Jeep Strokers

Just finished working over Edelbrocks new 4.0 Jeep cylinder head.
The purpose of this thread is to help evaluate the head in it's stock form as it comes from Edelbrock, and how well it
responds to larger valves and port work.




Edelbrocks assembled version comes with OEM diameter valves measuring 1.910 for the intake, and 1.500 exhaust.
The 7120 heads I do is usually loaded up Chevy LS valves measuring 2.000 and 1.550.
The Edelbrock comes with a 1.600 OD seat, so no problem running a 1.550 exhaust valve but because their infinite wisdom
(sarcasm) of putting in a 2.000 OD seat for the intake I reluctantly had to cut my 2.000 Manley valves down to 1.970




The one major significant change that Edelbrock made was in their combustion chamber and was one of two areas
that really responded to the reworking.




When installing larger valves in a cylinder head its critical to pay close attention to the areas of the chamber walls
surrounding the valve opening. As the valve diameters increase, the edge of the valve gets closer to the chamber wall. To fully receive benefits from running a larger valve one has to address the problem of getting air/fuel past the valve and not allowing it to be chocked off by the chamber wall.




The other area that helped airflow was addressing the restrictive head bolt casing at the entry of the intake port.




Laying back the area of the casing and straightening up the runners gives the air fuel mixture a straighter shot to and from the valves.





So now it comes down to the Report card/Flow sheet.
Let me start with a few words about flow benches and engine dyno's. It's a tool much like anything you have in your toolbox or garage. Flow numbers aren't the final answer or judge just as HP and TQ numbers coming off a dyno sheet don't answer all your questions on how good your engine is. They are both tools that help to analyze, diagnose, and compare. As a example my flow numbers are approximately 5% greater on my flow bench than Edelbrocks. Much the same for Engine dynos. They can be real close but not exact from one to another. The key point is that if properly operated any flow bench or dyno can be very accurate and consistent.


My Flow sheet on the stock out of the box Edelbrock head.



Edelbrock head ported



My best flowing 7120 head

You've done an awesome job porting the Edelbrock head, and the flow numbers on the ported 7120 head look pretty amazing too.

looks like money spent is money saved. as far as i can tell from flow the numbers there. better off paying pottenger than paying edelbrock. i know that aluminum vs iron have different properties for different builds. but, after all that r&d, and years of waiting... i can't help but wonder how edelbrock still left room for improvement on the table. its aluminum, so i guess thats worth something(but not for what im building). i just think their new head is a little overpriced. P&P work on an iron head vs their aluminum head; considering cost and flows, i'll be paying russ.

biscuit wrote:looks like money spent is money saved. as far as i can tell from flow the numbers there. better off paying pottenger than paying edelbrock. i know that aluminum vs iron have different properties for different builds. but, after all that r&d, and years of waiting... i can't help but wonder how edelbrock still left room for improvement on the table. its aluminum, so i guess thats worth something(but not for what im building). i just think their new head is a little overpriced. P&P work on an iron head vs their aluminum head; considering cost and flows, i'll be paying russ.

And in all likely hood you will be making far less power.

krom wrote:And in all likely hood you will be making far less power.

Probably only slightly less. The difference in flow numbers between the ported Edelbrock and ported 7120 isn't that great. The only real advantages of the Edelbrock are the 28lb weight saving and the ability to run a higher compression ratio on the same grade of fuel.

Out of the box the edlebrock flows comparable to a 7120 on the intake and a little more on the exhaust. Any gain on on otherwise stock engine is in the improved chamber. Don't discount the edlebrock based on flow numbers alone. The improved chamber if exploited is worth quite a bit. The decsion is whether is it worth the $$ to you.

for me its not worth the money, im already over budget. plus, im not trying to spend that much to run on a higher compression ratio. the weight loss isn't worth it for me right now either. however, in a year or two, i might be singing a different tune. assuming the price comes down on the edelbrock, and other people with more money than i run it and figure out any flaws/concerns. my pocket is getting squeezed more than my 4.6. i'm still learning.

biscuit wrote: assuming the price comes down on the edelbrock

I can't see the price coming down for these heads unless there's a large enough demand for Edelbrock to produce them in greater volume.
Like I said in a previous post, I think it's come 20 years too late but I suppose it's better late than never.

Aside from all of the flow # speculatiuon. It'd be nice to finally see some dyno runs to see some actual gains. I agree with many here, flow numbers aren't the only thing to look at. Torque numbers can vary plenty within heads that flow similar cfms. The fast burn chambers in conjunction with redesigned ports on these heads will help make more power regardless. With the right port/chamber work as seen here.. even better results. Russ Are you going to get some dyno time on this head soon?
Great job! Excellent work!

Thanks, ..

Will be seeing some chassis Dino numbers after, but unfortunately nothing before as of now.

Thanks for the great pics and for some REAL, comparative, flow-testing! Your demonstrating some quality port work there! Edel should offer you some kick-backs for helping to promote their new head Curious to know how far you had to go to get those Exh-port #'s?? Like others have mentioned, I'd be delighted with the numbers you achieved on that 7120! I'll be excited to see some dyno results when you can post 'em!

What is the difference in pricing between the all done up ported 7120 head and the Edelbrock head? $2,000 vs $3,000?

going apples to apples, if both were to be PnP by machinist.

Edelbrock bare head is about $1,300.00

7120 is core(say $100)+ clean/checked/cut (guessing $250) so maybe about $450?
if you could find a 7120 cheaper then this could be cheapest route.

clearwater bare head $ 450.00


the above 3 options would get you to the bare head. Then you would have to add the cost of valve train/machinist hand work.

I need a 62cc chamber, to i opted to not go with the edelbrock. since i will be paying to have my heads built/PnP/larger valves/different springs, it seems i can get what i need out of an iron head for about the same as a complete edelbrock stock head. my ballpark situation is custom head= $1300ish. stock edelbrock = $1500ish custom edelbrock $2500??

I was partly into my build before i pondered the edelbrock. If i were starting from scratch, i may have looked into the edelbrock a little more.

Back from the dead to see dyno numbers

Any Dyno numbers?