304 Crow 4761 - good choice??

[EYY]

Where is the fun in that?

I didn't say don't use an aggressive lobe profile lol

 

[shane_3800]

I'm going to use a TP dual plane but I had a single plane last time. I cant remember which cam I had but it was a solid roller from 2500 or 3000rpm upto 7000rpm if I remember correctly. It made 420hp at the wheels which was down from the possible 550hp with the cam. That was a 355 with oversize valves but no bowl job or 3 angle grind.

The issue is head flow with cams in 90% of cases when power is down. You need enough air flow to feed the cam. TK383 has many articles on this subject on aussie V8's he is Tony Knight of Knight race engines and has made 620hp with a red block 308 and yes its 308ci with cast iron heads which runs in a torana in time trials and targa rallies. The most important part of an engine is the transition from the bowl across the seat radius into the chamber.

 

[Big_Bro]

Where is the fun in that?

I'd consider anything under .550 lift mild. Lift = flow = powa

Would it be best to use roller rockers with a big lift flat tappet cam??

I'm going to use a TP dual plane but I had a single plane last time. I cant remember which cam I had but it was a solid roller from 2500 or 3000rpm upto 7000rpm if I remember correctly. It made 420hp at the wheels which was down from the possible 550hp with the cam. That was a 355 with oversize valves but no bowl job or 3 angle grind.

The issue is head flow with cams in 90% of cases when power is down. You need enough air flow to feed the cam. TK383 has many articles on this subject on aussie V8's he is Tony Knight of Knight race engines and has made 620hp with a red block 308 and yes its 308ci with cast iron heads which runs in a torana in time trials and targa rallies. The most important part of an engine is the transition from the bowl across the seat radius into the chamber.

Your thoughts have been echoed with almost everyone I have spoken to, proper head work will give the results, however, some have even said that stock heads flow enough for the size cam I want to use!?? I do seriously doubt it...
I have been quoted up to 3000$ for my heads, that's a full reco, shaved, no porting, pretty much everything new.
I have checked out TK383's posts, that guy is an artist! Pics he posted of the head work he done were brilliant! Price also reflects the work lol

 

[Immortality]

I'd pocket port the heads but not enlarge the runners. A pocket port is a bowl job, clean up around the guide and the short side turn blending the bowl into the valve seat etc.

And yes, with a decent cam a rocker upgrade is recommended.

 

[shane_3800]

Would it be best to use roller rockers with a big lift flat tappet cam??


Your thoughts have been echoed with almost everyone I have spoken to, proper head work will give the results, however, some have even said that stock heads flow enough for the size cam I want to use!?? I do seriously doubt it...
I have been quoted up to 3000$ for my heads, that's a full reco, shaved, no porting, pretty much everything new.
I have checked out TK383's posts, that guy is an artist! Pics he posted of the head work he done were brilliant! Price also reflects the work lol

The biggest thing is the port might flow well after a bolw job/pocket port but if it's left untouched it's horrible.

 

[Big_Bro]

The biggest thing is the port might flow well after a bolw job/pocket port but if it's left untouched it's horrible.

I'd pocket port the heads but not enlarge the runners. A pocket port is a bowl job, clean up around the guide and the short side turn blending the bowl into the valve seat etc.

And yes, with a decent cam a rocker upgrade is recommended.

Thanks guys!
Looks like a bowl job might need to be on the cards!
Would there be any merit in match porting the heads to the inlet/exhaust manifold? Or could this possibly have a negative effect?
I thought roller rockers would be necessary, $730 for a bolt down adjustable kit almost makes me want to reconsider the cam size haha

Clearly I've never been down this path before and not likely to again (if the Wife has anything to do with it lol ) so it's a one shot game, build it big build it right the 1st time. I'll be asking question after question, reading and thread mining followed by more stupid questions etc.

I hope to make a start on getting the engine build under way before the end of November... lots of work to do!

 

[shane_3800]

Yea roller rockers on 7/16 studs is a minimum for high lift cams. You can get SBC stamped steel hight lift rockers for 7/16 studs that are used on circle track cars for cheap.

 

[Deuce]

Yea roller rockers on 7/16 studs is a minimum for high lift cams. You can get SBC stamped steel hight lift rockers for 7/16 studs that are used on circle track cars for cheap.

Holden V8 uses pontiac roller rockers, not sbc.

 

[EYY]

If you want to do it right, go roller cam from the get go. None of the pitfalls of hydraulic flat tappet - it's all benefit as far as performance is concerned. Costs a little more though it IMO worth it for the reliability.

 

[shane_3800]

If you want to do it right, go roller cam from the get go. None of the pitfalls of hydraulic flat tappet - it's all benefit as far as performance is concerned. Costs a little more though it IMO worth it for the reliability.

Not always. You get more valve open time:lift but you have to deal with the rollers. I've done serveral gen 4 V8's with lifter skid issues from low roller speeds. Roller cams were a race thing until people figured out they could alleviate roller skate (I know) with point pressure. The issue is worn engines struggle to keep the rollers from skating. Flat tappets are far less prone to failure if the first 20 mins of life is sucsessful. Even if you flatten a lobe on a flat cam all the gaskets arr fresh and reusable.