Reduced Base Circle Flat Tappet Lifters
Thread Starter
Pro
Joined: Apr 2010
Posts: 603
Likes: 249
From: Carson Valley
Reduced Base Circle Flat Tappet Lifters
I intend to run a Howards Cams hydraulic flat tappet, reduced base circle cam in a small block I'm assembling.
I can not find any information regarding lifters for such a cam.
Are taller lifters required when using a reduced base circle cam?
I see Howards Cams lists three models of lifter, Performance, Direct Lube and Max Effort.
The Direct Lube is taller than the other two yet it does not state if this is intended for a reduced base circle cam.
I emailed Howards for some other information, and asked about lifters. My question was not answered.
I'd rather not bother them too much until I have a better idea of what I need.
I can not find any information regarding lifters for such a cam.
Are taller lifters required when using a reduced base circle cam?
I see Howards Cams lists three models of lifter, Performance, Direct Lube and Max Effort.
The Direct Lube is taller than the other two yet it does not state if this is intended for a reduced base circle cam.
I emailed Howards for some other information, and asked about lifters. My question was not answered.
I'd rather not bother them too much until I have a better idea of what I need.
Safety Car
Joined: Oct 2004
Posts: 3,926
Likes: 739
From: Youngstown Ohio
Short answer, "no". The lifters are the same as for the standard base circle. Possible longer pushrods may be needed, but not always. The smaller base circle reduces the overall diameter of the cam so the lobes won't hit the rods in stroker engines.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
also makes more cam lift possible because the lobe can't be taller than the bearing diameter. why do you want a reduced base circle. it is a compromise for very high performance. not needed for street engines and shortens valve train life which race engine owners usually are fine with
Thread Starter
Pro
Joined: Apr 2010
Posts: 603
Likes: 249
From: Carson Valley
I plan to install a 3.75" stroker kit and have no way to know what my clearances will be until I get the parts in hand and installed.
I've read of others having interference between the rods and cam and would prefer to get the correct parts the first time.
If parts weren't on back order I may not mind having to exchange a camshaft if I get the wrong one the first time.
The stroker kit is already ordered and I don't know if I will be able exchange the standard rods for the clearanced rods, I'm waiting to hear back on that.
I've read of others having interference between the rods and cam and would prefer to get the correct parts the first time.
If parts weren't on back order I may not mind having to exchange a camshaft if I get the wrong one the first time.
The stroker kit is already ordered and I don't know if I will be able exchange the standard rods for the clearanced rods, I'm waiting to hear back on that.
Thread Starter
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Joined: Apr 2010
Posts: 603
Likes: 249
From: Carson Valley
Currently that is unknown.
I go through the Summit website, pick a few cams out (based on operating RPM range) and plug them into Desktop Dyno5 to see how the power curves look, then I check the DCR with the heads I want to run.
Three times I've settled on a cam, only to change my mind.
This is my first performance build. My career was operating and maintaining marine diesel engines, and I had rebuilt a few gas engines when I was younger.
I'm good with engines, it's the combining aftermarket components that's new to me.
I want to get it right, or at least close. I'm not averse to swapping the cam if I don't get it right the first time.
It's a learning experience.
This morning it occurred to me that I can mock up my rotating assembly with an old cam to see what my clearances look like.
I go through the Summit website, pick a few cams out (based on operating RPM range) and plug them into Desktop Dyno5 to see how the power curves look, then I check the DCR with the heads I want to run.
Three times I've settled on a cam, only to change my mind.
This is my first performance build. My career was operating and maintaining marine diesel engines, and I had rebuilt a few gas engines when I was younger.
I'm good with engines, it's the combining aftermarket components that's new to me.
I want to get it right, or at least close. I'm not averse to swapping the cam if I don't get it right the first time.
It's a learning experience.
This morning it occurred to me that I can mock up my rotating assembly with an old cam to see what my clearances look like.
Safety Car
Joined: Oct 2004
Posts: 3,926
Likes: 739
From: Youngstown Ohio
Depending on the cam you choose, you may or may not need a small base circle cam. My previous 383 did not require one, but my 427 and 440 stroker small blocks did. If you do get a small base circle cam, get a billet core cam.....they are stronger since the cam diameter is less.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
just about everybody who changes their cam profile either goes less or more aggressive than they wanted. few get it right the first time. what are you doing with the car? f
driving it with occasional full throttle for ***** and giggles? or some form of competition? and two words... roller lifters...
driving it with occasional full throttle for ***** and giggles? or some form of competition? and two words... roller lifters...
Last edited by derekderek; Nov 14, 2022 at 04:33 PM.
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Thread Starter
Pro
Joined: Apr 2010
Posts: 603
Likes: 249
From: Carson Valley
I'd like to take the occasional overnight trip in the car, and perhaps enter some competitions.
I've been testing various cams using Desktop Dyno5, I'm told the numbers can be reliable.
The original goal for my build was low RPM torque and not much over 5000 RPM.
After more thought and research I realized that I can have the low RPM torque, and top end HP.
The numbers I'm getting from the program show this, with conservative estimates on intake choice.
I have gone back and forth on roller vs. flat tappet cam.
I'm told retrofit roller lifters need inspected, one of my goals is durability and ease of maintenance.
I briefly considered solid lifters, that goes against the ease of maintenance.
If I knew I was going to be doing a lot of competition, and expected to be competitive, rather than enjoying the drive, I'd go for the more maintenance intensive build.
I've been testing various cams using Desktop Dyno5, I'm told the numbers can be reliable.
The original goal for my build was low RPM torque and not much over 5000 RPM.
After more thought and research I realized that I can have the low RPM torque, and top end HP.
The numbers I'm getting from the program show this, with conservative estimates on intake choice.
I have gone back and forth on roller vs. flat tappet cam.
I'm told retrofit roller lifters need inspected, one of my goals is durability and ease of maintenance.
I briefly considered solid lifters, that goes against the ease of maintenance.
If I knew I was going to be doing a lot of competition, and expected to be competitive, rather than enjoying the drive, I'd go for the more maintenance intensive build.
Last edited by AKjeff; Nov 14, 2022 at 09:31 AM.
Melting Slicks
Joined: Jun 2002
Posts: 2,844
Likes: 99
From: Orrtanna Pa.
I plan to install a 3.75" stroker kit and have no way to know what my clearances will be until I get the parts in hand and installed.
I've read of others having interference between the rods and cam and would prefer to get the correct parts the first time.
If parts weren't on back order I may not mind having to exchange a camshaft if I get the wrong one the first time.
The stroker kit is already ordered and I don't know if I will be able exchange the standard rods for the clearanced rods, I'm waiting to hear back on that.
I've read of others having interference between the rods and cam and would prefer to get the correct parts the first time.
If parts weren't on back order I may not mind having to exchange a camshaft if I get the wrong one the first time.
The stroker kit is already ordered and I don't know if I will be able exchange the standard rods for the clearanced rods, I'm waiting to hear back on that.
My 406 used standard 5.7 inch rods with a standard base circle cam with no clearance issue. The 3.75 stroke is stock for a 400.
Thread Starter
Pro
Joined: Apr 2010
Posts: 603
Likes: 249
From: Carson Valley
I didn't see the difference in the rods until after I placed my order over the phone.
Of course that was the perfect time to ask the question, if I'd known to ask it...
I left a voice mail and sent an email and haven't heard back yet.
I have a couple weeks until they receive the pistons so I do have a little time.
Of course that was the perfect time to ask the question, if I'd known to ask it...
I left a voice mail and sent an email and haven't heard back yet.
I have a couple weeks until they receive the pistons so I do have a little time.