GT350 Engine Refresh - Part 2

[ShatterPoints]

yeah, it’s pretty damn well balanced for stock suspension still Needs coil overs something fierce, though. Gets overwhelmed with big weight transfers and is a bit of a pig under initial turn-in. Hoping to stiffed things up this winter.

And it puts out ~540 to the wheels on my E85 tune

Factory is 1.3hz front and 1.5hz rear (springs) ride rate. What direction of weight transfer are you referring to? Lateral slaloms would mean a sway bar change, squat / dive would mean spring or shock change. The 350 has terminal understeer, which if you attempt to fight will throw the rest of the car off balance.

I am going to change my springs to 450lbs front and ~700lbs rear or 2.0hz front and 2.2hz rear(with a rear control arm change). The factory shock motion ratio is 0.7:1 which is pretty bad, that is how we can run 914lb rear springs and 194lb springs in the front (struts are roughly 1:1 motion ratio). My rear control arm change will INCREASE the MR to 0.77:1. (Plug** https://cortexracing.com/product/co...-adjustable-2015-2019-mustang-s550-and-gt350/ )

**Edit: I was corrected by Shogun** I misspoke when I quoted the shock motion ratio. I was going by memory and not what I wrote down. The factory shock MR is 0.7:1 and it is the factory spring MR that is 0.50:1. When the rear get swapped to the aftermarket control arm AND coilovers, the new shock AND spring MR will be 0.77:1


To keep things really short, a lower MR means the shock moves in this case 70% the distance the wheel moves. The less the shock moves the less distance and as a result less time to generate the appropriate damping forces. You have to make up for this by compensating / compromising other components and end up performing band aid after jerry rig after band aid etc.

I spoke with Cortex and they have the best customer service and knowledge base of any of the aftermarket companies I have spoken with. They also run a very similar spring rate on their GT4 car, and the shock forces I came up with are very near what they run as well. You could buy their off the shelf adjustable shocks and they will suit you plenty fine. JRI is made from former penske engineer(s) and you can request dual digressive and have the adjustments on separate circuits. Else they do a default adjuster that affects low speed Compression / Rebound and then High speed Rebound only. Which means you get some cross talk but it is a fairly standard way of doing things.

These are the shock forces I have for the custom valving cortex /jri will be doing for me(note* I have to adjust the fronts to reflect a small change in high speed forces I had to make in the rear):

Front

Rear

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[shogun32]

My rear control arm change will INCREASE the MR to 0.77:1

Except the MR of the shock IS currently 0.72'ish is it not? That the spring is 0.5 is not important.

they do a default adjuster that affects low speed Compression / Rebound and then High speed Rebound only.

uhhh, since when is there such a thing as 'high speed' Rebound? Compression, sure. The mass of the car is fixed and so it the wheel assembly. unless you're running multi-rate springs, the acceleration of the wheel assembly (or of the car) is directly proportional to the weights and spring rate and displacement. What have you calculated the max velocity to be from say a 1.5" displacement at the rear spring acting on the ~120lb wheel assembly mass?

I sure would NOT want to be in a car that had equal force curves for both compression and rebound!

Sorry OP, if I need to re-post elsewhere let me know which thread.

 

[honeybadger]

Factory is 1.3hz front and 1.5hz rear (springs) ride rate. What direction of weight transfer are you referring to? Lateral slaloms would mean a sway bar change, squat / dive would mean spring or shock change. The 350 has terminal understeer, which if you attempt to fight will throw the rest of the car off balance.

I am going to change my springs to 450lbs front and ~700lbs rear or 2.0hz front and 2.2hz rear(with a rear control arm change). The factory shock motion ratio is 0.5:1 which is pretty bad, that is how we can run 914lb rear springs and 194lb springs in the front (struts are roughly 1:1 motion ratio). My rear control arm change will INCREASE the MR to 0.77:1. (Plug** https://cortexracing.com/product/co...-adjustable-2015-2019-mustang-s550-and-gt350/ )


To keep things really short, a lower MR means the shock moves in this case 50% the distance the wheel moves. The less the shock moves the less distance and as a result less time to generate the appropriate damping forces. You have to make up for this by compensating / compromising other components and end up performing band aid after jerry rig after band aid etc.

I spoke with Cortex and they have the best customer service and knowledge base of any of the aftermarket companies I have spoken with. They also run a very similar spring rate on their GT4 car, and the shock forces I came up with are very near what they run as well. You could buy their off the shelf adjustable shocks and they will suit you plenty fine. JRI is made from former penske engineer(s) and you can request dual digressive and have the adjustments on separate circuits. Else they do a default adjuster that affects low speed Compression / Rebound and then High speed Rebound only. Which means you get some cross talk but it is a fairly standard way of doing things.

These are the shock forces I have for the custom valving cortex /jri will be doing for me(note* I have to adjust the fronts to reflect a small change in high speed forces I had to make in the rear):

Front

Rear

All directions. Dives too much under braking, squats too much under hard accelerations, and rolls AND compresses too much under lateral load. You can try increasing sway bar, but it still won't respond just right because it's under sprung and dampened. I have mine very well-balanced for how soft it is - it's just overwhelmed with all the aero. My biggest complaint is that it really struggles with quick direction changes and medium-speed turn-ins. Just all around too soft. Hopefully will get a chance to fix soon-ish.

