427 cam options
Thread Starter
Racer
Joined: May 2016
Posts: 492
Likes: 35
From: Norwalk, Ct
427 cam options
Hey Vette family,
I have a 427 tripower that was built by the previous owner with a .710 lift cam and 12.5 to 1 compression. What cam would you recommend to get as close to a normal driver as possible?. I will obviously talk to the engine builder but I just wanted to get some thoughts on the subject.
I have a 427 tripower that was built by the previous owner with a .710 lift cam and 12.5 to 1 compression. What cam would you recommend to get as close to a normal driver as possible?. I will obviously talk to the engine builder but I just wanted to get some thoughts on the subject.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
is this a car or an engine? what are the head casting numbers? those domes are gonna be an obstacle to street use. unless 100cc or smaller closed chambered heads. then a 119cc head could drop that compression about 2 points. then a fairly normal cam could make it a fairly normal driver.
Thread Starter
Racer
Joined: May 2016
Posts: 492
Likes: 35
From: Norwalk, Ct
is this a car or an engine? what are the head casting numbers? those domes are gonna be an obstacle to street use. unless 100cc or smaller closed chambered heads. then a 119cc head could drop that compression about 2 points. then a fairly normal cam could make it a fairly normal driver.
Last edited by zblackz06; Jun 20, 2021 at 04:01 PM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Something doesn't jibe with the pistons.......first, the #767 doesn't exist in KB or Icon (who does KB forged now).....and to have a 12 to 1 dome on this, it would have to be huge......Neither KB nor Icon show a 12 to 1 piston for BBC......especially not for 427, it is much more difficult to have a high compression piston in a 427 as opposed to 454.
The pistons would have to be confirmed before any cam recommendation is possible.
Jebby
The pistons would have to be confirmed before any cam recommendation is possible.
Jebby
Thread Starter
Racer
Joined: May 2016
Posts: 492
Likes: 35
From: Norwalk, Ct
Something doesn't jibe with the pistons.......first, the #767 doesn't exist in KB or Icon (who does KB forged now).....and to have a 12 to 1 dome on this, it would have to be huge......Neither KB nor Icon show a 12 to 1 piston for BBC......especially not for 427, it is much more difficult to have a high compression piston in a 427 as opposed to 454.
The pistons would have to be confirmed before any cam recommendation is possible.
Jebby
The pistons would have to be confirmed before any cam recommendation is possible.
Jebby
All I know about this motor is that at some point it spun a bearing and the last owner had the motor rebuild why he put a huge came in it I will never know.
Sorry I rechecked the receipt and I see what you mean about the KB when he refers to the pistons.
Last edited by zblackz06; Jun 20, 2021 at 05:40 PM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
I didn't see any mention of the pistons on the receipt so I am assuming they are the stockers bit I will check with the engine builder and try to find out.
All I know about this motor is that at some point it spun a bearing and the last owner had the motor rebuild why he put a huge came in it I will never know.
Sorry I rechecked the receipt and I see what you mean about the KB when he refers to the pistons.
All I know about this motor is that at some point it spun a bearing and the last owner had the motor rebuild why he put a huge came in it I will never know.
Sorry I rechecked the receipt and I see what you mean about the KB when he refers to the pistons.
Jebby
Thread Starter
Racer
Joined: May 2016
Posts: 492
Likes: 35
From: Norwalk, Ct
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
12 to 1 is not a streetable compression ratio. pull a valve cover and see what casting number the heads are. are they cast iron or aluminum? my bet is on 3919840. 107 cc chambers.nothing about decking the block. so i will assume .020 in the hole still. .029 head gasket. with 30 cc domes you get 12.25 cr. swap those 107 cc heads for 119 cc heads and .041 head gaskets and you get 10.6. take 4 cc's of meat out of the chambers and you are down to 10.2. now you can put most any street or normal performance cam in and you have a streetable engine. still gonna scream. still be north of 475 hp. just won't idle like a top fuel funny car. so, norwalk. and that shop is halfway up the island. give him a call. he may have some ideas.
