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cam suggestions for 355

General engine tech -- Drag Racing to Circle Track

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superdirtbag2
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cam suggestions for 355

Post by superdirtbag2 »

Greetings and Thank you in advance to all who read and reply,

Building a bucket list 355 chevy for daily driver crewcab s10. Not a too mild mannered 355 tho...
afr vortec heads
190cc Street Head Flow Chart
.200 .300 .400 .500 .550
Int 135 213 253 276 279
Exh 110 158 190 207 211
edelbrock rpm vortec intake non airgap (gets pretty cold here). 735cfm holley, off of 428 cobrajet, with spacer(s) if/as needed. 1 5/8 long tube headers.
Shortblock= 9.7 :1 comp with 65ccheads...propersized dish and valve reliefs for above mentioned heads with zero deck and felpro head gasket. torqueplate honed line honed square decked etc...windage tray...possible block filler to bottom of freeze plugs, as current setup runs below 190 even in summer. Custom oil pan. Msd e-curve dist.

Have searched a few companies and filled out a couple forms for a solid roller...Comp for example showed a cs xr268 r10...or CS XR274 R-10.
After looking at these and the specs i guess my main question would be would the xr268 be better with a 1.7 rocker setup over the xr274 with a 1.6 rocker? Taking into account the 1.7 rockers effect on duration as well as lift has me stepping into territory I am not totaly understanding of. As well as the 110 lobe separation. I do need power brakes to work reliably.

The truck has a 2500stall converter, th700r4, and 3.73 rearend. It has a basic smallblock in it now, but am looking for more within reason...and yes I do realize thats a subjective statement, but none the less am wondering what the more knowledgable individuals on here have to say.

Again thank you God bless and Semper Fi

p.s. anyone willing to hoot a guess on hp/tq and rpm?
travis
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Re: cam suggestions for 355

Post by travis »

I’d lean towards the smaller cam of the 2 you listed. A street use vehicle, with an effective gear ratio in OD of about 2.6:1, will be happier with less overlap (and your compression)...and will still haul the mail with the rest of the components you have. I’d estimate around 425hp/430tq
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Re: cam suggestions for 355

Post by mag2555 »

Well if you run a atleast a .500" lift Cam then a solid 500 hp should be made, but for your overall set up I think 180 CC heads will serve you up with a more needed wider power band to work with that trucks weight.

If your stuck with those 190 CC heads then run a Cam that will get you .580" to .600" lift to get the best port air speed out of those heads you can.

If you fill the block your going to need more piston to wall clearance to not scuff up the skirts when riding the bottom of the Bores.
superdirtbag2
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Re: cam suggestions for 355

Post by superdirtbag2 »

I do have the 190cc heads already. If i am comprehendingit correctly, it appears I would need the smaller cam with a 1.7 rocker atleast on the intake to get the needed lift. I am having a hard time figuring/understanding the change it will make to the overlap and duration above .050",all of which i assume would have an effect on vac for brakes and such.
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Re: cam suggestions for 355

Post by cv67 »

those cams I believe havea fairly aggressive ramp. Sure you want to increase rocker ratio? Springs set up for it?
superdirtbag2
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Re: cam suggestions for 355

Post by superdirtbag2 »

Springs good for .650". PAC springs. Was thinking not being a super high rpm situation that they would be ok...? Also using heavywall pushrods. I was thinking the higher rocker would get me to the needed lift for the heads without too much duration being added...Just my thoughts on how to do it.
I would think it would take a custom grind to get there any other way i guess, and thats not beyond the realm of possibility.
jeff swisher
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Re: cam suggestions for 355

Post by jeff swisher »

Some numbers for you to chew on .
Flat top 327" with 64cc heads 180 afr competition series RPM intake 750 Edelbrock (other carbs were tried this one was best)
XE 276 roller cam was used and 1.5 rockers.
It made 421HP and 419 TQ Not bad for bolt on stuff. plenty of vacuum for power brakes.
I have found it is more the heads and velocity through the runners that makes a nice strong vacuum signal.

I have ran Ported iron heads on many 350" engines Runner size is 175cc after porting and the old comp magnum 292H which is 244@ .050 pulled 12" of vacuum. 1.5 rockers.
I then built another 350" and it had the same flat tops and same ported heads but larger cam a solid flat tappet 252-252@ .050 and .571" lift was what we got with 1.6 rockers ..it was ground on a 106LSA it pulled 11.5" vacuum.. plenty for the brakes on the black short bed truck.
https://www.youtube.com/watch?v=V46PRMRgtIA

I run a 230@ .050 and .480" lift in my heavy 4 door chevy in a 350" ported heads iron 175cc runners. It is not a light weight but it will pull my 20 foot Pontoon just fine across the state I get 11.5 MPG with the AC on pulling the boat. And the car has ran 12.86 in the 1/4.
https://www.youtube.com/watch?v=fB0vQECFAzE

I do not get too caught up in the max lift thing as there are ways to go quick and I need utmost reliability pulling heavy loads for 400+ miles at a time.
Not that lift would be a deal breaker you just need to figure what your ultimate goal would be.

I would say with 1.6 rockers you would be fine with any of those cams and should make good power.
Plan on shifting any of them above 6000rpm for best et.

