25.3 vs 25.5 chassis in a Turbo Buick

Red C5

Well-Known Member
I've got my 87 GN ready for cage and chassis work. Originally I was planning on going 25.5 but am thinking about 25.3. Curious if anyone's updated to a 25.3 from 25.5? I'd like to see some pics in a turbo Buick. Also not too familiar with how much more work a 25.3 cage is so any input is welcome. Thanks.

Peter
 

Red C5

Well-Known Member
Well I guess when my car goes to the chassis shop I'll discuss the options. Hopefully will be able to get some pictures along the way to share here.

Peter
 

Squid4life

Well-Known Member
Peter, I have a ton of pics of the 25.5 car I sold, including some with the body off. Let me know if you need any special pics for comparison. I have no idea what a 25.3 would include over a 25.5 though. Probably two extra bars somewhere. ;)

Hope all is well brother! Bout time you got busy on that GN! :)
 

Dusty Bradford

Well-Known Member
25.3 is more bracing along with paralleling the frame rails from the firewall to the rear of the frame. You have to look pretty close in the bottom pic to see where the bars run parallel to the frame the length of the floor pans. The bars from the rear package tray to the tail lights is the main difference in 25.3. I went a little overboard but I didn't want any fender wrinkle after my extreme frame notch. At my power level I still have a little wrinkle even with all of these bars.











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Red C5

Well-Known Member
Peter, I have a ton of pics of the 25.5 car I sold, including some with the body off. Let me know if you need any special pics for comparison. I have no idea what a 25.3 would include over a 25.5 though. Probably two extra bars somewhere. ;)

Hope all is well brother! Bout time you got busy on that GN! :)

Yeah it's been sitting way to long. Would really like to get it back on the road/track. I'll let you know if I need anything.

Thanks for the pics Dusty!
 
25.3 is more bracing along with paralleling the frame rails from the firewall to the rear of the frame. You have to look pretty close in the bottom pic to see where the bars run parallel to the frame the length of the floor pans. The bars from the rear package tray to the tail lights is the main difference in 25.3. I went a little overboard but I didn't want any fender wrinkle after my extreme frame notch. At my power level I still have a little wrinkle even with all of these bars.











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How fast that car runs, with the amount of stock stuff I see in the pictures is down right unbelievable , do you have any more pics of the cage?
 

Chuck Leeper

8/10's of a century!
Staff member
At 1 time, I was considering such work to be done w/ my LS car...During that investigation, I saw the "G box", that David Lemonds sells. It's a replacement for the rear x member. A NICE piece! Provides "stock location" for the suspension.
If you look at Dusty's car, you will see what I'm talking about.
 
At 1 time, I was considering such work to be done w/ my LS car...During that investigation, I saw the "G box", that David Lemonds sells. It's a replacement for the rear x member. A NICE piece! Provides "stock location" for the suspension.
If you look at Dusty's car, you will see what I'm talking about.

How much improvement did you notice over a stock susp?
 

turbobuick

Well-Known Member
Bringing this back from the dead since I cant seem to stay away from building Buick racecars!

Dusty I see you ran a bar from #1 crossmember to the bottom of the frame x-member which looks like an aftermarket one like a Merilatt? How did you tie that bar which would be the 2B bar to the rear of the chassis and can it be interrupted by the frame crossmember?

Here is a pic of the rear inner rail the chassis inspector made us add in the 25.3 car I built then Tommy finished and raced and now sold to James. We did not need this rail for 25.5 but did for 25.3 and the SFI books say NOTHING about this bar or how it needs to be attached.
 

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SCOOBY DOO

I'M NOT A MONSTER, I'M JUST AHEAD OF THE CURVE!!!
Dusty doesn't post here anymore. I assume he still works at PTC. Might try him there.
 

turbobuick

Well-Known Member
Thx I'll txt him and see if I can't get him to respond. I have same thread going on YB.com with little response, also called two NHRA chassis inspectors who are to busy to get back to me.
 

turbobuick

Well-Known Member
SW NHRA tech inspector and got a lot of very useful info. I posted it on YB

Any on 25.5 or 25.3 the factory rear frame rail can serve as the 2B bars as long as you dont take the frame notch to deep and leave enough frame there. If you go to deep you will need a second frame rail. If running a second frame rail he also said he would accept the 2B inner frame rail running from #1 to the bottom of the Merilllat x-member and from top of merillat back. Even though the bottom bar on Merillat x-member is 1.25 and top is 1.5
 
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