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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
It would be difficult to say if the cam is suited to the rest of engine combination, but the 114 LSA is a little wide for a 350. The 110 ICL would also tend to blow off low engine speed torque due to the late intake valve closing.
Your engine compression is the most important consideration when selecting any cam.
That cam in particular may be of some benefit with the Vortecs somewhat weak exhaust port. The problem is compounded if you have a small exhaust system. The extra duration built into the exhaust will help in that regard.
Overall, I would select a different cam. Something with a tighter LSA and an earlier intake valve closing will help.
The engine is a 350 cid L05 factory roller block.
Headers, 2x2,5" exhaust, Air Gap intake, Holley /QFT 650 cif DP. Compression is 9,3:1
6 speed manual trans T56.
The traditional LSA for a 350 from the aftermarket is 110. Cams are ground with 4 degrees of advance so ICL is 106. Even the 110 is a little wide (in the opinion of most experts). That said, finding a 108 or 106 off the shelf roller cam with reasonable street numbers otherwise is difficult to find. (At least I found it difficult). I ended up with a Comps Cams off the shelf roller.
One of my Vortec headed 350s had 10:1 static compression. With that SCR, Comps XR276HR worked very well. Cranking compression was around 180-190 psi. Ran on premium pump fuel.
With your slightly lower compression ratio (provided the number is accurate when considering the piston dish, piston to deck clearance, head gasket, etc) you may want to get the next size smaller.
If I were to do it again, I'd go for the same specs as the 276 but ground on a 108-106 LSA and a 104-102 ICL.
Keep the lift less than .500" unless the heads have been ported ny someone with experience with the Vortecs. Plenty of porters ruin those heads excellent intake port.
I installed it 4* advanced on a Cloyes single roller timing set, and run it with 1.7:1 roller rockers, LS6 springs, and Comp 787 retainers.
EDIT- With the 1.7 rockers the effective cam duration and lift is about when compared to running 1.5:1 rockers. I actually degreed this cam into this engine after making a factory lifter a solid roller and this is what I found with the 1.7s.
220/228 @ .050
.536/.536" lift
105* ICL, 111* ECL (4* advanced)
Making LSA 108*
Plenty off off-idle grunt and pulls very strong through the midrange. It pulls strong up to the 5,800 rpm shift points I have programmed. When I say plenty of off-idle grunt, it is pulling around 12,000+ lbs with the stock torque converter and 4.56 rear gear and not a slouch doing it. 6,200 lbs Express van + 6,000 lbs travel trailer.
Currently have it pulled apart yet again. Replacing the L31 marine intake manifold with a TPI setup. Well TPI based setup as it is a ported Edelbrock Vortec TPI base, SLP runners that have been siamesed, and siamese ported upper plenum with a LT1 throttle body.
Now THAT'S interesting.
The 108 LSA is the deal maker there.
Advancing it certainly helps to bring the IVC more in line with the lower compression of the OP. Not sure how opening the exhaust valve earlier would effect something like pumping losses.
Is there a cam card available?
Now THAT'S interesting.
The 108 LSA is the deal maker there.
Advancing it certainly helps to bring the IVC more in line with the lower compression of the OP. Not sure how opening the exhaust valve earlier would effect something like pumping losses.
Is there a cam card available?
My cam did not come with a cam card but then again neither my 395' marine cam or my 502HO cam for my 8.1 came with one either. GM ships these cams in a cardboard tube.
Not sure on how advancing the cam helped or hurt pumping losses but I wanted to bring the torque curve on a little earlier in the heavy Express van especially since I tow heavy trailers that are about like towing a parachute. My travel trailer is near box shape that is 23' long, 8' wide and 11' tall. Pulls down the road at 65-75 mph in overdrive turning 2,600-3,000 rpm on flat land and up small hills. A long hill will put me in 3rd @ 65 mph and about 3,600 rpm.
I will also say I recently put electric cutouts between the high flow cats and the muffler. It really loves the reduction in backpressure in the mid-high rpm range.
I'll have to check that out. Thanks.
And I should qualify my earlier statement regarding the 110 LSA being too wide for a 350.
That would be a Gen1 350 with typical heads. Not any of the LS variants with superior head flow. That changes the whole spec for cams.
I'll have to check that out. Thanks.
And I should qualify my earlier statement regarding the 110 LSA being too wide for a 350.
That would be a Gen1 350 with typical heads. Not any of the LS variants with superior head flow. That changes the whole spec for cams.
I like the GM cams because they come on billet steel cores not the cast core junk Comp and a few other cam suppliers are throwing out. After several lobe failures in different engines, I went back with the factory steel cam core and have not had issues.
GM has a great running roller cam that comes in its newest 357 HP SPO Vortec 350 crate engine. Part number 12677151..
It is a steel billet roller cam that works with the production Vortec springs & retainers...
215/223 @ .050
.473/.473" lift
108* LSA, 109* ICL (109* ICL, 107* ECL).......
I certainly wouldn't recommend trying to run this cam with "production Vortec springs" that someone has on their heads from an L31 Vortec engine. Used or new, they will not support the rev range of that cam.
