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Building a Gr4 replica

push1267push1267Member
Finished. Total weight saving is 7,5 kg (16,5 Pounds) - 6 kg from the skin alone.

The skin has a slight curveture to it both directions, but it wraps very nicely round the stiffer inner frame without having to use an english Wheel.

The lid fit the car very nicely. I need to take Pictures of the lid fitted to the car tomorrow.

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push1267push1267Member
quote:
Will the hose from the dry sump oil pump go into the cockpit? Or is that temporary...

I think that's what the braided hose with the thermo-covering on it is...


That's temporary - the lines are just joined to seal the oil system. There will be a u-turn fitting with the return line to the dry-sump tank.
Btw - it's a RoushYates 358 D3.
Last edited by push1267
push1267push1267Member
The internals of the motor are all RoushYates spec. It was sold of their nascar program a few years ago when they went from the D3 engines to the newer FR9 engines. This one has done one race since last refresh (400 miles)

It's a nationwide spec. roller engine, compared to the Flat tappet Cup motors. A little less power and torque, around 800 HP and 530-550 Ft-lbs, compared to the Cup motors around 850-870 HP - still (a lot) more than my skills can handle.

I will need to detune a little (I think), probably a less aggressive cam to lower max rpm to around 8000 and maybe thicker headgaskets to lower compression to under the current 12.1.

The block is a 9" deck R451 dry sump with a Bryant crank (3.260 stroke), Plankl rods and Mahle pistons (4.15 bore). Heads are Yates D3s with titanium valves, retainers and locks and jesel valvetrain. Carburator is a Holley 830 nascar.

I'll be taking my chances with the ZF, after all, aren't they supposed to be able to handle 550 Ft-lbs ?? Eeker
Last edited by push1267
bosswrenchbosswrenchMember
ZF strength will be the least of your problems unless you decide to contest one of the Vintage endurance racing series in Europe. On most public roads, you simply cannot use that much power for more than 5 or so seconds, so the combination will have a much longer life than in competition. More pressing may be the flexing you'll experience from the rear of the chassis. Seam-welding the whole car from the firewall back plus some sort of chassis stiffening system will help. As you probably already know, the stock upper bay-brace is useless, as are the aluminum aftermarket bars. You'll have fun sorting out what you need in shocks, anti-sway bar sizes and tires/brakes. FWIW, with a slightly too-big cam and aluminum heads at 10-!/2:1 or slightly higher, you can probably use the highest possible pump gas without needing an octane-additive. Keep us posted on your progress in taming the beast!
push1267push1267Member
quote:
You can't run in Europe vintage racing series with that engine ... It's not FIA legal


Maybe if I paint it blue they won't notice !! Cool

Yes, I know it's not legal - my intention is to use it for the Danish Hillclimp series in the open class and maybe some invitational events where they have very relaxed ruling.

I'll need yet another engine if I'll do the historic races Embarrassed .
push1267push1267Member
OK, I'm trying to get back into this project and find the time and motivation to carry on. So, here's a few updates I did sometime ago:

The factory gr4 cars had aluminum skins on the headlightbuckets, so I thought I would wan't that too :-). From an old rusty set of buckets, I made this set of lightweight headlight buckets with aluminum skin and all excess metal cut off.

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push1267push1267Member
Again, as the factory cars ran quicker ratio steering (2.4) I wanted to add that to the car.
Thus, we did the "goodroc" quickrack steering rack conversion using a new Ford Escort MK1/Mk2 Heavy Duty short stem 2.4 ratio rack from Burton Power in the UK.

As described in Goodroc's thread, this conversion requires a little machining of the housing. Will be interesting to experiment with the position of the rack to evaluate the effect on bumpsteer.

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kidkidMember
quote:
Originally posted by Push1267:
Well, I suppose I was motivated enough to invest quite substantially in a set of high-end Intrax race coilovers specifically set-up for my car and it's expected use !


Great choice! The one thing I did different, was to have them set up in colors to my taste, as flashy colors do not fit a 71 car imo ;-)

push1267push1267Member
quote:
impressive that you can fit 8-piston calipers inside the 15" wheel.


