Mustang cams - piston to valve clearance

[twistedneck]

Edit: On the stock pistons the valve cut out radii are the same intake vs. exhaust. Also, boss exhaust valves fit just fine on the stock GT pistons.. As do the CJ cams.

Check out this clip from 2 guys garage where Kevin Byrd explains the Coyote cam phasing.

Mustang Engine 2011.mov - YouTube

Starting at 8:06 into the video he actually shows the Ford mapping. You can see that there is plenty of valve overlap peaking about 3000 rpm, this is where the main issues are with piston to valve clearance occur..

 

[hasty]

I've wondered about this myself, specifically, using the cobra jet 290* exhaust cam. Does anybody out there have any experience using the cobra jet camshafts in a Boss? (I know the GT need to have some clearance work for the cam follower since it's 13mm lift instead of 11mm)

Has anybody installed the Cobra jet cams out there?

 

[twistedneck]

I've wondered about this myself, specifically, using the cobra jet 290* exhaust cam. Does anybody out there have any experience using the cobra jet camshafts in a Boss? (I know the GT need to have some clearance work for the cam follower since it's 13mm lift instead of 11mm)

Has anybody installed the Cobra jet cams out there?

I have both the intake and exhaust cams installed but I now need to do a sanity check on the piston to valve clearance. Ford racing does not state that these require cam phaser limiters or lockouts, and these cams although slightly higher lift than the aftermarket cams that do need 20 degree limiters, they have much less duration and overlap. Also, since the cobra jet naturally aspirated motors do not have phaser limiters - this points to these cams still having zero interference even at peak overlap and lift.

I am researching now the best way to spin the motor with a big wrench while holding the cams at max performance mode i.e. max overlap. that would be a good sanity check.

the other issue, are these hydraulic lifters? and if so, how would you pump those up to get the true measurement?

This should have been completely figured out by FRPP, so i'm hoping they answer this question quickly.

 

[hasty]

I sent an email to Michael Rauscher at L&M engines (who does some cam grinds for these motors) and he confirmed that phase limiters are not needed. I got the same story from FRPP's tech line, but I could tell their guy is just looking at the same data that you find everywhere.

From what I can tell it looks like the Cobra Jet exhaust cam is even bigger in lift and duration that the Comp stage 3 NSR cams!

Are you using the Cobra Jet cams and have them running, or are you using Comp cams?

 

[twistedneck]

I sent an email to Michael Rauscher at L&M engines (who does some cam grinds for these motors) and he confirmed that phase limiters are not needed. I got the same story from FRPP's tech line, but I could tell their guy is just looking at the same data that you find everywhere.

From what I can tell it looks like the Cobra Jet exhaust cam is even bigger in lift and duration that the Comp stage 3 NSR cams!

Are you using the Cobra Jet cams and have them running, or are you using Comp cams?

Yea I also emailed Michael.. the Mahle Piston guys said the Cobra jet NA engines had 0.020" deeper valve pockets than the stock pistons, but that I should still be OK depending on 1. that CJ engines had full TIVCT and 2. that they had the usual 0.100" design clearance (in that case 0.080 would be OK w/ the stock piston). From speaking with Michael earlier he said the cobra jet cams are 'baby' cams still vs. the comp bump sticks. Even thought he lift is higher.. I assume the duration is much lower.

Love working on new stuff.. none of this is figured out yet.

 

[hasty]

I believe the Comp stage 3 is 286* of duration and 11mm lift Vs. 290*/13mm on the Cobra jet. The intake cam is virtually the same as a stock GT/Boss though, having only 1mm more lift and the same duration. The ramp rates may be a lot more aggressive on the comp grinds though. I know the Cobra Jet stuff is rated to withstand Ford's 150k mile durability standards.

I think it's interesting that Ford did not use a significantly larger intake camshaft on the Cobra Jet. They said they didn't find a lot of power increasing the intake side. I suppose it makes sense considering how weak the exhaust port is in comparison to the intake side. The Comp grinds are certainly a big departure from what Ford decided to do in the Cobra Jet program. There are people making over 500 RWHP on motor with the Comp stage 2 stuff, so it can't be too bad

The N/A Cobra Jet is supposed to be 12:1, so I knew the piston is a little different than the Boss piston. Well, that and the bore size is bigger on the Cobra Jet. That's a little unfortunate that you lose .020" of the margin of safety using the Boss piston.

It seems like everyone with any information is giving the green light on the Cobra jet exhaust cams though.

