SBC big bore heads on a 4” bore?

[Gotzy]

Howdy Everyone

I picked up a smoking deal on some SBC Brodix STS T1 227 cnc heads that are designed for a 4.125” bore but could I use them on a 4” bore engine?

I’ve seen posts on YellowBullet about guys talking about doing similar on BBCs and just using a gasket for the bigger bore. I can’t find anything regarding SBCs and if there’s enough real estate to do it.

Any thoughts or experiences welcomed.

Cheers
Stephen

[Alaskaracer]

Couple of things to check. First is valve contact. In some cases, the smaller bore won't allow the bigger valve without a relief. You'll need to check to see if everything will clear. Secondly, the smaller bore will kill some of the head's flow potential. They might not perform as well as they are capable of, and there is the possibility they might perform worse than a different set....No way to tell until you run them though....Head gasket should be sized based on bore, not head size.....you want the gasket bore to be as close to the cylinder bore as possible..

[mag2555]

According to the Brodix catalog listing they spec a Fel pro head gasket with a 4.166” bore and a minimum 383 cid with a minimum 12.5 to 1 compression and a power band of 4000 to 7500 to make use of that head.

With the 2.08” intake valve you had better think about notching that bore to get the valve itself to clear, but also to not choke off the flow.

You also need to confirm if with your current valve lift if those 2.08” valves will clear the notch in your pistons.

How much hp are you looking to make out of your 383?

If I where you I would get the head flow tested on a 4” bore and then see if it makes sense to keep them or resell them.

[Walter R. Malik]

Howdy Everyone

I picked up a smoking deal on some SBC Brodix STS T1 227 cnc heads that are designed for a 4.125” bore but could I use them on a 4” bore engine?

I’ve seen posts on YellowBullet about guys talking about doing similar on BBCs and just using a gasket for the bigger bore. I can’t find anything regarding SBCs and if there’s enough real estate to do it.

Any thoughts or experiences welcomed.

Cheers
Stephen

Be sure to use head gaskets where the bore is larger than the chamber in the heads.

[fordified]

Put layout dye around one of the chambers. Put the heads on the block with no head gasket and turn it upside down. Scribe the head around the bore and take the head off.

I’ll bet your fine as far as valve clearance is concerned. I would also bet that the intake side of the chamber is still inside or at the bore and only the exhaust side is bigger than the bore. No problem. You can leave the bore as is or notch it if it makes you feel better.

Remember it’s not 0.125 on one side. It’s 0.0625” on each side.

[Gotzy]

Thank you to you all for your responses

As It turns out I got myself a little confused in the Brodix catalogue

My Brodix heads are the Track 1 STS T1 227 which have the 2.08 & 1.60 valve package for small bore SBC's and not the 2.125 & 1.60 valve version for the 4.125+ bore engines.

Up shot is they will be fine on my 4.000" bore engine with the appropriate FEL-PRO 1003 or COMETIC C5399 head gasket to match the chamber as recommended by Brodix and Walter

Apologies for wasting your time folks.

Cheers

Stephen

[mag2555]

Don’t forget to confirm the radial clearance of the valves to the piston notches.