SHO NUT Performance Cams Page

Revised 6/12/11

We have worked with Colt Cams to come up with FOUR SHO NUT Performance exclusive cam profiles. Colt Cams is a company that specializes in high-quality cam grinding for a variety of vehicle applications, including the SHO. Our offerings are composed of four cam sets:

SHO NUT Performance Tri-Flow cams

SHO NUT Performance Plus 40 cams (Special order only)

SHO NUT Performance Plus 20 cams (Special order only)

SHO NUT Performance Plus 10 cams

The numbered name implies the additional lift over a stock MTX cam for the first two numbered cams (Plus 40/20), and a natural progression of numbers for the third numbered cam (Plus 10) (See below)

As a primer, here are the measured specs of the stock cams:

MTX Intake 0.348” Lift, 205° Duration @ 0.050”

MTX Exhaust 0.328” Lift, 201° Duration @ 0.050”

ATX Intake 0.328” Lift, 201° Duration @ 0.050”

ATX Exhaust 0.328” Lift, 201° Duration @ 0.050”

The ATX Intake chain flange is also advanced 4 crankshaft degrees relative to the MTX cam. As the Intake chain flange is what drives the Exhaust cam, this effectively advances the Exhaust cam in an engine with ATX cams by 4 crankshaft degrees, which also reduces the overlap by 4 crankshaft degrees. Compounded with less duration on the ATX intake lobe, there is substantially less overlap with the stock ATX cams. In total, there is 6 crankshaft degrees less overlap, 4° due to the advanced exhaust cam, and 2° due to 4° less intake duration (1/2 of the total duration difference). Note that if you are regrinding cams, it is critical that both intake cams be either MTX or ATX, or you will have mis-matched exhaust lobe centerlines between banks due to the 4° difference between MTX and ATX exhaust cam timing, as driven by the intake cam flanges. We carefully check each set of camshafts to verify that we have matching intake cams for each set of cams made.

To make our Plus 40 cams, we take MTX cores, add a 0.055” lash cap, and grind a new profile ‘straight up’ (i.e. same centerline as stock) which includes grinding the base circle approximately 0.055” and broadening the tip to increase the lift and increase the duration. In addition, quieting ramps are incorporated into our lobe profile to keep the valve train quiet and lessen the shock on the valve springs that you would otherwise get with extreme ramp rates. Quieting ramps are a new feature for SHO Performance cams. Since the tip is broadened, it is impossible to get all 0.055” as additional lift, since the stock lobe is quite pointy, and we need to account for wear etc. It is also not practical to grind more off the base circle – we are nearly into the shaft of the cam as it is, and clearancing of the cam journals is required to get this far (so the shims won’t hit the cam journals, since they are now 0.055” closer to the shaft of the cam, and would otherwise hit the cam journals if the journals were not clearanced properly, keeping the valves open – a bad thing).

To make our Tri-Flow cams, we take MTX cores, add a 0.055” lash cap, and grind a new profile which includes grinding the base circle approximately 0.055” and broadening the tip to increase the lift and increase the duration. For the ‘secondary’ lobe, which is mated the short fat runner that is only open over ~4000 RPM, we grind the same high lift/high duration ‘straight up’ lobe as our Plus 40 cam. For the ‘primary’ lobe, which is mated to the long skinny runner that is open all the time, we grind a lobe that is lower in lift and duration than the secondary lobe, and is retarded relative to the ‘straight up’ secondary lobe, to decrease overlap when only the primary runner is being used before ~4000 RPM. The amount of primary lobe retardation is such that the intake valves close at the same time. The idea is that when the secondaries are closed below ~4000 RPM, you have less overlap, intake lift and duration than when the secondaries are open above ~4000 RPM, and the runner to the larger lobe is no longer blocked. This mimics the effect of variable valve timing and lift without the usual hardware involved. Increased lift, duration and overlap is generally detrimental to low RPM operation, and advantageous to high RPM operation. Granted, there is an incomplete separation between primary and secondary intake ports in the head, so some cross-over may occur in the head, but the idea is that the direct air path is controlled by the secondary throttle plates to keep the effect of the large lobe in RPM ranges above ~4000 RPM when both runners are in use. Thus a Tri-Flow cam should have a smoother idle and more low end power than a Plus 40, while loosing little to the Plus 40 in the top end, when the long skinny runner is essentially a cork, and not flowing much air flow relative to the short fat runner, and thus the lower lift/duration lobe in the lower-flowing skinny runner is not much of a penalty. Colt Cams discusses the Tri-Flow technology in general here but the setup for the SHO is somewhat unique, as a different runner is used for the ‘primary’ and ‘secondary’ lobes, instead of the usual use of identical runners in other engines for both lobes. Their use of ‘primary’ (large lobe) and ‘secondary’ (small lobe) is also reversed relative to the normal SHO usage of the ‘primary’ as the low RPM runner which uses the smaller lobe in our application, and the ‘secondary’ as the as the high RPM runner which uses the larger lobe in our application. Thus the swirl effect may not be the same in the SHO application.

