Good morning everyone. This post is as much for a friend as it is myself but I will try to keep it brief. Basically we're both looking to do pretty healthy street oriented but strip ready small blocks. He'll probably end up doing a 406 or something similar as he has a line on a good SHP block. I've been accumulating parts for a build as I find them for steals or deals... Basically I am going to end up with a healthy 388 (3.8 stroke .030 over). I have next to nothing in the rotating assembly and block and I have the heads on my current engine.

Now aside from the displacement difference between the two engines, they'll both be 6.0 rod engines, both around 10.8:1 compression, aluminum headed (same heads on both) same valvetrain etc. But he doesn't want to run it out as much. I'm shooting for mid to upper 6000 RPM range for shifting, he wants to keep it around 6000.

We both are figuring roller cams although I'm leaning more toward a solid roller than a hydraulic although my block is a factory roller and it would be cheaper to do hydraulic. We both want to run the same cam. If we do solid, we're thinking like 238-242/244-248 on a 108-110 LSA with a .540-.580 lift. So basically a mild street roller, nothing crazy.

For a hydraulic we'd probably end around the same range on either a 108 or a 110 though I'd probably go closer to 236/242 in that case.

Now we're both still pretty far off from building these engines but I was just curious, If I do a tight lash lower lift street solid roller, Do I really have to worry about puking pin oiler lifters and always adjusting lash? We're both going to drive them a lot and it seems the benefits a solid offers are tangible but if they really aren't going to take all that well to predominantly street driving I'll go with a hydraulic.

If I use a good pressure oiled lifter like a morel/howards or isky or BAM or similar, do I really have to worry about it? I like taking trips in the car and so does my friend in his. Would the hydraulic if sprung correctly be adequate? I just don't want to build it and wish I had a little more, but I also don't want to end up replacing solid lifters every few years... I know what to expect going either way, I have maintained both in the past but, has tech gotten better in both areas that there isn't as much a gap? Just looking to get opinions and experience before we start moving forward.

Thanks in advance,

-Paul

 

There are a lot of (relatively) higher HP and higher RPM engines using hydraulic lifters. If the application is going to be mostly street-driven, the hydraulic begins to make more sense. Cram the largest valves you can find into the chambers without shrouding at the perimeter.

 

I see 6500-6700 RPM and hydraulic rollers as a non issue with the typical street/strip stuff. With the right valve train, that RPM is easily achieved. We've gone to 7000 with hydraulic rollers as well. What you'll have to keep in mind though is the intensity of the profile you go with and a valve train that's up to the task.

I'm in the cam development phase of a 357 project myself. All very preliminary although it's be a hydraulic roller for sure. I've had success in the RPM department with COMPs 26918 BeeHive spring along with the associated lightweight tool steel retainer so it'll be that again. PAC also has their 1219 conical spring that specs the same as the COMP. The smallish spring and light parts keeps things under control as the revs build.
Now, as an example of one spec I have is said to make peak HP at 6400 is 290/290 on a 108 LSA. (6400 peak with another 200-300 for overspeed). Now the question is, which lobe do I go with? If I check the profiles offerings from Jones Cams, I've a choice between 290° on the seat and 240° @ .050" or 290° on the seat and 230° @ .050" lift. One is a .360" lobe and the other a .330". There'll be a line somewhere that says one will outlast the other in terms of durability but will offer less area under the power curve for less engine output. So that's one thing to take into consideration.

As for anything, you have to be sure of the manufacturer. Finding all made in the USA parts isn't as easy as it seems. Johnson and Morel are two that come to mind as US made rollers. Same with the cam cores. Although COMP is grinding cams in the states, I can't say where the raw material comes from. Jones Cams offers 100% US stuff.

Now, FWIW, the right cam for the 383 will not be the right cam for the 406. You could spec a compromise that would cover both but optimally speaking, they're two different engines and would require two different cams.
As I'm sure you're aware, the cam will be a product of the CID, CR, RPM expected, induction, headers, etc. plus the application and the vehicle the engine will land in.

 

I was considering a 383 at one point and have considerable data collected on the cam spec. It was RPM limited as the heads were on the small side (see above) but HP was estimated to be pushing 500 with similar torque.
If you're interested I can lay some of that out here.

 

With good heads you will not need as much cam. My ~500 hp 383 peaks at 5,600 rpm with a 218 @ 0.050 intake lobe.

