Technical Cams that will not work well with a auto trans?

Had a 351-W built for my 55 Sunliner years ago that I specified a RV grind,well I figured out that it did not have one since it really started to come alive most likely above 2500 (no tach just guessing) and did not like the tall gears I had installed. From day one it had issues with the trans shifting into third and after four trans I decided to put a stock cam in and now it shifts like it should,I knew with in a year of driving it that the cam most likely was not what I ordered and had been planning on changing it but put it off since the engine ran good and have since got most of the parts to go back to a Y block thinking the engine was most likely built with miss matched parts. Of course no numbers stamped on the cam to tell just what it is but today is the first time I really had it out since the cam change and way better then it ever had so are there cams made that really should not be used with a automatic trans as I think I got one.

 

With a mismatched combo, you’d have the same issues with a manual transmission

 

I put a late model 302 and an AOD in my Fairlane had the E303 had roller in it with a stock converter. It bucked and chopped sitting at traffic lights and when slowing down. Too much cam for sure but I got 18mpg even with the 4:11's

 

Well, I'd bet that all too many of us would need more than one hand to count guys who we actually know and we have personally seen the cars that they put totally the wrong cam for the automatic trans and as often as not for the engine they have.
The cammed up car in the group that jumps a bit even against the brakes every time he drops it in gear and will roll along at a fast walking pace at an idle if you let it.
I always thought "RV" cam meant torque cam with a lot of low speed grunt, My buddy put a lot of them in engines he put together that came from a regrind shop here in the PNW, He would take them a load of good cores and come back with a small batch of reground cams. I never heard anyone complain about those cams and I drove a couple of rigs he put together that ran pretty decent.

 

It was supposed to be a RV grind but doubt it and was a cam the builder had in stock,the trans shifts much better and has a smoother idle plus the low end torque seems to have improved so all I know it's not what I wanted and I now have the correct firing order. Much happier now but it will be going back to a Y block in a couple years and that cam that was installed really did not like working with a automatic trans.

 

A vacuum gauge is your friend at a time like that .

Tommy

 

Cam and torque converter need to match

 

It was checked right before I changed the cam and was too low,in order to get it better the timing needed to be advanced a bunch where the vacumn advance had to be disconnected or severe timing ping. To get this engine to idle smooth the timing needed to be really advanced to where it would not start,this cam was not designed to run in the RPM range I needed it to and of course never got a cam card telling me the specs. After 15 years of trying to get it to run right and dealing with trans shifting issues I am glad that cam is gone,I did throw a rebuilt trans on the scrap pile thinking it was toast but it's now in the garage.

 

We are running a pretty healthy cam in the 427 SBC in the raven's roadster. We are of course running a pretty loose converter.

If you are running a "hot" cam you will need to run a looser converter (most of you say "stahl or stall" converter). The only time I can imagine a camshaft causing the transmission to not shift properly is if the transmission shifts are based solely on vacuum. Most transmissions, perhaps most modern transmissions for the purpose of the HAMB, use a governor as well as a vacuum modulator for this purpose. I can see that if you are running a healthy camshaft and your transmission is shifting below the power curve of the engine that this could be a problem. That can be adjusted by most transmission techs, most being the operative word here.

All that said, I do not run extreme cams on the street most of the time. If I am screwing one together that is very extreme I usually suggest a standard transmission or an automatic that is either built for go with the rest of the package or an automatic with a manual valve body.

Note when I say modern automatic I am not considering a late model computer controlled transmission.

 

Hard to believe you would just "order up" an RV cam and have ZERO idea what the duration and LSA was !
I'm certainly NOT a cam guru but I at least "know" what the specs are on an after market cam......
anywho, you could send the cam off to a grinder (like Delta Cams or Howard Cams) and ask them to read it for you AND then have them re-grind it to something you BOTH discuss for your application.
6sally6

 

There's so much more to it than just the cam. Like with any drivetrain build everything affects how a cam works, and what cam you choose. With the right rear gears for the weight of the car, the engine build, and what converter the owner chooses, an automatic can work as well or better than a manual stick trans.
Just can't say a certain cam is no good with an automatic. But you can say that long duration cams with close LSA's and low stall converters, might be an issue in a car with much weight, and tall rear gears. But in a lighter car, with lower rear gears, and the right converter the same cam can work wonderful.