Hopefully GM has better springs on the SPO crate engine mentioned. If not, first step would be to throw them in the trash; cheap springs that would do the job are commonplace.
The traditional LSA for a 350 from the aftermarket is 110. Cams are ground with 4 degrees of advance so ICL is 106. Even the 110 is a little wide (in the opinion of most experts). That said, finding a 108 or 106 off the shelf roller cam with reasonable street numbers otherwise is difficult to find. (At least I found it difficult). I ended up with a Comps Cams off the shelf roller.
One of my Vortec headed 350s had 10:1 static compression. With that SCR, Comps XR276HR worked very well. Cranking compression was around 180-190 psi. Ran on premium pump fuel.
With your slightly lower compression ratio (provided the number is accurate when considering the piston dish, piston to deck clearance, head gasket, etc) you may want to get the next size smaller.
If I were to do it again, I'd go for the same specs as the 276 but ground on a 108-106 LSA and a 104-102 ICL.
Keep the lift less than .500" unless the heads have been ported ny someone with experience with the Vortecs. Plenty of porters ruin those heads excellent intake port.
I certainly wouldn't recommend trying to run this cam with "production Vortec springs" that someone has on their heads from an L31 Vortec engine. Used or new, they will not support the rev range of that cam.
Hopefully GM has better springs on the SPO crate engine mentioned. If not, first step would be to throw them in the trash; cheap springs that would do the job are commonplace.
Not saying the springs should not be changed, HOWEVER that being said the SPO 350 per the parts list still uses STOCK vortec springs as does the Ramjet 350. Both have lifts in the .470-.480" range. LS6 springs and Comp 787 retainers would be a wise upgrade.
While the specs sound ok, I wouldn't use it myself. Not knowing what type of core or new-condition hardening it had, durability will be a crap shoot.
Originally Posted by Fast355
Not saying the springs should not be changed, HOWEVER that being said the SPO 350 per the parts list still uses STOCK vortec springs as does the Ramjet 350. Both have lifts in the .470-.480" range. LS6 springs and Comp 787 retainers would be a wise upgrade.
I know. GM meets their advertised hp numbers before the valves float at ~5000 rpm, +/- depending on which of those two cams you want to pick. Just advice for anyone using that 215/223 GM cam -- don't use stock Vortec springs, even if they're brand new.
And no, they didn't get that 5400 rpm power peak they show in the graph with Vortec springs...lol!
Your LS6 springs are a big jump up in capability; good move
As far as the cam goes, I have a few questions.
What is this for? A daily driver? A hot rod?
What grade of fuel do you available?
How accurate do you think your calculated compression is? I'd like to do a calculation myself.
But...
With 9.3:1 in a street/strip vehicle, I'd pick something along these lines:
That cam would put your dynamic compression around 7.8:1. That should give plenty of headroom against detonation but again that depends on the fuel you can get. That said, with the T56, I think that cam in a 350 would fly. With the 108 LSA, the overlap is enough to create a noticeable lope at idle. A higher stall converter is recommended but you have an infinite stall speed with the clutch.
86LG4Bird brings up a good point. Buying a used or reconditioned cam is a risky proposition. And a cam failure more or less wipes out an engine's internals. I've been through that with a flat tappet cam.
As for the springs, I'm in full agreement with the stock springs being inadequate. I bent a couple of valves on a missed shifts with my new stock Vortecs and a 218/.454" flat tappet cam. Zinged it to somewhere around 7000.
You say your heads are modified to handle the lift. I hope the springs are sufficient to handle a heavy hydraulic roller lifter spinning to 6000 RPM.
It's for a hot rod that weights 2860 lbs.
I use regular fuel.
The compression is according to factory specs. Not tested.
Engine has gone app 90000 miles and fels healthy. No blue smoke, dyno test showed hp and torque numbers as espected.
Vortec Beehive valve spring kit from Alex's Parts.
The only real concern is matching the cam to the CR.
I've seen L05's advertised at 9.3 and others at less than 8.5.
While the latter would be very streetable, and I think even on regular fuel (86LG4Bird has experience with regular gas and Vortecs I believe), the lower compression ratio version might be a little sluggish.
I do like that cam though. The added duration on the exhaust should help the weaker Vortec exhaust port. The tighter LSA gets the overlap to where you want it without having too much duration.
I may select my next cam out of the Howard's catalogue. I've way too much cam for my CR (long story) and the 108 LSA was spec'd for me and my RHS Vortec headed 350. Indirectly by David Vizard actually.
L05 engines came in different versions.
-Non roller blocks w/dished pistons and lower compression in vans and trucks.
-Roller blocks with non dished pistons and 9,3:1 compression in personal cars.
My engine is a roller block from a Buick Roadmaster station wagon.
The Howard 183215 cam that we speak of comes in 3 different versions: LSA 114, 110 and 108.
As mentioned earlier, the Chevy small block likes relatively low LSA. But the LSA 108 version is described to have "noticeable idle" and I'm not sure if I want that.