To make our Plus 20 cams, we take ATX cores, and as with the MTX cores, we add a 0.055” lash cap, and grind a new profile ‘straight up’ (i.e. same centerline as stock) which includes grinding the base circle approximately 0.055” and broadening the tip to increase the lift and increase the duration. Since the ATX intake cores have less lift to work with compared to MTX intake cores, even though we are grinding 0.055” off the base circle, we can only get about 0.020” more lift than a stock MTX intake cam, hence the ‘Plus 20’ name. Compared to a stock ATX intake cam, the increase is just as dramatic as it is for an MTX intake cam, (going from a stock ATX cam to a Plus 20 is approximately a 0.040” increase in lift), but for our purposes, we will compare all cams to stock MTX cams when quoting increases in lift etc.

Since the same exhaust cam is used for both MTX and ATX engines, the core is the same, and thus our exhaust cam spec is the same for Plus 40, Plus 20, and Tri-Flow Cams, i.e. approximately a 0.040” increase in lift. In other words, the ‘Plus 40’ exhaust cam is used for the Plus 40, Plus 20 and Tri-Flow cams. Thus the Plus 20 is really a Plus 20 intake / Plus 40 exhaust mix.

To make our Plus 10 cams, we take MTX cores, add a 0.035” lash cap, and grind a new profile ‘straight up’ (i.e. same centerline as stock) which includes grinding the base circle approximately 0.035” and broadening the tip to increase the lift and increase the duration. As with the first two grinds, quieting ramps are incorporated into our lobe profile to keep the valve train quiet and lessen the shock on the valve springs that you would otherwise get with high ramp rates. Since the tip is broadened, it is impossible to get all 0.035” as additional lift, since the stock lobe is quite pointy, and we need to account for wear etc. Clearancing of the cam journals is not required with the Plus 10 cam.

Here are the specs of the five cam offerings (the fifth is a combination of two grinds) – these are actual numbers and not some inflated ‘advertised’ number:

	SHO NUT Performance Tri-Flow Cams
Specifications			Compare to Stock MTX:		Increase from Stock:
	Lift	Duration @ 0.050	Lift	Duration @ 0.050	Lift	Duration @ 0.050	Overlap*
Secondary Int.	0.390	228°	0.348	205°	0.042	23°	24.5° (S) 9.5° (P)
Primary Int.	0.375	218°	0.348	205°	0.027	13°
Exhaust	0.365	227°	0.328	201°	0.037	26°
* Can be increased or decreased 6 or 12 degrees with our adjustable camshaft sprockets
All degree measurements are in crankshaft degrees. Divide by 2 for camshaft degrees.
	SHO NUT Performance Plus 40 Cams
Specifications			Compare to Stock MTX:		Increase from Stock:
	Lift	Duration @ 0.050	Lift	Duration @ 0.050	Lift	Duration @ 0.050	Overlap*
Intake	0.390	228°	0.348	205°	0.042	23°	24.5°
Exhaust	0.365	227°	0.328	201°	0.037	26°
	SHO NUT Performance Plus 20 Cams
Specifications			Compare to Stock MTX:		Increase from Stock:
	Lift	Duration @ 0.050	Lift	Duration @ 0.050	Lift	Duration @ 0.050	Overlap*
Intake	0.365	227°	0.348	205°	0.017	22°	20°
Exhaust	0.365	227°	0.328	201°	0.037	26°
	SHO NUT Performance Plus 10 Cams
Specifications			Compare to Stock MTX:		Increase from Stock:
	Lift	Duration @ 0.050	Lift	Duration @ 0.050	Lift	Duration @ 0.050	Overlap*
Intake	0.370	214°	0.348	205°	0.022	9°	11°
Exhaust	0.345	214°	0.328	201°	0.017	13°
SHO NUT Performance Plus 10 intake - Plus 40 exhaust Cam Mix
Specifications			Compare to Stock MTX:		Increase from Stock:
	Lift	Duration @ 0.050	Lift	Duration @ 0.050	Lift	Duration @ 0.050	Overlap*
Intake	0.370	214°	0.348	205°	0.022	9°	18°
Exhaust	0.365	227°	0.328	201°	0.037	26°

The Tri-Flow cam is targeted at someone who wants to reduce the negative effects of a ‘big cam’ at low RPM, while retaining the ‘big cam’ effect at high RPM. Of course, both cam timing and overlap can be independently adjusted with our SHO NUT Performance Adjustable Cam Sprockets.

