engine tuning... need help

[n247hp]

So i am getting close to drop in the engine after a year long built. I am running a stock 62t cases on ported 61x cylinders(widened exhaust and cleaned up transfers, 82mm) a 31cc dome riva head, stock carbs and a b pipe, stock ignition. I got 2 questions....

What would you recommend for ignition timing?
and
Where would I start with carb jetting.

Before i had nearly the same engine only 62t cylinders bored to almost 760cc's Do you think carb jetting from that setup would work on this engine??

Thank you

 

[#ZERO]

Did you check your compression yet, with 31cc domes you're probably going to need race gas?

I'd stick with the stock timing depending on your compression.

Here's a starting point for the jetting.

72.5 Pilot Jets
137.5 Main Jets
1.5 Needle & Seat
95 Gram Dull Silver Spring
1-Turn Low Speed Screws
1-Turn High Speed Screws

 

[n247hp]

I will test the compression tonight. Is there a general rule at which compression the race gas becomes a necessity? Also when you say the stock setting for the ignition, does that mean lining up the two marks on the case and the stator assembly? Thanks

 

[n247hp]

still stuck... Please help Should i get a new head with 35cc domes, cause i dont want to use race gas. I had trouble tuning my engine last year with this head so now i am thinking maybe this was a reason since i didnt know that i had to use race gas

any advice will help

 

[D-Roc]

compression, whats your compression?

 

[#ZERO]

still stuck... Please help Should i get a new head with 35cc domes, cause i dont want to use race gas. I had trouble tuning my engine last year with this head so now i am thinking maybe this was a reason since i didnt know that i had to use race gas

any advice will help

• 37cc - 170lbs - 91 Octane
• 35cc - 185lbs - 91 Octane
• 33cc - 200lbs - 100 Octane
• 31cc - 215lbs - 110 Octane
• 29cc - 230lbs - 115 Octane

Now check your compression. :thinkerg:

 

[n247hp]

Right Right. waiting for the woodruff key so i can assemble the thing to check the compression.

 

[Kennay]

You don't need a woodruff key if you are just going to check the compression. Slap that flywheel on there and tighten it down.

 

[n247hp]

the compression was 120 in each cylinder but that is due to incorrect size of the cylinder bore. When i purchased the cylinders i was told that they are 82mm but they are not. So i gota get them measured and get new pistons and might as well get a 35cc domed head while i am at it.

Sweet....

If anyone needs a head or 82mm wisecos check the for sale thread

 

[WaveDemon]

the compression was 120 in each cylinder but that is due to incorrect size of the cylinder bore. When i purchased the cylinders i was told that they are 82mm but they are not. So i gota get them measured and get new pistons and might as well get a 35cc domed head while i am at it.

Sweet....

If anyone needs a head or 82mm wisecos check the for sale thread

how did your cylinders get bored with out the machinist having the pistons in hand?

 

[WFO Speedracer]

They used the SWAG method,don't you know about SWAG? SWAG= scientific wild assed guess.

 

[blegan]

31cc Domes

Am I missing something here, if you have 31cc Domed heads the above posted chart claims 31cc @ 215 psi. But your comp. #s are @ 120 psi .Maybe Im missing something, that just doesnt sound right.

 

[n247hp]

i purchased the cylinders from some one and they told me that they are 82mm bore. so i got a set of 82mm wiseco pistons. but turns out that they are not actually 82mm bore cylinders. I guess i should have verified prior to assembling with a professional who would measure the exact bore

 

[krusty_45]

Or just buy a micrometer or a bore scope next time :Banane19:, but the best would be take it to a good machinist like you said. I never assume the size is what people say unless i measure it myself, especially when its my money going into the motor.

What happened to the thread that everybody just posted their set ups and jetting points so you can get a good start point? Did it ever get sticky"D?

 

[Matt_E]

http://www.x-h2o.com/threads/35841&highlight=compression+dome+size

 

[n247hp]

Or just buy a micrometer or a bore scope next time :Banane19:, but the best would be take it to a good machinist like you said. I never assume the size is what people say unless i measure it myself, especially when its my money going into the motor.

What happened to the thread that everybody just posted their set ups and jetting points so you can get a good start point? Did it ever get sticky"D?

This is my first build of such sort so i am learning. Sucks that this learning experience is costing so much and delaying the build. I feel like i will never finish this thing