So maybe I'll go for the compromise and buy the one with LSA 110. Not decided yet.
Last edited by Hotrodder; 09-26-2017 at 03:51 PM.
Reason: Bad spellings
I suppose the "noticeable idle" is subjective and that's something you would have to determine.
I can tell you this though. The overlap is 58° with the 108 LSA Howard's cam.
The Comp XR276HR (276/282, 224/230, 110/106, .502/.510) which I ran in my OEM Vortec 350, has 59° of overlap and is advertised as having a "choppy idle". With 10:1 compression, I had the idle tuned to 650 RPM and pulled about 12"-14" of vacuum. Hardly what I would call choppy at all. It did sound good, but really nothing to write home about. I had many comments that it sounded "great" but again there's that subjective thing again. It's all in your ability to tune the carb and ignition timing.
Going to a 110 LSA will move the intake valve closing to 61° from 59° (ABDC) and bleed off a little cylinder pressure and torque. Overlap is 54°. The DCR drops a little more than a tenth to 7.69 from 7.8. My thoughts are that 7.8 is on the low side already but I've also learned that compression isn't the be all and end all. Ignition timing is far more important, from both a performance and fuel economy standpoint. I'd say you could run either cam on regular 89 octane and have a full timing curve (along with vacuum advance) with no trouble.
To sum it up, you'd probably be hard pressed to tell or even test the difference between the two cams but my preference would be the tighter LSA and the resulting tweak in output.
Those B-car TBI engines have flat top pistons with 6cc worth of valve relief as built from the factory. I would run a 0.16" compress steel shim head gasket to get better quench. Should end up about 9.8:1. His car slightly defies normal thinking on DCR because it is so light that it could not be run at full load for very long without having issues besides detonation to worry about.
My 18cc dished TBI engine with a steel shim gasket and Vortec heads was about 8.9:1 static and about 7.4:1 DCR with a 208/214 @ .050 cam on a 114° LSA and ran a full 34° of timing by 2,800 on 87 octance in my heavy G20 van. I did have to pull 6° of timing at peak torque at 3,600 rpm thanks to the TPI setup making for a weird timing dip in the spark map between 3,200 and 4,000 rpm. My L31 in my heavier Express van at 9.4:1 static and the GM 196/206 @ .050 marine cam giving 8:1 DCR had difficulty running 24° of timing at 2,600 rpm, 30° of timing by 4,500 rpm and 32° by 5,000 rpm without knock retard on 93 octane in the summer months. The engine in the G-van with TPI base and siamese ported SLP runners made far more torque than the Express did with the L31 Marine intake. There is more to consider than just compression and dcr to making power. What I mean by that is even if two engines are running the same exact DCR the VE of the engine effects the octane requirement as well. A stock engine at say 80% VE is going to tolerate more timing on the same DCR compared to a race engine with 95-100% VE. Tuned runner intakes often get over 100% VE as well where they resonate.
His car slightly defies normal thinking on DCR because it is so light that it could not be run at full load for very long without having issues besides detonation to worry about.
Not exactly sure what you mean by that.
Originally Posted by Fast355
There is more to consider than just compression and dcr to making power. .
Something I'm painfully aware of...(from a failed high compression ratio combination that I ended up with somewhat accidentaly)
Hence the statement below...
Originally Posted by skinny z
... I've also learned that compression isn't the be all and end all. Ignition timing is far more important, from both a performance and fuel economy standpoint..
All of that aside, as far as the OP is concerned, it's the purpose of vehicle and his desired result that will shape the camshaft selection.
Originally Posted by Hotrodder
. But the LSA 108 version is described to have "noticeable idle" and I'm not sure if I want that...
From a purely performance standpoint, the LSA is selected based on the cubic inches and intake valve diameter (or more precisely intake port flow but the valve diameter serves well enough). Overlap is then selected based on the intended use. Little overlap for your tow truck, lots of overlap for an all out race engine. The rest falls into place. The lift is based on the peak flow numbers or the limit of the valvetrain. From a maximum output perspective, the typical Gen 1 OEM configured cylinder headed 355 (23 degrees and stock port locations) likes a 107 LSA. That's from thousands of experiments performed by people far more knowledge on the subject that I'll ever be.
If the preference is not maximum output, such as the OP has suggested with his desire for a smooth idle, then the 107 LSA target doesn't work here. Spread things out a little to satisfy the idle requirements and pay attention to the maximum RPMs as you might otherwise.
What I mean by that is a high hp engine in a light weight car cannot stay at WOT for a long period of time without either exceeding the speed limit or getting to very dangerous speeds. That means the DCR can be slightly higher because the engine will not be able to sustain wide open throttle for a long period of time. Where I may have to limit my engine to 9:1 compression so that I can drag 12,000 lbs GCVW up a mountain pass at near WOT for miles, his sub 3,000 lbs car will not experience the same heat load.
Also if I were building am engine to run in high altitude say Denver, Colorado and the surrounding area, I would probably up the compression ratio a full point or more higher and just retard the timing at lower altitudes.
09-21-2017, 02:35 PM
