520 inch build for street business

[slimtastic]

ok so im starting to get a rough idea of what my next motor build will be and a couple major questions are sitting in the way that i need pointers on. my build is based around a tall deck bbc and the planned displacment is 520 cuin, so ill lay out the basics of my build to this point

max rpm redline 6500-7000
4.375 stroke
4.35 bore
6.700 rod length
planned compression 8.5-8.8 with custom pistons
build around pump gas 93oct for 90% of operation
planned for 900-1000 WHP on 93
planned boost under 15 lbs oct
88-91 mm single turbo

planned heads- tfs-41400008
360 cc intake
122cc chamber
solid roller .700 lift

planned cam specs... im thinking a custom cam for the odd cubic inches
intake lift .702 at valve
exhaust lift .702 at valve
intake duration (seat to seat) 295.
exhaust duration (seat to seat 305
LCA 115
intake center line 115



my main questions are about the cam. this is a rough idea of what i think would work good with the combination ive laid out at this point but id love some of you in the "know" to critique the cam ive spec'd.

also what kind of roller rockers? am i really gonna need 1200$ shaft mount rockers like i see everyone getting or would a good set of stainless bodied comp roller rockers do the job for .700 lift?


also any other questions and comments about the combination at hand are more than welcome. i just need to see if im headed in the right direction for my power goals

 

[daverr]

looks like you have a great build ahead. The question i have for you is , if your going to use a tall deck block why stop at 520ci???

 

[slimtastic]

well the offical deck height is 10.180, and the bore at 4.30 has just over .250" around every cylinder which should be good for boost. i was gona go with a larger swing but id rather get a better rod ratio that is afforded by a 4.375 swing and a 6.7 rod vs a 4.5-4.75 swing and the same rod

 

[Dusty Bradford]

Never cut corners on valvetrain. It will always bite you eventually. I run T&D shaft mounts with the needle bearing tips.

Bore size is ok but make sure you have enough room for the valves with such a small bore. I like a 4.5 bore personally. I think 4.25x4.50 is a great combination. A tall deck isn't needed but I'm assuming your just using what you have already. My big block is 9.8 deck.

 

[slimtastic]

well whats a safe bore thickness limit for a 10-15 lbs application? complicated question i know... can i really afford to bore it out more for what im planning?


any thoughts on the cam?

 

[daverr]

well the offical deck height is 10.180, and the bore at 4.30 has just over .250" around every cylinder which should be good for boost. i was gona go with a larger swing but id rather get a better rod ratio that is afforded by a 4.375 swing and a 6.7 rod vs a 4.5-4.75 swing and the same rod

Im going to assume that your plan build is on a GN and going to keep the turbo theme. I want to do a similar deal with my street Buick since I never had a bbc.My dilema is whether to use a turbo or just go with a 1000hp 615" pump gas on motor drive anywhere engine. If your using a tall deck bbc you could almost reach your goals without the lag of a turbo.

 

[slimtastic]

well yea for one its still a turbo regal so id rather keep it boosted. and i also dont wanna run around with 1000 Hp all the time in the street so a low compression high head flow 520 seems like a better option as i can ramp inboost as needed

 

[daverr]

sounds good. post pics of the build, definitely interested in seeing this project.

 

[Dusty Bradford]

My bore size is 4.6 and will run over 30# once I get a chassis to handle it. lol. It has been 157mph to the 1/8 on only 23#. Bore size isn't an issue you have to worry about. There is plenty of room. You want to make sure you have enough bore size so the valves aren't shrouded.

Post your cam duration specs at .050

 

[slimtastic]

262 int 270 exh. at .050

the cam is prolly what i need help on the most. ive never spec'd for a motor this big