I’ve been looking at cam specs for the Summit Racing Pro LS Truck camshafts and I have a question. I’ve noticed that many of the specs now list the lobe separation angle (LSA) spec with a plus number added. The cam I’m looking at is the Pro LS Truck 8718R1 cam. The LSA specs are listed as 112+2. But the actual specs say the LSA is 112 degrees. So what does the +2 refer to? It’s something new that I’ve never seen before and I’m not sure what it means.J.L.
This is a great question with, for once, a simple answer.
But don’t worry, we’ll expand our answer just so everyone understands what we’re talking about. The short answer is that the +2 refers to how the cam is ground relative to the LSA and the cam’s intake centerline. The +2 in this instance means it has been machined with two degrees of advance built into the cam, placing the intake centerline at 110 degrees BTDC.
But let’s take a closer look to make sure everyone understands this explanation. Lobe separation angle is the angle between the intake and exhaust lobes for a given cylinder and is expressed in camshaft degrees. Using the COMP Cams illustration at the bottom of this article, you can see that the intake lobe centerline (the left lobe) and the exhaust lobe centerline (on the right) are both displaced 116 degrees away from the TDC centerline.
The lobe separation angle is the sum of the two angles divided by two or 116 + 116 = 232 / 2 = 116 degrees. If we advance the intake lobe two degrees to 114 degrees BTDC, then the LSA would be 114 + 116 = 230 / 2 = 115 degrees. This is accomplished during the actual grinding of the camshaft and cannot be altered. Cam companies often add this advance because this improves low-speed torque. Not all cams are ground with advance built in, but it is very common.
Before this shortcut description, the best way to figure out if the cam had been ground advanced was to check the intake centerline figure. If the intake centerline number and the LSA number are both the same, then the cam is not round with advance. But if the intake centerline is 110 degrees and the LSA is 112 degrees, then the cam has been ground with 2 degrees of advance built into it.
In the case of the Summit Racing Pro LS Vortec Truck Swap Camshaft, the LSA is expressed as 112+2. As you suspected, the cam is ground with a 2 degree advance with a LSA of 112 degrees. This means that if you were to degree the cam, you would find the intake centerline would measure 110 degrees BTDC. In this case, there is no reason to further advance the camshaft because the factory has done it for you. The new listing as 112+2 merely points out that the cam has been ground with two degrees advance in the cam. This shorthand description tells you everything you need to know.
Summit Racing Pro LS Truck Camshaft (SUM-8718R1) Specs
|Intake Centerline in this case is 110 degrees BTDC.|
very go info
It still sounds like ‘string theory’ and ‘spooky action at a distance’ to me.
Nice post https://www.onallcylinders.com
i purchased the gm 19210721 hyd roller camshaft. gm cams do not come with a cam card. but i found that the lift was .632 on both lobs ..the duration is 254 on in and 264 on exh and the lsa is advertised as 112 degrees. when i install the cam straight up the centerline is around 106..and also .by three other guys who know how to do it. it always comes up 105-106. i installed my lunati to check the cam sprocket and chain for accuracy and it comes in 110 like the cam card says. i understand that the lsa is different than the intake centerline but can it be that different.? why has gm not given the centerline number for this cam???? i even called the gm performance group and no one knows .
I have a 1999 Chevy silverado, 5.3 liter, vin T, LM7 engine with a bad cam gm# 12560966. Can I replace the 1999 cam with a 2000 gm# 12560967 cam? Would any re-tuning reprogramming be required?
Trucks and SUV with Vortec engine
Year Part # Duration* Valve Lift LSA
LR4 and LM7
99 12560966 191/190 .457/.466 115.5
00-04 12560967 191/190 .457/.466 114
the 03-04 LM7 used the 12560967 camshaft
I have a1969 gto with a455 block and ported polished 69 heads and 30 over dished pistons and a 780 hollers vacuum secondary card.What cam can I use.Thanks.
I have a vehicle that has a Suzuki J20A DOHC inline 4. What is the lobe separation angle? How much lift can I go? How do I get a choppy idle?
I have a Chevrolet Malibu 1979 4.4lit 267 v8 engine.
Very small 3.5″ bore size.
I`m doing a complete overhaul of the machine.
But i would like more horse power from the engine.
Car haw now original 120hp,i ve been asking around several places here in
how i could get more hp but they are all saying that this engine cannot be tuned bicouse bore is 3.5″ I will 280-350 hp is that bossible?
I have the car body replaced so i cant change the engine,
i know that i could get a new 350 for about 3000-4000dollar.But i cant change the engine.the law is like that here.
Thats why i m asking you if you could help me and tell me what i should do.to the engine to get 280-350 hp out of it.
Could you make me a list (parts number )whose parts i needed?
And how mutch parts cost.
Kind Regars and greetings from Finland.