SBC cam help

[GARY C]

Got this unit running and racing this weekend and am definitely under welmed. Went basically the same speed as the old combo. Seems like basic mistake of to big of parts on the wrong short block. We had at least hoped to go a little faster with the 383 for this season.

First time out gonna take some tuning time, the 11.1 compression is kind of a too much for pump gas and not enough for race engine. Play with jetting, timing, shift points and carbs if you have another 1 0r 2 and see what you get but you may find it needs more compression.

[steve cowan]

Got this unit running and racing this weekend and am definitely under welmed. Went basically the same speed as the old combo. Seems like basic mistake of to big of parts on the wrong short block. We had at least hoped to go a little faster with the 383 for this season.

i think the 227 will be nice on the 427sbc
personally the biggest valve i will use on a 4.030 bore is a 2.05'' after that there is alot of valve shrouding going on and i dont have the experience to make a 2.08 valve work correctly,i am not saying it cant be done,i am am saying i have not done it.
doesnt the 227 head have a 2.10'' intake valve ??
383 ci @ 7000 rpm is looking at 2.61'' MCSA
the 227 afr has a MCSA of 2.340'' so you would think it should work but it looks like not the case here probably due to big intake valve,bigger and slower intake runner and not enough time (rpm) to make it work,there is alot more to the whole package but this is just my observation regarding the 227 head

The AFR 227 I dealt with for a 421 had a 2.100, they were pre eleminator versions.
Here is a simple method Vizard taught me for unshrouding valves consistently.
https://www.speed-talk.com/forum/viewtopic.php?f=1&t=46308

hi Gary,
i remember that thread and you put that one up on my 165 dart head thread,
i was more thinking on the the line of cylinder bore shrouding,i remember reading a few years ago where we should be thinking on the lines of 51% of the bore being the max valve size for that bore
EG - 4.030'' bore x 51% = 2.05'' valve approx
this is only what i have researched and i could be wrong or reading it incorrectly??
any ideas would be appriciated

[Monza355]

Got this unit running and racing this weekend and am definitely under welmed. Went basically the same speed as the old combo. Seems like basic mistake of to big of parts on the wrong short block. We had at least hoped to go a little faster with the 383 for this season.

How does the time slip compare to last years combo ?
Are the 60 ft’s the same ?

[6.50camaro]

The new cam is 15° bigger on the intake and 18° bigger on the exhaust. Was any changes made to shift points and launch . The new cam most likely raised the power band higher by 600-800 rpm. Might need more gear now. Dan

[Scotthatch]

Looked over some numbers on this ...

If you look at weight / ET a basic calculation puts HP at 471 HP

The last motor should have made 576 HP

Your redo should have bumped you to 728 HP

The intake is listed for both heads so I am going to assume it flows enough ...never tested one

Are you still running the 850 HP carburetor?

And is there a air cleaner?

Also what did it feel like peak rpm was ? You should have bumped it 1200 to 1400 rpm

[GARY C]

i think the 227 will be nice on the 427sbc
personally the biggest valve i will use on a 4.030 bore is a 2.05'' after that there is alot of valve shrouding going on and i dont have the experience to make a 2.08 valve work correctly,i am not saying it cant be done,i am am saying i have not done it.
doesnt the 227 head have a 2.10'' intake valve ??
383 ci @ 7000 rpm is looking at 2.61'' MCSA
the 227 afr has a MCSA of 2.340'' so you would think it should work but it looks like not the case here probably due to big intake valve,bigger and slower intake runner and not enough time (rpm) to make it work,there is alot more to the whole package but this is just my observation regarding the 227 head

The AFR 227 I dealt with for a 421 had a 2.100, they were pre eleminator versions.
Here is a simple method Vizard taught me for unshrouding valves consistently.
https://www.speed-talk.com/forum/viewtopic.php?f=1&t=46308

hi Gary,
i remember that thread and you put that one up on my 165 dart head thread,
i was more thinking on the the line of cylinder bore shrouding,i remember reading a few years ago where we should be thinking on the lines of 51% of the bore being the max valve size for that bore
EG - 4.030'' bore x 51% = 2.05'' valve approx
this is only what i have researched and i could be wrong or reading it incorrectly??
any ideas would be appriciated

On the bore we usually tapper it in the intake side to match a Fel-Pro 1003 head gasket as well as matching the chamber. Some feel that any thing beyond a 2.055 valve causes to much shrouding but there have been many examples of a 2.08 working well if done correctly.
I have also seen 51.5, 52 and 52.5% quoted but I don't know if you can hang your hat on any of them.

[prairiehotrodder]

Same AFR titan plastic intake (don't buy one unless you like oil leaks and problems) same QFT 850 carb with a 1 inch super sucker spacer. Same air cleaner (cones style with a breathable lid). Car has 4.56 gears which was to much for the old motor, seemed like it was over - revving in the traps by a couple hundred rpm. That's partly why we figured the bigger cam and heads would really help. Admittadly the cam and heads will want more compression and cubes now and the air was very humid at the track. Last years best was 10.80 at 123. Now it runs 10.88 at 122 with more cam and way better flowing heads. My buddy is still at the track so I will get another update as to how it ran today. I suggested dropping the exhaust, trying a different air cleaner and removing the carb spacer. Just as easy things to try.
Brian

[GARY C]

Same AFR titan plastic intake (don't buy one unless you like oil leaks and problems) same QFT 850 carb with a 1 inch super sucker spacer. Same air cleaner (cones style with a breathable lid). Car has 4.56 gears which was to much for the old motor, seemed like it was over - revving in the traps by a couple hundred rpm. That's partly why we figured the bigger cam and heads would really help. Admittadly the cam and heads will want more compression and cubes now and the air was very humid at the track. Last years best was 10.80 at 123. Now it runs 10.88 at 122 with more cam and way better flowing heads. My buddy is still at the track so I will get another update as to how it ran today. I suggested dropping the exhaust, trying a different air cleaner and removing the carb spacer. Just as easy things to try.
Brian

Yes, test what you can, I have seen air cleaners and spacers help and hurt.

[rustbucket79]

Without thumbing through the pages, what is his (actual) stall speed on the launch?

Is the 60' time worse (not due to traction) as it takes a bit to get the engine into it's power band?

[Scotthatch]

Same AFR titan plastic intake (don't buy one unless you like oil leaks and problems) same QFT 850 carb with a 1 inch super sucker spacer. Same air cleaner (cones style with a breathable lid). Car has 4.56 gears which was to much for the old motor, seemed like it was over - revving in the traps by a couple hundred rpm. That's partly why we figured the bigger cam and heads would really help. Admittadly the cam and heads will want more compression and cubes now and the air was very humid at the track. Last years best was 10.80 at 123. Now it runs 10.88 at 122 with more cam and way better flowing heads. My buddy is still at the track so I will get another update as to how it ran today. I suggested dropping the exhaust, trying a different air cleaner and removing the carb spacer. Just as easy things to try.
Brian

Know anyone that can let you barrow a bigger carb for a run ?

[prairiehotrodder]

After adjusting the valves and running on the second day we finally ran a 10.73 which is slightly faster than last year. Hopefully we can keep moving forward.

[rustbucket79]

How does this year's 60 foots compare to last year?