Headers for AFR 185's

[mikemustang289]

I currently have longtube 1 5/8 headers 3 inch collectors and 2 1/2 inch exhaust.

The headers are an oval port design, and I'm looking to run AFR 185's on them. I can see that port mismatch may be a problem between the headers and heads. Is this something to be concerned about?

Engine is a 302, cam xe274hr, 224/236 .555/.565 if that helps.

I have read this may actually help scavenging? I don't want to buy new headers, at least not for the time being anyway. Do you think this is a concern since we're only talking about a 302? I don't see how 1 5/8 could be a restriction considering the engine size and cam?

 

[RacEoHolic330]

any reason why you're running 185's on a 302?

 

[Grn92LX]

Maybe try and grind them as needed?

I assume you have aftermarket pistons or notched stock pistons? I don't see the 185's and that cam fitting. If you have the p to v clearance the 185's are the way to go over the 165's.

 

[mikemustang289]

any reason why you're running 185's on a 302?

Any reason not to? I have pistons to clear 2.02's, From all the tests I've seen 185's make more power over 165's throughout almost all of the rpm range, I don't care much about low end torque, the engine will never see below 4K after 1rst gear with the ratio's I have shifting at 6000.

Plus in the future I may build a 331 or 351 and these heads will swap right over and work fine.

the 185's actually have a 180cc intake runner, About the same as the edelbrock performer RPM's (181cc) and the same size intake valve, but overall they outflow them.

 

[Grn92LX]

You made the right choice.

What pistons are you running? Flat tops?

 

[mikemustang289]

You made the right choice.

What pistons are you running? Flat tops?

TRW-8KH273CP30 They are hypers, -8cc dish, so the 58cc chambers will work good to get that compression up, blocked has been 0 decked too which should help.

Are springs that come with the afr's good above .550?

 

[5spd GT]

If you want a higher average powerband. Stick with the 165's...plus you won't have all these problems to have to contend with.

 

[The Fox]

I would agree that 165's are the smarter choice. Sure 185 is "more gooder" but your current combp doesn't need that. I could see if you had at LEAST a 331 or a blower but really these heads are OVERKILL for your combo. Just looking out for you, you would DEFINATELY benefit more from 58cc 165s.

 

[mikemustang289]

Go to AFR's websight, MM&FF did a shootout in Dec. 00' between 165's and 185's both on the same 302, with a little more cam than what I intend to run.

The 185's made more torque from 3000 all the way too 6200 were both engines peaked, the 185's making over 20ft-lbs more torque

I don't see the point in going with 165's, the Edelbrock Performer RPM's outflow the 165's on the intake and fall about 20cfm short on the exhausts at peak lift.

The afr 185's and 165's exhaust flow is nearly identical. The only major difference between the heads is the intake flow numbers, the 185's begin to outflow the 165's at about .300 all the way to .550 about 20cfm more

If the 185's are too much then I will consider the RPM heads, I think I can give up about 20cfm on the exhaust vs. the 165's and not have if be such a drastic effect considering the cam has 12degrees more duration on the exhaust.

 

[5spd GT]

mikemustang289 - Remember that it is the entire combo. Numbers at peak lift don't mean much. I would expect the 185's to take over at "peak lift"...but how often are you at "peak lift"

If you look at the test, they are under different characteristics.

The 165's actually beat the 185's to 3500+rpm. Look at the test that is using the same camshaft.

The parts they added to both sets of heads are more suited for a track car...the 185's fit better in all those categories and yet the AFR 165's where right there. The 185 combo had more timing and fuel to help it as well...the 165's were still there with them

This is also with a "302" with no accessories and drivetrain loss to worry about. I like a bit more torque/power down low to help with that. Hence: AFR 165's...

 

[mikemustang289]

Ok, I see your point, but that was with a b303 cam which is a single patter grind.

Now, strictly comparing afr 165's to the RPM heads, the both flow nearly identicle on the intake side, the exhaust is where the 165's win out. However, I am running a split duration cam, and I won't have the mismatch from exhaust port to header flange with the RPM heads as I will with the 165's. So, being that the 165's are about $300 more, is it still worth the cost over the RPM's for an extra 10 or so HP?

 

[5spd GT]

Well Mike, that is up to you to make that choice. Do you want that extra 10 horse for $300 bucks? Some people are willing to give up their a/c for that extra 5hp. Not me. Somepeople give up driving characteristics with aggressive cams (poor idle, no low-end) in exchange for those extra 10hp. The list goes on...It's all in what you want

 

[mikemustang289]

All I want is low-mid 12's, I could really care less which name brand heads are capabale of getting met there, but at the same time I don't want to throw money away. I think I'm just over analyzing the whole decision, regardless of which head I choose, I doubt I will see a significant difference at the track.

 

[5spd GT]

Your probably right...good luck!

 

[Grn92LX]

Mike you made the right choice. You'll easily get your goal. The 185's are $25 more than the 165's, you did it right. Only problem I see is your compression may not be what you want it to be with that -8cc dish piston. I would go for a custom cam but your 12 second goals don't really require it.

 

[Rick 91GT]

I have been avoiding responding to the thread but....

Here's what the math says as far as compression goes....