Last edited by derekderek; Jun 20, 2021 at 07:27 PM.
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Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
https://www.ebay.com/sch/i.html?_fro...+head&_sacat=0 https://www.ebay.com/itm/16491288572...YAAOSw2bpgId8q https://www.ebay.com/itm/192672510758?epid=1866749529&hash=item2c dc2d3326:g
2gAAOSwl3xbrVBp these are the 3 most common open chambered rectangle GM heads. they are hard to find and the aluminum aftermarket heads may be a better way to go. another option is flat or 12 cc domed pistons. then you can keep the correct dated left st louis under your hood heads. i think it may be possible to mill 10 or 20 cc off those pistons and not have to replace them. jebby and i aren't the only 2 people that know a little about big blocks... mark. vortecpro. another person to try to talk to. one thing. iron rectangle big block heads. more were installed on mercruiser engines than on chevy cars. anl lots of performance boat guys think this 325 cc port is too small now that they swapped their pissy little 454's for 572's. so boat shops may be a place to look for these. if you find some that were on a boat. post a pic of the water passages. the 2 end exhaust valves guides. #2 and #7 can rot right through.
2gAAOSwl3xbrVBp these are the 3 most common open chambered rectangle GM heads. they are hard to find and the aluminum aftermarket heads may be a better way to go. another option is flat or 12 cc domed pistons. then you can keep the correct dated left st louis under your hood heads. i think it may be possible to mill 10 or 20 cc off those pistons and not have to replace them. jebby and i aren't the only 2 people that know a little about big blocks... mark. vortecpro. another person to try to talk to. one thing. iron rectangle big block heads. more were installed on mercruiser engines than on chevy cars. anl lots of performance boat guys think this 325 cc port is too small now that they swapped their pissy little 454's for 572's. so boat shops may be a place to look for these. if you find some that were on a boat. post a pic of the water passages. the 2 end exhaust valves guides. #2 and #7 can rot right through.
Last edited by derekderek; Jun 20, 2021 at 07:33 PM.
Thread Starter
Racer
Joined: May 2016
Posts: 492
Likes: 35
From: Norwalk, Ct
12 to 1 is not a streetable compression ratio. pull a valve cover and see what casting number the heads are. are they cast iron or aluminum? my bet is on 3919840. 107 cc chambers.nothing about decking the block. so i will assume .020 in the hole still. .029 head gasket. with 30 cc domes you get 12.25 cr. swap those 107 cc heads for 119 cc heads and .041 head gaskets and you get 10.6. take 4 cc's of meat out of the chambers and you are down to 10.2. now you can put most any street or normal performance cam in and you have a streetable engine. still gonna scream. still be north of 475 hp. just won't idle like a top fuel funny car.
Melting Slicks
Joined: Oct 2008
Posts: 2,154
Likes: 69
From: Regina Sk Canada
My old 427. .060 with Eddy Oval port RPM performer heads, holly single plane intake. 11.25-1 compression, cam was a hydraulic roller .585/.585 with .245/.255 @ .050 on a 112 LSA. 1-7/8 header made 550 Hp and 513 tq. was very streetable.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
11.25 with aluminum heads is rough equiv of 10.25 with iron heads. i did find these in summit catalog. no longer available. https://www.summitracing.com/parts/UEM-KB767KTD-060 don't know if they are even chebby.
Team Owner
Joined: Mar 2002
Posts: 44,699
Likes: 1,835
From: Huntsville AL
Something doesn't jibe with the pistons.......first, the #767 doesn't exist in KB or Icon (who does KB forged now).....and to have a 12 to 1 dome on this, it would have to be huge......Neither KB nor Icon show a 12 to 1 piston for BBC......especially not for 427, it is much more difficult to have a high compression piston in a 427 as opposed to 454.
The pistons would have to be confirmed before any cam recommendation is possible.
Jebby
The pistons would have to be confirmed before any cam recommendation is possible.