I don't remember the part number, but ford also grinds a cam that's 290*/11mm lift for use with GT heads that haven't had clearance added for the rocker arm (basically a "low lift" Cobra jet exhaust cam). That might be worth while if a person was worried about durability, or didn't want to do any machine work. I doubt there would be a major drop in power vs. the actual Cobra Jet cams.

 

[twistedneck]

The cams total advertised duration has little to do with the actual duration at 0.050" lift or the cam centerline. Its those two items that are more aggressive on the comp cams. Regardless of the lower lift or advertised duration.

I agree that this should be ok, but the last thing I want to do is grenade a motor. Also pulling it back apart to clay it will cost me hundreds of dollars since its already assembled...

Ford racing just needs to tell me the following.

1. Cams centerline.
2. Clearance in the cobra jet n.a. Engine.
3. Confirmation the cobra jet n.a. Engine has full 50 degrees of ti-vct or did it have limiters?

 

[hasty]

I hate to say it, but I was going to get in touch with Rob Denewith, the developer for the Cobra Jet programs and ask a few question, but found out he wasn't among the living anymore. Sad story, but I digress...


It seems like the Cobra jet has use of variable timing because the idle quality sounds pretty good. I wouldn't think they would idle as well as they do if the cams were locked in place at max high-rpm performance. At this point, everyone has indicated they would be OK (but you know how that can go lol)

I'd certainly be interested in your conclusions from your clay testing.

(By the way, Rob said that they swept the cams at various positions to determine the best cam advance/retard curves, so that would indicate to me that they definitely have the phasers operational on the Cobra jet cars)

It seemed like Ford only advised locking the cams if you were running a box that doesn't allow cam timing changes (like a current model FAST)

 

[twistedneck]

confirmed with Jesse today that the CJ N.A. engine has full 50 degrees of TiVCT. No limiters.

He also confirmed they had the same amount of clearance as the Boss, so I should be OK with 0.020" less than that. So I am going forward w/o the limiters.

 

[hasty]

Yeah, I ordered the cams and rod/piston assemblies yesterday (already have the boss crank, intake, and should have the valve springs soon)

This should be a pretty fun motor in a notchback.

Just out of curiosity, do you know where to get a shop manual or other source of information for rebuilding the 5.0 TiVct? I don't know what all the specification are for installing the head and main bolts, and I don't have instructions for installing the camshafts. (I'm sure this is pretty easy, but I've never actually worked on a DOHC Ford before)

 

[twistedneck]

That combo will make a fox seriously fast.. Did u order the CJ cams? What piston and rod? Not sure about shop manual. Grimace on allfordmustangs may know

 

[hasty]

I'm using the Boss rod/piston assembly. Stock GT/Boss intake cams and Cobra jet exhaust cams. (with boss intake, ported heads, and long tube headers)

The Cobra Jet intake camshafts are the same as stock stuff except it's 13mm lift instead of 12mm. Denewith said there wasn't a big increase in power using them, but they used them anyway because they were already on the shelf because they were originally slated to be used in the Boss 302 program.

They said the exhaust cams picked up substantial power if long tubes are used, and I'm going to have headers anyway due to the motor being installed in a fox body and the stock manifolds won't fit.

More or less I'm doing every "affordable" worth-while mod and primarily using off-the-shelf Ford parts because they are relatively cheap.

 

[twistedneck]

I'm using the Boss rod/piston assembly. Stock GT/Boss intake cams and Cobra jet exhaust cams. (with boss intake, ported heads, and long tube headers)

The Cobra Jet intake camshafts are the same as stock stuff except it's 13mm lift instead of 12mm. Denewith said there wasn't a big increase in power using them, but they used them anyway because they were already on the shelf because they were originally slated to be used in the Boss 302 program.

They said the exhaust cams picked up substantial power if long tubes are used, and I'm going to have headers anyway due to the motor being installed in a fox body and the stock manifolds won't fit.

More or less I'm doing every "affordable" worth-while mod and primarily using off-the-shelf Ford parts because they are relatively cheap.

I thought about that too.. those cams are expensive. $800 bucks for 1mm extra lift - same everything else was hard to stomach. I should have my car running and dyno tested by the time you start buiding - hopefully. Still waiting to hear back from the Ford engineers on the CJ cam duration so it can be precisely tuned. Not that it will change piston to valve clearance, but... FYI - aftermarket valves tend to be a little thicker and this was making Livernois nervous about the clearance w/ stock pistons and the CJ cams. They were 100% ok with the boss valves.

 

[hasty]

I question weather there will be substantial power gains by playing with the cam phasing a lot vs. what has been working for a GT/Boss with headers and off road exhaust.

