EFI head on carbed engine
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EFI head on carbed engine
I was wondering if an EFI head will swap easily with my carbed head. I was at the junk yard to get some EFI ex manifolds and the could not resist the getting the head as well.
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That thread is about porting. It's written for the SB6 but the principles are the same for the BB6.
That thread is about porting. It's written for the SB6 but the principles are the same for the BB6.
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The conventional wisdom on EFI heads is not to cut them for larger valves. They would be shrouded even worse and deshrouding ruins the fast burn. Porting will still help. Polishing usually refers to the combustion chamber; I'm pretty ambivalent on the benefits once you get past cleaning up ridges or casting flash that could turn into a hotspot. It's going to be covered in carbon soon enough anyway...
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I'd suggest you register over there. Good site and some good people. Wouldn't say they are anymore knowledgeable than people here but sometime a different point of view.
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Just a couple of points.
The EFI heads are more prone to cracking than the carb heads. Make sure you have it magnafluxed before you use it. If you do any porting, be very conservative, they are thin wall castings.
If they have a different style rocker arm, make sure your valve train is properly set with the new head. I don't recall all of the flavors, but some rockers are adjustable, some are not. Just make sure you get the right amount of compression on the lifter piston.
The EFI heads are more prone to cracking than the carb heads. Make sure you have it magnafluxed before you use it. If you do any porting, be very conservative, they are thin wall castings.
If they have a different style rocker arm, make sure your valve train is properly set with the new head. I don't recall all of the flavors, but some rockers are adjustable, some are not. Just make sure you get the right amount of compression on the lifter piston.
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I think a magnaflux is around $35 or so. Call around to a few shops and see what they charge.
Also have them check to see if it's flat. If it's warped, you'll need to have it planed, which I think is around $80.
Also have them check to see if it's flat. If it's warped, you'll need to have it planed, which I think is around $80.
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Luckily I live in the racing capital of the USA, Charlotte NC. Magnaflux cost me 5 bucks. The guy raced straight sixes for 40 years. Between the great people on this site and him, I can't go wrong.
So, porting and polishing... Do I need to use carbide bits? Or can somebody recommend, the best, kit of bits to get? (best= cheapest to get the job done properly).
Then match to mr. gasket #260.
Then use that size all the way back?
So, porting and polishing... Do I need to use carbide bits? Or can somebody recommend, the best, kit of bits to get? (best= cheapest to get the job done properly).
Then match to mr. gasket #260.
Then use that size all the way back?
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I've got to know. Now, I would tell anyone to get their head(s) and block checked for cracks before starting in on any machine work, but every time someone mentions "EFI head" folks start chiming in on how they're more prone to crack that carb heads.
Is this just conventional wisdom or has someone actually compiled data on head cracking in 300s? Where are they more prone to crack? And why? They're made by the same company in the same factory as the carbed heads before them, right? So what is it about EFI heads that makes them more likely to crack? The two extra bolt holes tapped for the exhaust manifolds? My carbed '86 has the EFI manifold bolt pattern for the intake/exhaust manifolds. Should I be worried about cracking?
I'm not saying EFI heads aren't more likely to be cracked, but where does this particular factoid come from?
Is this just conventional wisdom or has someone actually compiled data on head cracking in 300s? Where are they more prone to crack? And why? They're made by the same company in the same factory as the carbed heads before them, right? So what is it about EFI heads that makes them more likely to crack? The two extra bolt holes tapped for the exhaust manifolds? My carbed '86 has the EFI manifold bolt pattern for the intake/exhaust manifolds. Should I be worried about cracking?
I'm not saying EFI heads aren't more likely to be cracked, but where does this particular factoid come from?