Jebby
https://www.summitracing.com/search/...=UEM-IC767-070
Thread Starter
Racer
Joined: May 2016
Posts: 492
Likes: 35
From: Norwalk, Ct
So I got a hold of the engine builder who seems to remember the engine...basically he said it is a built motor like stated before and that it will never be streetable without a rebuild.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
I get 11.67 to 1 with those pistons......I think you could go backward to a cam with 250@.050 and you would be ok.......what is the cranking compression now? Check one cylinder and post.......this will be the tell.
They call all those pistons "12.5 to 1" like LT-1 350 pistons are "11 to1"....which is bullshit. a 43cc dome won't get you over 12 to 1 with a 3.760 stroke.
The builder built a 100% bracket race engine......even has the bracket cam......
It is not ideal.....but with careful cam choice and distributor timing/curve.....it could work.
What heads are on this?......pull a valve cover and find the number.
And if the builder said "built motor", lose his phone number.......*eye roll*
Jebby
They call all those pistons "12.5 to 1" like LT-1 350 pistons are "11 to1"....which is bullshit. a 43cc dome won't get you over 12 to 1 with a 3.760 stroke.
The builder built a 100% bracket race engine......even has the bracket cam......
It is not ideal.....but with careful cam choice and distributor timing/curve.....it could work.
What heads are on this?......pull a valve cover and find the number.
And if the builder said "built motor", lose his phone number.......*eye roll*
Jebby
Last edited by Jebbysan; Jun 29, 2021 at 08:14 AM.
Thread Starter
Racer
Joined: May 2016
Posts: 492
Likes: 35
From: Norwalk, Ct
I get 11.67 to 1 with those pistons......I think you could go backward to a cam with 250@.050 and you would be ok.......what is the cranking compression now? Check one cylinder and post.......this will be the tell.
They call all those pistons "12.5 to 1" like LT-1 350 pistons are "11 to1"....which is bullshit. a 43cc dome won't get you over 12 to 1 with a 3.760 stroke.
The builder built a 100% bracket race engine......even has the bracket cam......
It is not ideal.....but with careful cam choice and distributor timing/curve.....it could work.
What heads are on this?......pull a valve cover and find the number.
And if the builder said "built motor", lose his phone number.......*eye roll*
Jebby
They call all those pistons "12.5 to 1" like LT-1 350 pistons are "11 to1"....which is bullshit. a 43cc dome won't get you over 12 to 1 with a 3.760 stroke.
The builder built a 100% bracket race engine......even has the bracket cam......
It is not ideal.....but with careful cam choice and distributor timing/curve.....it could work.
What heads are on this?......pull a valve cover and find the number.
And if the builder said "built motor", lose his phone number.......*eye roll*
Jebby
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Get a cranking compression number too….
Jebby
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
those are possibly high compression pistons that fit his closed chamber early heads. let's hope. you can find chambers up to 122 or so. you can also open up any 118 chamber to 123-124. buy back some streetability. pistons are cheaper than heads, until you start having somebody install them.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
those are possibly high compression pistons that fit his closed chamber early heads. let's hope. you can find chambers up to 122 or so. you can also open up any 118 chamber to 123-124. buy back some streetability. pistons are cheaper than heads, until you start having somebody install them.
Jebby
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,126
Likes: 4,486
From: Marlton NJ
If you really want a normal street driver, even as wild as a normal solid lifter BB, you need a new set of pistons.
CR and cam duration go closely together.
You cannot reduce one without reducing the other.
Then you can get a more normal street cam. You know with like 30 degrees less duration.
Both Derek and Jebby are knowledegable.
But that's my 2 cents!
CR and cam duration go closely together.
You cannot reduce one without reducing the other.
Then you can get a more normal street cam. You know with like 30 degrees less duration.
Both Derek and Jebby are knowledegable.
But that's my 2 cents!
Last edited by leigh1322; Jun 29, 2021 at 02:16 PM.