Are 215cc heads too big for a 355?
Are 215cc heads too big for a 355? ive always read to keep the heads around 195 or so for good street driveability. bigger heads always get a reputation of needing to be revved very high to make power due to lack of velocity. however the new L92 heads are proving that wrong but those are an LS1 based head and are completely different than a SBC setup.
that being said, are 215cc heads too much for a built 355 running the stock ecu (7300rpm limit) for a street driven car with an appropriate cam?
that being said, are 215cc heads too much for a built 355 running the stock ecu (7300rpm limit) for a street driven car with an appropriate cam?
that much head will make you soft on the bottom end however if you are using a power adder like n2o it will pick up big time!
i really never thought alot of head would be a bad thing till i started messin with cars!
i really never thought alot of head would be a bad thing till i started messin with cars!
how much loss is hard to say,i can say this my friend built a nice 355 solid roller,4000 stall,4.10s and a large head similar to your size the car ran in the 12s(12.6) n/a on a 175 plate he ran 10.20s.finally listened to a few friends,swapped the heads to a dart 195 that had the same portwork and ran in the 11s first time out on the motor,60' times went from 1.7 to the 1.5 range.so i would leave the big heads to large CI motors,you can over-head a motor just like some people over-cam a motor
The runner volume will not effect that but the min. cross sectional area will dictate where you make peak HP with a certain cubic inch and where the TQ curve starts and stops.
Runner volume alone is not the problem but if the cross section is too large, low velocity at the valve job or if the port is shaped wrong, you can lose low or mid range TQ. Runner volume is just a bi-product of the port having certain measurements in certain areas and being shaped a certain way.
A 215 cc intake port may or may not be the best choice depending on gear. stall, weight, etc, but if you are gonna be shifting anywhere near 7000 RPM, you would want more than 195 cc.
Runner volume alone is not the problem but if the cross section is too large, low velocity at the valve job or if the port is shaped wrong, you can lose low or mid range TQ. Runner volume is just a bi-product of the port having certain measurements in certain areas and being shaped a certain way.
A 215 cc intake port may or may not be the best choice depending on gear. stall, weight, etc, but if you are gonna be shifting anywhere near 7000 RPM, you would want more than 195 cc.
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Originally Posted by 1bdbrd
how much low end am i gonna really going to lose compared to a slightly less flowing 195cc head?
I've run AFR 210's on anything from 355 to 388 cid and never was unhappy with the low-end. Cam choice and compression ratio will affect low-end torque more than a few extra cc's in the head.
Mike
Both good post's from both mike and lloyd.. that's one of the largest misconception's of cyl head's.. You can put a large head on it.. but w/ the right work for your "COMBO" you can easily have a killer setup.. As well as have room to grow in the future rather than buying a entire new set of heads... Speak in depth to your head guy about your plan's/goal's and most of all budget.. 
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Originally Posted by engineermike
Not more than 10 - 15 ft-lb.
I've run AFR 210's on anything from 355 to 388 cid and never was unhappy with the low-end. Cam choice and compression ratio will affect low-end torque more than a few extra cc's in the head.
Mike
I've run AFR 210's on anything from 355 to 388 cid and never was unhappy with the low-end. Cam choice and compression ratio will affect low-end torque more than a few extra cc's in the head.
Mike
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Yeh I have told people my head CC and their eyes popped out, I have been told MANY times my car will be a turd under 4500 rpm. Cam and torque converter technology has come along way baby. EFI does not suffer like carbs with a larger cc head, carbs need a stong"signal" from vacuum to work properly. There is a point of diminshing returns on head cc vs cubic inches though....it has gone up with the advent of EFI...but it is still there. Also gotta remember runner CC is also a function of runner length, most people don't take that into account.
David
David
