Don Terrill’s Speed-Talk

How do you (you personally) decide when to go with a catalog cam or have a custom cam made?

How do you evaluate a cam listing that does not include important information about the design such as acceleration values and a graph of the curve?

If, for example; you were buying a hydraulic roller for an 454 BBC, what would bring you to the conclusion that the catalog cams did not provide what you need?

How does price figure into the decision for you?

I do alot of marine work and most times a power increase is wanted as well as more RPM range which always
comes with more cam. the LSA for marine stuff is very critical to keep water out of the engine with too much
overlap. Most of what we do uses 114 lsa and if looking at catalogue stuff its almost 99% tighter with the increase of
lift/duration in most cases they seem to range from 108-110 lsa.

Also if a firing order change to say the LS firing order instead of the common 4/7 swap.
While the LS firing order is gaining popularity in the BBC market like it did in the sm blk market the std. cam type for non factory roller is easy to get while the HYD.factory roller replacement seems harder if not impossible even custom to locate.

ProPower engines wrote: ↑Sun Aug 11, 2019 4:31 pm I do alot of marine work and most times a power increase is wanted as well as more RPM range which always
comes with more cam. the LSA for marine stuff is very critical to keep water out of the engine with too much
overlap. Most of what we do uses 114 lsa and if looking at catalogue stuff its almost 99% tighter with the increase of
lift/duration in most cases they seem to range from 108-110 lsa.

Also if a firing order change to say the LS firing order instead of the common 4/7 swap.
While the LS firing order is gaining popularity in the BBC market like it did in the sm blk market the std. cam type for non factory roller is easy to get while the HYD.factory roller replacement seems harder if not impossible even custom to locate.

Quick, sort of off-topic question. I'm not very familiar with all of the nuances of marine engines and their differences from automotive based engines. Is it normal for marine mfg's to use stock automotive cams in their marine engines?

For example, I just looked at a single example that I knew of off the top of my head, the Mercruiser 4.3 V6 and it appeared to be running a stock 94-95 'W' code camshaft. Is that sort of thing normal?

well just what i have seen and its fk all , alot of the lower stage 1-2 cams are designed around stock set ups , flow intake maybe with a few mods decat and things , but when you flow heads completely change intakes of seriously modify , from the guys I know they look for custom , but i have read here from the likes of larry that he feels with a specific flowed head there were a few off the shelf cams that would work in the range , so i too am waiting for others to join in on this

WoundUp wrote: ↑Sun Aug 11, 2019 4:59 pm

ProPower engines wrote: ↑Sun Aug 11, 2019 4:31 pm I do alot of marine work and most times a power increase is wanted as well as more RPM range which always
comes with more cam. the LSA for marine stuff is very critical to keep water out of the engine with too much
overlap. Most of what we do uses 114 lsa and if looking at catalogue stuff its almost 99% tighter with the increase of
lift/duration in most cases they seem to range from 108-110 lsa.

Also if a firing order change to say the LS firing order instead of the common 4/7 swap.
While the LS firing order is gaining popularity in the BBC market like it did in the sm blk market the std. cam type for non factory roller is easy to get while the HYD.factory roller replacement seems harder if not impossible even custom to locate.

Quick, sort of off-topic question. I'm not very familiar with all of the nuances of marine engines and their differences from automotive based engines. Is it normal for marine mfg's to use stock automotive cams in their marine engines?

For example, I just looked at a single example that I knew of off the top of my head, the Mercruiser 4.3 V6 and it appeared to be running a stock 94-95 'W' code camshaft. Is that sort of thing normal?

On the smaller marine engines they do use factory stuff which is usually 112 through 115...or not much .050" or overlap

In my opinion the old "use wide LSA for marine engines " hurts more than it helps.