Notice the splitter scraping

It also scrapes going into T1 a lot. If this pic was taken .5 seconds later, you'd see a puff of saw dust

Happy to keep this convo going in my personal thread or in a new one. But please keep this one related to engine builds. Trying to keep it as informational on the engine stuff as I can

 

[ShatterPoints]

Except the MR of the shock IS currently 0.72'ish is it not? That the spring is 0.5 is not important.


uhhh, since when is there such a thing as 'high speed' Rebound? Compression, sure. The mass of the car is fixed and so it the wheel assembly. unless you're running multi-rate springs, the acceleration of the wheel assembly (or of the car) is directly proportional to the weights and spring rate and displacement. What have you calculated the max velocity to be from say a 1.5" displacement at the rear spring acting on the ~120lb wheel assembly mass?

I sure would NOT want to be in a car that had equal force curves for both compression and rebound!

Sorry OP, if I need to re-post elsewhere let me know which thread.

I'll shoot you a DM

Happy to keep this convo going in my personal thread or in a new one. But please keep this one related to engine builds. Trying to keep it as information engine as I can

Understood, was not mean to de-rail.

 

[honeybadger]

Things have been moving along slowly. As seen above, all the pistons showed signs up melting due to oil burn. Tim believes that because oil burns like a torch, the oil burn is likely what melted the pistons. No signs that it was from the tune. A combination of the type of leak (consistent, through the valve stems) allowed a consistent burn. New pistons have been ordered

As far as the oil leak itself, looks like the valve stems are undersized a bit as a result of being over polished. Heads were taken to a different shop yesterday so Tim could use his buddies more power vacuum checking machine to run some additional tests. In the meantime, Tim has contacted US Seal about getting custom seals made.

 

[ShatterPoints]

Things have been moving along slowly. As seen above, all the pistons showed signs up melting due to oil burn. Tim believes that because oil burns like a torch, the oil burn is likely what melted the pistons. No signs that it was from the tune. A combination of the type of leak (consistent, through the valve stems) allowed a consistent burn. New pistons have been ordered

As far as the oil leak itself, looks like the valve stems are undersized a bit as a result of being over polished. Heads were taken to a different shop yesterday so Tim could use his buddies more power vacuum checking machine to run some additional tests. In the meantime, Tim has contacted US Seal about getting custom seals made.

Are the valves factory or did you have work done to them? Is there head work we should perform to resolve OE issues?

 

[honeybadger]

Are the valves factory or did you have work done to them? Is there head work we should perform to resolve OE issues?

Heads are a "build" from RGR that included a port/polish job and then upgraded bronze guides, valve springs, retainers, and valves. I've had quite a few issues with them. I do NOT recommend folks going this way (builder, parts are fine).

Intake valves are the upgrade Ford Performance valves (made in Germany vs. Mexico) and the Exhaust valves are the Ferrea Super Alloy. I can't say for sure how they got undersized, but they've always burnt oil...

Stock heads and valve train are fine for most stuff. When it comes to extended track abuse, better PAC racing valve springs and Ti retainers is a good idea.

 

[shogun32]

I do NOT recommend folks going this way (builder, parts are fine).
...
Exhaust valves are the Ferrea Super Alloy. I can't say for sure how they got undersized, but they've always burnt oil...

If your builder is ace then I don't see how you can conclude the (exhaust) parts are fine. Clearly they are not and never have been. Ask your builder to buy guide material and ream to size. He'll need to use collets to stay on-axis. Or find an exhaust valve supplier that knows how to center-less grind correctly.

 

[honeybadger]

If your builder is ace then I don't see how you can conclude the (exhaust) parts are fine. Clearly they are not and never have been. Ask your builder to buy guide material and ream to size. He'll need to use collets to stay on-axis. Or find an exhaust valve supplier that knows how to center-less grind correctly.

ahh, I don't think I was clear. I was referring specifically to the original BOM used for the heads. The original parts list is fine and widely used by others. I was saying I had multiple issues with RGR and don't recommend them (you can read the original engine build thread for more details there - I'm not out to bash anyone).

As far as my parts in these heads and the current situation, Tim at MPR is taking care of it as he should. I'll share the details once the plan is finalized.

 

[olaosunt]

Thanks again for your meticulous documentation

So are the intake valves sold by Ford Performance an upgrade if you have a 2016 engine /older heads ?

 

[honeybadger]

Thanks again for your meticulous documentation

So are the intake valves sold by Ford Performance an upgrade if you have a 2016 engine /older heads ?

Assuming you have the OEM valves, yes. The OEM valves are hallow where these upgraded Ford Performance valves are solid. At least that was what I was told.

 

[bauern]

Thanks again for your meticulous documentation

So are the intake valves sold by Ford Performance an upgrade if you have a 2016 engine /older heads ?

Assuming you have the OEM valves, yes. The OEM valves are hallow where these upgraded Ford Performance valves are solid. At least that was what I was told.

The FP valves made in Germany (M-6507-M52) are hollow and were the original OEM valves for the Voodoo. If you have a 2016up to whenever they changed to the Mexico supplier you have the FP valves already.

The FP350S kit ($1900) uses solid valves, pac springs and Ti retainers.

 

[olaosunt]

So are the ones made in Mexico solid ?
is that what you get if you order them from Ford parts ?
whats the advantage to having solid valves ?

 

[Strokerswild]

whats the advantage to having solid valves ?

The valve head is less likely to depart from the stem.

 

[bauern]

So are the ones made in Mexico solid ?

-They are hollow as well.

-Ford Performance (FP) (M-6507-M52) state made in Germany
Fordparts gets you made in Mexico.

-Strength.

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