My 383 is very similar to this one in overall specs. Almost identical power curve as well. Same man ported the heads on both. My heads intake ports outflow the ported LT1 castings by 15-20 cfm. Slightly smaller cam on a tighter LSA but a 1.7 rocker on mine.

 

Yeah as said above with good heads cam can be relatively small to make good power. But for reference a 230 deg at .050 hyd roller will go mid high 6000’s rpm for shift with a short runner intake and a head like a 195 cc AFR

if you do the valvetrain right and with mild roller lobes, a solid can live for a long time. It seems excessive spring pressure really wear them out and ofcourse lack of oiling on the rollers. The pressure fed ones seem to solve alot of that. I run solid in my big block and its been good so far. You do need to check lash every now and then. I only run shaft rockers and Sometimes the adjusters come loose, almost like you need to slighty overtorque them but that creates stress on the rocker arm.

but you really dont need a solid on something like that. A hyd can do it, it will have enough duration and lift. A 406 can typically use 5-10 deg more duration than a 383 even though they have the same stroke.

 

Thanks for the input guys. As far as the heads, they're profilers and before they go on the mill I will have them sent out and worked over. Nothing crazy but some port work to them would help a bunch.

I hear what you all are saying on the cam and the 406/383 wanting different cams. I was figuring since he did not want to run it out quite as much that specing the same cam on both would probably put them both in the range we're looking for but it is probably best to just get exactly what is needed for each.

Both cars are stick though his is a bit heavier than mine with a taller tire, the overall gearing is comparable so the weight is the biggest difference.

As far as the hydraulic vs solid, i get what you all are saying and because of that, thr next statement will sound childish but... I really like the sound lol. That being said it really sounds like I wouldn't be gaining much other than sound at my current target for the build... so it would be the smarter option to go with a hydraulic.

Now one other question, since it is a factory roller block, would the stock dogbone setup be capable of handling those rpms safely or would I be better using a tall link bar roller?

I appreciate the input.

 

Dogbones are fine just dont go too small on base circle with a ton of lift. You really wont need much lift. Mid high 500’s with a 1.6 is good. If you can find some gm ls7 type lifters or johnson equivalent that will work good.

else a link bar style. Cost a bit more for the good stuff typically

406 and 383 having same stroke can use similar cams, the 406 will just peak a couple hundred rpm less than the 383

 

Are these both street engines?
Or are they single in purpose like drag racing only?
The reason I ask is if they're race only, or nearly so, then there'll certainly be a difference in the cam spec.
For street or street/strip or track, then not so much.
Besides the RPM peak points, there'll be a difference in the dyno curve as the LSA's aren't necessarily suited one to the other. Street driving tends to absorb that. Some even prefer it.
I can offer one bit of advice with regards to the OEM rollers.
While I've heard good things about the LS7 version, I can say for a fact that the more pedestrian variety found in the Gen 1 aren't very happy at higher RPMs. The leak down is unacceptable and there's component seperation when you spin it up. It's been reported that this is due to the lifter body becoming distorted and allowing the hydraulics to collapse.
We experienced this in one of our 355's that was a 6500-7000 RPM drag racer. At the end of a pass the engine sounded like 16 little sewing machines for one or two minutes. Swapping out to COMP's tool steel lifters solved that problem.

 

The bigger the engine proportionally to the intake valve and port size, the tighter you want the LSA. Bigger engine will want more overlap then a smaller one. Where a 383 does well with a 106 or 108 LSA a 406 will want a 102-104 LSA. If you were to run say a 110 LSA in a 400 with a 2.02 valve you are shooting yourself in the foot when it comes to torque production. 400s 4.125 bore will really work well with a 2.08 or 2.10 intake valve.

 

Ideally you want the valve to be 50-52% of bore diameter. Build the port around that. 2.050 for a 383 works well. 2.08-2.100 works nice for 400” deals.

 

I was looking at morel like a 7717 or similar, the equivalent to an LS7 but hopefully a little better... As far as lift, I was planning on keeping it under .580 at the valve on mine. I have a nice set of 1.52 full rollers that I plan on using, so if I sacrifice a little lift so be it.
10-4 on the OE lower level lifters. The cars are going to be mostly street, he'll probably do more strip than myself though. But I don't plan on going cheap on stuff that can ruin the build, not worth saving a few bucks in a critical area. If good lifters in the factory retention system work well I'm fine with that.
I was planning on running a 110 LSA in the 388, and if he happened to use the same so be it. I've been reading and doing some math and it seems for what I want a 106 with like 236/242 degrees of duration would probably be ideal for what I am looking for... I believe he was planning 2.08 intake. I'm probably sticking with a 2.02 because it would seem it isn't worth the extra hassle on a 4.030 bore for what I want out of it.

