When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hi folks, as you can see, I don't post much on this forum. Reason? So much knowledge here, that I do searches for my questions, and 98% of the times they've been answered. This is an awesome place. This time however, the more searches and reading I do, the more indecisive I get. So many opinions and variables. Hence, my head is about to explode. I want to do a heads and cam combo some time during the first quarter of 2019. I want a strong street performance with emphasis on torque. Not looking to rev beyond 5,000-5,500 rpms. The car is a weekend toy to enjoy driving and cruising to car shows, with the occasional stomping a bit on the gas for the feel good factor. Reliability and longevity is a concern. Smooth or choppy idle doesn't matter as long as it has good vacuum for the brakes, a/c, etc. The car runs great now, but has no *****. All show and no go. This baby needs to drive like a Corvette should. Here's the car info currently:
1973 L-48 block(dished pistons?) with World Products S/R (stock type) heads with Comp Cams 1.52 roller tip rockers. The engine appears to have been rebuilt with a mild cam of sorts, at some point prior to me.
Edelbrock 2101 manifold, Holley 4175 Spreadbore carb, stock air cleaner, stock distributor with electronic conversion kit.
McJacks 1.5/8" shorty headers, 2.5" dual exhaust pipes, with Hooker Aero Chamber mufflers (essentially straight through).
Stock Muncie wide ratio 4 spd, 3.36 rearend.
Power steering, power brakes, air conditioning. I think I covered everything.
A compression check on the engine reveals: all cylinders at 150, except for three at 145. The engine is tight with no leaks.
I've narrowed down the heads to Pro-Filer 185cc with 64cc chambers assembled with springs for flat tappet cams (1.250 springs, 100lbs seated, 320lbs opened, .550 lift). My dilemma is the cam selection. I filled out the forms for cam recommendation from Lunati and Howards weeks ago, but haven't heard from them. I checked with Comp Cams and was recommended the XE274h, but I think that's not right for this engine. I had narrowed it down to Lunati 262 cam, but reading about the aggressive "modern" type of cams wiping out lobes (intake duration at .50 to valve lift safe level of over 47.5%), I spiraled into an abyss of cam selection. Then I was looking at Howards CL112571-12 with a less aggressive design, looks good but not sure. Every cam that I think would work good with my combo, doesn't meet the over 47.5% rule! Roller cams are a bit out of my budget.
Oh, almost forgot to ask, would the springs on the Pro-Filer would suffice, or should they be changed to the recommended ones from the particular cam manufacturer?
I'm seeking advise from the knowledgeable gurus here, and from those with experience with similar combo to what I'm trying to do, that have put millage on and haven't had any cam failures. Any advised would be appreciated. Merry Christmas
You didn't mention the cc of the existing S/R heads but if you're not going to rev over 5000 then keep the heads you have and invest in a good roller cam.
Last edited by Dynra Rockets; 12-21-2018 at 02:32 PM.
The overall compression is low........I suspect a dished piston.........but even so, The Pro Filer should wake it up over the S/R Torquer..........
I am stuck on the old Comp Magnum grinds because they break in nice and make great sounds........a 270AH Magnum 12-211-2 would be a good choice here......
Howards has some split patterns in this duration and lift range.........team either with 1.6 rockers for around .500 lift........ .500 is about where most non CNC aftermarket heads start to nose over on the flow bench....so take advantage of that.
Those springs would be fine......but I like Isky's "Z/28" spring they have had for a million years.....
The old Magnum grinds make comparable power to any newer fast ramp design......it would be impossible to tell apples to apples.......
I have a 292H Magnum ground on a 108 LSA in my 406 and I love it........if I want to split hairs for power I will jump to a roller.
I recently built a 355" for a 70' Nova SS.... It was 9.5-1 compression, 1.94 valve Double humps, I used an XE268 Comp cam, RPM Air gap intake, 650DP and 1 5/8" full length headers. I didn't dyno it, but the car runs its *** off, makes good power to about 5500, starts slowly nosing over at 5700 ish... I used a Hughes GM25 converter and it has 3.55 gears. If it didn't run mid 13s I'd be surprised. It only has 215/70/15 BFGs and from a 30 roll in 1st it destroys them.
All in all, I think the XE268 is a good cam for a <400 hp build, makes 13 hg of vacuum and idles nice. Just follow all of the precautions on the break in, I used the comp break in oil and an additive, then changed the oil right after the break in. So far, so good.
I recently built a 355" for a 70' Nova SS.... It was 9.5-1 compression, 1.94 valve Double humps, I used an XE268 Comp cam, RPM Air gap intake, 650DP and 1 5/8" full length headers. I didn't dyno it, but the car runs its *** off, makes good power to about 5500, starts slowly nosing over at 5700 ish... I used a Hughes GM25 converter and it has 3.55 gears. If it didn't run mid 13s I'd be surprised. It only has 215/70/15 BFGs and from a 30 roll in 1st it destroys them.
