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The front end of my '65 327 A/C car is significantly lower than the rear (~2") , but I don't believe that was the case on other factory A/C cars. The A/C car has new original springs on the front. I know that there's extra weight on the front of the A/C car, but is it enough to make a 2" difference in wheel well height? The rear on the A/c car is about the same height as my FI car. Was there a special spring on the factory A/C car?
Doesn’t look it, but the rear of the red car is the same height as the entire black one. It’s tough to find lower springs for the rear of one of these. Higher, easy, lower, not so much.
Is the A/C supposed to have different springs on front than the other?
Check your AIM, UPC 3 sheet A6 for front height grade-to-sill molding. (For a '66 w/C60 option only, it's (minus) - 0.56"
Check your AIM, UPC 4 sheet B5 for rear height grade- to-sill molding. (For a '66 w/C60 option only, it's (minus) - 0.24"
IIRC, the same front spring (3851100) was used all '65 327's w/standard suspension, with or without C60.
The front end of my '65 327 A/C car is significantly lower than the rear (~2") , but I don't believe that was the case on other factory A/C cars. The A/C car has new original springs on the front. I know that there's extra weight on the front of the A/C car, but is it enough to make a 2" difference in wheel well height? The rear on the A/c car is about the same height as my FI car. Was there a special spring on the factory A/C car?
Mike
Get the corvette central rear adjustable spring mount kit , part num 582059 take it up or down all you want.
Last edited by torinodude59; Jun 15, 2026 at 02:54 PM.
the same front spring (3851100) was used all '65 327's w/standard suspension, with or without C60.
This is correct. Last year I replaced the front springs in my 66 L79/C60 and used springs from Coil Spring Specialties - their 3851100 copy. After installation and a drive around the block, the front settled right on the AIM specs.
I like them lower, but it’s not for everyone, I know.
Below is with MOOG small block, stock height springs, with 1/2 coil cut off and 8” rear spring bolts.
Heights vary significantly with spring brands, so you might be happy with those, being nearly 2 inches higher, before I cut them.
They’re also significantly shorter, which makes installing them a piece of cake, plus they ride nice, with Gabriel gas shocks.
This one had unknown front springs, that were an inch or so higher when I bought it, but a year later, this ! So longer 8” rear bolts evened it out. Both cars measured around 24.5 inches from floor to centre of the fender, with 205-70s
The big block cars had different springs for AC cars so I would expect the SB cars did too. The AIM had a chart showing the different springs from memory. Here is the height chart for the front. The spring selection chart was on another page I believe.
The big block cars had different springs for AC cars so I would expect the SB cars did too. The AIM had a chart showing the different springs from memory. Here is the height chart for the front. The spring selection chart was on another page I believe.
The big block with C60 was spring PN 3888251 per my 1967 AIM UPC 3 sheet A4.
The standard spring was 3851100
The F40 spring is 3832518
and the L36 spring w/o AC is 3888250 (or 3888256, my AIM is hard to read)
The SB spring was the same AC or not. you can see the effect of the AC weight in the chart you posted, the front end "Z" dimension drops around 3/4" from a non AC car.
I remember going through this with Coil Spring Specialites as they first sent me the BB with AC springs for my L79 with C60 and the car sat way too high. Doing our research we realized that the L79 with C60 used the standard spring. They sent me a pair of them and the car sits pretty much spot on. I'll have to go back and check my notes but I'm pretty sure this was the outcome.
My '65 was restored 36 years ago to NCRS standards. AC car, 327/300, four speed. Just had it at the AACA Southeast Nationals meet last weekend....going for a Repeat Preservation award.
Per the AIM, as near as I can tell, my black FI car is level at ~8.50" (within the 8.17/9.17 tolerances specified in the AIM for an L79).
The A/C car on the other hand, should be lower, in the range 7.14 / 8.14. The front of the rocker of the A/C car is in fact at 6.94 (outside the tolerance of 7.14/8.14) , but the rear is way up at 9.00 on the drivers side and 9.25 on the passengers side. Both are well over the the 8.14 max in the rear.
It would appear that I DO need to lower the rear. This is too much adjustment to merely adjust the nut down and eliminate the cotter pin by using a prevailing torque nut. A rear spring lowering kit should do so with minimal effort.
