Aftermarket/Replacement Cylinder Head Rule Change
 

Any News as to how the HP factors will be effected with the new rules combining them with OEM heads?

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Where are you seeing the aftermarket head rule I am missing something ? I know several combos allow them but I didn't see any new rule about them

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Its coming out with the HP releases next week. NHRA is deleting all the different HP factors and combining them all in to one factor for each combo that has approved aftermarket heads.
I was wondering if anyone knew how they were going to determine the new "single HP factor" where the OME head was rated higher than the aftermarket head HP factor and vice-a versa?

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Cylinder Head rule has NOT! been approved yet, they are having another meeting next week

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Nice, and you guys think that there are NO crate motors in NHRA....

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Maybe Mike Crutchfield can give us an update.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Its getting real hard to find some of the older factory heads that are 40 years since they have been produced. I welcome the ability to start with a brand new casting. Just keep the original valve size, port volume and chamber volume as original on the NHRA head CC volume list

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Give everyone a stock replacement aluminum intake too and there you go.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Just say "no".....to aftermarket heads.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

I could be wrong but I don't think it is practical to use the Edelbrock head on the Max Wedge, the port mismatch would be quite a challenge since you cant enlarge the ports. If they raise the iron head HP to the aluminum head HP the factor would be higher than the original.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Guys you are missing the point here.


Aftermarket heads are already accepted with a HP penalty. There is talk that they will become "replacement" heads and this result will eliminate the different factors of OEM vs. Aftermarket heads for the combos that currently have them.
Trying to find out "if" this does go through, what will happen to the two hp factors that are currently different?

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Conceptually, when you place a different hp factor on an engine because of the use of replacement heads (aftermarket or OEM), you have essentially created a new engine for the books. The problem is the way that classification is calculated since it uses a weight break of one rating and then the weight of the new hp factor. Eliminating the differential of ratings will simplify the calculation for the guys in the field, which is always a good thing since it helps eliminate confusion and mistakes.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

So does this mean that if a combination has been factored 20 HP now its gonna go back to the OG HP rating??

Example 396 Iron head is 375/385
396 Alum head is rated at 405HP

Both heads go back to 375?

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

It makes sense to me that there would not be a penalty in superstock. heads can be modified extensively. Stockers should keep the penalty for the aftermarket heads. My opinion anyway.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

5hp off only for aftermarket head.....

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Boy, I didn't see that coming...aftermarket heads for SBC in Stock. With a 5hp penalty.

NHRA Tech Department makes updates/corrections to the Stock Car Classification Guide
Jan. 1, 2018



The NHRA Technical Department recently made changes to the Class Guide.

Buick 98-99 added missing pages to website

Chev 62-79 added SBC replacement heads for Stock

Chev 2015 Camaro 376 365 corrected shipping weight Stk/SS

Chev 1969 Corvette 350 300 separated auto/man transmission

Ford 2010 330 500 added Stock weight breaks

Ford 2012 330 510 added Stock weight breaks

Plym 1968 Barracuda 426 425/505 separated from non SS/AH

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

I looked up one of the Edelbrock heads for a SBC and it listed 185cc intake runner, the others were 172cc to 175cc intake runner. NHRA specs are 172cc intake and 65cc exhaust, how in the world can a stock racer use replacement heads that are so far out of whack from each other?

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

You mean like the LD340? :rolleyes:

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Looks like Dwight is going to be busy!

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Does Edelbrock then make a SBC head with intake runners 161-165 CC's? Edelbrock is the only approved head? All I have seen is 180 CC and up.

Steve Teeter STK 6380.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

One of the listed heads is close in CC to the stock specs. This rule is good for guys in the cylinder head business. Now we need a head approved for the Pontiac.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

NHRA Approved Aluminum Cylinder Heads

http://www.edelbrock.com/automotive/...approved.shtml

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

I have done research on SBC replacement heads and Dart should be the only one approved for Stock. If NHRA is looking here you go.
"DART" WISSOTA #30424361 or #10024361 bare casting plain and simple.I don't believe replacement heads are needed and why would you allow so many with totally out of whack specs. This head is the only one close to Stock, it is cast iron and is very close to your aftermarket specs.If you ever do teardowns you can police one head easier than 8 different ones! Yeah and by the way why isn't it on the list?

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

What a can of worms they've opened now....
The Edelbrocks, aside from the fact that they're aluminum, are made for 2.02/1.60 valves and 1.46" springs. So many more grey areas have just been created, and for what?? "But I can't find any old castings!" BS!! I'll buy that line for other brands, but for small-block Chevys?? Get off the couch.
Well, now there's another 5G just to keep up. Thanks.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Dart or Engine Quest cast iron replacement style heads would have been the correct choice.

However, I'm guessing that neither of them went to the trouble or expense to submit anything.

Anyone who has been through the NHRA approval wringer for anything will understand, especially if they've had parts rejected for subjective illogical reasons.

Aluminum heads for Super Stock make sense, considering the alterations allowed, and the easier repair of aluminum. For Stock, not so much, they just allow cheaper and easier cheating.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

I think that we are missing the point on these replacement heads...

Runner volume is just one way to compare castings...

With the new replacement castings I would like to know what the flow numbers are from each head..

Just because the volumes are the same it has nothing to do with air flow or the horsepower that they are capable of making..

It looks like another can of worms just got opened for Stock...

Just sayin'

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

If the HP number is low enough, it doesn't matter what head is on what engine.....Take a look at Nitro Joes stats and see who's at the top of the heap in all classes!!!


Still no answer as to how they are combining and reducing to combos.


Anyone care to put their 2 cents in???

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Since the new heads come with 2.02 valves to you have to make them comply with the 1.94 valves or run them as they came?

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

I can remember a time when a friend submitted a replacement head to NHRA. He was told to bring the new head to a national event along with an OEM head for comparison . The head was looked at by techmen who knew what they were doing. They rejected the head because the intake runner and combustion chamber had been changed in the new casting.

One wonders if the same procedure is used today when a new head gets accepted. By the way, who is accepting all this stuff anyway?

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

The Aftermarket head has to retain the same specs as the head it's replacing.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

....

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Junior Super Stock

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

I agree with Bob, no need for all the choices. You know the flow figures will be all over the map. NHRA needs to choose one brand that is readily available (after all they are only doing this because stock castings are to hard to find for a SBC) and apply whatever HP they show!

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Everyone needs to realize that we all need replacement heads if we want to continue to race Stock And Superstock. The replacement head has to have the same spec as the OEM it is replacing. This is no different than the FE Ford, Big Block Dodge and Big Block Chevy. If anyone thinks the port shape is worth something major in a .400" lift Stocker you probably read to many "High performance Books".
Just relax and grow with the times....

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Good point !
That makes Pure Stock the New STOCK !

Saw it coming !
Not sure it is a bad thing.
More racers will select these heads over time.
Hope it simplifies Tech seeing the same Head on more cars.

D

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

So... how do you plan on getting the 172 cc intake port down to 165 cc without epoxy or welding? That's the problem.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

the mopar 273 has a replacement head WAY bigger than factory cc so do some others, if you live in a humid climate you would welcome the not rusting property
of aluminum.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Its actually pretty easy. Thats what we get paid to do.

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Sounds like NHRA now has Crate Motors !

Re: Aftermarket/Replacement Cylinder Head Rule Change
 

Ok... .140 off the intake rail and some extra, extra thick intake gaskets!!!