All in all, I think the XE268 is a good cam for a <400 hp build, makes 13 hg of vacuum and idles nice. Just follow all of the precautions on the break in, I used the comp break in oil and an additive, then changed the oil right after the break in. So far, so good.
13 hg of vacuum is plenty for power brakes and a/c car? I have 3.36 gears with 4spd tranny, you think that cam will work ok, good torque? This will be using the Pro-Filer heads.
73Ray;
I feel your pain. So many choices now days.Similar decisions as to what I am going thru now.
I'd recommend keep it simple. Your original heads are good if they are the 64cc ones, but iron. You originally had 8.5 CR and should now have about 9.5 that's great. If that's ok, just keep 'em. The Pro-filer heads might give you a little more HP but not much, for there $600 cost, but they are aluminum and lighter.
If yours need rebuilt anyway then why not.Your unknown "performance cam" is probably larger than you require, and kills compression.
I'd suggest a stone stock 300HP cam, but the Nostalgia Plus from Comp cams. It's a little better than the original, and has nice mild lobe ramps for long life.
Alternatively you could run the larger L-79 cam, but it would only help over 4000 rpm, and I don't know if you would even notice below that. Your 9.5 CR should result pretty close to the original 300 or 350 hp power output, but they are basically the same below 4000, but you will definately feel it at 5500.
I would strongly suggest two items to make the hydraulic cam live: (No need to go to the $800+ expense of a roller.)
1- Brad Penn oil, or other high zinc, or a zinc supplement. Modern oils do not have this and the cam will die without it.
2- EDM lifters with an extra oiling orifice.
Enjoy it!
The 300 HP motor is real strong to 5200 and you have mild gears so it would be a great match. The L-79 definately has a little more to it.
All the xtreme enrgy and magnum cams have faster ramps, and only make more power beyond the rpm range you are interested in.
I just saw you have the 76cc heads, so a switch to the 64cc ones would really help the compression and wake it up.
13 hg of vacuum is plenty for power brakes and a/c car? I have 3.36 gears with 4spd tranny, you think that cam will work ok, good torque? This will be using the Pro-Filer heads.
i certainly wouldn’t go any smaller then that, especially with a 185cc head. That baby is gonna want to rev with those heads. Ours is very torquey but with the stall converter, it makes it that way.
In my 71’ 350/270, it was stock compression, stock 882 heads and had a Crane L79 cam (222*/.447”). It had. The Performer 2101, Q jet, 1 5/8” headers. With the stock T400 converter and 3.08 gears, the car was a total dog. It made 200 rwhp and ran 15.0s@91 mph. That lesson for me was, if you are gonna mod it, then MOD it...otherwise leave the stuff stock.— My point is, use the 185 heads, 64cc to bump compression, put a decent cam in it, headers and exhaust and actually gain something worthwhile.
It definitely has some potential with a good top end on it. Use the RPM intake at a minimum.
Your cranking compression tells you your compression ratio is pitifull. Good choice in going to the185 profiler. For long term use would stay away from the really fast ramp cams like comps xe or luntai voodo. With your 5500 rpm goal you are right a 274 xe comp to much duration.
Here is the XE268 in the 355 Nova I built....just if youre curious how it sounds.
Another cam I've used is kind of an older design, its a Crane Z274. Its 224*/230* and like .465/480" on a 110 LSA... I used this in a 66' L79 327 with lowered compression, ported 462 double humps. Its a 4 spd car with 3.70 gears...However it has stock intake, stock manifolds and side pipes etc.... The 355 in the Nova feels noticeably faster then then one. I'm sure the side pipes kill this one tho….
Leigh1322, excellent advise. Thank you. Things are starting to make more sense. And yes, the heads that are on the car now are S/R, which stands for stock replacement. Identical to stock heads. Probably installed because of warped or cracked original heads. Just guessing.
Your cranking compression tells you your compression ratio is pitifull. Good choice in going to the185 profiler. For long term use would stay away from the really fast ramp cams like comps xe or luntai voodo. With your 5500 rpm goal you are right a 274 xe comp to much duration.
ok good, that’s what I thought about that cam. Thought I’d stay on the mild side for this engine.
Here is the XE268 in the 355 Nova I built....just if youre curious how it sounds.
Another cam I've used is kind of an older design, its a Crane Z274. Its 224*/230* and like .465/480" on a 110 LSA... I used this in a 66' L79 327 with lowered compression, ported 462 double humps. Its a 4 spd car with 3.70 gears...However it has stock intake, stock manifolds and side pipes etc.... The 355 in the Nova feels noticeably faster then then one. I'm sure the side pipes kill this one tho….
