390 Build
Super Moderator
Joined: Apr 2004
Posts: 34,499
Likes: 2,811
30/30? Why so much? I thought this might be an issue, so I looked up a couple things. Short version here, go to the last paragraph:
Undersizing Crankshafts Your customers need clarity in terms of the old 10
Mahle goes to .040.
MAHLE Product Catalog
C8AE are ok, but are you going to have them gone through--guides, hardened seats etc? Price that out and compare it to aftermarket heads. You will need seals and springs too, but the cam supplier will have the correct springs for whatever cam you get.
Undersizing Crankshafts Your customers need clarity in terms of the old 10
Mahle goes to .040.
MAHLE Product Catalog
C8AE are ok, but are you going to have them gone through--guides, hardened seats etc? Price that out and compare it to aftermarket heads. You will need seals and springs too, but the cam supplier will have the correct springs for whatever cam you get.
Thread Starter
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Tuned
Joined: Nov 2009
Posts: 261
Likes: 3
Cast crank I have is already 20/20 and needs a definite clean up. Thanks for the crank read. I'll be curious to what the grinder says.
Got a quote on calibrating a torque wrench....just bought a new one, on sale for less than what a cal would cost. Sheez.
Got a quote on calibrating a torque wrench....just bought a new one, on sale for less than what a cal would cost. Sheez.
Logistics Pro
Joined: Mar 2005
Posts: 3,771
Likes: 80
From: tujunga, calif
All other things being equal, you have a smaller cylinder pushing into the same space as the larger cylinder. So the 390 would have a lower compression ratio and lower cylinder pressure.
Compression Ratio Calculator - Competition Components
Compression Ratio Calculator - Competition Components
Thread Starter
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Tuned
Joined: Nov 2009
Posts: 261
Likes: 3
Thanks for the help thus far guys, I do appreciate it.
I have a rod question. I was hoping to re-use one of two sets of rods that I have. Both are basically of unknown service life. Considering the condition the same, is there a preference between:
C6AE-C
C7AE-B
??
I haven't checked the bolt sizes to see of there is a difference. Visually, the toe of the C6 rod is curved and smooth rather than having a "foot" of sorts.
I have a rod question. I was hoping to re-use one of two sets of rods that I have. Both are basically of unknown service life. Considering the condition the same, is there a preference between:
C6AE-C
C7AE-B
??
I haven't checked the bolt sizes to see of there is a difference. Visually, the toe of the C6 rod is curved and smooth rather than having a "foot" of sorts.
Junior User
Joined: Aug 2002
Posts: 93
Likes: 0
From: S.E.Mo
Isky 256/262
I'm almost 100% sold on the ISKY 256 cam. It's a mellow cam, but I think I've resolved myself to making this a mellow build.
Question about timing gear sets. I've always known Cloyes as being the best brand, they have several variations at Summit. Any recommendations?
Summit Racing Part Number: ISK-351256
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 1,500-4,800
Intake Duration at 050 inch Lift: 202
Exhaust Duration at 050 inch Lift: 202
Duration at 050 inch Lift: 202 int./202 exh.
Advertised Intake Duration: 256
Advertised Exhaust Duration: 256
Advertised Duration: 256 int./256 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.492 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.492 in.
Valve Lift with Factory Rocker Arm Ratio: 0.492 int./0.492 exh.
Lobe Separation (degrees): 112
Computer-Controlled Compatible: No
Grind Number: 256 Supercam
I've been looking for the 256/262 dual pattern, but isn't jumping out for sale on the net- not sure if the grind was never good, or I'm just looking in the wrong places? I don't see it on ISKY's site.
Question about timing gear sets. I've always known Cloyes as being the best brand, they have several variations at Summit. Any recommendations?
Summit Racing Part Number: ISK-351256
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 1,500-4,800
Intake Duration at 050 inch Lift: 202
Exhaust Duration at 050 inch Lift: 202
Duration at 050 inch Lift: 202 int./202 exh.
Advertised Intake Duration: 256
Advertised Exhaust Duration: 256
Advertised Duration: 256 int./256 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.492 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.492 in.
Valve Lift with Factory Rocker Arm Ratio: 0.492 int./0.492 exh.
