Under performing 357 sbc

[F-BIRD'88]

Make up port floor tongue inserts to fill the floors of the intake ports to speed up the ports.
Play with the insert contour to get it right.

[dazimm531]

Thanks to all!!
Great info here It sounds like I need a smaller intake port to wake up the combo.
Thoughts on the cam with a smaller intake runner?

[Mummert]

256-260 int, will get a 357 in the 72-7500 range with your style of head. the exhaust should be based off of the exhaust system. If your running headers and collecters only, about 5 degrees less exh duration will be pretty stout. If you start adding tail pipe or collecter extensions to it than you need more exhaust duration.
I've had decent luck reverse engineering the exhaust lobe to fit the current exhaust sytem with pipemax.

Obviously giving as many specs as you can to a cam expert could be a good way to go.

[willisonTfosdik]

Thanks to all!!
Great info here It sounds like I need a smaller intake port to wake up the combo.
Thoughts on the cam with a smaller intake runner?

That cam should work well with smaller heads & better intake.

Mine is 4.040x3.48

264/272 .686 .630. 108 in at 104

A little more compression with Dart 215’s & a SV

750 alky carb on a 2” spacer

Tight 5700 converter with 4.88’s & weighs 300lbs less in an old upright roadster with 14.5x32’s

1.21 3.60 5.65@120 shifted at 7200 & crosses @ 6400 1/8th

Put the right heads on yours & it should fly.

[rewguy]

The heads stock only move about 290s cfm on my bench and for that size runner it makes them a turd velocity wise. You port them and really wake them up but then they are larger than what you can use. As they are now with your combo the heads are already borderline. The older hurricane intakes are not as nice as the newer ones. However either way they are decent but not great. Porting helps them too.

I can tell you through several conversations.....larry meaux does not put a lot of stock in ports being too large for the cfm. He said thats a typical trait of the BBC rectangle port.......and that 260 fps is about the slowest fps that still makes the expected horsepower. Even as big as the runner on a 235 is.....it will still be 260+ fps, and honestly shouldn't cost power. For example.....LS3 ports that stock flow 320 cfm. Similar size to cfm. But those 6.0's haul the mail.....period. Too slow is rarely an issue. Too fast is usually it. I'd guess neither in this case. Is the head ideal? Probably not......but I bet a 290 cfm head with a 210 runner wouldn't make much difference.

[rustbucket79]

Get that engine on a dyno, cam timing, tuning, and the resultant graph can help with converter and gear selection. Knee jerk response is you need more converter stall. 350/glide is yawn inspiring. More cubes would definitely help.

[WeingartnerRacing]

The heads stock only move about 290s cfm on my bench and for that size runner it makes them a turd velocity wise. You port them and really wake them up but then they are larger than what you can use. As they are now with your combo the heads are already borderline. The older hurricane intakes are not as nice as the newer ones. However either way they are decent but not great. Porting helps them too.

I can tell you through several conversations.....larry meaux does not put a lot of stock in ports being too large for the cfm. He said thats a typical trait of the BBC rectangle port.......and that 260 fps is about the slowest fps that still makes the expected horsepower. Even as big as the runner on a 235 is.....it will still be 260+ fps, and honestly shouldn't cost power. For example.....LS3 ports that stock flow 320 cfm. Similar size to cfm. But those 6.0's haul the mail.....period. Too slow is rarely an issue. Too fast is usually it. I'd guess neither in this case. Is the head ideal? Probably not......but I bet a 290 cfm head with a 210 runner wouldn't make much difference.

Yes but I would rather have 285ft per sec. It will make more power and run better. I’m not arguing for a smaller head but one that moves more air for that size.

[WeingartnerRacing]

Just for reference my personal 355 12to1 has 241cc head flows 323cfm made 672hp@7500 on methanol. I like a little large with runner.

By the way someone recommended a cam not to far off from mine used in this. 252/258

[GARY C]

Just for reference my personal 355 12to1 has 241cc head flows 323cfm made 672hp@7500 on methanol. I like a little large with runner.

By the way someone recommended a cam not to far off from mine used in this. 252/258

What kind of tq at what rpm? It seems the bigger head has a higher peak tq rpm and the op may need to look at an under performing combo as oppose to an under performing 357..

[levisnteeshirt]

I would put a 617 gear in it or 630 with that much tire , and 272/280-104 and a 7000 stall ,,, , it's a 350 , wind it

[randy331]

On a running 355 cube engine, 44.375 cubes and speed of the piston determine port speed, not the flow bench.

Randy

[novafornow]

I agree with Eric. I did a circle track engine with those heads and they suck as cast. Yes they are a little large, but I would still port them and GET THE RIGHT CAM. A large port will be more sensitive to cam selection than a smaller fast port. Just the opinion of a typical garage hack.

[Mummert]

The heads stock only move about 290s cfm on my bench and for that size runner it makes them a turd velocity wise. You port them and really wake them up but then they are larger than what you can use. As they are now with your combo the heads are already borderline. The older hurricane intakes are not as nice as the newer ones. However either way they are decent but not great. Porting helps them too.

I can tell you through several conversations.....larry meaux does not put a lot of stock in ports being too large for the cfm. He said thats a typical trait of the BBC rectangle port.......and that 260 fps is about the slowest fps that still makes the expected horsepower. Even as big as the runner on a 235 is.....it will still be 260+ fps, and honestly shouldn't cost power. For example.....LS3 ports that stock flow 320 cfm. Similar size to cfm. But those 6.0's haul the mail.....period. Too slow is rarely an issue. Too fast is usually it. I'd guess neither in this case. Is the head ideal? Probably not......but I bet a 290 cfm head with a 210 runner wouldn't make much difference.

BBC has "no" valve area per cu/in.. You cannot compare two engines with different curtain areas in a velocity discussion. One has the choke point at the valve and one has it back at the pushrod. When your velocity fall in the tank, you'll suddenly start finding miracles in overly aggressive port textures, kind of like the Ford Boss 302 guys.

[GARY C]

The tech info these days sounds like it's coming from politicians...

You need a fast slow port with slow fast gental sharp radius's with good cfm that doesn't flow through a big small valve with a critically sized ports right between 150 and 300 cc should get the job done without fail... if you have the correct solid hydrophilic flat tappet roller minimum full travel cam with shaft stud rockers with 0 W 10/15 30/40/50 mineral synthetic used new oil.

Hi, I am Gary C and I approve this message... Maybe.

[ClassAct]

The tech info these days sounds like it's coming from politicians...

You need a fast slow port with slow fast gental sharp radius's with good cfm that doesn't flow through a big small valve with a critically sized ports right between 150 and 300 cc should get the job done without fail... if you have the correct solid hydrophilic flat tappet roller minimum full travel cam with shaft stud rockers with 0 W 10/15 30/40/50 mineral synthetic used new oil.

Hi, I am Gary C and I approve this message... Maybe.

You're in rare for today Gary.