Man, that Nova sounds great! All muscle car looks and sound! I’m going to make a list of these cams suggested and do some research on them. This certainly helps a great deal from exploding head syndrome.
Your car with 8.5 CR will be soggy, and the mentioned 71 even with a better cam had the same and was also soft, especially with 3:08 or 3:36 gears.
The 300HP cam with 9.5CR will be a torque monster, and have a dead smooth idle. I had that exact engine, trans & gear setup in my 68 SS350 Camaro and it ran fabulous. 100% stock.
The L-79 cam is a decent bump up mostly upstairs, it also has a little bit more noticeable idle, but good vacuum.
The XE268 cam I also love. It may only give you another 10HP with stock manifolds. The rpm peak starts to move upstairs some more. And the much tighter lobe center makes it sound pretty good&nasty, but it does retain power brakes etc. Ran it, loved it. . However the almost 6000 rpm peak of it may be starting to move outside of the rev range you mentioned. And it would really like some more gear, headers, etc. Then it would really come alive, like the 70 Nova mentioned. In my Z28 it ran mid 13s with 3:55s, and headers, etc. Any more cam than that and you would really require more compression, gears, headers, etc.
It all depends how much you want to spend....AJ and I both love HP, but I am tempering my recommendations a lil more because you said cruiser and <5500.
Note that I don't necessarily believe the power ratings this software puts out, but it is excellent for making cam comparisons like you are doing here.
ok good, that’s what I thought about that cam. Thought I’d stay on the mild side for this engine.
edm hole are put in solid flat tappets not anything like that for a hydraulic that i know of. A factory l 48 cam and the oringal 300 hp cam were both the same cam. They used a 195 at 0.50 intake dur. And very poor lift .390 int. .410 ex. They pulled from just off idle to 4500 rpm. I know you no longer have that cam just using that for reference. I bought a 72 vette l 48 back in 1973 was my first vette. I also had an l 82 its cam int. Duration was around 224 at .050. IMO i would do a cam in the 210 to no more then 215 for the rpm range your wanting. Would do a mild split of about 4 to 6 degrees more exhaust duration then the. Int. The pro filer heads will be far better at all rpms for you not just higher rpms. But yes if you did want to increase your rpm range they certainly will keep flowing air for you up higher.
Your car with 8.5 CR will be soggy, and the mentioned 71 even with a better cam had the same and was also soft, especially with 3:08 or 3:36 gears.
The 300HP cam with 9.5CR will be a torque monster, and have a dead smooth idle. I had that exact engine, trans & gear setup in my 68 SS350 Camaro and it ran fabulous. 100% stock.
The L-79 cam is a decent bump up mostly upstairs, it also has a little bit more noticeable idle, but good vacuum.
The XE268 cam I also love. It may only give you another 10HP with stock manifolds. The rpm peak starts to move upstairs some more. And the much tighter lobe center makes it sound pretty good&nasty, but it does retain power brakes etc. Ran it, loved it. . However the almost 6000 rpm peak of it may be starting to move outside of the rev range you mentioned. And it would really like some more gear, headers, etc. Then it would really come alive, like the 70 Nova mentioned. In my Z28 it ran mid 13s with 3:55s, and headers, etc. Any more cam than that and you would really require more compression, gears, headers, etc.
It all depends how much you want to spend....AJ and I both love HP, but I am tempering my recommendations a lil more because you said cruiser and <5500.
Note that I don't necessarily believe the power ratings this software puts out, but it is excellent for making cam comparisons like you are doing here.
Yes, trying to keep it around that 5,500 rpm area because of stock lower L-48 block, and street driving. Don’t get me wrong, I like horsepower, but I think this lower block shouldn’t be pushed too much over the edge. And in my age, I’m slowing down a bit.
edm hole are put in solid flat tappets not anything like that for a hydraulic that i know of. A factory l 48 cam and the oringal 300 hp cam were both the same cam. They used a 195 at 0.50 intake dur. And very poor lift .390 int. .410 ex. They pulled from just off idle to 4500 rpm. I know you no longer have that cam just using that for reference. I bought a 72 vette l 48 back in 1973 was my first vette. I also had an l 82 its cam int. Duration was around 224 at .050. IMO i would do a cam in the 210 to no more then 215 for the rpm range your wanting. Would do a mild split of about 4 to 6 degrees more exhaust duration then the. Int. The pro filer heads will be far better at all rpms for you not just higher rpms. But yes if you did want to increase your rpm range they certainly will keep flowing air for you up higher.
So this Howard’s cam cl112571-12, with 215 int. 225 exh. Duration and .455 int / .465 exh lift and 112 Lsa . Rpm range 1,200-5,500. That’s within ballpark of what you’re saying? Or still too much?
12-21-2018, 01:55 PM
Head about to Explode!