I've used really narrow angles like 106 7 and 8 in marine engines without any problem of water backing up into the exhaust...but I wouldn't do that on a stock through prop exhaust

Most set ups dump way to much cooling water into the exhaust,, best way is to restrict it enough to cool everything and not a lot of idling before pulling it out..then a quick throttle blip out of the water to explell any water

SchmidtMotorWorks wrote: ↑Sun Aug 11, 2019 3:52 pm How do you (you personally) decide when to go with a catalog cam or have a custom cam made?

How do you evaluate a cam listing that does not include important information about the design such as acceleration values and a graph of the curve?

If, for example; you were buying a hydraulic roller for an 454 BBC, what would bring you to the conclusion that the catalog cams did not provide what you need?

How does price figure into the decision for you?

In general the generic LSA of a shelf cam rarely gives you optimum valve events, if you do find one with the needed duration and lsa for your application the lift on a shelf cam is usually more conservative then many would prefer, if you stick with lobes from the mnf catalog the price of a custom cam is usually the same as a shelf grind.

If you have your valve events then you have your overlap and lsa or visa versa, combine that with rocker ratio and lobe lift and you have narrowed it to a handful of lobes and unless you are going to test all of those on the dyno then you probably will never know a difference between them.

I will add that is shelf grinds were close enough then the oem and pro race teams would not be specing custom cams.

SchmidtMotorWorks wrote: ↑Sun Aug 11, 2019 3:52 pm How do you (you personally) decide when to go with a catalog cam or have a custom cam made?

How do you evaluate a cam listing that does not include important information about the design such as acceleration values and a graph of the curve?

If, for example; you were buying a hydraulic roller for an 454 BBC, what would bring you to the conclusion that the catalog cams did not provide what you need?

How does price figure into the decision for you?

Most applications do not need or are even better power makers with aggressive flanks and "on the edge" specs" which need special attention with other parts.
Sometimes a catalog cam is just right, sometimes it is just close, (usually the generic ones), and sometimes you just can't get there with anything other than "custom".

My opinion is that most experienced engine builders have a pretty good background of what is preferred however, the average person is usually at the mercy of catalog descriptions.

A big factor is if it's a mainstream engine or not.

You could spend days looking through sbc and Ford cam choices online till you get dizzy.

Other stuff,, not so much

gmrocket wrote: ↑Sun Aug 11, 2019 7:02 pm A big factor is if it's a mainstream engine or not.

You could spend days looking through sbc and Ford cam choices online till you get dizzy.

Other stuff,, not so much

For engines without much selection available that makes sense.

I'm curious what makes a person stop looking at the catalogs and order a custom cam.

So far, too wide of LSA seems to be common.

I suspect that many of the cores used for narrow LSA were designed for wide LSA so hardness may not be ideal.

SchmidtMotorWorks wrote: ↑Sun Aug 11, 2019 7:13 pm

gmrocket wrote: ↑Sun Aug 11, 2019 7:02 pm A big factor is if it's a mainstream engine or not.

You could spend days looking through sbc and Ford cam choices online till you get dizzy.

Other stuff,, not so much

For engines without much selection available that makes sense.

I'm curious what makes a person stop looking at the catalogs and order a custom cam.

So far, too wide of LSA seems to be common.

I suspect that many of the cores used for narrow LSA were designed for wide LSA so hardness may not be ideal.

Probably only if your going really narrow then a custom core is going to add to cost.

Maybe Mike will chime in on what cores are available and when they cost extra.

Most catalogue stuff is pretty generic, made to work ok when selected by the average guy with basic knowledge.
Lobe centres are often too wide to allow for a tendency to pick too large a cam.
Intake & ex lobes are often in the same lobe family so ex lift is higher than intake.
Often there is too much duration split.

If you want better than 100% ve & an engine that goes beyond the sum of it's parts the only choice is custom.

In the last, say, 20 engines I've built I would have used 1-2 shelf cams & only because they were mild mannered street engines & the shelf cams were so close to what I wanted it wasn't worth going to a custom.