The calipers were originally designed as F1 calipers in the early seventies, so they are designed to fit inside 13" wheels (I think that is what is used in F1?). Detomaso at some point in 1974-75 decided that they would homologate them for the Pantera.

Kid, you're right about the color of the coilovers, I should have thought about that !! :-). Red goes with the exterior of the car !!. What version of the intrax shocks are you using?

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Last edited by push1267
kidkidMember
quote:
Originally posted by Push1267:
Kid, you're right about the color of the coilovers, I should have thought about that !! :-). Red goes with the exterior of the car !!. What version of the intrax shocks are you using?


1K2 with titan coating. Back then I just asked whether a black/grey finish was possible, which was, and as far as I can remember, at no extra cost (my invoice doesn't mention it as an extra neither). :-)
push1267push1267Member
The block is a Ford racing R451 dry sump block and is highly modified by RoushYates. Note that the block appears to have been polished/machined on all inner surfaces.

The lifter bores have offset bronzebushings and a cam tunnel is installed around the cam.

Not shown is the oil scavenge system that pull oil from the lifter valley via the dry sump pump

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push1267push1267Member
I talked to RoushYates (actually through SRI Performance which distributes Roush Yates parts) and they send me a 40 page file of the history of the engine. Last rebuild in 2010 before it was sold of. Hasn't been run since.

They included the dynorun after last fresh-up Eeker Eeker

Thinking about limiting the revs to 7000 ... Cool

Not entirely convinced that this is of my engine, as the roller motors usually does not rev beyond 9000 but parts in the engine does match the buildsheets

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joulesjoules"Racing is Life, anything before or after is just waiting" - Steve McQueen
What is Rousch recommended refresh/rebuild interval on the engine? I bet in NASCAR they tear them down after every weekend!

A lower rev limit would be wise to get longevity, but where is the cam happy for vintage racing?

If I drop my race engine shifts by 1000 rpm to 9500 I get maybe another 250 miles between rebuilds....
push1267push1267Member
quote:
What is Rousch recommended refresh/rebuild interval on the engine? I bet in NASCAR they tear them down after every weekend!

A lower rev limit would be wise to get longevity, but where is the cam happy for vintage racing?

If I drop my race engine shifts by 1000 rpm to 9500 I get maybe another 250 miles between rebuilds....



Yes, Roush takes them apart every race and freshen them up - typically 400-500 miles. The files for this motor shows very detailed monitoring of each component with miles and last replacement. It's not clear how many miles they put on all parts, but some are replaced every race.

With the kind of racing I intend to do, I would expect a much longer service life. I may restrict it to 7500-8000 rpm, so it will not run anywhere near it's potential.

That was my initial thought about purchasing this engine, an engine with high quality parts that I can run below it's full potential with good durability. The 351C is just more fragile, and I'll only consider that if I wan't to run the FIA sanctioned races.

Regarding the cam, I ordered a cam degree kit, to help determine duration and lift. The files show a 325C cam (duration maybe), with lift around .825 in/ex.

I am considering increasing head gasket thickness (Cometic gaskets come in many thickness and are reusable), and reducing lift/duration by changing rockers arms. This engine run a 2.1:1 rocker arm ratio, and by changing that to maybe 1.9:1, lift is reduced by around 10% and duration profile is lowered too (by how much I'm not sure). Rocker arms are available used/new from Yates, at reasonable prices.

I cannot lower rpm too much as the D3 heads are ported for high rpm, - they flow around 420 cfm on the intakes.
There's an interesting article about them at D3 heads

/Kristian
T tomsealbeachMember
Wow, wow, wow....it's been a while since I looked at your project and not sure where to start...but suffice to say your dedication to this project is incredible. There are so many nice parts and great craftsmanship going into your build....not sure which gets more drool....the chassis work, the motor, the hubs/brake hats/disc rotors, the brake calipers, the shocks, the motor, the valve train components, the motor crank & rods. Holy smoke, just fantastic! Your build is what so many of us just dream about at night!
push1267push1267Member

Very long time since I updated this thread. Not much work going on sadly.

