Best heads for a 421 turbo motor
 

Hi All,

I am trying to decide which heads to purchase for my next buildup. I will be building a single turbo 421 gen 1 sbc 8.5-1 comp with a dart little M block and solid roller. I pretty much know what my bottom end will consist of but I am undecided on which heads to use. I will be using a carb style single plane manifold converted to fuel injection and possibly a t91-t100 thumper turbo or similar size for 25psi of boost on race mode. This will be street strip combo with a 7500 rpm redline (mainly strip but want to be able to drive to car shows,etc). I will need custom exhaust headers regardless and was wondering if I should go the 18 degree route or just stick with standard 23 degree heads. I know that the intake ports on 18 degree heads are superior to the 23 degree heads but the exhaust ports look to be fairly similar. I am basically want to build the combo to produce up to about 1500hp(low 8 sec high 7 sec ET @165+mph) at max boost so i know I will need good heads. Does anyone have any experience to share with which heads would be the most cost effective way to reaching my power goals?

Thanks in advance,

Matt

Re: Best heads for a 421 turbo motor
 

Very large.....

Re: Best heads for a 421 turbo motor
 

I say with 25lbs of boost.......... any head will work. That's a LOT of boost!

Re: Best heads for a 421 turbo motor
 

You are right, but the larger the port and valve the less boost that will show and the more air goes in the cyl to add fuel to to make a bigger POP= more HP. Cross section area goes out the window with a forced induction. Ya have to work the power adder harder to show the same boost on a large v small port engine,which is no problem for a well set up 100mm turbo.

Re: Best heads for a 421 turbo motor
 

Re: Best heads for a 421 turbo motor
 

Unless you already own a killer set of 23º heads, there's no reason to go that way for what you're trying to achieve.

How much are you prepared to spend on a set?

-Mindgame

Re: Best heads for a 421 turbo motor
 

I know I can get a used set of 18 degree nascar heads for around $4500 for the entire top end of the motor with intake and shaft mount rockers. I am looking to spend around $3500 for heads with porting and valves but that might go up depending on what I would need for my goals. I would liek to stay with a 23 degree head just for simplicity but if I need an 18 degree head or if going another route will be more cost effective I will go that route. Any information or advice on what heads to go with would be greatly appreciated. I am thinking I will need a set of heads that flow very well to acheive my goals.

Also, I am going to build a 8.5-1 406 little M with a PT94 single turbo after talking to a turbo guy today about the combo. I am going to be using Oilver billet crank and rods and a set of JE heavy duty dished turbo pistons. I do not mind using shaft mount rockers but I would like to know what the best heads for my money will be for the level of performance I want to acheive. I was thinking either 18 degree heads, All-pro 23 degree, and/or AFR 215rr, etc. Also, If anyone can recommend a head porter to talk to about porting the heads for a turbo combo I would greatly appreciate that info as well.

Thanks for the help in advance,

Matt

Re: Best heads for a 421 turbo motor
 

Why'd you decide to go with a 406 instead of the 421? Have you given any thought into using Dart's iron eagle block?

Re: Best heads for a 421 turbo motor
 

Keep shopping the race heads.

If I were doing this and wanted to keep costs down I'd start with a good used 18º head. On that note, the sb2.2 stuff is getting easier to find. I've seen heads go for $2500-3000 a set, complete with used Ti valves. The intake combo can be had for ~$350. And the rocker and shaft setups are often in the same price range. So ~$4000 isn't too far off the mark for a complete induction package.

If I had to go 23º for some class restriction, it'd definitely be a raised runner head of at least 230 cc (If RR were allowed). I'd probably opt for a bare set of Pro Action RR and have them worked over. The RR AFR 215 is IMO too small for what you are attempting to do. If you decide to go back to the idea of building the 421, you're going to need a very large head. The Pro Action 256 or a race head would be the only options I'd look at.
Either way, do the math carefully here, cause you'll need a set of shaft rockers, springs, retainers, locks, machine work, valves.... things are starting to add up real quick.

A strong NA motor makes for a strong turbo motor so don't go making sacrafices in the name of "the turbo". A good cylinder head guy will know this and he'll do what it takes.

Good luck.

-Mindgame

Re: Best heads for a 421 turbo motor
 

Interesting…. And I have to agree, but boost is king.

At one time I was involved with Corky Bell who did a Turbo Supra for me. Basically I provided a new car, he did all the R+D and the car was available for customers to test drive and to the media for publicity. I simply was the driver.

At the same time he did another shop car doing a Mustang for Todd Gartshaw whom was his director of marketing and who is now is the director of marketing for Baer Brakes.

Both cars were featured in Motor Trend with the goal of my car as an overall performance car but the Mustang was to be the first of it kind to go over 200 mph.

With that said…….I kinda had an insider’s view of what Corky did to the Mustang to make enough power to push basically a shoe box to 200 mph. I saw him change cams try different porting, different heads, etc. etc. But what really made the difference was boost. It was doing the big intercoolers and getting the boost up there that really did the trick.

Better heads will always help, but was nothing compared to that extra 5 lbs of boost.

Re: Best heads for a 421 turbo motor
 

I would rather rpm the motor a little more with the 406 and because the car will see a street time I wanted to kill a little low end torque. I have thought about the new iron eagle but I have not researched it enough to decide exactly.

Matt

Re: Best heads for a 421 turbo motor
 

Thanks for the reply mindgame! Looks like I will be calling around to find a set of used 18 degree nascar heads. Does it matter what cc the combustion chamber is? Or can I just run a bigger dish piston to get compression down? I want to keep the compression at 8.5-1 up to a max of 8.8-1.

Thanks again for your help.

BTW after seeing some pictures and thinking about it I might go with a set of twin turbos for under the hood reasons as it would be easier to fit 2 smaller T61's or T70's than a huge T94 under the hood.

Best regards,

Matt

Re: Best heads for a 421 turbo motor
 

A big part of this is going to be cross section..... The boost and the cubes are the big factors on that. I agree that boost is the big player here but if you are going to start with something, you might as well get the head that will get you the cross section you need to get where you want to go.... A 18 deg head is most likely going to get you there, where you would need a odd ball 23 deg casting to get you where you want to be.

You might want to look at the Garrer GT42 Turbo if you are looking at T70's newer design and it's much more efficent.

Bret

Re: Best heads for a 421 turbo motor
 

thanks for the reply Bret. I will look into the Garret GT42's. All the information is greatly appreciated.

Best regards,
Matt

Re: Best heads for a 421 turbo motor
 

NiCe Fat Set of All Pro's ;) Since your going 94.. I guess i'll have to go 106 now .. :(