Lobe Separation (degrees): 112
Computer-Controlled Compatible: No
Grind Number: 256 Supercam
I've been looking for the 256/262 dual pattern, but isn't jumping out for sale on the net- not sure if the grind was never good, or I'm just looking in the wrong places? I don't see it on ISKY's site.
Thread Starter
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Tuned
Joined: Nov 2009
Posts: 261
Likes: 3
Thank you for the confirmation that the ISKY cam I'm looking at is a decent application for an old truck.
For inquiring minds, the block is at the shop. I ordered a dizzy bushing through DSC. Heads are in process. Still need to bring the crank to a grinder.
Need to weigh the two different rods to see if there is a weight difference & go to the POR site to see what color this block is going to become. I'm partial to Ford royal blue....but have an import motor I'm doing soon too- and I'm thinking something neutral, aluminum gray?
Still curious if anyone has input to the rods (looks like they are really similar) and timing set recommendations??
For inquiring minds, the block is at the shop. I ordered a dizzy bushing through DSC. Heads are in process. Still need to bring the crank to a grinder.
Need to weigh the two different rods to see if there is a weight difference & go to the POR site to see what color this block is going to become. I'm partial to Ford royal blue....but have an import motor I'm doing soon too- and I'm thinking something neutral, aluminum gray?
Still curious if anyone has input to the rods (looks like they are really similar) and timing set recommendations??
Super Moderator
Joined: Apr 2004
Posts: 34,499
Likes: 2,811
Timing set: Cloyes or other fine brand, pick one:
Timing Chain and Gear Sets - Double roller Timing Chain Style - Free Shipping on Orders Over $99 at Summit Racing
Rods: Is there any difference in the fastener? Are they the same length?
You want 6.486-6.490 length. NOT 6.538-6.542.
Have them shot peened and resized. Use ARP fasteners. Good for 6000 RPM plus.
Timing Chain and Gear Sets - Double roller Timing Chain Style - Free Shipping on Orders Over $99 at Summit Racing
Rods: Is there any difference in the fastener? Are they the same length?
You want 6.486-6.490 length. NOT 6.538-6.542.
Have them shot peened and resized. Use ARP fasteners. Good for 6000 RPM plus.
Thread Starter
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Tuned
Joined: Nov 2009
Posts: 261
Likes: 3
Both rods have the same size bolt and are within 0.02 oz of each other. The C7 rod looks like a more well defined forging, the C6 rod appears "rougher."
Thanks for the advice on shot-peening.
Thanks for the advice on shot-peening.
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Thread Starter
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Tuned
Joined: Nov 2009
Posts: 261
Likes: 3
Minor setback today. Yesterday I brought both cranks I have, 390 & 391 into a "crankshaft" shop. The gent at the shop mentioned the 391 would cost a fair penny to re-work to be 390 friendly, which makes sense. I got a call from the shop today that the 2U cast crank I had that was 0.020" under has got a nasty crack. I didn't see it myself, but now I'm stuck with a few, more expensive, options. Shop has a crack free cast crank, freshly ground 0.020"....about $350, or I try re-working the 391 crank, for probably the same amount of money, if not more.....and then there's looking at stroker options.
My last ditch of insurance is to measure the stroke on my choco milk holding, what I believe to me, 360m in my truck now, to make sure it truly is a 360.
Just goes to show, you never know what you get second hand.
My last ditch of insurance is to measure the stroke on my choco milk holding, what I believe to me, 360m in my truck now, to make sure it truly is a 360.
Just goes to show, you never know what you get second hand.
Thread Starter
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Tuned
Joined: Nov 2009
Posts: 261
Likes: 3
I'm about to submit my monster order to Summit and had a question regarding oil pumps. Do you guys know if there is a difference between the oil pump for a 391 versus the 390? I have the dizzy bushing, just not sure if there is a difference in pump or the length of the drive shaft?
I'm planning on using the original 391 oil pan as it appears preferred over the stock front sump....Just hoping it will work on my '73 F250. I haven't double checked...yet.
Curious what you guys are running for distributors? I believe my 360's will work just fine. A PO converted the points out. The aftermarket units are sexy, but I've had to draw the line on the bolt-ons....they can come afterward...dizzy, headers, intake...are for a different day, and adds about $1K I don't need to spend right now.
Interesting thing about the 391 dizzy is that it has a mechanical tach drive on it. I presume for the governor.