However, I thought it would be cool to do some historic graphics on the car. So here's what we came up with. Not all done and still need to change the Pantera script a little, it's too fat, but otherwise pretty close.

Replicating the Dubois car #2860 in it's 1972 Spa-Francorchamps livery.

Period correct yes, polically correct, not so much :-). 

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IMG_2604

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Last edited by George P
push1267push1267Member

OK, loooong time since some updates on this project.

After deciding to run the Gr4 car in the Danish Hillclimp series, and getting confirmation that it is in fact possible to classify the car in the Competition (B) Class for modified cars, I seem to have found some motivation to try and move the project along.

We did go through the engine - just to make sure everything is fine. So everything was inspected cleaned and found fine and put back together.

We replaced the main and rods bearings (some trick Elliot Coated parts from Yates), Cometic gaskets and vacuum seals and the crank was polished (just as a precaution). But everything were looking good.

Also had Scott at Eatmon Race Engines design a new cam for it, that moves the powerband somewhat down - i.e. with a max power around 8300 rpm but with a  stronger more usable midrange. Still a pretty aggressive cam with a duration of 266/270 at .050. Power is reduced to around 750 hp.

The RYRE D3 heads had the titanium valves replaced,  installed new PSI valve spings to match the cam and was vacuum tested.

Just need to degree the cam (the cam has 102/103 centerline) and the engine is all ready.

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push1267push1267Member

Thanks for all the comments - to Simon, the belt drive on the engine is a Roush Yates.

Here's a little bit of an update on the project - it's been going a little slow but I did finish most of the modifications to the front-end of the car. Remember the car is being build to replicate the early gr4 Panteras (from pictures), as they looked when they first hit the track i the spring of 1972.

Here's the front - the huge oilcooler, brake ducts w/scoops cut into the front, modified grill (yes, I cut up a perfectly fine early chrome grill to copy the gr4 look - awesome !!!:-) ), aluminum headlight buckets incl manuel raising mechanism, aluminum hood and just finished copying the blade spoiler in aluminum (need paint).

Pretty time consuming work

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Last edited by push1267
joulesjoules"Racing is Life, anything before or after is just waiting" - Steve McQueen

Fantastic work as always, many of the current crop of Group 4 race cars seem to have acquired the later GT5 style air dam. What brand tires do you have? I would be interested to see the headlight mechanism. Will you be  replicating the adjustable sway bars as well?

Last edited by joules
push1267push1267Member

Yes, the Gt5 airdam is probably much more effective than the simple blade spoiler - but that's not the point in this build :-).

The wheels are the Marvic Gr4 magnesium reproductions , 10X15 front and 14X15 rear. The tires are Avon all weather historic race tires, 10.5/23.0-15 and 14.0/27.0-15, that was what I was recommended to use by Patrick Hals.

For the raising of the buckets, I keept the the original gear, and removed the motor and did some trimming of the brackets (had to because of the radiator). So I can raise the buckets manually with the emergency knop. The whole set-up is removable including the aluminum bar. I only have this older not so good picture - I have made some smaller trimming and changes to the set-up since then.

I intend to have the original adjustable Gr4 sway bars fabricated. I do have the drawings and measurements of them, including the modifications that were done to the a-arms and the chassis - the center mounts were moved outwards in the rear.

I would need to find a company that can build the sway bars though - any leads? Julian, if you are interested in a set for your car too, maybe we can figure something out.

Kristian

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Last edited by push1267
timsterentimsterenMember

Hi Boss,

are you sure that it was a Holley 4778 that was specified in the supplementary parts list for GR3 and GR4? I think it only says List 213, which doesn't seem to correspond to anything, and everything I have seen posted seems to suggest great confusion about what the mysterious Holley 213 carb is. I speculate it is a date code and someone messed up when writing down the Holley model number and put the date code instead.

Cheers Tim

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