 

If you goal is 6,800 rpm that can be done with 226-232 @ 0.050 intake duration with good heads.

 

Tighter lsa may bring peak rpm down some for a given duration. Also, tends to make for a peakier torque curve. Wider lsa can sometimes flatten the curve abit below peak and after peak, making more average across the rpm range. But not always. Usually some extra exhaust duration will help extend rpm range in the hp curve beyond peak. I ran a 230/245 on a 109 in my 383. Peak hp rpm was 6200 but it would take a 6800+ shift. Curve extended flat to 6500-6600 before starting to drop off. I also ran some nitrous so the duration was good for it. But good heads can also make nice power with lesser duration split with a moderate lsa. Better the head in both flow, and port area for the combo the wider the lsa you can get away with. For a street car that sees some track time, i wouldnt go under 110 imo if duration is around 230 on intake. Especially with a stick shift. 108-110 is as tight as you really need. If you gear car right anyway, you’ll be in the upper rpms where wider lsa benefits you anyway.

 

I know this combo VERY well lol.

231/239 with AFR 195's on a 350. You want more RPM, it always has more RPM!

When it comes to lifters, GM LS7 lifters for anything under 7000rpm basically is fine as long as valve train weight is kept under control. They are even good beyond that too for a few hundred rpm.

 

Unless you are unlucky enough to get some of GMs low quality garbage that fail in under 20K. I had a couple in a set lockup the rollers and trash a cam. A friend of mine had a set takeout the cam in his 6.0L. Another set in an engine I tuned for a customer had one wipe a cam in a 5.3L. The rollers failed and locked up on all 3, munching the cam. I actually returned a set as well that a customer had for a cam swap in a 6.0L I was swapping. Rollers were dragging and the needles were sticky feeling on 3 lifters out of the box.

 

236/242 compares to COMPs XR288HR which is 288/294, 236/242 with 110 LSA. As it is that's 71° of overlap. That can be difficult to tune. Moving to a 106 LSA with the same seat to seat duration moves that overlap to 79°. That's getting up there.

 

Seems to asked before. What are the advertised numbers for that cam?

 

I just read over Mike Noonans 383 LT1 build. It made 542 hp at 6,000 and 520 tq from 4,600-4,900 rpm with a dual plane intake and an 850 carb. At 6,500 it was still making 524 hp. It made 505 ft/lbs at only 3,700 and 483 at 3,500. The cam was 234/238 @ 0.050, 0.602/0.584 lift with 1.65/1.60 rockers, 112.5 LSA and I think a 108 LSA.

 

Well that's kind of it... I know I have to crutch it a bit because the intake isn't going to be ideal and the exhaust isn't ideal. I would ultimately like to improve on this engine what the current mill is... 224/230 at .050 on a 112 and .510/.517 lift. The car is about what I want though it is a little lazy down low even though it isn't... does 300+ ft-lb from 2000 up to about 5800 RPM and rolls off. Power peak is 5800. I really want to extend both sides a little. Going 383 will probably give me the bump I am looking for down low and going up a bit in cam will give me the top end because of the limitations of the rest of the parts I am working with. I could improve the exhaust but I really like the sound and look it currently has. The intake is the way it is because of my TBI setup... Yes I am shooting myself in the foot. Yes I like to cause myself hours of stress because of the dumb choices I make. Yes I like to torture myself.
This is also true. I was looking at the XR288 as a reference although I think I'd probably call someone like bullet when I finally settle in on what I think I want. Not worth the hassle half assing it if I can do a little better with a custom grind. Again though, who knows. Maybe I end up with a shelf grind. The amount of overlap and tunability is something to consider for sure though.

 

I had talked to Mike Jones at Jones Cams about a proposed 383 as I mentioned earlier.
Here's a screenshot a my post with the two different cam specs and an explanation for the 2nd recommendation.



If you're interested in a fair bit of reading but some excellent content, check out the thread.
https://www.thirdgen.org/forums/tech...ecs-383-a.html

The specific profiles can be found on his website.
If it were me, and it will be, I'll have Mike take all of my current engine data as well as the vehicle application and go with his spec.

