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street, alloy headed 351 w how much comp to run? 

 

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 Post subject: street, alloy headed 351 w how much comp to run?
Posted: Sat May 01, 2010 6:20 pm 
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yeah i know i said i bought protoplines, but that fell through, so i just bought some edelbrock E street alloy heads, now the drama i have is that the chambers are 60cc and i have 40 over flat tops, this will give me approx 10.9:1 compression which one person is telling me is perfect, but the bloke actually putting it together wants about 9.5. i can get a 16cc dish piston which will give me approx 9.4:1. the bloke i bought the heads off is a performance engine biulder and says this is too low and will waste the heads i just bought. the dude who is putting it together reckons ggod, however he rebuilds standard engines for boats and the accosional hot V8.

i hope you all kept up cos im confused, im building a nice street engine and am chasing 400ish hp. not after numbers just a good strong engine,

oh and ill be running a air gap manifold, and prob a nice hydrolic cam with about 300 lift, ill be copying edelbrocks 451hp and that crate engine has 9.9:1 comp. :? my head hurts!!

http://www.edelbrock.com/automotive_new ... ford.shtml

 

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 Post subject: Re: street, alloy headed 351 w how much comp to run?
Posted: Sat May 01, 2010 8:26 pm 
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If your running 10.9:1 CR, you'll need a cam of no less than 35/75 and 0.550" valve lift.
Run it with about 2* cam timing advance, regraph the dizzy so it has about 14* initial, and maybe use an ICE ignition system...you'll need it for that CR.....and a carby of about 780 CFM with a single plane intake.....tune length 4 into 1's.......you'll be looking at 320 to 350 rwhp....with good torque.

 

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 Post subject: Re: street, alloy headed 351 w how much comp to run?
Posted: Sat May 01, 2010 8:55 pm 
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NSW, Australia

what fuel you going to run with 10.9cr? i run 10.5 to 10.2 on lpg and premo petrol

 

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 Post subject: Re: street, alloy headed 351 w how much comp to run?
Posted: Sat May 01, 2010 9:07 pm 
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VIC, Australia

ill be running no less than 95 but most likley if the comp stays high it will be a diat of premo, did think about a gas research system but a carb looks better.

i reckon the heads and valves will just about be on the limit with .550 of lift the specs list that as max, but the bloke i bought them off says he tested them and they can go a bit higher. he also flowed them, and reckons out of the box we can get 480hp, but a engine guru in melbourne has made 575 on an engine dyno with a minor clean up!!

so you reckon 10.9 cr isnt too hight for a streeter as long as i have the package to suit? will the air gap be too small? if i drop the piston down 20 thou from the deck it will be approx 10.4, would that be a little nicer to live with

 

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05 BA futura wagon, dumped, 19s, limo tint ( now the wifes car!

BA XLS ute 3V V8 manual, paceys, CAI and underdrives, good work car!

67 XR fairmont factory V8currently in pieces undergoing full resto one day will make a sweet cruiser!

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 Post subject: Re: street, alloy headed 351 w how much comp to run?
Posted: Sat May 01, 2010 9:55 pm 
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I think you'll be fine with 10.9(I ran 10.6:1 with my 3V headed cleveland) but if you use an MLS gasket from Cometic you can get them in different thicknesses if you don't have enough height left in your deck. Is your block unmachined at the mo? Is it an early block with the 9.480" deck or the later 9.503" deck?...hopefully the latter! '69-'73 blocks are 9.480 and '74-up are 9.503.
A C9OE-8 is a '69-70 block and a D2AE-BA is a '71-'74 block. A '74 block is D4AE-DA and '74-'80 is D4AE-AA.
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 Post subject: Re: street, alloy headed 351 w how much comp to run?
Posted: Sat May 01, 2010 10:11 pm 
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provked wrote:
ill be running no less than 95 but most likley if the comp stays high it will be a diat of premo, did think about a gas research system but a carb looks better.

i reckon the heads and valves will just about be on the limit with .550 of lift the specs list that as max, but the bloke i bought them off says he tested them and they can go a bit higher. he also flowed them, and reckons out of the box we can get 480hp, but a engine guru in melbourne has made 575 on an engine dyno with a minor clean up!!

so you reckon 10.9 cr isnt too hight for a streeter as long as i have the package to suit? will the air gap be too small? if i drop the piston down 20 thou from the deck it will be approx 10.4, would that be a little nicer to live with

you need 98-100 octane which varies a lot at the pumps,so to be safe try 10.4-5,you have to cc the heads and deshoud the valves + any clean up in the cambers,recalculate the cr,triall assemble the motor and use plastocine on the piston tops to measure valve clearance,you may have to fly cut the piston tops for the valve clearance.or use dished pistons to decompress it to 10.4\1 cr.this is your homework,pistons,cr,valve seat pressure and lift load on the cam and valves,valve seats can be cut at 1,2,3 angles and the same with the valves.a lot to think about and buy only once,the right stuff.whats going to stop this beast-major brake upgrade next,and transmission.

