427 Bypass Hose leaks...

[Richard M.]

Zero in the archives........This is on a 427 L71.

I had to pull stuff apart to fix some leaks. Also had to change the hub on the water pump. It had the wrong one(a 8 holer).

These repro clamps for the bypass hose, or the bypass hose itself is giving me leaky troubles. I tighten the clamps to their max, no more tighten-up, and the hose wiggles around the nipples on the manifold and WP. New one on the WP. The clamps are Wittek#39's. Is that right? When I first ran the engine a while back I had to add a stinking SS worm clamp on the WP nipple to keep it dry.

Is it the hose or the clamps? Any recommendations? Maybe the repro hose isn't thick enough for the clamps. I was thinking of using some nice Jubilee closed worm clamps leftover from the Jag projects. They work really nice but I just can't make myself do it.

Rich

[Ronald L.]

Re: 427 Bypass Hose leaks...

Richard, what year 68/9?

[Richard M.]

Re: 427 Bypass Hose leaks...

Sorry forgot to say '67 427.

[Ronald L.]

Re: 427 Bypass Hose leaks...

I was reading your story on the 427 motor break-in for the first time, so ...

If you have the correct clamps, they should not leak if the nipples are not overly pitted which I did not see in your pictures. Where did you get your clamps? I changed my hoses about a year and a half back and the big box clamp kit was OK in this area. The other clamps were wrong and I could not get them on the hoses but that was a 'big box vette shop error'.

Now if you are saying the hose appears too thin...

original was 1.15 OD, the rubber thickness was about .2, if your hose OD is significantly thinner, that may be a contributor. The repro I took off was a .18 thickness, notable to the exacting eye, but no issues with clamps.

Are you working to get this car up here for the NCRS national?

[Richard M.]

Re: 427 Bypass Hose leaks...

Thanks for the info.....

Both from Zip, WS-501 hose and HC-614 clamps. The hose I have is marked GM 3860302, and measured wall thickness is 0.16" and 1.08" OD on one end & 1.1" on the other end. What? ID is0.750". I'm not liking the 0.16" dimension.

The '53-'70 Parts catalog I have says 3860302 is for 66-67 wo/A.I.R, 68-69 exc HD, and is 1 1/8" OD(1.125"), & 3/4" ID. This one is 1.080" on the WP end that is giving me trouble. The 3x2 intake end is 1.10". I only put it that way to see the writing. Both nipples measur 0.750" so it's not those.

This hose is junk! I'm going to have to wrap tape or something under the clamp to make it work.

This little stuff can drive one crazy.

Rich

edit.....Yes this is the car in that other "L71 Guidance' thread. Not for the Nationals....Going away soon though.

[Richard M.]

Re: 427 Bypass Hose leaks...

Ok, Just figured out what to do. I don't have a week or 2 to play around with vendors and their suppliers to get them to make the "correct" thickness and dimensions on these hoses, so here goes.....

I just cut small strips of this self sticking bonding tape. It's made of silicone rubber and when you stretch it it sticks like crazy. I use it for repairing cloth braided engine harnesses on the jags, so here it comes in handy for Corvette reproduction anomalies. I stretched and wrapped about 2 or 3 times around the hose ends. All covered by the clamps.

Tight as a drum now with plenty of room for more tighten-up on the clamps.

Rich
p.s. I spent all day since 6AM doing enormous tasks on this car and everything was going so well. I just can't believe it took me over an hour to install one stinking little hose so it won't leak. (ok include a little TDB and picture time!)

[Ronald L.]

Re: 427 Bypass Hose leaks...

That is way too thin, .18 is off a standard aftermarket hose.

No doubt the part number was the reason to get this, but fundamentally they are making the part too thin. Its an extrusion and this stuff comes off the die at 45 feet per minute so it won't be a one-off problem and all the big box stores share and swap sell so they will all have the same too thin issue.

[Gene M.]

Re: 427 Bypass Hose leaks...

The hose should fit fairly tight on the nipples without even tightening the clamp. If it does not, get a better hose that is correct size.

Using tape and adhesives to "fix" the situation is NO GOOD.

[Richard M.]

Re: 427 Bypass Hose leaks...

Gene,

I agree but there is no correct GM marked hose now available with the correct markings. What else can I do? The hose is the wrong wall thickness and OD.

The tape is under the clamp to increase the OD of it so it will clamp tightly. I DO NOT see a problem with that.

[Gene M.]

Re: 427 Bypass Hose leaks...

Gene,

I agree but there is no correct GM marked hose now available with the correct markings. What else can I do? The hose is the wrong wall thickness and OD.

The tape is under the clamp to increase the OD of it so it will clamp tightly. I DO NOT see a problem with that.

First of all it does not look right. The hose looks squeezed down as it curves up to high. Looks like length is too long on lower leg. Hose s/b a 90 form not "s" shape. You can spray chevy orange over the hose and clamps as it should be and not have to be concern with the part number stamping.

[Richard M.]

Re: 427 Bypass Hose leaks...

You know........You're right. It looks like crap. It was late when I finished last night and I can even see it in the pictures now myself.

It's becoming the bypass hose from Hell. I'll do it over again, cut the length off some at the WP end and try it again.

Thanks,
Rich

[Dennis S.]

Re: 427 Bypass Hose leaks...

Richard
I had an ongoing problem with mine, turned out to be a corroded nipple on my Bill Mock rebuilt water pump, which was never changed. The lower one was. As my engine was being rebuilt, we had to heat the nipple to remove and put in a new one. With a new hose from Dave Walters and a little orange paint...good to go.

[Richard M.]

Re: 427 Bypass Hose leaks...

Dennis, Dave Walters hose???? Please more info how I get one.

[Dennis S.]

Re: 427 Bypass Hose leaks...

Dennis, Dave Walters hose???? Please more info how I get one.

Richard
When we spoke about engine testing I mentioned his name to you. Call Dave at Walters Engineering 305-254-6798. I was up in his warehouse today and you would not believe all the NOS parts and whatever that he has. Not that he is in the parts selling business, but he may very well have the hose you need. Don't worry, he won't hose ya.
Dennis

[Richard M.]

Re: 427 Bypass Hose leaks...

Right, now I recall. Brain is mush lately. I spoke to Wendel back in Oct/Nov and he gave me Dave's # but we never set up to dyno the engine. I'll try him tomorrow. Thanks for the reminder...

Rich