I know there's been talk about this but I never read a "for certain" answer.

My engine is bored 4.100 right now. I know the optimum bore for the LS7 heads is 4.125.

What problems will I have with putting the LS7 heads on my 4.100 bored engine?

How much cfm will I lose from the head flow, will it really kill it?

Thanks.


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The only way to find out is to speak with someone who has put these heads on a motor and flowed them on a 4.100" bore. I think it may be a while before you have access to someone who will tell you this information. Places to ask would be Lingenfelter, ET Performance, HPE, etc. Good luck!!!

 

Your 4.1 bore is only .030 less than the bore of the ls7 block. You would only be losing .015 on the edge of each side of the combustion chamber. I can not believe 15 thousands would hurt your flow by a measureable amount.

 

Thats good to hear, I really don't want to have to bore mine again to 4.125.

 

.025 is the actual bore difference

 

Theoretically, since none of us have LS7 heads, the heads will fit block bored at least to a 4.060". That's the number all the performance shops have been giving so at least bore-wise, you're good to go. But, the valve angle on an LS7 head is 11 degrees as opposed to 18 degrees on an LS1 so your pistons would have to be notched accordingly.

 

Isn't the ls7 head 12*, and the ls1/6 15*?

Also, would you still get 'some' ability to run a larger cam than you would with no flycutting, on 15* pistons? IE, I know they aren't 12* cuts, but shouldn't you still get some relief out of the 15* notches?

 

i'm not sure if the ls-7 is either 11 or 12 degrees..... but its one of the two, and yes. the ls1/ls6 heads are 15* heads. i do believe that the lesser valve anle allows you to run higher compression/bigger cam with out the need to have reliefs in the pistons. someone please correct me if i'm wrong.

 

I think the LS7 heads are 12*, and the C5R heads are 11*

I think 15* pistons would work ok with the 12* heads. You may not be able to run as big of a cam as if you had pistons notched with 12* reliefs, but I think you'd be able to run a bigger cam than if you had no notches at all.

Can someone confirm this?

 

[QUOTE=Greg Fell]I think the LS7 heads are 12*, and the C5R heads are 11*

Sorry, I guess I just got them confused. As for the LS1 heads, my information came from an Engine Masters magazine and since being corrected I have found that it was false information.

 

Talk to Jason at TSP. He gave me a little info on the LS7 heads.

 

The shallower valve angle will gain some clearence but we are talking a 2.00" stock ls1 valve or even a 2.08" aftermarket intake valve for the ls1/ls6 head compared to a 2.20" valve for the ls7 head, that's a big difference in valve size which will negatively impact piston to valve clearence. Who knows if it will offer more or less over the ls1/6 heads. You gain p/v clearence from the shallower angle with the ls7 head but you loose it with the much larger intake valve of the ls7 head.

For clarrification purposes the ls1 heads are 15 degree, ls7 12 degree, and c5-r are 11 degree. I don't know if there is much of a difference but one must also take into acount the valve centerline (where the valve stem location is in relation to the center of the bore) comparatively with the ls1.

All these things will influence what bore size is minimum for these heads, what bore size is optimal for these heads in relation to flow, and what gains or losses in piston to valve clearence you'll experience by switching to the ls7 head.

 

So, is it agreed that using LS7 heads for a 4.100 bore would show no loss of power over a 4.125 bore?????

 

anything smallet than 4.125 will show some signs of loss of power and anything over will gain power is the general rule of thumb.