Read a lot on that question, but just need your opinion on those heads in a miata.

I'm thinking about a set of Performer RPM to replace my Gt-40.

 

I would do some research and reading on AFR heads, had them on two 5.0's and very happy with the performance.

 

Those Edelbrock heads are a significant upgrade over stock GT40 heads, and, they are lighter. The Edelbrock heads are a sensible street performance head. If that's what you want/need, that's the kind of head you should be looking at. On the other hand, for max performance they leave a lot on the table compared to more race oriented offerings. The better race-type heads generally wont accept stock manifolds. That limits you to either what the manufacturer offers(normally all-out race-type manifold(s), or making something custom yourself. It's important that the heads, camshaft. compression, intake manifold, and fuel system all compliment each other. Having just one component that is more "radical" than the rest can easily result in less power rather than more. There is also the issue of user friendly. Once the novelty wears off, an overly radical street engine isn't fun anymore.

 

I want a trouble free, street engine. Want to keep the stock cam with 1.7 rocker. Maby change the 19lbs injector for 24. Also want to keep my gt-40 explorer intake with my 65mm tb.

 

I use the iron GT-40's because (with my dad's machine skills) they provide about 75% of the performance of AFR's at under 10% of the cost. If I had to pay to have someone other than my father do the head work I don't think they'd be as attractive. AFR's are in my "long range" plan for my current car.

-Jason

 

what kind of work you did to your head? I know AFR are the best but i see the performer rpm on sale a 499 each

 

While it's doable, a fair amount of work is needed to bring GT40 heads up to what the Edelbrocks are out of the box. Per what MRM331 posted, after buying parts and paying someone to do the work the Edelbrocks are looking pretty good.

 

My father is very secretive when it comes to his cylinder head work. He's stated that he'll pass the knowledge on to me when he's on his death bed.

GT-40 as good if you are assembling a junk yard engine and they are a no-cost option over the E7 heads the Mustangs came with. They are also good if you have the ability (or a close family member with the ability) to work them over as my father did. If I had to pay for the work I would start with a AFR or other aluminum option.

He's worked over a few sets of AFR's as well. He gets similar gains over stock from them.

-Jason

 

I have been very happy with my TFS Twisted Wedge heads.

 

Edelbrock Win... Just buy a top end from a guy's.





Come with 1.7 rocker. Did you think 24pounds injector can be good?

 

I like the science of the TFS Twisted Wedge. They will be my head of choice for all my builds. As far as the AFR, it's a great product. The TFS heads turn the valves which helps flow with a small chamber. in the 5.0 world, this is the biggest argument. Everybody goes back and forth between the TFS and the AFR. Rarely does anyone consider the Edelbrock or other brands, but you probably won't notice the small HP bump between the AFR/TFS and Edelbrock, so why not save the cash? Edelbrock just came out with the EStreet heads and I think they're supposed to be pretty good.
The main reason I ruled out AFR is that they flow test on a 4.060" bore block which is not stock because a SBF won't bore 60 over without cooling problems. Seems deceptive to me to tout a product's advantages using an aftermarket block that most people can't afford and don't use.
Summit has the TFS on sale now for 530 each. You'll need new pushrods, but that's probably a better bang for the buck than Edelbrock.

 

I am so glad this internet thing works and your article really helped me. Might take you up on that home advice you.

 

Spammer alert! Spammer alert!!

Lynn B.

 

This is my first time i visit here. I found so many useful information and many thing I interested, nice to see that. especially its discussion.I guess I am not the only one having all the leisure here! nice!

 

^^^^ You should be fine with 24's.