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Discussion Starter · #1 ·
Someone that has Corvette C4 front suspension, 1984-87.

Can someone please supply me with the location of the center location on the C4 member to locate the spindle center to the frame?
 

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Someone that has Corvette C4 front suspension, 1984-87.

Can someone please supply me with the location of the center location on the C4 member to locate the spindle center to the frame?
Are you looking to set the wheel base or centering the cradle side to side? If side to side the first thing you have to do (if you haven't already) is set up a center of the chassis string from front to rear of the chassis if possible. From the centerline you can then reference the lower control arm bolt holes in your cradle to both center it side to side and to make sure they are parallel to the center of the chassis. I set a 5 ft straight edge across my jig and use a square to set it 90 degrees to the centerline string. From there I measure to the face of the rear lower A frame mount on each side to square it and then simply center the lower A frame holes to the chassis center. I do all of this with the A frames removed and all thread rods inserted all the way through the lower control arm holes.I have fabbed a jig cradle to actually hold it. Maybe I answered your question. If this isn't the info your looking for let me know and I'll try again. It's not too difficult just time consuming!
 

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Discussion Starter · #3 ·
Thanks for the advice. I will definitely do that. I have build a jig to hold the frame but I have a position of the spindle center from the gauge hole on the frame front to back to the stock setup but I can not see where the spindle center is on the C4 frame assembly to reference to this position after I remove the front of the frame.
 

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Thanks for the advice. I will definitely do that. I have build a jig to hold the frame but I have a position of the spindle center from the gauge hole on the frame front to back to the stock setup but I can not see where the spindle center is on the C4 frame assembly to reference to this position after I remove the front of the frame.
I have scribed lines on my frame jig on either side as a reference of the spindle center or wheel base. To set the C4 cradle when I was building my jig I left the A arms and hubs on it using the straight edge I mentioned before,across the hub face at ride height I measured back to chassis center from each side of hub to get wheels turned straight and then used a plumb bob from the center of the hub down to my scribed line and adjusted as needed. You can do it this way as long as your c4 clip hasn't had the alignment shims removed from the upper a frames. If it has your caster being off would impact then your axle center.
 

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Discussion Starter · #5 ·
OK I see what you are saying but I my be missing this. How do I align the cradle to be in the center to the wheel opening front to back? I must be just missing this.
 

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OK I see what you are saying but I my be missing this. How do I align the cradle to be in the center to the wheel opening front to back? I must be just missing this.
I made the scribed marks on my jig using the same method I described for the c4 with my original front end still on my chassis. I think you might be able to calculate that dimension from the datum holes in the chassis though. Check out the drawing library here on this site. If you can't figure it out let me know and I'll try to help you.
 

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If you build your jig with the original suspension in place, you can just locate the wheelbase before cutting off the old IFS, and put the C4 hubs in the same place. You don't want to strip the cradle before setting it.
I can't find one right now, but there are C4 IFS jig build pictures around the internet, with the location of the firewall body mounts, front hubs, and core support being key reference points.
Depending on which C4 you have, the width will be different from original, but wheelbase will be the same.
Do you already have the jig in place with no original IFS to refer to?

The other spec that's up in the air, so to speak, is the height location of the cradle to determine your chosen ride height, and the rotational angle of the cradle to determine the caster.
 

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If you build your jig with the original suspension in place, you can just locate the wheelbase before cutting off the old IFS, and put the C4 hubs in the same place. You don't want to strip the cradle before setting it.
I can't find one right now, but there are C4 IFS jig build pictures around the internet, with the location of the firewall body mounts, front hubs, and core support being key reference points.
Depending on which C4 you have, the width will be different from original, but wheelbase will be the same.
Do you already have the jig in place with no original IFS to refer to?

The other spec that's up in the air, so to speak, is the height location of the cradle to determine your chosen ride height, and the rotational angle of the cradle to determine the caster.
I agree, I spent a ton of time deciding what tire size I would run and then my desired stance for the car. I went to a ton of cars shows and with the owners permission rolled under their car with a tape measure and measured frame heights front and rear to the ground to understand how high I wanted my car to sit and the front to rear rake. Once you have those three items set the front and rear heights can be fairly easily calculated for their location.The lower A frames on a C4 should be level front to rear and level from the mounting bolts outward through the center of the ball joint at ride height. Once you get all that figured out. I would recommend mocking all your front clip pieces in poster board or cardboard to figure out all your best angles at your tube intersections. If you can draw it in CAD it can save you a lot of time trying to work them out for your tube size.
 

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Discussion Starter · #9 ·
I have the Frame sitting on the jig with the front of the frame still on. I made a plate mount with the core support cradle position and plates with the three holes giving me the bolt hole locations for the bumper mount on both sides. I still need to make a center line of the frame. I did look at the other setups with the C4 setup and notice that the front frame pieces look very similar to each other. Are their drawings or information about pieces? I was trying to see if their could be marks or holes on the cradle that give me the center so that I could us this to align to the marks from the stock wheelbase.
 

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I have the Frame sitting on the jig with the front of the frame still on. I made a plate mount with the core support cradle position and plates with the three holes giving me the bolt hole locations for the bumper mount on both sides. I still need to make a center line of the frame. I did look at the other setups with the C4 setup and notice that the front frame pieces look very similar to each other. Are their drawings or information about pieces? I was trying to see if their could be marks or holes on the cradle that give me the center so that I could us this to align to the marks from the stock wheelbase.
I really never needed to mark the center of the cradle, I just measured or referenced the lower A frame bolts to the centerline. I did make plates on my jig to bolt the front spindles to at ride height but only used them to make the jig for the cradle. I set them at ride height based on tire size and desired frame height and from the center of the chassis and at my front axle centerline (wheel base). My cradle is an 85 model and if I remember right its 59" hub to hub. Once I did that I set up my cradle jig to pick up the lower A frame bolts front and rear and the face of the rear lower a frame where the bolt comes through. Once you do that you can take your A frames off and work from your cradle jig.
 

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Discussion Starter · #11 ·
Thanks I will work with that and build the rest of the jig with that in mind. Looking at the lower arms on the C4 did you use the level from the upper part of the lower arms or the ball joint face on the bottom? Sorry about all the questions.
 

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Thanks I will work with that and build the rest of the jig with that in mind. Looking at the lower arms on the C4 did you use the level from the upper part of the lower arms or the ball joint face on the bottom? Sorry about all the questions.
No problem on the questions. Ive had a lot of help from here so I'm glad to payback when I can.Theres actually no real good way to do that as your going from the pivot point of the A arm at the bolt to the actual centerline of the ball joint.I judged that as best I could with a two foot level And took a measurement from the jig up to the A frame bolts. Remember my hubs were jigged at ride height so I was then setting cradle height by adjusting my cradle jig height to level the A frames. You have to be conscience of where your new tubing will intersect with both the cradle and your splice point of your new tube to the original frame. Again poster board or cardboard templates are your best friend. I'd mock it all the way from your targeted splice point to the front bumper mounts. Watch the drop down portion closely if you plan to use your stock sway bar and mount it to it.
 
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