The Plus 40 cam is targeted at someone who wants maximum top end power in a motor with ported heads and dramatically increased displacement, i.e. stroker or big-bore motor that is used for high RPM road racing. The Plus 40 cam may not produce any more power than the Plus 20 when put in a 3.0L or 3.2L with stock heads, but may have a rougher idle due to the increased overlap. Of course, both cam timing and overlap can be independently adjusted with our SHO NUT Performance Adjustable Cam Sprockets.

The Plus 20 cam is targeted at modified cars with stock heads and a 3.0L or 3.2L. Note that the 4° exhaust cam advance/overlap reduction (compared to an MTX cam set) in the ATX core is carried through to the Plus 20 cam, and thus the Plus 20 cam set will have 4.5° less overlap than the Plus 40 cam, while retaining the Plus 40 exhaust profile. As before, both cam timing and overlap can be independently adjusted with our SHO NUT Performance Adjustable Cam Sprockets.

The Plus 10 cam is targeted at a stock or near-stock motor, and should have more low end torque than the other two numbered cams, by virtue of reduced lift and duration and overlap, and thus boosting power all the way through the power band, compared to stock. As before, both cam timing and overlap can be independently adjusted with our SHO NUT Performance Adjustable Cam Sprockets.

The Plus 10 intake – Plus 40 exhaust cam mix is targeted at a forced induction car that needs minimum overlap and maximum exhaust lift and duration. Both the Plus 20 and the Plus 10/40 mix give minimum overlap and maximum exhaust lift and duration, but the Plus 20 (actually the Plus 20 intake – Plus 40 exhaust mix as noted above) does it by advancing the (plus 40) exhaust cam and keeping lots of intake duration, while the Plus 10/40 mix does it by reducing the intake duration while keeping the exhaust timing stock. As before, both cam timing and overlap can be independently adjusted with our SHO NUT Performance Adjustable Cam Sprockets.

Pricing, including lash caps and a shim rental and excluding core charges/refunds is listed on our Performance page. Shipping/handling is extra, and is $45. This is waived if you pick up the cams at Colt Cams.

The shim selection for the rental is selected knowing that since these are ‘unworn’ lobes, the required shims will be a few sizes thinner than we usually supply for worn stock cams. If you know the shim sizes in your motor, i.e. from your last 60K service, then let us know, and we can choose the shim selection appropriately.

If you are rebuilding a set of heads, and can get valves that have a stem that is 0.055” longer than stock (above the keeper), you do not need lash caps, and eliminating them from the supply allows the price to be reduced by $100. E-mail us if you are doing this.

Gaskets are extra. It is recommended that you purchase an upper gasket set (less head gaskets if you are not removing the heads) to get all the gaskets you need for a cam change.

The core charge is $100 for a set of used cams in good shape*, and must be MTX** – we no longer accept ATX cores as the +20 is special order only, and we have plenty of ATX cores on hand. They MUST have good bearing journals*.

* lobe tip wear is acceptable, since we grind so much off the tip to broaden it. Damaged lobes will be evaluated on a case-by-case basis. Cam cores with damaged bearing journals will be rejected.

** as mentioned before the difference between the ATX and MTX cams are the intake cams. There are various ways of telling the intake cams apart. Two are:

1. Look for the KOA lettering on the intake cam next to the wrench flats. If it present and the lettering is obviously raised just like the exhaust cam, it is an MTX intake cam. If it is ground off the shaft of the cam (it may still be visible, but not raised, or it may simply be an extra ground-flat ring around the cam, in the same place as the lettering on an exhaust cam), then it is an ATX intake. Make sure that both intake cams match in this respect to make sure you have a matched set.
2. Compare the intake lobe height to the exhaust lobe height. The MTX intake will have a taller lobe than the exhaust cam lobes by approximately 0.020”. The ATX intake will have a lobe the same height as the exhaust cam lobes.

The core refund is $100 for MTX cores. Please note that it is NOT required to send in cores at all, if you wish to simply pay the core charge outright and keep your own stock cams, if it’s too much work/hassle to return cores to Colt.

