New Build 340/420 Questions

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YO7_A66

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I have been working on this build this year and a couple of weeks ago I broke in the SFT (252/256 109 CL) cam, then I installed the inner valve springs and ran it for another 15 minutes or so and now it has about 45-50 minutes of total run time.

I just completed the cranking compression checks and the lowest was 189psi and the highest was 197psi with an overall average if 192psi. I have 93 octane in it now and plan on using that until I have the tune up close. My first question would be, what are my chances of dropping down to 91 octane (Promaxx/Sidewinder heads)? This is a street build with a 727/3:91 gears/275 rear tires. My initial is currently 24 and I have not checked the total just yet (no VA). I do plan to check it this coming week to see when it is all in.

Break In Oil: I have apx 50 minutes of run time and I am plannning on keeping the WIX oil filter and the break in oil in it for the first few test drives. Then changing out to another WIX filter and Penn Grade oil. Any concerns?

Thanks
 
Sounds good to me. Get that engine oil up to temperature so the zinc can work.
 
24 timing is way too much. Do you have the vac. adv. hooked up? Does the dist. have lighter springs in it? If it does start at 10 and if not start at 12. Leave the vac. line off and pluged for your first couple of drives. 93 octane with those numbers will be a gamble. Spark knock is no joke and will ruin a fresh build fast. ps did you use a quality comp. gauge? what is your comp ratio and did you cc everything?
 
I’m going to say this again.

Your cylinder head materiel does NOT matter when it comes to compression ratio. NOTHING.

I’m not going to explain (again) why this is, but the fact is aluminum heads do not change how much compression you can run, nor do they reduce detonation with the exception of absolutely loading the engine for long periods of time.

Just like in the Engine Masters test, they had to heat load the engine similar to what would happen in the real world if you were pulling a 7% grade for several miles and never down shifting.

If someone does that then to me that’s a driver abuse issue.

You should always use the highest grade if pump fuel you can get. Premium pump fuel has much more strict controls on the garbage the blenders can use.

I would not even back the car out of the shop without knowing total timing and at what rpm that is.

With your cranking numbers you better make double damn sure the curve in the distributor is spot on.

For you, that means probably less initial (I’m going to guess you’ll need 16-18 initial) and then you need to keep the curve so that at peak torque you have 22-24 at peak torque. After that the curve should be 1.5-2.0 degrees per 1000/rpm to peak power.

You’ll need to get a vacuum gauge on it and figure out where you can start the VA but I suspect you’ll need to delay it’s start and reduce its total advance.

You say your cam is on a 109 CL. Are you saying it’s on a 109 ICL or is it on a 109 LSA?
 
No VA and 10.7 measured.

This week, I will check the curve and see what rpm the timing is all in by and adjust to 32 for now. Then check to see where the initial ends up which I will assume will be less than 24.
Cam is a 109 installed at 105.

Thanks guys
 
Do what you want but starting small and going up isn't going to hurt anything. Is it real 93 or does the gas station have 87 pumped into their tanks and mix it? Even back in the day my friends wondered why they could run (say) 220 at my station but they had spark knock at the cheaper place down the street using 230 or 240. Ever try testing e85? Believe me I've seen 50% to almost 90%. So you are saying 44-46 degrees total. Not on my motors.
 
YO7_A66 said:
No VA and 10.7 measured.

This week, I will check the curve and see what rpm the timing is all in by and adjust to 32 for now. Then check to see where the initial ends up which I will assume will be less than 24.
Cam is a 109 installed at 105.

Thanks guys
Click to expand...
Good starting point.
 
YO7_A66 said:
No VA and 10.7 measured.

This week, I will check the curve and see what rpm the timing is all in by and adjust to 32 for now. Then check to see where the initial ends up which I will assume will be less than 24.
Cam is a 109 installed at 105.

Thanks guys
Click to expand...


Good plan.
 
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