NA Big Bore Engine Build - Input Needed

[tad240]

Picked up a used T50 short block that I want to couple with my FR500 intake and Comp 106300 cams. Need some input regarding heads / valves / valvetrain components. Primary use will be road racing / HPDE Track days & street. Want to be able to take advantage of the FR500 intake rpm capability. Car is relatively lightweight - Factory Five Cobra replica.

My initial plans are 03/04 heads since they are compatible with the intake and typically offer the best bang for the buck. Questions surround any advantage to O/S valves or porting to support the additional displacement of the big bore and the higher revs. Stock followers OK? Just looking for some input on the best bang for the buck head / valvetrain set-up. Want a good practical & reliable set-up to take advantage of the increased displacement and revs without spending ridiculous $.

[Ben99GT]

Best bang for the buck; stock valves, stock followers, basic bowl blend, Brian Tooley Racing springs with stock retainers.

[na svt]

Originally Posted by tad240

My initial plans are 03/04 heads since they are compatible with the intake and typically offer the best bang for the buck. Questions surround any advantage to O/S valves or porting to support the additional displacement of the big bore and the higher revs. Stock followers OK? Just looking for some input on the best bang for the buck head / valvetrain set-up. Want a good practical & reliable set-up to take advantage of the increased displacement and revs without spending ridiculous $.

.5mm OS intake valves will increase the flow a good amount as long as the valve seat IDs are also enlarged. Stock exh valves are fine but as with the intakes, the seat IDs should be opened up. I would not put heads on a BB without first opening up the seat IDs, especially on the intake side. OS intake valves are cheap as is opening up the IDs; great bang for the buck.

Stock followers are good unless you are looking for every last ounce of hp. As previously mentioned the BTR springs are great.

[rcodemach1]

This is good info. How much should the seats be opened up? I imagine you still want the airflow path to narrow from the port and then widen as it goes past the valve? Any quick links to pics or airflow numbers? Also what is a good source for 0.5 OS valves?

[na svt]

Open the seats to 90% of the iv dia and 85% of the event dia.

Sivalves.com

[rcodemach1]

Thanks.