If you can send cams ahead of time, or have your own shims, you avoid the core charges. All cores are returned to Colt Cam’s **NEW** address:

COLT CAMS

2325 264^thStreet

Aldergrove, BC, V4W 2L5

Canada

TEL: (604) 856-3571

IMPORTANT!! – It is VERY important that you write ‘Damaged camshafts for repair and return, value less than $10’ on the package and the customs slip when you send it out. You are welcome to insure it for up to $100 (insured values of more than $100 seem to get subject to customs charges, especially with UPS), but make sure that no value shown on the box or paperwork attached to the box is more than $10. This is critical to ensure that the package gets through Customs without any problems. If you do not include the above wording on the box, or use excessive insurance, we will adjust the core return by any customs/brokerage charges paid to receive the cores. If you are checking shipping costs, a set of cams weighs about 20 lb. If you use USPS (recommended, UPS seems to be more aggressive about charging brokerage), USPS air parcel is ~$35 with $100 insurance and takes up to 4-10 days. USPS ground parcel is ~$25 with $100 insurance, and takes up to 4-6 weeks.

IMPORTANT!! – be sure to remove the cam gears and the shutter wheel on the end of the one exhaust cam before you package them! If you leave them installed, the cam gears will invariably rub on the cam journals and damage them. Cams with damaged journals will NOT be accepted as cores!

Camshaft break-in is 20 minutes at 2000 RPM, and don’t forget to assemble the cams with the provided lube. A TwEECer is a good way of setting your idle speed.

Want more technical info and pictures? Keep reading ….

While the specs of the cams can tell a great deal of the story, one way in which our cams really shine is the lobe-to-lobe consistency. Here are caliper measurements taken from a set of Plus 40 cams, and as you can see, the consistency in lift is near-perfect, +/- 0.0005” (half a thou) across ALL lobes. In addition, the base circle consistency across each cam is basically just as good, +/- 0.0015” (one and a half thou), and even +/-0.0025” (two and a half thou) across all cams, so even the cam-to-cam consistency is excellent. This means that the selection range of shims required is now governed by the consistency of the head and valves, and not the cam (see more below). Note that since these measurements were made with a caliper, they are not exact as those made with a micrometer, or better yet, a dial indicator with the cam mounted in the head or in V-blocks. However, caliper measurements are easy to make, and reasonably repeatable, so for our purposes, it worked for what we were trying to do.

Click here for individual lift, base circle and lobe height measurements

In other words, the quality of the grind speaks for itself. This level of consistency is a new benchmark for SHO Performance cams.

Here is a record of the shims required to shim the above set of Plus 40 cams to 0.008” for the intake, and 0.012” for the exhaust (middle of the spec for a blower car, as it’s not a good idea to shim a blower car tightly). If they had been shimmed to 0.006” and 0.010” (normal for a N/A car), each shim would have been 2 sizes thicker as noted as well. You will notice that all lobes were +/-0.002 when measuring with a sample measuring shim (2450, a common shim, used to measure the clearance to see what shim is needed to achieve the correct clearance). We have recorded the required shim spread - this low spread goes to reinforce the consistency of these lobes. You will also notice that the required shims are sizes that are readily available – we have plenty of these sizes for our rental kits – no need to go searching for obsolete super thick or super thin shims or even custom lash caps to make these super-consistent and properly-sized cams fit. Of course, if your heads have been rebuilt with new valves or reground seats, then you may have shim size issues, but this relates to having changed the geometry of the heads and valves, and NOT the cams. In these cases, thicker or thinner shims, or custom lash caps may be required. If you have had your heads rebuilt with new valves and/or have had the seats reground, and need custom lash caps, let us know, and we may be able to help you out.

Click here for sample shims and clearances

As before, the quality of the grind speaks for itself. This level of consistency in required shims (and the ability to use standard-size shims for all lobes) is a new benchmark for SHO Performance cams.

Pictures – note how pointy the stock lobe tip is, and how broad the Plus 40 lobe tip is, and notice how little is left of the base circle. Though not shown, the Plus 20 intake lobes would look near identical to the exhaust lobes shown, since both ATX intake lobes and exhaust lobes (MTX or ATX, both are identical) are the same, and thus our grind is the same for both.

http://www.shonutperformance.com/Stock_intake_lobe.jpg

http://www.shonutperformance.com/Plus_40_intake_lobe.jpg

http://www.shonutperformance.com/Stock_exhaust_lobe.jpg

http://www.shonutperformance.com/Plus_40_exhaust_lobe.jpg

http://www.shonutperformance.com/Exhaust_lobes_plus_40_on_right.jpg