Thoughts on working the TFS streets at the bolt hole area??

I have read and heard on stock max ported heads that taking off as much of the head  bolt hole bump area as possible help extend power band. Being a raised runner head with smaller  then some of the others exit. I  figured it be worth a shot. Being a 521 heard the exhaust needs help to make good power to 7,000, might use 10 degree spread on cam. Plan on street driving so 270-280 .050 be about as big as I'm willing to go. Figured a little more CC port might help the exhaust too? Forgot to mention ports flow 260 cfm without a pipe. Average 385 cfm intake for now.

ED468 wrote:I have read and heard on stock max ported heads that taking off as much of the head  bolt hole bump area as possible help extend power band. Being a raised runner head with smaller  then some of the others exit. I  figured it be worth a shot. Being a 521 heard the exhaust needs help to make good power to 7,000, might use 10 degree spread on cam. Plan on street driving so 270-280 .050 be about as big as I'm willing to go. Figured a little more CC port might help the exhaust too? Forgot to mention ports flow 260 cfm without a pipe. Average 385 cfm intake for now.

Open the hole to 5/8", then port it till you just break through, then install brass or stainless tubing in the hole.

Checkout Kaase's 521 dyno sheets. I think your peek will be a little lower than his P-51's.

https://www.429-460.com/t27219p75-jon-kaase-sr71-cylinder-heads

Kaase likes the bigger is better, and a few others like to open up the bolt hole on the exhaust that I have seen.

[quote="rmcomprandy"]

ED468 wrote:I have read and heard on stock max ported heads that taking off as much of the head  bolt hole bump area as possible help extend power band. Being a raised runner head with smaller  then some of the others exit. I  figured it be worth a shot. Being a 521 heard the exhaust needs help to make good power to 7,000, might use 10 degree spread on cam. Plan on street driving so 270-280 .050 be about as big as I'm willing to go. Figured a little more CC port might help the exhaust too? Forgot to mention ports flow 260 cfm without a pipe. Average 385 cfm intake for now.

Open the hole to 5/8", then port it till you just break through, then install brass or stainless tubing in the hole.[/quote


What Sealor hold up to exhaust heat? High temp silicone?

ED468 wrote:

rmcomprandy wrote:

ED468 wrote:I have read and heard on stock max ported heads that taking off as much of the head  bolt hole bump area as possible help extend power band. Being a raised runner head with smaller  then some of the others exit. I  figured it be worth a shot. Being a 521 heard the exhaust needs help to make good power to 7,000, might use 10 degree spread on cam. Plan on street driving so 270-280 .050 be about as big as I'm willing to go. Figured a little more CC port might help the exhaust too? Forgot to mention ports flow 260 cfm without a pipe. Average 385 cfm intake for now.

Open the hole to 5/8", then port it till you just break through, then install brass or stainless tubing in the hole.[/quote


What Sealor hold up to exhaust heat? High temp silicone?

When you make them "press fit" or "on-size" fit, no sealer is necessary.
Although, it isn't necessary, I use a bit of "Milk of Magnesia" so they go in easier.