C3-71 LT1 suspension questions

[Peter M.]

Am under impression that the 71 LT1 came with a heavier duty suspension that base 350. Specifically that the shocks were heavy duty but what else I do not know.
Does anyone know what the specs would be for front and rear and where you get these parts today?

Thanks

[Duke W.]

Re: C3-71 LT1 suspension questions

I'm not aware of any suspension changes for the LT-1, but if you have a '71 AIM the LT-1 option section will call out any parts that are different from standard production anywhere on the vehicle.

No optional suspensions are shown for '71, but the ZR-1 package included HD springs, front bar, and shocks from the earlier SB HD suspension parts bin.

Duke

[Joe L.]

Re: C3-71 LT1 suspension questions

Peter and Duke-----

Duke's absolutely correct; for 1971, LT-1s had exactly the same suspension as every other small block Corvette (i.e. base engine Corvettes since no other small blocks were offered that year). This included front springs, rear spring, front stabilizer bar (no rear bar was used on small blocks until 1975's Z-07 option), and shocks. No HD shocks were available on 71 Corvettes as a stand-alone option.

If you got one of the handful of ZR-1 optioned cars for 1971, then F-41 HD suspension was part of the package, including heavy duty front springs, HD 7 leaf rear spring, larger diameter front stabilizer bar, HD shocks, and HD lower rear shock mounts.

[Chas Kingston]

[Terry M.]

Re: C3-71 LT1 suspension questions *TL*

Geezer,
Someone changed it before you got it. The 1970 LT1 suspensions were the same as standard suspension.
Deep in the AMA specs for all three years there is a mention of LT1s receiving HD rear suspension components. I have yet to figure out what they are referring to. The LT1s I have had a chance to look at, and there has been lots of them, show no signs of any heavy duty suspension components - unless they are also ZR1s, in which case they have the F41, but no rear sway bar from the factory, ever.

[Duke W.]

Re: C3-71 LT1 suspension questions

Here I go being picky, again. The ZR-1 package included the HD suspension components that were included in the '63 Z-06 and '64-'65 F-40 package for small blocks.

F-41 was the HD package for BBs and includes the F-40 components, plus the rear anti roll bar that was base on all BBs. Technically F-40 and F-41 substituted the same components on either SB or BB, but in the case of the BB the 9/16" rear base was part of the base BB suspension and remained when F-41 was specified.

Duke

[Joe L.]

Re: C3-71 LT1 suspension questions

Duke-----

I don't think so. F-40 was the RPO nomenclature used for the HD suspension package for 1963 (Z-06 only) and 1964. In 1965 the nomenclature was changed to F-41, but included the same components as F-40. For 1965, if not for later years, F-41 was available with small block engines. NO rear sway bar was included for small blocks.

The rear sway bar was always part of the big block engine option package and was never part of an F-40 or F-41 package. However, a rear sway bar was part of the FE-7 HD suspension package starting with the 1975 model year and continuing through the 1982 model year. FE-7 was also available for the 1974 model year, but it didn't include the rear sway bar. You did get a rear sway bar in 1974 if you also ordered the LS-4 engine, with or without FE-7.

[Joe L.]

Re: C3-71 LT1 suspension questions

Terry-----

As authoritative as they may seem and appear, I have found the AMA Specifications to be sometimes inaccurate. The inaccuracies only affect about 0.5% of what's there, but I would expect the rate to be very close to, if not exactly, 0%.

The most glaring inaccuracy that I have found is the AMA Specs that indicate that 68-69 Corvettes with automatic transmission used no AIR system but, instead, used the CCS emissions control system. This is TOTALLY incorrect. I don't think that a single 68 or 69 Corvette was built without AIR.

There are several other inaccuracies that I've found in the AMA specs and there may well be many more that I am not knowledgeable enough to discern.

[Duke W.]

Re: C3-71 LT1 suspension questions

Joe -

The NCRS Spec Guide lists F-40 HD Suspension as an option for '64 and '65. I consists of the unbundled HD suspension parts from '63 Z-06. It was only available on SBs, not with L-78, which had it's own street tuned, spring, bar, and shock package.

Beginning in '66 F-41 was only available with L-72. The former Z-06/F-40 parts were substitued for the standard BB suspension parts, and the 9/16" rear bar that was included with base BB suspensions remained.

I figure it was renamed F-41 from F-40 to distiguish that it was only available on SHP BBs and was no longer available with SBs even though the substituted parts - springs, front bar, shocks, and rear lower shock mount were identical to the previous F-40, The fact that these HD suspension parts were no longer available on SBs was a reflection of Chevrolet's new emphasis on the BB for racing.

Volume 9 No. 4 Corvette News has an article on all the HD options - M-22, F-41, J-56, and N-03. I've extracted the following quotes.

"...F-41 for Turbo-Jet V8s only." (This statement may not be completely accurate as I don't believe that F-41 was available with the L-36 390 HP 427"

"Owners of 1966 models with 327-cubic-inch Turbo-Fire V8s competing in BP may improve handling by ordering heavy-duty suspension components previously released for 327-cubic-inch V8s." (Of course, the parts list that one would need to order are the same as the parts substituted for regular production parts when F-41 was ordered.)

Duke

Duke

[Joe L.]

Re: C3-71 LT1 suspension questions

Duke----

Yes, I was incorrect on F-40 ending with the 1964 model year; it did continue through 1965. The change to F-41 may well have been a reflection of the revised applicability of the HD suspension package. However, the rear bar was never part of any suspension package until 1975's FE-7.

[Duke W.]

Re: C3-71 LT1 suspension questions

The interesting part is that the exact same substitute pieces (the bill of materials) made up the F-40 SB package and the F-41 BB package, so why wouldn't they have continued to offer the HD suspension package on SBs either as F-40 or F-41?

From a production standpoint the same parts were substituted for regular production parts with either engine type. The only difference in the final outcome was a 9/16" rear bar on the BB because it was part of the base suspension, and F-41 did not substitute another. Likewise, the base SB suspension did not have a rear bar and the HD package did not add one.

My guess is that they just wanted to emphasize the BB as the ultimate racing Corvette, so they decided not to offer the HD components with SBs even though it would have been a no-brainer to do so. That, and maybe the fact that after '65 there was no mechanical lifter SHP or FI small block until the LT-1 in '70. The ZR-1 package in '70 signaled that Chevrolet again wanted to offer an engine and supsension package that was plant-ready for B-production.

Duke

[Tom R.]

Re: C3-71 LT1 suspension questions

I may have missed something here but believe in regards to C3 LT1 suspension...you both said and agree on the same points.

[Duke W.]

Re: C3-71 LT1 suspension questions

Yes I believe we agreed that the '70 LT-1 did not have a "special" suspension. Springs, shocks, and front anti-roll bar were the same as the base 350/300.

We got off on a tangent about F-40 and F-41.

Duke

[Terry M.]

I agree. *NM* *TL*

[Tom R.]

Re: C3-71 LT1 suspension questions

And you did get off:) And these are healthy debates...helps to retain our convictions without the necessity of making cerebral adjustments to that knowledge base!