things to think over: inspired by Mark Herbert

[Jim Ratto]

Herbert taught us all a lot of neat stuff, if we cared to pay attention, and Mark was one of those guys you had to pay attention to, if not for his technical expertise (vast) then for his wit and humor
 
My favorite quote he used to post was "let's go race calculators"

He made mention of 45mm vents making his motor MORE driveable because it sent less of a shockwave to emulsion tubes than the smaller ones. Anybody ever follow this? I assume MArk claimed this because he tried it and it worked. It sort of makes sense. What do you guys think?

I always wanted to have a week off of everything and try a large-ish cc motor with long duration (FK89), conservative ports and small-to-mid-sized venturies. I built something like this, with 278' @ .050" but with little 44IDF Fiat carbs.... and it didn't run well at all in mid range. I think with 48's, but maybe 40mm vents it would have. A lot of ignition advance, high airspeed, long overlap, jetted to "feel" the pulses from small vents and overlap.....

what do you guys think?

Mark, miss you. You would have talked back and forth for 50 posts or so here....

Jim

[Rick Meredith]

Wouldn't you also have less vacuum and velocity with 45s? I would be afraid that the fuel wouldn't stay suspended.

And I miss him too! 

[wolfswest]

...

[Jim Ratto]

He made mention of 45mm vents making his motor MORE driveable because it sent less of a shockwave to emulsion tubes than the smaller ones. Anybody ever follow this? I assume MArk claimed this because he tried it and it worked. It sort of makes sense. What do you guys think?

I'm not an enginebuilder at all but the guy that made my engine used 45mm vents in my IDA's...  I havn't drove another high power bug yet, execpt a crappy 1914 IDA engine so I can't realy compare with other setups...  But, what I can say is that it runs just fine.  Here in Belgium aren't that many high power shops and most of them are in type 4 or german look stuff...  Everybody told me here in Belgium that it's nearly inpossible to drive IDA's on a streetengine, it is to big and you don't have any torque and it only works well @ high rpm's...

My engine proves that everybody here is wrong, It's got plenty of torque, makes around 190hp top end power and it drives like a normal daily driver.  I can use in granny style, shift @ 2k rpm and it just runs super!  no stottering, no lack of power...  Maybe the 45mm's are the reason maybe not, I can't tell...  but this is my experience.

I will ask Steve what cam he used because I'm not sure of it, I think it is a fk89 but I'm not sure.  I will double check that and post it here so we can get a better image of the engine...

Dem

Hi Dem, thanks for your thoughts. Would you mind sharing your engine specifications? Thanks....

[wolfswest]

...

[Steve D.]

Larger vents drive smoother because they take power away from the low end where real drivabilty is- jet the thing fat and it will drive smoother also.

Lots of fuel + low vacuum signal = cadillac cruise.

[Mike Maize]

Hey Jim, Your post about Mark made me remember that waaay back on the other forum when I was kicking around engine combos two people private e-mailed me to give me their feedback....You and Mark! You don't even know how thrilled I was to have you two guys of all people giving me the "inside" scoop. Mark offered to help me get Fuchs, get heads done for me, etc...what a great guy, bummed I never got out there to meet him. Thanks for sharing your time dude, it makes a difference for us out of the way Cal-lookers

[louisb]

Thanks for sharing your time dude, it makes a difference for us out of the way Cal-lookers

I agree. Jim has been kind enough to answer a lot of my stupid questions.

Thanks,

--louis

[SOB/RFH]

I do miss Mark a lot.....

He told me and conviced me to go with the big vents as, he claimed "it does not give a strong signal to the second venturie while the air is pulzing as it will on low rpm:s" so it does pick up less fuel compared to a small venturied motor ......I set up a 2232 with CNC heads and a FK89....pulls strong till 4000 rpm then it takes of like a rollercoaster.......driveable and working smoothly!! A good tip from a good fellow!   

Once I talked high compresson ratio on street motors with Mark........He claied that we europeans had better gasoline then in the US...."True" i said, "but what compression ratio did Porsche use in So Cal".....Silent followed............" ehhhh need to hang up man, some one is comming" he said and quickly hang up.....time got by and........ and lo and behold he built the SSB motor with more than 10:1 CR He was so happy to drive that high CR motor on crappy gas .......Mark knew how to share a welth of information and also knew how to take it in information when it was pointing in the right direction!!

[Jim Ratto]

what kind of jets Sven did you have to use to run w/ 45?

I'm guessing 180-185? Go large on air correct too or did you go small, i.e. Cobra jet stack or 906 Porsche stack down like 150 a/c or smaller?

[SOB/RFH]

We went with 185:s and it hauled ass!! If I remeber right we used 65 idles...............Wish it was summer here but it is cold and damp.......... 

[louisb]

We went with 185:s and it hauled ass!! If I remeber right we used 65 idles...............Wish it was summer here but it is cold and damp.......... 

Your making me think of keeping the 44 vents in my IDAs.

--louis

[Diederick/DVK]

We went with 185:s and it hauled ass!! If I remeber right we used 65 idles...............Wish it was summer here but it is cold and damp.......... 

Your making me think of keeping the 44 vents in my IDAs.

--louis

And wonder why I bought 37s, while they had 42s.

[Jim Ratto]

We went with 185:s and it hauled ass!! If I remeber right we used 65 idles...............Wish it was summer here but it is cold and damp.......... 

I went swimming last night. By accident. sorry...