i have a 68 mustang j code 302 with an edelbrock performer intake manifold and edelbrock 600 cfm carb, i don't know if the cam has been changed, but with what i have on it now how much hp would this add? my car is emission tested so i wanted to know what other aftermarket parts i could put on it with out affecting the emissions.

 

the 289/302 4barrels made about 220HP stock. This 220 was measured without any alternator, airconditioning etc etc. This has changed and engines are measured with their accessories (gross HP, brake HP). with manifold and carb on it's own I'd say you are at just above 200 real HP. with headers and aftermarket exhaust system (not restrictive) maybe 220HP. if all else (cam, heads, etc) is stock

 

kalli if i added a cam and heads and headers how much would think i would have then?

 

with decent aluminum heads (trickflow TFS, AFR165, Edelbrock perf rpm), a nice set of headers, matching cam you should get up to 350 (the performer intake might be holding you back a bit then, the 600cfm carb would be ok)
But yes, it's a lot of money you're looking at right there. Further the whole rotation assembly and ignition system must be in good shape.
The stock rotating assembly won't hold much past 5500 and HP is a calculation that heavily depends on high RPM.

For example Remi has a set of edelbrock heads, standard rotating assembly, xe256H cam, headers and he measured 260HP at the wheels on a dyno which is probably 300HP at the engine.

Then 2+2 has just posted a link to a different thread where someone made 320HP with a stock 289, a specific camshaft and probably loads of port work on the original heads.
check this current thread:
https://mustangforums.com/forum/clas...2-mustang.html
there's a link in it

In short, quite impossible to tell as it depends on all other components like rotating assembly and ignition as well. Let's say your piston rings are weak letting a bit of the compression pass you'll loose power, so adding more to it will not have the same effect

Kalli

 

i have a buddy who is selling a 86 h.o. engine from a mustang would i get better hp and performance from this if i put all the parts you talked about on this engine? i could get some cast iron gt40 heads pretty cheap would these compare to the heads you talked about?

 

not a hard fast rule but here is the rule of thumb I use:
5% HP gain going from restrictive manifold/carb setup to good intake and dialed in carb.
5% HP gain by adding a matched free flowing exhaust system.

I think a 10% HP gain is realistic with intake/carb and exhaust upgrade. Some folks quote bigger HP gains from intake and carb swaps but I have a hunch the claims are a little inflated. all jmho.

 

Think of GT40 heads as a intermediate step between stock heads and all out performance heads. If you are running stock heads, the GT40s will be better, but still not as good as performance heads. Kalli hit on this, but keep in mind that you can increase the air flow of the engine through new heads, intake, carb, and exhaust, but the cam is the brains of the engine. A higher lift and duration cam will allow you to utilize the potential of the other components, by stretching the power band up and allowing the engine to breath thus giving you more horsepower, but then your engine become more of a race engine than a daily driver. Everything is a compromise...cost vs performance...performance vs streetability.

What are you goals? If you just want a little more pep, you can get that through a mild cam, some decent heads like the GT40s, a decent intake and carb, and an unrestricted exhaust. If you want a screamer, then that is a different story.

As for the 302H.O., the 302 is just a slightly longer stroked 289. Given the same heads, intake, and cam yes the 302 will make a little more power because it has more cubic inches. Who knows what shape the 302 is in, so the cost analysis will be up to you. The stock 302h.o. was still only 225hp and 300lb-ft, so there really is not much difference with what you have unless it has been altered.

 

just on a note, the 86 302 HO might have a roller cam (would anyone know for sure?), and if in good shape with the GT40 heads that's already a good (and cheap) starting place. but ya, urban said it already. it depends what you want from the engine. if you go more than 300HP then you probably will have to start upgrading the rest of the car so you won't pull it apart. nice thing about the 289 is that they have shorter stroke, so with a solid bottom end you can rev the crap out of em.
but let's say your engine and ignition is in good nick, the GT40heads with good cam and intake/exhaust should give you 300 for little money. all depends on what you want and how much you want to spend ... and if you can do all that yourself

 

thanks for all the info i am looking for around 300hp at the rear wheels, sounds like that is do able with my stock block i am going to be blowing it apart for a rebuild to see how my block looks my car has been upgraded with a beefed up c4 and i am going to put in my 9inch soon, the 86 h.o. is a roller cam the reason why asked about it was to see if the rotating assembly was better then the stock one i have he has stock heads and edelbrock air gap intake on it less than 50k on the engine for $300

 

300rwhp is going to need good heads and a cam, as well as better internals and every bolt on there is. A stock 289/302 block is good for a round 400-450rwhp if tuned properly. But getting an honest 300rwhp isn't cheap or easy.