 

Well said. Everything needs to balance out with everything else.

 

Next time I will build the engine myself,the guy that put it together was supposed to know what he was doing but heard horror stories after I picked it up so I got scammed on that one. The engine ran good and was dependable but just was not what I was expecting from what I was told it would be,it seems to be running good now and only took me 15 years to finally figure it out. While I was trying to figure out what was going on started to research on building a Y block to put in it.

 

At one time I read anything over 220 degrees duration at .050 would be considered a hot cam. How each cam reacts with each engine differs. A so called RV cam is in the 256 to 268 degree advertised duration. In a big engine it gives a smooth idle, maybe a little lope, maybe not. An old Isky 262 advertised duration cam in a Chevy 350 in my old C10 gave great low end, and made me feel like a king. A size larger cam, an Isky 278 advertised in a 283 in the same truck was a slug. Put the 283 into a 56 GMC with a 4 speed, and a better head, it was, comparatively speaking, a rocket. Most cams for small blocks are marketed towards the 350 cubic inch range engines(350,351,360)drop one cam size for each engine 25 cid range. (327, 340, one size, 302, 2 sizes ) size being what's offered by the manufacturer. I would define an RV cam as 204 to 214 degrees at .050, with a wide 114 LSA. Lift in the . 425 to .450 range. These ranges generally work well with stock converters. More duration, than 220 @ .050, and narrower LSA, 110 or less will lead to compatibility issues with the stock converters. The cam manufacturer is the best place to call when sizing. This generic explanation can be expanded upon by others, as it does have enough holes to drive a battleship through, but hopefully helps. As to shifting, that's a transmission issue, can't see a camshaft affecting shifting

 

I put an engine in a 57 chevy for a retired guy from my work. It was a GM crate engine (ramjet 350/350 hp) in front of a stock 4L60 with a stock converter. It was a pooch. He wanted to put a higher numerical gear in the rear because it left so poorly, couldn’t even spin the tires. I told him to put a looser converter in it and he was really against the idea. He said he didn’t want the car slipping/ reving just for a cruiser. I tried to explain that there is a wide range of converter stall speeds and to trust my advice. He listened to someone else and put a 3.70 gear in it. Still wouldn’t spin the tires. He brings it back to me sort of suggesting I did something wrong with the install. I told him Im putting a converter in it, and if it isn’t any better, I would eat the labor. He grudgingly agreed. I put in a converter that was built based on the actual engine dyno sheet. When the car was back together, it was a whole new animal. It idled nicer, dropped into gear much less harsh, and it would fry the tires. He was so happy with the car all he ever talked about after that (to other people)was the importance of a properly matched converter.

 

One believer out of so many who won't ...

 

Some guys get into a box and never leave it. If you have a builder who's mainstay is racing shit everything he builds will follow that. "...and I always put the cams in at..." and other foibles that have no business in a driver. That may be all it is. I did an OT street rod for a guy. Fkn engine had long equal length stepped headers. It's a 302 truck motor for fuck sakes. Nothing radical, but those things created 1 packaging issue after another. Has some Edelbrock EFI that's a bitch to tune as well. Who knows where else these drag race guys were going elsewhere in the drivetrain. It happens, a LOT. Sadly with no numbers anything short of a spare bullet and a degree wheel makes it all a guess. I'm thinkin you have a double roller 3 key timing chain? And also, some cams are ground to be installed advanced/retarded by design. Sometimes ya gotta at least cut a window in the box and look out now n then. May very well have been the install vs the grind. Low vac is a tell. Maybe...

 

Yes, converter stall speed and cam need to work together. For example, one friend here put together a 350 Chevy for another friend to put in his 4wd pickup, with TH350 trans. Builder asked owner if he wanted a "cam" in it, owner unknowingly replied yes. Well, let's just say a Comp 280H does not work well in this situation, to keep the idle high enough while in gear, it was turned up so high that it slammed into gear, and when at a stop vibrated the mirrors so bad they became a weekly maintenance item. We solved all of this by installing something a bit more mild, like the hottest recommended TBI spec cam. When a cam manufacturer says you need a manual trans or a looser converter, you can bet that you will.

 

Ford 302, E6 heads, E303 Cam, Edelbrock intake and 600 CFM carb, FMX with stock converter, 2.73 gears in 2 ton OT car.
Assembled from parts-on-hand, definitely underwhelming. Brake vacuum not so good.
Wind it out, it comes to life...