My guess is that the front may come up slightly when the rear drops. We'll see.
The big block with C60 was spring PN 3888251 per my 1967 AIM UPC 3 sheet A4.
The standard spring was 3851100
The F40 spring is 3832518
and the L36 spring w/o AC is 3888250 (or 3888256, my AIM is hard to read)Tom
Notice below that all '66s with A/C used the same replacement spring as the '66 & '67 427s with A/C. Not sure why '65 wouldn't/couldn't use the same heavier spring.
Last edited by barkingrats; Yesterday at 10:42 AM.
Per the AIM, as near as I can tell, my black FI car is level at ~8.50" (within the 8.17/9.17 tolerances specified in the AIM for an L79).
The A/C car on the other hand, should be lower, in the range 7.14 / 8.14. The front of the rocker of the A/C car is in fact at 6.94 (outside the tolerance of 7.14/8.14) , but the rear is way up at 9.00 on the drivers side and 9.25 on the passengers side. Both are well over the the 8.14 max in the rear.
It would appear that I DO need to lower the rear. This is too much adjustment to merely adjust the nut down and eliminate the cotter pin by using a prevailing torque nut. A rear spring lowering kit should do so with minimal effort.
My guess is that the front may come up slightly when the rear drops. We'll see.
Thanks,
Mike
i
Ive never made sense of the rocker panel heights in those GM charts ( dim J). If your suspension measures within the chart tolerances it won’t be close to the “J” dimension usually.
It would appear that I DO need to lower the rear. This is too much adjustment to merely adjust the nut down and eliminate the cotter pin by using a prevailing torque nut. A rear spring lowering kit should do so with minimal effort.
My guess is that the front may come up slightly when the rear drops. We'll see.
I doubt the front will rise noticeably if you lower the back.
I have a set of longer, stock looking rear bolts, with castle nuts, that take cotter pins, so they are or were available.
Per the AIM, as near as I can tell, my black FI car is level at ~8.50" (within the 8.17/9.17 tolerances specified in the AIM for an L79).
The A/C car on the other hand, should be lower, in the range 7.14 / 8.14. The front of the rocker of the A/C car is in fact at 6.94 (outside the tolerance of 7.14/8.14) , but the rear is way up at 9.00 on the drivers side and 9.25 on the passengers side. Both are well over the the 8.14 max in the rear.
It would appear that I DO need to lower the rear. This is too much adjustment to merely adjust the nut down and eliminate the cotter pin by using a prevailing torque nut. A rear spring lowering kit should do so with minimal effort.
My guess is that the front may come up slightly when the rear drops. We'll see.
Thanks,
Mike
Rear will be high is you installed new/rebuilt training arms, new rear spring cushions, or did other rear suspension work and tightened all the locking hardware without the car being on its wheels and rear spring compressed to specification ride height (by adding weight to rear before tightening bolts). Once bolts are tightened, things want to hold that set. You can loosen all the bolts/nuts and start over again..........or try to fix by modifying factory hardware (not recommended). Your choice.
Per the AIM, as near as I can tell, my black FI car is level at ~8.50" (within the 8.17/9.17 tolerances specified in the AIM for an L79).
The A/C car on the other hand, should be lower, in the range 7.14 / 8.14. The front of the rocker of the A/C car is in fact at 6.94 (outside the tolerance of 7.14/8.14) , but the rear is way up at 9.00 on the drivers side and 9.25 on the passengers side. Both are well over the the 8.14 max in the rear.
It would appear that I DO need to lower the rear. This is too much adjustment to merely adjust the nut down and eliminate the cotter pin by using a prevailing torque nut. A rear spring lowering kit should do so with minimal effort.
My guess is that the front may come up slightly when the rear drops. We'll see.
Thanks,
Mike
Rear will be high is you installed new/rebuilt training arms, new rear spring cushions, or did other rear suspension work and tightened all the locking hardware without the car being on its wheels and rear spring compressed to specification ride height (by adding weight to rear before tightening bolts). Once bolts are tightened, things want to hold that set. You can loosen all the bolts/nuts and start over again..........or try to fix by modifying factory hardware (not recommended). Your choice.
If the rear spring was replaced with non-OEM than you may or may not be able to get factory ride height.
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'65 body height with air conditioning
