Weird low rpm problem

[dbeardslee]

Craz - the 1/4 refers to the type of lobe grinding which, in turn, dictates the type of use. Other grinds are 3/4 race (as you mentioned), full-race, street-grind, etc. Back in the day the 1/4 grind was popular as you could still drive it on the street. That 318 was another great motor. Don't get me started on station wagons - I drove a '70 Bonneville wagon (when dad got through with it) with a 455 big block when I first got out of the army. Talk about a land yacht - all it needed was a sail .

[Crazcnuk]

I realize that, but it was more of a marketing thing that us 'simpletons' could understand.

When you get into Duration, lobe centers, etc, etc, it gets a bit complicated for the average guy flipping through a catalog.

When I bought the cam for my Pontiac, I went with a 292 duration, lopy idle job with .385 lift at the cam. It chugged like a 1 cylinder russian farm tractor.

Now the options are incredible. The cam in my 502/502 is actually considered MILD for the motor, and it puts out over 500hp. There is a cam, from Crane, that will jump it to 640hp. I was sticking with the mild one so that when I put the blower on....

[dbeardslee]

Craz - Did you have to beef up the motor mounts, or did you just use the stockers? Seems like with that much horse power the engine might want to get up and walk away all by itself .

Back on topic - I found the permacoil's I needed, along with ford 2.3L gaskets. I drilled out the offending hole on #3, tapped it, installed the insert, trimmed the gaskets, and rehung the carbs. I couldn't take it out, as it's raining right now, but I did let it get good and warm sitting in the garage with a fan blowing on it. I colortuned and synched, and it's looking pretty good so far. The vacuum fluctuations on #3 are gone, mixtures look good, and it's idling nicely. Of course the real test is the road, so as soon as this rain stops I'm going for a test ride, but for now I'm cautiously optimistic.

[Crazcnuk]

On the Pontiac, no, I was 16, if you mean the Monte, it has Polygraphite mounts (engine, tranny, body, steering...)

[dbeardslee]

After action report

I got a little break in the rain, so I went for a test drive. I still have a small low rpm stumble, but nothing like it was. At least now it's acting predictably and I'm pretty sure that issue can be solved in the carbs. It acts kind of fuel starvy from 1k up to 2.5k (right where the mains kick in, hmmmmm). I'm going to try putting the floats back down where I had them before, and see what I get. They're close to 27mm right now, but I think when I set them I was compensating for other things.

Ivan-a take this opportunity to thank Ivan. You were right on target with the valves. I don't think that was the only problem I was dealing with, but they were due for adjustment (almost exactly 6000 miles - maybe those yamaha guys that wrote the manual did know what they were talking about ), and it made a big difference.

And thanks to everyone else for their suggestions - especially the Ford 2.3L gaskets. They are working fine, and were much easier to trim than it would have been to cut new ones, and besides, the last one's I cut developed a leak. I think the permatex ultra grey would have worked if I had used a thicker bead. I didn't want to take a chance with it squeezing out and potentially getting sucked into the combustion chamber, so I only used about a 1/16" bead. Even with that I had to pry those little buggers off. I didn't use any sealant on the Ford gaskets - just greased them lightly and put them in place. That way the next time I have to remove the hangers I won't have to do my Alexiev of Russia impersonation to get 'em off .

[DGXSER]

Doug, sounds like you are down to some carb tuning now!!! woohooo!! Glad you got her figured out. (The only women we can ever hope to figure out, our bikes!)

Now, get that dang bracket made up and hook it up before you have to repeat this circus act!

[dbeardslee]

Don - I made a gleaves bracket the other day. I'm thinking the weight of the carbs bouncing around, and the poor condition of the threads at the top of the #3 flange are probably responsible for the vacuum leak. I definitely don't want a repeat of this problem so I made the bracket the day it was mentioned/posted. I'll show you the next time I see you.

[DGXSER]

Awesome Doug!! I am sure it will be a thing of beauty.

[dbeardslee]

I over-engineered it a little bit - you'll love it .

[egleaves]

I over-engineered it a little bit - you'll love it .

To an engineer, there is no such thing as "over-engineering".

[DGXSER]

Thats like the cup half full or half empty...no such thing...the bloody thing is just twice as big as it needs to be!!

Hey Doug, I bet we can lay out some areas to cut out to lighten it up without loosing strength as well! Give me a chance and we will be adding gussets and bending edges for strength too!

[egleaves]

Reading about this bracket just reminded me of something. I replaced some parking signs for my wife's office, and to the sign hanger go the spoils....I have 18 or 20 pieces of sheet aluminum that are about 18" x 18" x 1/16". They have something printed on one side, but blank on the other, and would make great stock for custom brackets and the such. Don, Doug, anyone else in the area, if you want a piece or two of it let me know.

[dbeardslee]

Betsy's a happy girl...

Two trips into the carbs today seems to have done the trick. On the first try I set the floats right at 25.7 mm, colortuned and synched, and she ran about the same. Pulled the plugs and they showed rich but colortune showed the higher rpms to be fine. Went back into the carbs and replaced the #47.5 pilots with #45's, colortuned and synched, and she's back to pulling stumps. I took her down to my favorite test hill, which is easily a 15% grade in one spot, and she walked up it at 1100 rpms, and when she started to bog on the steep part she accepted the throttle input and took that at 1250. Not bad for an XS with a 750 FD. The idle was a little high, and I adjusted it down to 1000 rpms. I think she would have pulled it at a lower rpm, but the idle setting prevented me from trying. The sun's shining, temperatures perfect, and this kid is going for a ride .

Thanks again to everyone for all the help - this one was tricky.

Don and Eric - somehow I knew that over-engineered line would garner a response.

[John]

I hate engineers

They seem to build the machine around the which ever part is the hardest to remove. Ever try to change a heater core in a 90's Mustang or T'bird?

[dbeardslee]

John - I changed one in a '74 Corvette that was a royal pain. I had to - the passenger foot compartment was filling up with antifreeze . No where near as difficult as the slant-mount radiator though. That car was a pleasure to drive and a booger to work on. I swear, if you didn't use the right profanity those parts would not go back together.