 

Oddly enough, that is (the first spec) about what my machinist said I should run... We were talking about where I picked up a few of my parts from and one of the vendors sells a custom grind like so: 233/239 .560/.569 on a 110 LSA... Slightly more intake duration but he basically said don't shoot for the moon, that'll make good power up to around 6200 on a dyno (they showed me the sheet) and drive damn nice. Maybe I should back down a little and keep it safer... though upper 6k shifts sound lovely... I could reach out to jones and get a recommendation and bullet as well, though I suspect it would be similar to what everyone else has said here... smaller than I think I want and less aggressive. Which I have done in the past... pick the cam I really want then go down a size or two... Has worked nicely so far.

If I was closer to building the thing I wouldn't mind calling but I feel like I'd be wasting someone's time being I am still probably 2 years from actually finishing the long block. It's a no rush project. I do appreciate everyone.

I thumbed through that thread all day, it was a good read.

 

I am actually considering a cam change in the 383 in the van too. Single pattern grind is what I am considering. Something around 224-228 @ 0.050 on a 110-112 LSA to bleed off some of the dynamic compression and spread the power curve out a bit.

 

Here are three cams Torque Master created for a 10:1 383.
Keep in mind that TM is all about maximizing torque for given cylinder head and compression ratio. It's also WOT results as would be seen on a dyno or the drag strip.










I was mostly interested in the minimum required intake port CFM for that 10:1 CR. All single pattern although I have dual pattern files as well. These results imply a free flowing exhaust as in open headers or a near zero loss muffled arrangement.
Cranking compression was at or near 200 PSI in all cases. And a tight 106 LSA as you'd expect from something Vizard engineered.
500+ lbs-ft of torque all around.
With better heads it would easily top 500 HP but as it is, you can see the peak HP RPM is 5600 or less so the output isn't necessarily there.

You can take those seat durations and target the .050" numbers.
The 279 cam in the first example could easily be had with 224-228.
But I'm not sure this is a van cam given your stated goals. But you could pull a house with it!

I'm just throwing this out there to stir up the conversation.
My 357 may get a TH spec'd deal too unless Jones can talk me out of it. 288/288/108 with peak HP RPM at 6300. Less than 250 CFM port too which is roughly my target. Flow bench said 255@.550".

 

I have noticed Vizard likes single pattern a lot. I know he has explained over the years various reasons why but the most common seems to be more torque for street. Granted the right cam for the application still applies but I don't know. Never seen anything that outright proves it works best one way or the other, just data from builds that seem to go at each other at times.

 

The single pattern is directed at an engine platform that has the needed capacity on the exhaust side. So from a racing perspective, that exhaust wouldn't be crippled like it is on my heap. A little experiment a few years back with nothing more than a cutout just before the single muffler showed gains in MPH and ET in the 1/8 mile. Open headers with a spec'd collector length is where I want to go next.
For heads that don't have a good ratio or a fully mufflered exhaust would probably benefit from a dual pattern.
​​​​​​The heads too, with the ratio between intake and exhaust plays a part too.

 

joe sherman loved exhaust duration. Race motors almost always have a lot more duration to extend power past peak rpm

 

I was going to ask you that.
Is it extended exhaust duration that allows power past peak?
Or is it something more?
And where is that additional duration applied? On the closing side? So holding the exhaust open longer to what effect?

 

I get that. It's just generally whenever I see similar cams in single and dual pattern the dual usually seems to do better almost always. I get there is more going on than just .050 duration differences but it would seem the dual pattern is generally going to be the better choice. I trust Vizards judgement and knowledge but it seems rare in a moderate street strip you'd have ideal I/E ratio flow and for that matter as stated, a lot of race cars use split patterns too. I know my exhaust beyond the head is poor so a single pattern wouldn't be optimal in my case I'd think...

 

I/E flow ratio does not mean much outside of numbers on a piece of paper from a flow bench.

 

Something from a post Mike Jones made a few years back on this subject.
FTR: I reference Jones a lot because he's one of the few cam grinders that regularly explains the ins and outs of cam designs. A very approachable guy who also cuts through the BS on cams as it's often spread across the internet.
From 2019:

Answering this query.
Does a longer exhaust duration offer any benefit on a “normal” daily driver? Does a little more exhaust duration hurt anything at part throttle operation?