 

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 Post subject: Re: street, alloy headed 351 w how much comp to run?
Posted: Sat May 01, 2010 11:53 pm 
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as pete can vouch, i have done a lot of homework, and asked a few questions, im only a panel beater, so i can sling some bog pretty good, but im flying a lil blind now, im learing, but slowley. my plan is to buy once thats why i went for the edelbrock heads, its a 69/70 block c9oe, ah well, how much comp can you pull out with the head gaskets? also not sure if its been decked, its been built but who knows, hope to get it to the machine shop this month. if i can get low 10s cr i think ill be a little happyer,

as for the brakes, at the moment ill run an XF upgrade up front with slotted rotors and i have a disk brake 9 inch already built ready to go. i also have a C4 auto with a standard rebuild and s**t kit but i dont think that will cut now, its funny i only spoke to pete about a month ago about building a stocker!! how times change

also i can get of the shelf cast dist pistons with -16cc is 9.4 ish too low for a tuffish engine.

pls forgive me and my questions, im trying to make my brain a sponge!!

 

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05 BA futura wagon, dumped, 19s, limo tint ( now the wifes car!

BA XLS ute 3V V8 manual, paceys, CAI and underdrives, good work car!

67 XR fairmont factory V8currently in pieces undergoing full resto one day will make a sweet cruiser!

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 Post subject: Re: street, alloy headed 351 w how much comp to run?
Posted: Sat May 01, 2010 11:55 pm 
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Age: 35

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Ride: eb 's' and '67 xr fairmont

Location: Sunbury
VIC, Australia

we checked the heads today, the chamber is 60cc spot on.

 

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05 BA futura wagon, dumped, 19s, limo tint ( now the wifes car!

BA XLS ute 3V V8 manual, paceys, CAI and underdrives, good work car!

67 XR fairmont factory V8currently in pieces undergoing full resto one day will make a sweet cruiser!

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 Post subject: Re: street, alloy headed 351 w how much comp to run?
Posted: Sun May 02, 2010 1:16 am 
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NSW, Australia

provked wrote:
we checked the heads today, the chamber is 60cc spot on.

its just that it all goes hand in hand,more hp=trans upgrade=brakes=suspension,the dollars dont stop

 

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 Post subject: Re: street, alloy headed 351 w how much comp to run?
Posted: Sun May 02, 2010 8:02 am 
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You should be fine at 10.9:1 compression on alloy heads with BP Ultimate or similar if your cam has around 225 (or more) @ 050. Alloy heads can typically take an extra point of compression over iron heads before they detonate. Your engine builder is still thinking iron heads. If you intend to run a smaller duration cam, then it would be a good idea to take the 20 thou off the top of the pistons.

 

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 Post subject: Re: street, alloy headed 351 w how much comp to run?
Posted: Sun May 02, 2010 9:54 am 
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You will be fine on 95RON at that compression(10.6:1). My engines are 12:1 for the mini and runs on 95RON all day, the Subaru at 12:1 on the same juice but starts knocking if it gets a little warm so I switch to 98RON in the warmer months.

For long haul where heat can be an issue load up with the top stuff but stay 95 unless your preference is to give BP another 6cpl for not a lot of gain.
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 Post subject: Re: street, alloy headed 351 w how much comp to run?
Posted: Sun May 02, 2010 1:20 pm 
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Ride: eb 's' and '67 xr fairmont

Location: Sunbury
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well you blokes all seem to agree with the what i have come with all the research i have done, ill have good chat with me engine builder, if he doesnr agree, ill get the bloke i got the heads off to build it,

as for the money factor, i know its gunna hurt, but its a long time project, been going for 5 years, so whats another 2! i have a lot of contacts for autos, and engins so ill save some coin there will still add up but. the way i see it, do it once do it right. even if it takes double the time. which it will with a 5 month old girl and one wage.

 

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05 BA futura wagon, dumped, 19s, limo tint ( now the wifes car!

BA XLS ute 3V V8 manual, paceys, CAI and underdrives, good work car!

67 XR fairmont factory V8currently in pieces undergoing full resto one day will make a sweet cruiser!

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