Just finished another 355" with E street heads # 5089 and the 230@ .050 .480" lift on a 106 LSA for a buddies truck a 1985 chevy.
It ran a bunch of 13.0's with an initial bog. I think was from the hurricane intake and cold air.
Should be some 12's in it once it is sorted out.
Brakes work perfectly.
But his 305H cam and 210cc heads gave only 5.5" vacuum and brakes did not work and it would not run 19's in the 1/4.
Get 12.5" from the current cam.
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Re: cam suggestions for 355

Post by GARY C »

superdirtbag2 wrote: Thu Jan 16, 2020 7:48 am I do have the 190cc heads already. If i am comprehendingit correctly, it appears I would need the smaller cam with a 1.7 rocker atleast on the intake to get the needed lift. I am having a hard time figuring/understanding the change it will make to the overlap and duration above .050",all of which i assume would have an effect on vac for brakes and such.
Rule of thumb is a 1.7 vs 1.5 will make your engine see a 4 degree bigger cam shaft due to opening the valve quicker in relation to piston position, I doubt that you would see any difference if you was to do a rocker test at the track as you are only looking at a few hp but definitely factor the rocker you will run with your cam choice.

Block fill will not effect you water temp, this would be better regulated with a t stat, it will however heat the oil that cools your main bearings and could be bad on a street driven vehicle. Or at least that was my experience with filled blocks.
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superdirtbag2
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Re: cam suggestions for 355

Post by superdirtbag2 »

Again thank you for reading and posting.
Will definately chew on the numbers. Interesting combos there with the driven results you have experienced. I am trying not to get caught up in the BIBS as far as max lift dictating my cam choice, I do need fair lift to get the heads to utilize the available lift as they seem to flow good all the way thru.
I am hoping to use a solid roller knowing that springs will be pretty stout to control valve train...any thoughts on longevity in a streeter?
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Re: cam suggestions for 355

Post by jeff swisher »

I have no idea on longevity in a street car with roller cams that have a lot of pressure.
Rollers scare me a bit as I have seen more of those fail than I have seen flat tappet failures.

But that was way back and roller lifters and cam tech are much better today.

Some others may chime in on longevity .
I used to drive 70,000 miles a year and failure would not be good for me.
I ran a 235-245 @ .050 on a 108LSA with .500" lift solid flat tappet for 70,000 miles and pulled it to stick in a cam for better MPG and the cam and lifters were perfect. It had seen 8500rpm 2 times during a second gear to neutral shift a buddy did.
Normally I shifted at 7600 with that one..It was a Herbert cam.

I gave it to a buddy with lifters in order and he ran it in his dirt car for 2 years without failure and pulled it to try a different cam.
That was back in 1998. The lifters were Herbert also and no oil holes and I ran oil restrictors in my engine. Yep on the street.
Minimum of 50 miles a day driving in that car. It went 11.50 in the 1/4 but was a tick less than 3000 lb race weight. 350"
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Re: cam suggestions for 355

Post by cv67 »

If looking for longevity I wouldnt worry about a little more lift, 1.5 or 6 and call it a day
never felt a difference in going up on rocker ratio...your valve job will thank you. Im no expert though.
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Re: cam suggestions for 355

Post by trmnatr »

superdirtbag2 wrote: Thu Jan 16, 2020 7:48 am I do have the 190cc heads already. If i am comprehendingit correctly, it appears I would need the smaller cam with a 1.7 rocker atleast on the intake to get the needed lift. I am having a hard time figuring/understanding the change it will make to the overlap and duration above .050",all of which i assume would have an effect on vac for brakes and such.
The 1.7 rocker won’t add any duration at .050” as that’s solely.050” tappet lift which is controlled by the camshaft lobe however the higher rocker ratios will provide more valve lift and make the seat duration at the valve longer with more valve area under the lift curve
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Re: cam suggestions for 355

Post by GARY C »

trmnatr wrote: Mon Jan 20, 2020 1:52 am
superdirtbag2 wrote: Thu Jan 16, 2020 7:48 am I do have the 190cc heads already. If i am comprehendingit correctly, it appears I would need the smaller cam with a 1.7 rocker atleast on the intake to get the needed lift. I am having a hard time figuring/understanding the change it will make to the overlap and duration above .050",all of which i assume would have an effect on vac for brakes and such.
The 1.7 rocker won’t add any duration at .050” as that’s solely.050” tappet lift which is controlled by the camshaft lobe however the higher rocker ratios will provide more valve lift and make the seat duration at the valve longer with more valve area under the lift curve
Actually seat to seat changes little to none but the .050 is effected, the only change is once it leaves seat or that is what I experienced using a degree wheel and 3 different rocker ratios. 1.5 vs 1.6 is 2 degrees more and 1.5 vs 1.7 is 4 degrees more at .050.
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superdirtbag2
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Re: cam suggestions for 355

Post by superdirtbag2 »

I can see how the duration could change ie: seat to seat and at .050", but would it be an exponential change or a constant change. I have noticed lobe lift times rocker ratio seems to be almost exponential so to speak, taking into account that it is at a singular point and not a measurement BETWEEN 2 points. I have been leaning towards the 1.7 to get needed lift for heads without stepping up to the next cam in list of some catalog. I do see that i am walking a line between losing vacumm by increasing overlap with the 1.7 rocker. Hence the reason to adk you guys :D
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Re: cam suggestions for 355

Post by jeff swisher »

1.7 ratio in a sbc is not worth the expense in my book for the small gains.
Read a little here about it.

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