[/quote]

On the smaller marine engines they do use factory stuff which is usually 112 through 115...or not much .050" or overlap

In my opinion the old "use wide LSA for marine engines " hurts more than it helps.

I've used really narrow angles like 106 7 and 8 in marine engines without any problem of water backing up into the exhaust...but I wouldn't do that on a stock through prop exhaust

Most set ups dump way to much cooling water into the exhaust,, best way is to restrict it enough to cool everything and not a lot of idling before pulling it out..then a quick throttle blip out of the water to explell any water
[/quote]

Thats my point. Where on say a BBC engine the cam profiles used are very tame by comparison and the power levels reflect that. But if you want an extra 100 HP then the cam has to get much bigger along with the intake etc etc etc but the point is when looking at a shelf cam in the .600 to.650 lift range most are about 108 which is too tight. They really like 114. I had Mike Jones do me a pair that worked out to be 116 or 117 lsa but they also were an LS firing order as well
for a pair of 496 BBC engines.
Also in marine stuff idle quality and speed must match the drive gear needs. They don't like more then 750 rpm to engage
and docking is hard with a engine with bad idle manners which stalling can be an issue with the low speeds required to go from forward to reverse without damaging the drive gear.

the exhaust in a cruiser is much different then a ski boat and the manifolds that must be used have an inherent issue
of allowing water into the system if there is too much overlap on the cam..

Even if the manifolds are cooled by a heat exchanger system that riser must be able to handle the entire amount raw water it takes to cool the system, In larger boats they are not done that way because of heat exchanger size requirements to get the job done so they are raw water cooled.

Again what I am referring to is a large boat with enclosed engine bay either single or duel engines where durability
has to be foremost and good manners for operation is paramount as most boaters have no clue how to tune
or time correctly so it just have to work and be smooth operating under all conditions.

95% of the engines we do have no shelf cams used as well

SchmidtMotorWorks wrote: ↑Sun Aug 11, 2019 7:13 pm

gmrocket wrote: ↑Sun Aug 11, 2019 7:02 pm A big factor is if it's a mainstream engine or not.

You could spend days looking through sbc and Ford cam choices online till you get dizzy.

Other stuff,, not so much

For engines without much selection available that makes sense.

I'm curious what makes a person stop looking at the catalogs and order a custom cam.

So far, too wide of LSA seems to be common.

I suspect that many of the cores used for narrow LSA were designed for wide LSA so hardness may not be ideal.

When your into the 106 or less LSA for a non mainstream engines in the solid or hyd rollers it's a tuff deal ..round lobes are like trying to find a white rhino

Same with flats.

Planning way way ahead for that is important, or impossible.

I almost never ever use a shelf grind. IMO, there is no reason to when there are companies out there like Jones, Cam Motion, Bullet and many, many others to use. The cost is essentially the same. The time frame isn't usually a big deal. A week isn't a big deal to me.


I can tell you when I was ordering half a dozen to 10 cams a week, not a single cam I ever ended up with had a catalog equivalent. Not one. Not just LSA, but the @ .050 and seat timing were never the same, and the intake and exhaust lobes never matched.

Il pay for a custom grind every single time. I had customers complain about the small extra cost, the extra time or whatever else they can think of, but not one ever complained after they came off the dyno and made it to the track. Or the street.

SchmidtMotorWorks wrote: ↑Sun Aug 11, 2019 3:52 pm How do you (you personally) decide when to go with a catalog cam or have a custom cam made?

How do you evaluate a cam listing that does not include important information about the design such as acceleration values and a graph of the curve?

If, for example; you were buying a hydraulic roller for an 454 BBC, what would bring you to the conclusion that the catalog cams did not provide what you need?

How does price figure into the decision for you?

are you talking a custom lobe?

If you a have details on all the lobes that's a different story....most manufacturers can do any over their lobes , except on real narrow angles ..but a custom lobe is totally different