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Discussion Starter #1
dyno results
I have purchased a 1968 YH block 428 375 hp engine, it has 3 angle valve job with 6x heads being hogged out to 2.18 and 1.89 I have headers and 1966 tripower stock and cam reads 474 lift with 304/296 duration compression has been lowered to 10.1 My question is what do you think estimated horsepower/torque would be for this engine. Someday I will get to a dyno for real results. Thanks!
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Exhaust is 2.5 3 angle valve job, no mention of head port rocker ratio 1.50,
Cam specs;ERSON degrees of duration 228 235 intake open 38 overlap 81 exhaust closes 43 intake closes 78 exh opens 83 valve lift int .472 296/306 exh valve lift .472 exh gr lift 315 degreeing cam int open 4 tdc overlap 11.5 exh close 44 exh open 47.5 gr lift intake .315 Thanks for any info you can give me!
 

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I've been running 93 octane with booster with no problems yet, it does have harden valve guides for todays gas. Any one else running this comp ratio had any problems?
 

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You could be getting lucky. Still, I'd heartily recommend that you frequently inspect your spark plug tips using a magnifying glass, looking for "shiny specks" until you're sure you're not having problems. There is such a thing as detonation that isn't pronounced enough for you to hear as knocks, but can still chew up your piston tops (where the shiny specks come from) over time.

I think you may have meant hardened valve seats, not guides, yes?

It's pretty unusual for someone to be able to run at 10:1 with iron heads and pump gas without having problems.

Bear
 

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Thanks Bear,
I will check and yes I meant hardened valve seats. Would a 9:5 0r 9:1 comp ratio be recommend for today's gas? Or what octane racing gas should I use with current 10:1 ratio? Thanks for your help!
 

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Discussion Starter #8
Exhaust is 2.5 3 angle valve job, no mention of head port rocker ratio 1.50,
Cam specs;ERSON degrees of duration 228 235 intake open 38 overlap 81 exhaust closes 43 intake closes 78 exh opens 83 valve lift int .472 296/306 exh valve lift .472 exh gr lift 315 degreeing cam int open 4 tdc overlap 11.5 exh close 44 exh open 47.5 gr lift intake .315 Thanks for any info you can give me!
 

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Sorry for the delay, bud, gone for the weekend. I had to rough in a couple things, no tri-power in my data base, but with an 800 cfm Holley double-pumper and the rest of what you gave us I get 432 hp @ 5250 rpm and 479 ft-lbs @ 3500 rpm. I've run a few engine builds with actual dyno results on this software and it's usually a little optimistic, but you still got a healthy motor there. Maybe one of the real engine builders has better tools...

Scott
 

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Bear, you think that late-closing intake valve is helping him out with lower dynamic compression in spite of the 10:1 static number? I get 7.1:1 with the Wallace Racing calculator, ain't that in the okay range for 93 octane?
 

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Thanks RUNNINGLEMANS I know when the deuces are in she jumps to 6000 rpm real quick with no problems Tons of Torque down low even with 3.55 gears. I estimated 425=450 HP so I wasn't far off. I appreciate all the info
 

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You'll find opinions all over the map on the whole "dynamic compression" question. The theory says late intake closing helps manage cylinder pressure --- and it does --- until the engine gets up into the rpm range where volumetric efficiency starts to rise dramatically, and the cylinders are getting nice and full due to the effects of air flow velocity, inertia of the gas column, and all that (which is the real reason for longer valve durations and late intake events in the first place). At or near peak VE the cylinders are getting filled and you're making max pressure anyway (and cylinder pressure is starting to build long before that intake valve closes just from the effects of air flow velocity and inertia). The one thing that does help is rpm - as rpm increases, there's less time available for hot spots to set off the chain of events that leads to detonation - so there's a chance you can "get lucky". Here's the thing though --- everything else being equal, a 10:1 engine of the type, size, and realm we're talking about here is only going to make a whopping total of maybe 5-8 HP more than a 9.3:1 engine. Is it really worth getting that small amount of power if it also comes with having to constantly worry about trying to keep the motor from eating itself? Not for me :D

Bear
 

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Discussion Starter #13
Sorry for the delay, bud, gone for the weekend. I had to rough in a couple things, no tri-power in my data base, but with an 800 cfm Holley double-pumper and the rest of what you gave us I get 432 hp @ 5250 rpm and 479 ft-lbs @ 3500 rpm. I've run a few engine builds with actual dyno results on this software and it's usually a little optimistic, but you still got a healthy motor there. Maybe one of the real engine builders has better tools...

Scott
Hey I forgot to ask you is there a 1/4 mile simulator that will estimate ETS? Thanks!
 

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Would a 9:5 0r 9:1 comp ratio be recommend for today's gas? Or what octane racing gas should I use with current 10:1 ratio? Thanks for your help!
 

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Thanks Bear,
I will check and yes I meant hardened valve seats. Would a 9:5 0r 9:1 comp ratio be recommend for today's gas? Or what octane racing gas should I use with current 10:1 ratio? Thanks for your help!
 

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What are you stockers doing about gas with the OEM comp ratio? Wasn't it 10 or 10.5:1? I guess I could look it up, but is anyone having issues with detonation/pre-ignition? Do you pour in an occasional 4-5gal of race fuel or is there a prefered booster? Most boosters are just solvent with slow burn rates and do little to bump octane ratings, so I hadn't considered any of them. Is my stock 66 389 (in a 65 with the 65 tri-power top end) going to argue with me? My initial thoughts were to reduce the total advance in an effort to reduce the tendency for fuel problems because we never know what's in these tanks in the midwest. So many questions, sorry...
 

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666bbl, this topic has been addressed many, many times. Please do a thread search on compression ratio/pinging. In a nutshell, your '65 is going to 'argue' with you. 10:1 means about 100 octane, you may be able to squeak by on 95-98. I run TEL 130 in my '65, or mix race gas. I don't drive it much. It's a true 10.75 (surfaced heads 64cc chambers) CR, with a big cam, 3.36 gears, and a 4 speed. Retarding the timing will not really help....it'll be sluggish and run hot. The best solution for an early 389 is to install dished pistons for a 9:1 CR on the rebuild.
 

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:agree: Big time.... and furthermore, that's what octane rating MEANS. "Burn rate". The higher the octane rating, the slower the fuel burns. Higher octane fuel makes LESS power than lower octane fuel, not more.

Bear
 
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