I know this isn't necessarily true, but I'm thinking that whatever has been working with regard to the intake camshaft timing on a stock GT will remain the same. There may be some exhaust scavenging effect from using headers, but if you have full exhaust I wouldn't count on it above 6000 rpm.

The CJ exhaust cam has 27* more advertised duration. If it's ground on the same centerline, that would mean 13.5* more overlap vs. stock. There's your benefit with long tubes from the scavenging effect, and additionally, from the flow numbers I've seen on a ported head, going from 11mm to 13mm lift will increase the flow number by about 4.2%.

When you factor stock head & ex. cam vs. ported head & CJ ex. cam the percentage of CFM increase through the exhaust port is 17.2%, so there's no doubt about power being found in these mods if the exhaust system isn't a major restriction (running stock manifolds and converters)

I am going to go out on a limb and say that there will be a few horsepower to be found by some extensive testing on the camshafts, but whatever cam phasing has worked for a stock Boss or GT with headers/ off road mid-pipe will probably be acceptable unless you are looking for every last horsepower and have a lot of time to play on the dyno.

I'd assume with major reductions in exhaust backpressure your combo may tolerate slightly more spark advance than a stock setup.

 

[twistedneck]

I wonder how long these motors will go before the chain starts stretching and the phasers get closer and closer to max overlap, not to mention out of time a little. with the factory coyote chain tensioners that pump up under high rpm, that could cause the chain to stretch prematurely. too late for me I didn't get to replace the tensioners. maybe when this comes back out in a few years i'll put the tensioners in, new chains, and some of the super sweet MMR guides.. they are nice.

http://www.modularmustangracing.com/TivCT LB 1.jpg

but the key point with these cams is to not let the valve springs wear out because the cobra jet guys with the same cams upgraded the springs over the boss springs, for stability at 8200 RPM and to combat boost - not sure which or both. Livernois supplied them but i'm sure mmr has similar ones. does allowing full 50 degrees of vct help peak HP and torque? i'm not sure..

 

[Rickety]

I'm pretty much doing the exact same thing.....I plan on using a 6R80....Then a TVS once I get it running well NA, Im curious how the CJ Exhaust cams work with boost.....

I'm using the Boss rod/piston assembly. Stock GT/Boss intake cams and Cobra jet exhaust cams. (with boss intake, ported heads, and long tube headers)


More or less I'm doing every "affordable" worth-while mod and primarily using off-the-shelf Ford parts because they are relatively cheap.

 

[F8L SN8K]

I wonder how long these motors will go before the chain starts stretching and the phasers get closer and closer to max overlap, not to mention out of time a little. with the factory coyote chain tensioners that pump up under high rpm, that could cause the chain to stretch prematurely. too late for me I didn't get to replace the tensioners. maybe when this comes back out in a few years i'll put the tensioners in, new chains,.

Funny you mention that, we started to make some primary manual tensioners and hydraulic secondary chain tensioners that actually put the force on the slack side of the chain for both the 4.6/5.4/5.8s and the 5.0s. The secondary tensions both face down on the old modulars and the new 5.0s both face up on the secondary. Doing this so that one of the cams won't be retarded at high RPM.

 

[hasty]

I'm pretty much doing the exact same thing.....I plan on using a 6R80....Then a TVS once I get it running well NA, Im curious how the CJ Exhaust cams work with boost.....

I'd say they are awesome for a blower. I don't know how well they would do on a turbo car though. I'd guess that the regular boss exhaust cams would be better for a turbo if you wanted to spool quickly.

I think a tvs type blower would make some big power on a built motor, but I'd be leery about running a lot of boost with 11:1 compression. I doubt you could get away with too much on pump gas. I'd say 800 crank horsepower would be possible on pump gas considering people have made close to 600 N/A with heads/cam/etc though.

 

[twistedneck]

Funny you mention that, we started to make some primary manual tensioners and hydraulic secondary chain tensioners that actually put the force on the slack side of the chain for both the 4.6/5.4/5.8s and the 5.0s. The secondary tensions both face down on the old modulars and the new 5.0s both face up on the secondary. Doing this so that one of the cams won't be retarded at high RPM.

What do you think about the MMR tensioners? Wont they help solve the deflection issues?

If the exhaust cams get more and more retard due to a slack chain that's not quite as bad at high rpms right? isn't the ideal centerline on the exhaust of an NA pretty high? ie. 112 or more.

I know some folks on yellowbullet said they leave the exhaust cam parked to work properly with turbos. now clue why that works.

 

[twistedneck]

Quick update - I can confirm that the cams do NOT cause a piston to valve clash at least with my tune and moderate driving so far. Not saying they will never hit - as the phasers wear out or we add more overlap to the tune.. but seems ok for now.