Jetting noob :)

[Jesse/DVK]

I would like to know your thought on jetting for my new engine.

Setup:
DPR 69mm c/w
94mm mahle
Scat i beam
041 39x35.5 heads ported
Engle fk8
Straight cuts
etc.

And offcourse new 48 IDA's on big beef's.

I'm looking for a basic jetting to break in the engine and than start to jet it.

Something like this?
37mm vents
60 idle
165 main
F7 emulsion
200 air corrector

What jets should I buy extra? What is 'normal' to deviate from a basic setting?

Thanks!

[lawrence]

My engine is very similar to yours. The jets that you have now will work for the break in, but changes can be made to make the engine run great. What is your compression ratio? You should buy 50 idle jets and 60 idle holders. If they are too small you can drill them larger. See if you can borrow or rent someones jet drills. Your main jets are most likely too large; something from 130-145 should work better. The 200 air corrector is a good start; mine happens to be 180. F7 emulsions are fine, but see if you can borrow others to see how your engine responds. Remember that all engines are different so some experimenting is necessary. There is a good amount of IDA information on this forum, so pour a coffee and do some reading Good luck and have fun!

[Jesse/DVK]

Thanks for your info . CR is around 10.5 / 10 : 1

[Lanny Hussey]

IMHO, your guess looks pretty close although mains will likely be around 150. Keep in mind Doug Bergs saying 'the engine will tell you, not vise versa'

[Rasser]

Still think that C/R is a bit high 

[Jesse/DVK]

Thanks.

Do you think Rasser. Why? I have looked to calculate dynamic compression but I got different outcomes..

[Rasser]

If your intended use is mostly streetuse. Then it is just my personal opinion that 10.5:1 is too much for a fk8 cam.  I would aim for 9.5:1. But offcourse opinions differ, I just wouldn´t wanna risk having an engine that gets too hot, or even worse "pinging" (pre ignition).

Have you looked at what C/R other people run with their fk8 cam, and what they use their car for (race, cruising?) ?

[Jesse/DVK]

How much deckheight is to much? With 1.5mm deckheight I get 9.97:1. After 1.5mm it's better to gain some CC's I guess? To keep squish.

edit: @ Rasser. I got my CR from a topic you also answered to . http://cal-look.no/lounge/index.php/topic,7035.0.html

Will look in other CR. But mostly Americans run lower CR for the lower octane fuel. I'm going to run 98 octane.

[67worshipper]

i agree with rasser.my cars running 8.5:1 with a fk8 and does the job without the hassle.dropping it a little would keep your nerves in check should be sweet engine BTW

[Rasser]

How much deckheight is to much? With 1.5mm deckheight I get 9.97:1. After 1.5mm it's better to gain some CC's I guess? To keep squish.

edit: @ Rasser. I got my CR from a topic you also answered to . http://cal-look.no/lounge/index.php/topic,7035.0.html

Will look in other CR. But mostly Americans run lower CR for the lower octane fuel. I'm going to run 98 octane.

Back then you talked about a w120 cam, but now you have chosen the fk8 - good choice!

I still think 10:1 is a bit too high. It could work just fine, but I would like to go down just a bit, and then not have to worry so much.

If your problem is that your heads have been cut down too much, then I would go for the 1.5mm deckheight, and check if you could safely remove some material (3ccm) from the chamber. Are the heads allready unshrouded for the 94mm bore?

Remeber dual springs!

[Jesse/DVK]

They are now for 90.5mm. Will have them bored for 94mm and cut for dual springs. Will talk with the machine shop about unshrouding. The heads are 43cc now. I already have bugpack 4046 dual springs lying around.

[67worshipper]

you should be able to get it down a little jesse

[Arry]

I would like to know your thought on jetting for my new engine.

Setup:
DPR 69mm c/w
94mm mahle
Scat i beam
041 39x35.5 heads ported
Engle fk8
Straight cuts
etc.

And offcourse new 48 IDA's on big beef's.

I'm looking for a basic jetting to break in the engine and than start to jet it.

Something like this?
37mm vents
60 idle
165 main
F7 emulsion
200 air corrector

What jets should I buy extra? What is 'normal' to deviate from a basic setting?

Hi Jesse. I have a 1915 similar to yours, only with a 120 cam.
I'd say the jets are good, but I would try a smaller main (between 135-150). I have 135 on mine now, but with a 120 air corrector.
I feel the 10:1 comp is a little too high for a k-8.

[Rasser]

If they are only 90.5mm now, then you should be able to remove some material on the sides of the chamber when they are bored to 94mm.

[Jesse/DVK]

Ok guys, thanks for your answers. Think about going for 46ccs. 3ccs should be easy to get I think. With 1.5mm deckheight that makes 9.5:1.

About the deckheigt. What is better for temperatures? Shims under the cilinders to get a deckheight of 1.5 or set the deckheight at 0 and than install a copper head gasket of 1.5mm.

Thanks!

[Jim Ratto]

I would like to know your thought on jetting for my new engine.

Setup:
DPR 69mm c/w
94mm mahle
Scat i beam
041 39x35.5 heads ported
Engle fk8
Straight cuts
etc.

And offcourse new 48 IDA's on big beef's.

I'm looking for a basic jetting to break in the engine and than start to jet it.

Something like this?
37mm vents
60 idle
165 main
F7 emulsion
200 air corrector

What jets should I buy extra? What is 'normal' to deviate from a basic setting?

Thanks!

that 60 idle should get you where you need to be but the idle and idle air holder has the most profound effect on street car overall performance, meaning you can work until 2020 on getting main jets to pull 4500-7000 but if the car runs badly off idle or in progression, you'll hate driving the car and end up being another guy that claims "48IDAs can't run good off ilde on street cars"
I'd come down on mains like other guys have said...make doubly sure float levels are PERFECT and ensure fuel pressure.

[Jesse/DVK]

Thanks guys for your help. Just set my floats today on 5.5 mm with help of the Haynes manual.

This is what I will start up with.

37mm vents
60 idle
150 main
F7 emulsion
200 air corrector. with the stock 120 air holder?

Anyone an idea about my deckheight question? What is better for temperatures? Shims under the cilinders to get a deckheight of 1.5 or set the deckheight at 0 and than install a copper head gasket of 1.5mm.

[Bruce]

What is better for temperatures?

It's not gonna make any difference either way.