Cam Selection

[art38]

I know another stupid question on cam selection. Well here it goes. 65' block, .030 over, 333 reworked heads with large valves, Ross 10:1 pistons, dual quads, 700r4 trany, 3:23 gears. I had the Isky 296 Hyd flat tappet and started to wear a lobe, so I'm considering a solid roller. I don't race this thing it's in my 38 Chevy coupe, but I'm concerned about durability of flat tappet cams because of the oils. I want durability, reliability and somewhat low maintance. What I have been told is the solid roller is not like solid flat tappet which require a lot of adjustment, does not require the typical cam breakin and is modern oil friendly. I'd like to hear all the pro's and con's. I'm open to suggestions.
Thanks,
Art38

 

[mpris]

Just my opinion, but if this were something I planned on driving on the street and putting any significant miles on, I would go with a hydraulic roller. I don't believe you will get the reliability and durability you want out of a solid roller and you can still get pretty good performance from the hydraulic roller. It seems that recently there have been more problems with solid rollers than in the past. Maybe its because there are just more of them now, but I am using a hydraulic roller from Crane. I am sure there will be different opinions forth coming.

Poocho

 

[buildit]

solid roller

The first question to be asked is, how much room for valve lift do you have? My older Isky catalogue lists the 296 Hyd equivalent for BBC at only .510 lift, with a wide 114 lobe seperation angle. Even the mildest solid roller will have much more lift, sooner.
Looking at your combo of OD trans and 3.23 axle ratio, something like Comp's Street Roller series #4871/#4872 lobes, .612/.626 lift, 224/230 @ .050 lift for intake and exhaust, on a 110 degree lobe seperation angle, would be one choice. . Ross piston's standard valve pocket depth SHOULD handle this lift/LSA, but clearance would still need to be checked. I would also use Comp's roller lifters with the EDM'd oiling holes for the roller bearings. And full roller rockers are required. Screw-in studs. Custom length, heavy duty 5/16 pushrods. Pushrod clearance in heads has to be checked. Mild roller springs required. Something like 150/450 lbs. You may have to shorten valve guides to get enough operating clearance.
A hydraulic roller would be nice for your application, but cost even more.

 

[art38]

Mpris,
So what Crane combo did you use? I spoke with Crane last week and they were pricy. Tell me more about what you used.

Art

 

[bubbletop1961]

In my sbc Ive been driving for almost 3 years with a sollid roller. .575 lift. Its beeen great. Didnt wear out springs like I thought it would. And didnt need to many adjustments. The hydraulic would be a great choice also just with a little added cost. I would also recomend screw in rocker studs. I did break one of those last year. Thank you rev kit for holding it all together. ARP has 2 grades of studs. For not much more you can get the better ones. And considering Ive never seen a stud girddle for these engines it would be a wise choice to get the best stud you can.

 

[art38]

Your thoughts

I'm thinking of the Comp Thumpr Cam # 11-600-8. It a roller cam. It's 227/241@.050,.547/.530. CompCam said I could go with Hyd or solid lifter and valve spring would be around 130-150. Any comments, good , bad, anything.

Thanks,
Art38

 

[Ronnie Russell]

good

 

[1958 impala]

Cam

Art'
I think the comp cam would be a good choice and stick with Hyd lifters soo much easier just my two cents worth.

 

[art38]

Spec's

Here's the spec's on the cam that I'm thinking of from Comp Cams (it's a Thumpr Series cam).

Grind # 283thr7, ADV 283/303, 227/241@.050, .547/.530 (IN/EX), 107 deg Lobe Sep. I already had someone tell me that I will not like the 107 deg. I'm also planned on solid lifters, is this a mistake too. I thought a little lopey idle might be cool in the rod. My thoughts are I don't put more than a 1000 miles a year on this car so having to adjust the valves isn't that big a deal and the solids cost less, but maybe the hyd is worth it. I think I should be alright with lift using the Ross pistons. All comment are welcome.

Art38

 

[bubbletop1961]

I believe the thumper series is new. Its supposed to have a bad a@@ Idle sound. In return for a loss is the overall power number. It is a minimal loss for the gain of a sweet idle. Probably why it has a 107lsa. Sounds like a great idea if you ask me. If your not out racing everyweekend and do alot of cruising it sounds good. As far as sollids go. They also offer great sounds and performance. And I dont mind getting in there every once and a while to udjust the valves. Youll find it more for you comfort than anything. Their usually pretty close. The sbc cam I have now has a 114 lsa. I think it sounds like a tractor

 

[art38]

bubbletop1961,
So you think I should be alright with this? I don't want it to sound like your tractor (you know what mean), but I was thinking it may not be to bad, maybe the cam is ok, but I might be pushing it with lifter. I just don't want to mess this up. This my second time build this thing, the first time the cam went flat.

Art38

 

[jim_ss409]

I think that cam should be pretty good. It's not a very big cam and it's got a tight lobe angle so it it should have lots of low end and mid range torque. The tight lobe angles and extra exhaust duration will certainly make it sound like a bigger cam at an idle, but it should smooth out by the time you get up to about 1,500rpm. I think a cam like that will make the engine really snappy. I think it will work pretty well in a light car like you have. If you want a smoother idle you could look for a cam with a wider lobe separation angle, like about 110 or 112 and a little less exhaust duration.
I noticed that it has a lot of advertised duration compared to the duration @.050 and it doesn't have a lot of lift so it's not what you would call an aggressive cam. You should get years of trouble free driving with ether solid of hydraulic lifters.
I'm pretty sure you won't have any piston to valve clearance problems but it's easy to double check that when you install the cam, just to be sure.