The answer to both questions is, it depends.
At part throttle, you have vacuum in the intake, so the CFM in the cylinder doesn't change, but the density is lower. With less mass in the cylinder, you don't need as much area to evacuate the cylinder. Have more area then you need on the exhaust will lower the velocity of the exhaust charge during overlap, and lesson the pull on the intake. If you shorten up the duration, you will increase the exhaust velocity, and increase the pull on the intake. The issue is, if you shorten up the exhaust duration, and don't move the lobe centers, you reduce the amount of time the exhaust has to pull on the intake, during overlap. This can be just as harmful to efficiency, as the slow exhaust velocity. To fix both issues, you either have to shorten the exhaust duration, and change the exhaust centerline, so the exhaust closing is the same, or you keep the duration and centerlines the same, and reduce the area, by lowering the lift, and lobe area.
This is what we did with restricted carb, circle track engines. At first, we went smaller on exhaust duration, and changed the centerlines. That made the engines much more efficient below peak HP. The issue was, the power fell off faster beyond peak HP, because even though the carb was restricting the mass into the cylinder, it still needed more time(duration) to evacuate the cylinders, at the higher RPM's. It's not uncommon for a restricted carb, circle track car, to turn over 1,000rpm past peak HP RPM, so holing on to the power is extremely important. At this point, I started designing exhaust lobes for these restricted classes, that had the same amount of seat duration I would have used, if it was a non-restricted engine, but I reduced the area of the valve lift curve to match what was needed to evacuate the mass of the restricted engine. The peak HP RPM was the same, and the power curves, up to peak HP RPM looked about the same, but the new exhaust designs held the power, another 400-500rpm.

So, like I said. It depends. For every application, there is an optimum exhaust valve lift curve. It could be longer then the intake duration, or it could be shorter. There is no "You need "X" more(or less) degrees on the exhaust" answer.

 

in my opinion power extends or holds on since the duration is long enough to allow more time to evacuate cylinders at the higher rpm. Kinda like what mike jones mentioned with his circle track motors about needing more time to evacuate cylinder, which means more duration. It seems to work well. Even a lot of lsx cams have shown up with larger duration splits, even tho exhaust ports are typically ok on most lsx heads.

 

That's about what I remember darin morgan saying lol. I am only partially the right engineer by trade but as with everything "there is a lot more going on then meets the eye." I do know I/E is what everyone likes to cite as the reason for why but I agree... flow is a number on paper. While a useful tool there are a lot of other things to consider. And like dynos flow benches can be tweaked.

 

Isky has ALOT of good cam theory on their website as well.

I know my cam needs less exhaust lobe because it picked up power with a 1.3 exhaust rocker.

 

So I sent out a couple feelers, one to Jones and one to bullet. Still waiting to hear back from bullet but I gave them both the same specs: 6700 shift point 6300 power peak. I laid out the flow on my heads and the numbers of all my components. The specs are as follows:
240/250 @.050 and .570/.547 lift. On a 110. Seems a little aggressive on the spread but maybe not... I'm curious to see where bullet falls.

 

Seems alot bigger than you need but jones would know i guess. Thats more like a 406 cam to me

 

Exactly my thoughts... On a tight lash solid I could see numbers like that but it does seem a little more aggressive than would be needed... I also reached out to cam motion too just to see where they would end up too. If everyone comes back around the same numbers then I have my answer lol.

 

What heads did you have?

 

Profiler 195s, angle plug and 64cc chamber

 

What did you specify as an exhaust system on your recommendation forms?
In my example above, the 1st spec had an 8° split. But the exhaust lobe profile was less aggressive than the intake as well. .353" lobe lift vs .348".
When I went for a 2nd request and emphasized the racing aspect with open headers, the spread shrank to 4° and the lobes evened up as well at .360" each.

Do you have flow numbers for the Profiler's? I'm curious as to I/E ratio (FWIW) and how it compares to mine. (Ported 175cc iron heads).

 

I haven't put my exact set on a flow bench however plenty of other people have. I simply used the lowest as delivered flow numbers for them I found published... not that there is huge differences between them. I will most likely have the valve job redone and the bowls touched up before they go on this engine though so that can skew things and I did mention that.
Head flow:
.200 .300 .400 .500 .600 .700
I 134.7 188.6 237.0 268.6 274.1 269.4
E 107.1 140.1 165.5 182.8 198.0 206.5

For the exhaust it is 1-3/4 long tubes into dual 3" and an x-pipe just past mid way, it necks to 2.5 closer to the rear to clear the axle and then drops to 2.25" through the mufflers. It is far from ideal for what I want but it just sounds so damn good I'd hate to change it. But I am aware that exhaust is probably holding me back even right now.