 

I had a buddy get a double lung transplant. In the hospital for a month and a half, gets released home and dies sometime during the evening of the second night. True story.

Now, I'm going to spin this into a reply, just wait and see.
Knowing this cam talk and converter talk, well it's a thing. Throw in a bad lifter and shit gets right complicated.

This double lung thing...kind of like the cam, has a bit of unknown. And just like the lungs, I'm guessing with mine anyways, they have a range of function that work best, and under certain loads.

While I'm still trying to understand it all better, and some might be blaming the wife, it is easier to change the cam then the conditions to support it. Advance / retard timing, adding a blower/single carb. Tires super tall and narrow over short and fat. That kind of thing.

Moral of the story... a cam made for sitting on the couch won't be a good choice for racing.



And breathing is important.

 

What ever this cam was did not seem to be too radical but if the conditions were right I could detect a slight lopey idle and really did not seem like it needed a looser convertor. When discussing the build the builder was told it was going to have a tall gear and mainly used for highway driving but did not get what I was expecting,stated out with 2.75 gears and noticed it done better with the 3.00 gears I later installed but could have used more. Should have just requested a stock cam and everything would have been fine for how I was going to drive it.

 

Once again, @theHIGHLANDER makes a very valid point. And as quality control issues seem to pop up more frequently in recent years it begins to make more sense to degree any new aftermarket camshaft during installation.

https://www.enginebuildermag.com/2016/04/valve-timing-events-and-the-order-of-importance/

https://www.motortrend.com/features/intake-valve-closing-point-critical-maximizing-performance/

From what I've come to understand over the years, intake valve closing is the most critical cam timing event. In general, closing the intake earlier will improve lower RPM performance with a slight trade-off of power at higher RPMs. I would think that an "RV" cam would be ground with this in mind. But variously acceptable tolerances in the manufacturing of cams, crankshafts, timing gear sets and chains can add up to a cam being installed "straight out of the box" with actual opening and closing events that can be a few (or more) degrees advanced or retarded from the ideal.

Some years ago a friend had a stock 454 in a C30 crew cab. It ran "OK" with a slight, occasional, off-idle stumble. But the owner decided it had enough miles on it to need a new timing chain and gears. They in fact did have enough slop in them that the cam timing was probably running 2 to 4 degrees retarded. With the new timing set installed the off-idle stumble disappeared and manifold vacuum at idle picked up about 1/2 to 1 inch. At the time I was surprised that a new timing gear and chain set could make that much of an improvement. After a while I began to understand why that was.

 

My thoughts a stock trans in a 300 inch motor don't go past 215 deg. at .050 lift cam.

 

I wish the cam I removed had some numbers so it could be identified but it's going to be a mystery and will be thrown in the scrap pile.

 

May be something decent. Some can tell you how to figure it’s specs with v blocks and a dial indicator.
But good thing is you’re satisfied with how the car runs now.

 

Cheater lobe lift check. Measure the base circle with a dial caliper. Set the dial at zero and measure the overall lobe. Multiply by rocker ratio. Hope that makes sense.

 

Helped a buddy out about a decade ago. He had an original mid 60's Ford product that we don't speak of here. The 289 had never been touched, had just over 100k on it, 4 speed 3.00 gear. He took it over to a local machinist for a cleanup and hone. I did the reassembly with new rings, seals and gaskets. Machine shop provided a new "performance" cam.

The thing was a slug. Fiddled with it over and over, was down on power no matter what. Finally pulled that "performance" regrind out, installed a Comp 256. Car ran so much better in all ranges, and picked up quite a bit of mileage too.

Devin

 

It does have a 302 firing order and my 65 Custom 500 has a 302 and manual trans but need to find out exactly what it is if I put it in another engine.

 

Did you piddle with it for over 10 years like I did,it ran ok and went to Florida six times thae way it was but was fighting third gear shifts in the C-4 the whole time and drove me crazy.

 

JYJeff.....before you "throw-it-in-the-scrap-pile"....... send it out to a cam grinder (there's a bunch of 'em) and get them to read it for you. I doubt it would cost much and most would probably waive the fee IF you let them re-grind it to something better suite for your combo....
6sally6