 

[art38]

Thanks for the input Jim. So no one thinks it will be too rough, it is a hotrod, but it needs to be streetable. I don't race this at all. I don't want something crazy, but like it to be sound cool. It does get alot of attention just because of the engine itself, not too many W motor in rods, but theyare starting to pop up more. I planning on ordering this today. Like to get as many comments as I can, good , bad, whatever.

Art

 

[bubbletop1961]

Not a lot of replies for you. I was hoping to hear some other opinions also. I like the cam. It sounds great. Is it more agressive than most guys with cars that never see the track, Yes. But Ive been doing the same for the last 3 years in a sbc. I dont take the car out of town, but it gets alot of street driving, Sat night cruise ins, Sat night late cruising. Driving it to work. couple trips to the track a year. I drive the hell out of it. Only problem Ive had is a rocker stud that broke and took a couple parts with it. (the reason for recommending GOOD rocker studs.) Ill throw up my cam specs just for comparrison reasons. The thumper series was designed for cars just like what your doing.
comp sollid roller 12-704-8
adv dur. int.300, exh. 309
dur @.050 int. 255 exh. 262
lift, .575 / .575
lsa 114

 

[jim_ss409]

The only thing I don't understand about the Thumper cam is the large advertised duration. I guess it's part of the rough idle plan. I think it should be okay, but if you wanted to get similar performance with a smoother idle something like Comp's XR282HR would also work. It has 230-236 @.050 Or you could go a step smaller to the XR276HR it has 224-230@ .050 Both of those cams have 110 degree lobe centers so they would have a somewhat aggressive idle. I see that the Isky 296 Hydraulic listed in Isky's catalog has really wide 114 degree lobe centers and 234-234 @ .050, The Thumper cam's duration at .050 is similar to what you had so it's not really too big, but it'll have a much choppier idle.
By the way, I notice that you don't put a ton of miles on your car but I thought I'd mention that cams with tight lobe centers tend to reduce your fuel economy.

 

[tripowerguy]

I was at a cruise in when a Camaro came in. The engine sounded absolutely ferocious. It set off an alarm on a Mercedes parked there. Everyone wanted to see what this engine was, A small block with a single 4 barrel. So if you want a cam that sounds really bad go with the Thumper, just know if you are running an automatic that it is going to jump around at idle. You are going to have to keep the brake applied hard to stop creep. If you use poly locks on the rockers, that is the ones that have a set screw to hold the setting, you won't have to make many adjustments. On my 58 I check the adjustment before any race and at the first of the year. I have never in 3 years had to adjust a valve. The stock nuts on the valves are worthless. If you are only putting 1000 miles on the car a year then go with either one although the hyd. lifter may be a little easier on the lifter because the lifter is always in contact with the cam, no clearance issues like with a solid lifter. The solid would be my choice if I was racing it but for a street driven engine I would go with the Hyd. There I should sit down now, I've expressed my opinion enough. Roy

 

[bubbletop1961]

The only thing I don't understand about the Thumper cam is the large advertised duration. I guess it's part of the rough idle plan. I think it should be okay, but if you wanted to get similar performance with a smoother idle something like Comp's XR282HR would also work. It has 230-236 @.050 Or you could go a step smaller to the XR276HR it has 224-230@ .050 Both of those cams have 110 degree lobe centers so they would have a somewhat aggressive idle. I see that the Isky 296 Hydraulic listed in Isky's catalog has really wide 114 degree lobe centers and 234-234 @ .050, The Thumper cam's duration at .050 is similar to what you had so it's not really too big, but it'll have a much choppier idle.
By the way, I notice that you don't put a ton of miles on your car but I thought I'd mention that cams with tight lobe centers tend to reduce your fuel economy.

Jim. I think your right on. There would some smoother cams that perform just as well. Havent heard one of these thumpers yet to hear what they really sound like. It will be intresting to hear if all the hype on them is really worth it.

 

[Ronnie Russell]

For what it is worth. Just tried to order cam from Comp Cams...... Was told, " no cores available." Next week before information is available as to when it might be. Crap !!!!! More delays........

 

[art38]

Ronnie,
Your right on the cam cores. I got the last one, that's kind-a why I was in a hurry to place the order.

All,
The Thumpr Cams is design to give you that lopey idle, but still provide streetability. I got the mildest verision of it, again they indicate it's not a race cam. I just hope it's not too choppy. This one also work with a stock converter so I would think it's not going to creep too much. I will be running roller rockers with the poly locks and the screw in studs, 130-140 springs. I think they said the lash should .006, so kind-a tight lash. They also stated if I don't like the solid roller lifters I could always change to Hyd rollers, it is a Hyd deisgn. As for gas mileage, come on does any of us consider this? In 2.5 years I've had this built, I have maybe at most 2500 miles. I trailer it to anything more than 60- 70 miles away from home, not that it a trailer queen, I just don't trust others around me (I already re-paint my front fenders 3 time). I which I had all this responds earlier, but enjoyed it anyhow. I will certinly post the out come later this month or early Nov. if the everyone is interested.

Thanks again guys, this site great. Maybe one year I'll make to your show.

Art

 

[jim_ss409]

I'd love to hear how the cam works. Be sure to let us know.
The solid lifters will actually reduce the duration a few degrees so I think you'll find it similar to your old cam, except that it'll have a rougher idle and it should make more overall power, especially in the 3,000 to 5,000rpm range.
Here's a link that has the sounds of a Thumper cam... http://www.compcams.com/thumpr/
Sounds good if you ask me.bang