 

I spent alot of time playing with Desktop Dyno 2003 as well as Engine Analyzer. I have learned how to make the results from both very accurate over the years. When the Pro Flo knock off goes on my 383, I am likely going with a Comp XR274R solid roller with Isky EZRollMax solid bushing lifters with oiling holes for the rollers. It is not a cheap upgrade, but it will reduce my dynamic compression ratio, make more power almost everywhere and with a spring and retainer upgrade give me valvetrain stability past 7,000 rpm while adding over 50 hp at 6,000 rpm. The XR274R is 274/280 @ 0.006. 236/242 @ 0.050. With a 1.6 rocker 0.602/0.608 lift. 110 LSA and 106 ICL. I will have Comp put it on a step nosed core so that I will not have to mess with a cam button. My 383 should make about 570 hp @ 6,500 at peak and 520 ft/lbs @ 4,000. The trade off was less then 20 ft/lbs @ 2,000 for another 1,000 rpm and nearly 80 hp gain at 6,500. By the ~3,000 rpm stall speed both are making nearly the same power. I also simulated part throttle by decreasing the intake airflow rating to ~200 cfm. At part throttle the solid roller shows as much as a 20 ft/lbs gain at 2,500 compared to the current 271/284 @ 0.006, 218/228 @ 0.050 on a 108 LSA hydraulic roller cam that has 0.578 lift with 1.7 rockers.

 

Like I said, for what I plan to do I don't want to commit to a solid if it really isn't going to be any better. Although if the above is accurate then maybe I'd reconsider but even then... I don't know.

 

I had an older SBC with the old Comp 270S and did not have to mess with the valve train once in the 100k miles I ran it. I pulled the valve covers off, checked the lash a couple of times, but never had to change it.

 

If you do the hyd right there wont be a gain with a solid that is worth the additional cost and maintenance. Theres 3000+ hp hyd roller motors out there. Ls guys turn them 8000 rpm. Just gotta set the lobes up right and keep valvetrain components light weight. You arent asking much out of a oem roller setup turning 6700. One of the good conical or beehive springs will work great keeping spring load down so the lifters dont have to fight it.

My bbc uses a solid however and very well scienced out, with very light springs. With a solid roller keeping spring load down is important for lifter life. I wouldnt be intimidated by a solid but you gotta spend more on a real quality lifter and valvespring. As with anything else, but atleast with oem hyd roller setup you can get lifters for much cheaper, and could get away with cheaper cam core. A solid roller you almost have to get a billet core.

 

Being a member of the broken beehive spring ruining a cylinder head club, I avoid them. You could not pay me to put them in any kind of performance engine at this point. I will put them in a Vortec head engine that is sub 6,000 rpm but nothing more then that. My LS and 8.1 both have dual springs.

At this point I also trust a chunk of billet steel more than most hydraulics. A properly setup solid valve train needs minimal maintenance. I have a 240K mile Nissan VQ V6 that is testament to this. DOHC Nissan engines do not use any kind of hydraulic lash adjustment. You set the clearence with buckets with shimmed thicknesses. At 240K it is still in the factory range although it will need the cams removed and the clearences adjusted. With the age and mileage I doubt it will ever be done and if it is, will get a valve job, head gaskets and a new timing set.

 

I'm thinking stick with the hydraulic... I don't mind the work one bit but I just don't know. I've got some solid stuff but they're all follower/flat tappet engines not a roller... Granted they need no work (check the lash once a year and it hasn't moved yet) but if it spends a lot of time idling around in traffic I think I could really beat it up even with a tight lash cam... But they sure do sound cool. Yes I'm a child.

 

The XFI family of lobes from COMP, those with a .360" lobe, tend to have a solid lifter sewing machine sound if that really floats your boat. At least mine did. That was a 274 advertised with 224@ .050". A little quicker than the XE lobes with 276 and 224. Beehives, tool steel retainer. 6500-7000 repeatedly. Just don't keep on doing that as the parts start to age. I learned the hard way.

I've also suffered a valve spring failure and only one even though we've run several sets over tens of thousands of miles. My one and only failure was with the XR288 and used 26918's. Other than the spring though, no other damage to report.

 

I hear good and bad things with the XFI lobes... and enough bad that I would prefer to stay away from that lobe and for that matter comp beehives... I'd probably run a PAC setup or if I want to hurt myself PSI...

 

I bought hardly used NASCAR PSI valve springs from ebay.
Something like less than 50 laps, and other car problems forced the car out of the race.
I figure that if the springs could stand up to 9500 rpm, then they can take anything that I would ask of them.