R5335

Mark, I hadn't seen anything on this since you last wrote on 11/10/24. So I too have just run into this issue. I'm hoping you found an answer. My story is similar. The original dual master cylinder was leaking and some fluid was getting into the booster. So I replaced the master cylinder. However, my mistake, I extended the booster push rod to what the manual said to 1.25 inches. Didn't take long to burn up the calipers. So replaced the calipers, had the rotors turned. Reset the push rod from the booster to match the new master cylinder, in my case 1" (actually 31/32). Then off I went and for a few rides ok. Shortly thereafter, pedal was very hard to push and brake the car. OK, videos and discussions with folks says it's a bad booster. So, sent that off to have it rebuilt. Report back was yes brake fluid got in and diaphragm was cracked and the wrong check valve. So, finally got that back. Put it all together, bench bled master cylinder, bleed the system 3 times. Now when the engine is off, brakes are hard to push as would be expected. However, like you, now when I turn the engine on, brake pedal goes to the floor! On top of that, the engine stumbles, loses some vacuum, about 5" Hg. Bleed brakes again, no change. Talking to the fellow who rebuilt the booster says it's a bad master cylinder. Damn thing is only a few hours old. I'm using DOT 3 fluid if that means anything. I'm at a loss as to what the issue is hence why I read your forum with great interest. It also appears when doing a search on the AOIA and SDC forums, this has been a familiar problem with a fair number of people.

very nice job. excellent work

I'd like to know more about the electric steering. I too have an R2/R3 with AC. it was modified many years ago by a previous owner. However, my car utilizes a hydraulic power steering unit. SO the pump is driven by the engine. Therefore, my setup is very congested and one of the brackets rub up against the bottom of the hood. So as I noticed from your photos, you had the ability to move the alternator where the power steering pump was, leaving plenty of room on top for the AC unit. I am really unhappy with my power steering setup, it's another mod and has caused many other issues below, it's a rack and pinion unit but interferes with the exhaust and oil pan. So the electric steering looks like an opportunity to fix a lot of problems.

Thanks all for your quick responses. Greatly appreciated

Thanks for that quick response. Do you know how much the R3 was shimmed up? If I recall correctly, the Avanti II's was raised about 3" for the corvette engines.

So an interesting topic and Dwight mentioned early in this discussion that caught my attention. His comment was that the R3 body was slightly elevated vs the R2/R1. This is the first I've heard this. I've read that when the Avanti II's came out with the corvette engines, the body was raised a few inches. So how much was the R3 raised above the R2/R1? I'm somewhat new to the Avanti ownership, and purchased a 64 Avanti in the spring. It had been modified extensively from an R1 originally to an "R2" but the air box is not an R2 hat but an R3 type box. With that, I've noticed that it "just" touches the underside of the hood and I've been trying to decide how to fix. The 3 options seem to be, a) change the engine mounts to something a little lower, b) add shims to raise the body like an R3 (if that is what they did) or c) replace the R3 type airbag with an R2 hat. Looking forward to the feedback

Once again, thank you for those quick responses. Glad to clear that up.

Question regarding heads for Avanti's or any Studebaker. I've reviewed the info on Head castings from Bob Johnstone's website and what I gather is the key difference in head castings for R1 (1557570) vs an R2 (1557582) vs lets say Golden Hawk (535976) or (1555294) appear to be the combustion chamber volume. Somewhere in the review was the comment that valve sizes were all the same regardless of head casting, with Intakes at 1" 17/32 and Exhaust 1" 21/32. My question is this. Is there any difference in intake & exhaust runner sizes/volumes? Are they all the same? Is it then true the only difference is combustion chamber volume? Are there any differences other than combustion chamber volume?

Thanks for the photos. Helps a lot for understanding the issue

Do you have a photo of the mating plate between the bell housing to block? Thanks

So, I was researching camshafts trying to understand what I've got and why and was wondering why the R1 and the R2 used the exact same camshaft? Watching a variety of "Youtube" videos, it seems as though the R2 might have had better performance with a different camshaft designed for positive pressure intake, ie "blower". What's the thoughts out there amongst the experts? Have any updated their camshafts for the R2 setup to improve performance?

Thank you mfg. I've been on the road so I hadn't had a chance to respond. Good info though and I was thinking about those engine mounts as a fix

Thank you for that quick reply. So to add to this question or next question. Is there a difference between a R2 intake manifold vs a R3 intake manifold? What I've noticed is that with the R3 air box, the air box is slightly rubbing up against the bottom of the hood. The insulation on the underside of the hood has already been removed, I presume because it wouldn't close with this air box. Even still, there is a slight rub.

Is there a difference between a R2 supercharger vs an R3 supercharger as far as performance? The obvious is the air box on top of the carburetor so because of that, I was curious if therefore there is a difference between them. Also, where on the supercharge can I find the model number/part number? Only thing I've found is "MS 2380". The air box on my car looks like an R3 and has a casting #/part # on the top of 1558946. My car that I just purchased has been modified over the years. The block number is a standard 289 cu inch with the casting # of 1554641. The heads are from a "golden hawk" with a casting number of 535976. The intake manifold has a casting # of 1557144. I'm still going over the engine and transmission looking for casting #'s/part #'s. The transmission has been replaced with a chevy 700 4R.