Compression Ratio Calculator v2.d
Thursday, March 09, 2006 7:46 am

* 302cid *

Bore Size: 4.000
Gasket Bore: 4.100
Piston Top Land Dia: 3.965
Stroke: 3.000
Connecting Rod Length 5.090
Compression Height: 1.600
Deck Height: 8.190
Ring to Top of Piston 0.250
Gasket Thickness: 0.039
Valve Notches Volume: 8.00
Dome Volume: 0.00
Volume Head: 58.00
-------------------------------------
:COMPRESSION RATIO: 9.200
-------------------------------------

calculation variables:

Piston to Deck: 0.000
Crank Throw: 1.500
Vol. Above Top Ring: 0.90 cc
Piston to Dec Vol.: 0.00 cc
Gasket Volume: 8.44 cc
Volume Clearance: 75.33 cc
Cylinder Volume: 617.78 cc
CID: 301.474

(notes/messages)
× Piston Flush with Deck


Although the 165 may be a better choice for a 302 based combo I think the 185's can work with the proper supporting parts, even with the lower compression. You mention building a larger motor in the future, the 185's will shine there with little work.

I think you need to use a custom cam that increases the dynamic compression to help use the flow that those heads have, along with a proper intake runner length to keep the TQ curve down low. I think you could use a Track Heat, RPM or RPM II for best results, maybe a Holley.

As far as the header goes you should be fine, if you want to optimize them weld the outside tube to the flange and fully port the inside of the flanges to make the flow smoother.

I personally am not a fan on the lobe on the XE cams. To answer your questions about springs the 274 will be a little to large for the standard AFR spring 120#, upgrading to a 130#-140# spring would be a much better idea. The lobe is too aggressive and you will not be able to control the valves in the upper rpm range.

FWIW, I used a stock bottom end 302 notched pistons 8.8:1 comp, 175cc runner head, longer runners then a 185, Holley intake with a 1" spacer, custom cam and went 11.8 @ 116mph, 3250 pound car....and I think it would have went .50's with more gear that it required.

My $.02 worth


David, How's the motor coming??

 

[Modular2v]

any reason why you're running 185's on a 302?

if he has the right pistons he would be stupid for not running 185s

 

[5spd GT]

David, How's the motor coming??

Keith called me tuesday morning and told me it is done! So I'm going to pick it up later next week when I get some time...I can't wait...I've been missing my little stang

If you do have the pistons to clear the 2.02 valves it probably would be wise to get the 185's. But for a 302 (and that is all) get the 165's. If you are upgrading to a bigger engine soon...doesn't really seem like anytime soon...I would get the 185's...

 

[mikemustang289]

Here's what the math says as far as compression goes....

Compression Ratio Calculator v2.d
Thursday, March 09, 2006 7:46 am

* 302cid *

Bore Size: 4.000
Gasket Bore: 4.100
Piston Top Land Dia: 3.965
Stroke: 3.000
Connecting Rod Length 5.090
Compression Height: 1.600
Deck Height: 8.190
Ring to Top of Piston 0.250
Gasket Thickness: 0.039
Valve Notches Volume: 8.00
Dome Volume: 0.00
Volume Head: 58.00
-------------------------------------
:COMPRESSION RATIO: 9.200
-------------------------------------

calculation variables:

Piston to Deck: 0.000
Crank Throw: 1.500
Vol. Above Top Ring: 0.90 cc
Piston to Dec Vol.: 0.00 cc
Gasket Volume: 8.44 cc
Volume Clearance: 75.33 cc
Cylinder Volume: 617.78 cc
CID: 301.474

(notes/messages)
× Piston Flush with Deck

I was considering using a thinner gasket, cometic offers some in .027 I believe to help bring the compression down.

At the moment I may just install the cam I have, and do a cam swap in the future if my goal of 12's is not met. How far off are these specs considering I don't want a race cam, I need to pass emissions testinng as well as I would like to maintain a decent idle and gas mileage if I can.

BTW motor is .030 over, so that should help compression a little as well.

 

[Rick 91GT]

I was considering using a thinner gasket, cometic offers some in .027 I believe to help bring the compression down.

At the moment I may just install the cam I have, and do a cam swap in the future if my goal of 12's is not met. How far off are these specs considering I don't want a race cam, I need to pass emissions testinng as well as I would like to maintain a decent idle and gas mileage if I can.

BTW motor is .030 over, so that should help compression a little as well.

The .027" gasket will not give you enough quench area, stay with a .039-.041". The 4.03 bore makes very little difference, as you can see below..

Compression Ratio Calculator v2.d

Thursday, March 09, 2006 2:45 pm

* 302 cid *

Bore Size: 4.030
Gasket Bore: 4.100
Piston Top Land Dia: 3.995
Stroke: 3.000
Connecting Rod Length 5.090
Compression Height: 1.600
Deck Height: 8.190
Ring to Top of Piston 0.250
Gasket Thickness: 0.040
Valve Notches Volume: 8.00
Dome Volume: 0.00
Volume Head: 58.00
-------------------------------------
:COMPRESSION RATIO: 9.299
-------------------------------------



calculation variables:

Piston to Deck: 0.000
Crank Throw: 1.500
Vol. Above Top Ring: 0.90 cc
Piston to Dec Vol.: 0.00 cc
Gasket Volume: 8.65 cc
Volume Clearance: 75.56 cc
Cylinder Volume: 627.08 cc
CID: 306.014


(notes/messages)

× Piston Flush with Deck


I've been 12's on a stock motor 169,000 miles I am sure you can meet your goals.... Good Luck!@