to fast over SSR

[steve cowan]

Short block ready,
010 4 bolt block
scat steel crank and H-beams with 2000 upgrade
JE pistons and Mahle ring pack,balanced bottom end.
Moroso billet oil pump and 7lt kickout pan
first comp flat tappet cam -
12-607-5
235*-242* @ 0.050''
270*-280* @ 0.015''
495'' - 507'' with 1.5RR
106 LSA.
intake lobe # 6015
235* @ 0.050'', 144* @ 0.200''
330'' lobe lift. tappet lift @ TDC 106*-0.082''. 110* - 0.068''
106 ICL +2 on belt drive
inop-10* btdc .incl - 45*abdc @ 0.050''
exop - 48* bbdc. excl - 16 atdc @ 0.050''
exhaust lobe # 6001
242* @ 0.050'', 152* @ 0.050''
338'' lobe lift, tappet lift @ TDC 106* - 0.94''. 110* - 0.080''
going to play with cam timing,lash loops,different rocker ratios,2 x different converters,
different intake manifolds,i might try my RPM airgap first,i have a ported VIC JNR and a couple of team G manifolds,i think a stock VIC JNR would go ok or a stock Holley Dorton intake.
i have 3 x different carbs,830 annular,850 demon,950 hp holley.
only headers i have 1 3/4 primary,short collector 3''.
i would like to use a set of tri-y as well but cant find any to fit angle plug head in my car.
hopefully heads back from machine shop this week,178cc intake runner 241cfm @ .500''-.600''
68cc exhaust runner,port size -105% of valve size CSA,320 ft/sec with pipe at the port opening
168cfm @ 0.600''
will recheck chambers after surface grind should be around 67cc which might net 10.5:1comp
the 383 with these heads will choke pretty early around 5600rpm,i am ok with that as i want a starting point and over time hopefully turn these heads into something reasonable and hopefully not hit water,i dont know how much meat these heads have,
any comments welcome

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[randy331]

Belt drive and an ati damper. Nice.

They just seem a little outta place for the rest of the build. LOL

What size is the ex throat ?

It should run good.

Randy

[MELWAY]

Intake ports look nice

Exhaust you could cut a bit more of guide boss to make room for flow as it transfers to the roof

[steve cowan]

Belt drive and an ati damper. Nice.

They just seem a little outta place for the rest of the build. LOL

What size is the ex throat ?

It should run good.

Randy

LOL Randy,
you are right about the belt drive is a bit of overkill,but as you know makes cam timing changes easy.this short block is the one that had the as cast pro 1 heads 215cc runner made about 510hp
122mph @ 3650pounds.
Randy,
any thought about using the solid flat tappet cams as far as being lift restricted,i think the duration and timing events will be a reasonable starting point but the 0.500'' valve lift will hold the engine back,is this a fair statement??
1.5'' exhaust valve @ 88% - 1.36'' throat

[steve cowan]

Intake ports look nice

Exhaust you could cut a bit more of guide boss to make room for flow as it transfers to the roof

James,
thanks for your input,this is my first head porting effort and i am happy with intake ports as far a sizing and shape that i wanted to start with,the pinch is small @ 1.85'' and a 1204 opening.
i am confident these sizes are going to make this engine fall on its face early but like i said i need a starting point,i could not bring myself to fit these heads as cast out of the box but would be the best starting point i spose.
i understand what you are saying about the exhaust guide boss,because of my inexperience i struggled a bit at first with the exhaust side,i didnt want to kill the head by over sizing the port to valve size and velocity,this is probably why the exhaust is just a fluff and buff port job,i read a old post where yourself and some other guys were talking about putting bias in the exhaust port towards the cylinder wall.

[randy331]

LOL Randy,
you are right about the belt drive is a bit of overkill,but as you know makes cam timing changes easy.

Yes they do. Can't beat a belt drive for cam testing.

Randy,
any thought about using the solid flat tappet cams as far as being lift restricted,i think the duration and timing events will be a reasonable starting point but the 0.500'' valve lift will hold the engine back,is this a fair statement??
1.5'' exhaust valve @ 88% - 1.36'' throat

I'd say your spot on about the flat tappet/lift limiting power potential.
If you compare the time/area at the valve in the top of the lift curve of a flat tappet vs roller of the same lift, it's surprising how much more time the roller spends in the upper lifts. And that time at the upper lifts is worth some power.
Kinda shows a little about how unimportant low lift flow is to making power. Otherwise there wouldn't a power difference.


Randy

[GARY C]

Randy, on your flat vs roller test how close were you able to keep the seat, .050 and .200 duration specs to determine what the upper lift was worth and if you can share how much power did you find?

[cjperformance]

LOL Randy,
you are right about the belt drive is a bit of overkill,but as you know makes cam timing changes easy.

Yes they do. Can't beat a belt drive for cam testing.

Randy,
any thought about using the solid flat tappet cams as far as being lift restricted,i think the duration and timing events will be a reasonable starting point but the 0.500'' valve lift will hold the engine back,is this a fair statement??
1.5'' exhaust valve @ 88% - 1.36'' throat

I'd say your spot on about the flat tappet/lift limiting power potential.
If you compare the time/area at the valve in the top of the lift curve of a flat tappet vs roller of the same lift, it's surprising how much more time the roller spends in the upper lifts. And that time at the upper lifts is worth some power.
Kinda shows a little about how unimportant low lift flow is to making power. Otherwise there wouldn't a power difference.


Randy

Yeah i think low lift flow was more of an issue when springs etc limited lift a lot and duration was the biggest key to allowing more flow/time off the seat

[digger]

The Low lift flow argument is nothing more than using "overlap" to help cylinder fill and that the cam timing needs to differ Depending on the flow characteristics

[randy331]

The Low lift flow argument is nothing more than using "overlap" to help cylinder fill and that the cam timing needs to differ Depending on the flow characteristics

Is it really that simple ?

Randy

[digger]

The Low lift flow argument is nothing more than using "overlap" to help cylinder fill and that the cam timing needs to differ Depending on the flow characteristics

Is it really that simple ?

Randy

I think it is based on what "supporting evidence" the proponents put forward

[GARY C]

The Low lift flow argument is nothing more than using "overlap" to help cylinder fill and that the cam timing needs to differ Depending on the flow characteristics

Is it really that simple ?

Randy

I think it is based on what "supporting evidence" the proponents put forward

I think it would depend on if it's in reference to flow bench only or if it's in relation to crank angle/piston position. It seems most people only think about it in terms of flow bench but never connect it to valve timing in the actual engine.

[digger]

Low lift flow seems to refer to flow bench low lift flow.

[GARY C]

Low lift flow seems to refer to flow bench low lift flow.

It is, I think it would be better understood or taught when it helps or hurts if it was referenced to cam and piston, maybe flow at TDC?

[randy331]

Low lift flow seems to refer to flow bench low lift flow.

It is, I think it would be better understood or taught when it helps or hurts if it was referenced to cam and piston, maybe flow at TDC?

Probably more to it than that, but piston position and direction has got to be part of it.

Randy