Is this a good time to consider a new torque converter....or should I leave the tranny alone? I have had no problems with my C6 - just not sure if it's a good swap out while I'll have everything apart? like a clutch? Recommended stall?
Thanks again for the help and reading along.
I'm planning on using the original 391 oil pan as it appears preferred over the stock front sump....Just hoping it will work on my '73 F250. I haven't double checked...yet.
Curious what you guys are running for distributors? I believe my 360's will work just fine. A PO converted the points out. The aftermarket units are sexy, but I've had to draw the line on the bolt-ons....they can come afterward...dizzy, headers, intake...are for a different day, and adds about $1K I don't need to spend right now.
Interesting thing about the 391 dizzy is that it has a mechanical tach drive on it. I presume for the governor.
Is this a good time to consider a new torque converter....or should I leave the tranny alone? I have had no problems with my C6 - just not sure if it's a good swap out while I'll have everything apart? like a clutch? Recommended stall?
Thanks again for the help and reading along.
Thread Starter
|
Tuned
Joined: Nov 2009
Posts: 261
Likes: 3
Goodies are arriving. ISKY Super 256 cam arrived with new lifters. Holley 600 carb, new fuel pump, oil pump drive, and sweet double roller Cloyes timing set. Water pump and high volume oil pump are on the way. Picking up the new cast crank (ground -0.020") tomorrow. Should be picking up the block this coming Thursday while dropping off the crank for balancing and rods to be reconditioned. I'm going with KB Silvolite Hypereutectics. C8AE-H Heads should arrive (machined) Thursday. Also need to drop off the oil pan, pickup and timing cover. POR 15 aluminum color paint on the way.
Stuff still left for me to address: looking at getting an Edelbrock RPM intake, on the fence about an aftermarket dizzy, need to check for fit for the old full size 391 oil pan, order engine mounts, make a decision on air cleaner (aftermarket or stock).
How decent is the stock rocker arm assemblies for a mild build? I've noted that spacers can be used to replace the shaft springs. Rockers are ok for re-use?
Stuff still left for me to address: looking at getting an Edelbrock RPM intake, on the fence about an aftermarket dizzy, need to check for fit for the old full size 391 oil pan, order engine mounts, make a decision on air cleaner (aftermarket or stock).
How decent is the stock rocker arm assemblies for a mild build? I've noted that spacers can be used to replace the shaft springs. Rockers are ok for re-use?
Cargo Master
Joined: Dec 2015
Posts: 2,544
Likes: 322
From: Harned, Ky
I'm about to submit my monster order to Summit and had a question regarding oil pumps. Do you guys know if there is a difference between the oil pump for a 391 versus the 390? I have the dizzy bushing, just not sure if there is a difference in pump or the length of the drive shaft?
I'm planning on using the original 391 oil pan as it appears preferred over the stock front sump....Just hoping it will work on my '73 F250. I haven't double checked...yet.
Curious what you guys are running for distributors? I believe my 360's will work just fine. A PO converted the points out. The aftermarket units are sexy, but I've had to draw the line on the bolt-ons....they can come afterward...dizzy, headers, intake...are for a different day, and adds about $1K I don't need to spend right now.
Interesting thing about the 391 dizzy is that it has a mechanical tach drive on it. I presume for the governor.
Is this a good time to consider a new torque converter....or should I leave the tranny alone? I have had no problems with my C6 - just not sure if it's a good swap out while I'll have everything apart? like a clutch? Recommended stall?
Thanks again for the help and reading along.
I'm planning on using the original 391 oil pan as it appears preferred over the stock front sump....Just hoping it will work on my '73 F250. I haven't double checked...yet.
Curious what you guys are running for distributors? I believe my 360's will work just fine. A PO converted the points out. The aftermarket units are sexy, but I've had to draw the line on the bolt-ons....they can come afterward...dizzy, headers, intake...are for a different day, and adds about $1K I don't need to spend right now.
Interesting thing about the 391 dizzy is that it has a mechanical tach drive on it. I presume for the governor.
Is this a good time to consider a new torque converter....or should I leave the tranny alone? I have had no problems with my C6 - just not sure if it's a good swap out while I'll have everything apart? like a clutch? Recommended stall?
Thanks again for the help and reading along.
391 dist has a mechanical governor build into it and did have a mechanical tach drive, the exta fittings where for connecting the governor to the governor controlled carb. It doesn't make a good dist for non governor apps.