that we use the .006" duration to calculate DCR for the sake of detonation otherwise it doesn't matter.
It is just good to know what each cam company is doing.

The 292 Erson with 0.478" lift would require you to go back to a stock 1.6 ratio rocker unless you want to go to a roller rocker.
The compression ratio could be higher and you could zero deck the pistons.

The Erson 292 cam would push the power band upwards of 5000 rpm but unlike the 300 you would lose some of the low end torque below 2000 rpm.
You would want to advance the cam around 3 to 4 degrees when you install it.

It is up to you.

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Re: 240 valve size?

Post #18 by 68Flareside240 » Mon Jun 24, 2019 12:37 pm

Gotcha. I have been reading up on cam measurements and was just wondering why measuring there. Thanks for clarifying. Apprecaite the the input on the cam. I want something with a good idle, but don't want to change too much. I am sure that E270101 will be fine. I have found that cam and lifters for about $220 online. Hope to have more info on deck height and valve height Wednesday. Thanks again for the input. Slowly learning.

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Re: 240 valve size?

Post #19 by Max_Effort » Mon Jun 24, 2019 2:57 pm

Not to add any confusion, but I think Erson list advertised at .004" tappet rise. That makes their advertised look just a little larger than some others. It's just a few degrees, no big deal, carry on...

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Re: 240 valve size?

Post #20 by THE FRENCHTOWN FLYER » Mon Jun 24, 2019 3:16 pm

Cam companies put clearance ramps on each end of their lobe profiles. These have gentle ramp rates to gradually take up any valve train play and gently put a pre-load on all the valvetrain components - lifters, pushrods, rockers, valve assemblies. Nothing is totally incompressible and these gentle ramps compress all these parts and get them ready to do their job of lifting the valve open. They also softly land the lifter on closing so no valve train shocking bouncing motion is set up.
These ramps generally take up the first .006" of the profile - off the base circle - and no appreciable valve motion occurrs.

The .050" lift point is an accepted standard of where any appreciable intake valve flow starts, so that has become a useful norm to compare the effectiveness of different cam profiles - more so than the advertised duration numbers. [I kinda take issue with the part about "no appreciable flow below .050". That may be a function of valve seat design and throat design. Especially on the exhaust side. But I digress...] I see the need to standardize the .050 point for the consumer to have something tangible to go on. (Do some of you old-timers still remember the early years of hot rodding where all we were told was that the cam was Street, Half-Race, Three-Quarter Race, or Full Race?)


I still have a valve cover on my truck that says "3/4 Race". Get it? - six cylinders, not eight? 3/4 Race? It gets chuckles.
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Re: 240 valve size?

Post #21 by drag-200stang » Mon Jun 24, 2019 3:26 pm

Well, yes I do.
The younger guys laugh about a 3/4 cam missing part of the lobes.
They simply have not been there, done that or they would understand. :wink:
Last edited by drag-200stang on Mon Jun 24, 2019 3:30 pm, edited 1 time in total.
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Re: 240 valve size?

Post #22 by pmuller9 » Mon Jun 24, 2019 3:27 pm

Yep I still remember the days of just street and race referenced cams and having to go to the car dealer to get a lot of performance parts.

Max_Effort wrote:Not to add any confusion, but I think Erson list advertised at .004" tappet rise. That makes their advertised look just a little larger than some others. It's just a few degrees, no big deal, carry on...

That's what we are going to find out when 68Flarseside240 takes actual measurements if the Erson cam is used.

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Re: 240 valve size?

Post #23 by 68Flareside240 » Mon Jun 24, 2019 7:21 pm

Thanks for the help. Great info FTF, backed up what I was reading on Erson's site. I have decided to go with their E270101 cam and lifters. $226 to my door. Already have a few questions after looking at the cam card, but I'll hold off until a little closer. I hope to answer my questions in the next few weeks. Thanks again.

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Re: 240 valve size?

Post #24 by pmuller9 » Mon Jun 24, 2019 9:27 pm

What would you like to know about the cam card info?

The intake opening point is referenced to timing before TDC so a -2 indicates 2 degrees ATDC.
The intake closing point is ABDC

The exhaust closing point is referenced to timing ATDC so -10 would be 10 degrees BTDC.
The exhaust opening point is BBDC.

This is based on the advertised duration of a fixed cam where the intake always opens BTDC and the exhaust always closes ATDC.

The card specs the cam to be installed 4 degrees advanced with the intake centerline at 106 degrees ATDC.

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Re: 240 valve size?

Post #25 by 68Flareside240 » Tue Jun 25, 2019 4:28 pm

I had to go back through and refresh my brain on what is actually happening with the camshaft in relation to crankshaft, and it all makes sense now.

When it comes to cam lift and subsequently valve lift, I know that cam lift will be 0.448", which when using a 1.75:1 rocker equates to 0.784" of maximum valve lift. Is that correct? How much is too much valve lift in these motors (I know there are some variables there)? Would you use this number to measure valve spring pressure at fully open?

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Re: 240 valve size?

Post #26 by sandboxer » Tue Jun 25, 2019 4:59 pm

68Flareside240 wrote:I had to go back through and refresh my brain on what is actually happening with the camshaft in relation to crankshaft, and it all makes sense now.

When it comes to cam lift and subsequently valve lift, I know that cam lift will be 0.448", which when using a 1.75:1 rocker equates to 0.784" of maximum valve lift. Is that correct? How much is too much valve lift in these motors (I know there are some variables there)? Would you use this number to measure valve spring pressure at fully open?

The 0.488 accounts for the lobe height x the rocker ratio (1.6) so is the lift the valve sees.
As I edit my own post I realize that I should never wake up from a nap and pretend to be smart:)
Last edited by sandboxer on Tue Jun 25, 2019 5:41 pm, edited 1 time in total.

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Re: 240 valve size?

Post #27 by 68Flareside240 » Tue Jun 25, 2019 5:10 pm

Gotcha. I thought that number looked a little large for this motor. So that 0.532" is the number to check open spring compression?

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Re: 240 valve size?

Post #28 by Max_Effort » Tue Jun 25, 2019 5:24 pm

68Flareside240 wrote:Gotcha. I thought that number looked a little large for this motor. So that 0.532" is the number to check open spring compression?


No.

The cam is .280” lobe lift

.280” x 1.6 = .448”

.280” x 1.75 =.490”

What you measure will depend on the actual rocker ratio (it can vary from the stated ratio)

And the rocker geometry

And how well you set the dial indicator up.

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Re: 240 valve size?

Post #29 by bubba22349 » Tue Jun 25, 2019 9:31 pm

THE FRENCHTOWN FLYER wrote: (Do some of you old-timers still remember the early years of hot rodding where all we were told was that the cam was Street, Half-Race, Three-Quarter Race, or Full Race?)

I still have a valve cover on my truck that says "3/4 Race". Get it? - six cylinders, not eight? 3/4 Race? It gets chuckles.


:rolflmao: FTF that's great but you should have put a picture of your valve cover too! I remember seeing those kind of cam grinds talked about back in the day too. :thumbup: :nod:
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Re: 240 valve size?

Post #30 by Max_Effort » Wed Jun 26, 2019 6:09 am

Getting OT, but Crane cams (owned by comp now) is marketing 3/4 race cams. It's just one of their energizer grinds with a new name.
Give the people what they want...

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