jeff1000man

Just got back from a day at the dyno. Learned a lot today. If any of you are in the Houston area, take a trip over to Owen's racing and see Joe. Great professional guy to work with and very knowledgeable.

Now onto the question at hand. I was allways taught that on a blower engine, the further you could stretch out the carbs from the rotors, the more power you could make.

I built this engine last year, it i just a mild 468CI witha 250 blower and an intercooler. Never could get it tuned on the dyno I was using last year as it would hit a brick wall at 4500 RPM's. Wouldn't ever make over 550HP. I put it into the boat anyway, and it ran like a bat out of hell until around 4500 RPM's again. I ran it up to around 5000 and it would detonate real bad. Never could figure out anything except a bad tune up, but it was set up very conservative. Ran it at 29 degrees timing and 5 lbs boost. Twin 750 carbs.

Took the engine apart over the winter just to see if there was anything that I could see. Couldn't find anything. Took the engine over to Owens and he found a few things wrong like ring gap variance, A few valve springs were not exactly right, but still in tolerance.

Put it back onto the dyno today and started working around with the idle circuits and the primaries. Notices that the fule consuption rates were all over the place. We started with the obvious, checked likage and syncronization between carbs. Checked for jet variations. Didn't really find anything wrong.

Pulled the carb spacers off the engine and bolted them straight to the blower and BINGO. Everything was 200% better looking. Picked up an instant 100 HP and the power climbed all the way through the end of the pull at 5500 rpms.

Now is it true that you are supposed to use carb spacers or not.

niceguy

Jeff, glad they got you fixed up. Is Deon still over there? To be honest, I didn't think spacers would cause that kind of issue. I know on our drag motors, we never used spacers. I learn something new everyday.

RunninHotRacing163.1

Notices that the fuel consuption rates were all over the place.
Larrys told me fuel consumption & BSFC #s dont matter on these motors only NASCAR so they can figure there fuel and not run out ..So now are they important pices of the puzzle or not ??

jeff1000man

Only important if you want it to run right. I learned a lot today that I have had problems with on most of the engines that I have put together.

By consumption rates, I mean one carb would use more than the other, and then it would flip flop. Meaning the signal was not staying consistent. It was a clue that ended up helping us solve the puzzle.

I assume that if the carbs are not using fuel equally front to back, it could cause a lean condition or detonation etc...

We managed to get the carbs together without sending them off to a carb expert like Nickerson etc.. I am glad, since I am running out of cash on this project.

To bad I just sold those other engines I had or I would loan them to you.

RunninHotRacing163.1

To bad I just sold those other engines I had or I would loan them to you.

C@@l as long as i can hold them at 4000 rpm and not lean them down

jeff1000man

I ran them at 5K with a busted piston and still gaining speed. They would turn to 6000 like it was 2000. They were good engines, I just needed the money, so I had to let them go.

ezstriper

I ran a 1" on my 177 setup...seemed to work well...guess all setups diff.....Rob

Smitty

iTrader: (1)

I my travels spacers should only be used on N/A motors.