Do some of the posters here read that I have a set of cast iron rams horn manifolds that are 2-1/2 inch outlet.....and going directly into a Magnaflow 2-1/2 exhaust system.????

Many keep calling this a stock system, and it is not. Stock is 2 inch.

 

This is a side issue, but also one of my thoughts. You keep talking about saving money, and I agree that buying AFR heads is expensive. If I buy the Profiler head I listed, which has flow numbers very similar to AFR, the price is less than all less performing aluminum heads on the market.

 

I want to thank all of you for your comments, even if I don't like hearing some of it. I should not ask if I don't want to hear answers!!

So, if I were to go with headers, do you have any suggestions on brand names, and please address these fit issues I seem to think are real.

- Apparently, due to the raised exhaust ports on aftermarket aluminum heads, like AFR and Profilers, there is an interface problem with the idler arm, especially a heavy duty Moog that I have.

- What about the fact that the steering box is so close to the header that the steering box is being cooked at all times.

I lean toward 1-5/8 inch Hedman Headers Elite, as they have 3/8 flange, 14 gage tubing, and coated. Does anyone have any fit experience with these?

 

Billa, are you saying that the XR270HR is too small a cam for an AFR 180 Eliminator head?

 

Quench a little tight for street driver. Leave little room for wear/tear, carbon buildup, etc. Ok for race engine where you tear it down every other race.

 

Flow numbers can be skewed depending on what flow bench your using, with or without pipe, exhaust port size and other factors, Intake port size is also questionable. Measured actual on a Dart 180 it was almost 200. That said back to back dyno testing shows AFR consistently produce the highest flow vs actual port size of any head made. If you can afford them buy them, you will not regret it. That cam is fine and a good match for your build. Your looking at 420 HP and great bottom end and midrange with your trans, gear and combination. The Headman elites and your existing exhaust slightly modified to work with them is a great choice. They are ceramic coated and will not increase interior temperatures. The ramhorns will cost you a lot of power on this build, even 2 1/2" ramhorns. There are quite a few very experienced builders that have voiced there opinions on this thread and that is what you asked for. Listen to what they are saying. Even a stock L48 will wake up noticeably with just a set of headers and exhaust upgrade. The better the engine build the more difference the exhaust makes. If you decide to go with the ramhorns bump up the split on the exhaust duration on the cam to 12-14 degrees higher than the intake duration you have. It will help but still won't make the power of your existing combination with the full length headers. You might get 1/2 the difference back.

 

Check this. The ports on the AFR 180 is only raised .100". One tenth of an inch will not affect clearance.

 

This is what drives me crazy as an amateur in knowing what is correct. Everything I read is that 0.040 is the best quench, and nowhere do I see anything about this being too tight for street and carbon buildup, etc.

Billa, Mako, and all engine experts, please weigh in on this. I could replace the Felprop 1094 0.015 gasket with a Felpro 0.026 gasket, to increase quench up to 0.051.

 

[QUOTE=iwasmenowhesgone;1585792084]Brezinski racing has 2 1/2 Ram horns...that have been ported and opened up to use a felpro 1404/1405 exhaust gasket, are those the ones you purchased? Also the exhaust system you bought is it 2 1/2 from the manifold back? Do you have the magnaflow part number. I am in the same boat as you concerning headers and looking at all options

 

[QUOTE=Tjf2000;1585792985]No, I have an excellent set of original GM 2-1/2 inch rams horn manifolds that have been used, but look like new.

The Magnaflow number is 16836, made for 74 Corvettes, but obviously can be used on any Vette with a two hole crossmember.

 

[QUOTE=iwasmenowhesgone;1585793047]Thanks

 

.040 quench is perfect. Measure the outlet ID on your ramhorns and the donut gasket ID. Look up inside the outlet.

 

Here is a good article. Yes .04 is a good quench to shoot for...in a perfect world and in a perfect enviroment. Good efficiency and power; but, for a street machine i would like to error on safe zone. .045-.047. Unless you are going for all out power. For a large stroker I feel more comfortable .049-.052. Again for a street machine.

http://www.chevyhiperformance.com/te...earance_guide/

 

I run .040 & havent had any issues.

 

In my comments about stepping down in heads and came was just to keep everything matched. if thinks dont match you could create flat spots in the TQ curve or drivability issues. Also the advantage to the aluminum heads over iron is more weight savings. Iron is more efficient because it retains the combustion heat. That is why with aluminum heads you may need more compression to make the same power if comparing an identical iron head.
Yes I do believe that the AFR head will perform really well even with rams horn manifolds, but much much better with headers.
I do understand your concern with headers but with the right parts it all works well. I have AFR with Hooker 1 5/8 long tube headers. I also have a moog heavy duty idler arm and it clears and I did not need to dent anything. I also can tell you that these headers clear both a stock gear box and a borginson box. On a previous post I had a link of my build and I do have photos showing the clearances of theses headers.
O one think that I dislike is that I do have the painted headers and the paint only will last a few years. My buddy has the same headers on his 80 with the Jet Hot coating since I believe around 2007 but it is starting to peal around the collector area.
In high school my 71 C10 with a 406 small block was running 13.3-13.4 quarter miles but I made a change from 2 1/2 rams horn manifolds to hooker long tube headers and with only that change(and richer jetting to tune for the headers ) it ran a 12.9!
Please dont get me wrong, not trying to say its a bad build, just needs some tweaking to get everything to match. It will be a blast either way!

 

Back to the OP's heads question.

Why not use a set of GM's fastburn aluminum heads?
Install beehive springs that match your roller cam needs.

A little higher CR and good flow.
Plus they have the outer valve cover bolt hole openings (old school look) and they have accessory holes in the ends for easy mounting of ac, ps, alternator, etc.

I do agree with the others - a good set of headers made to fit the Corvette would help a lot. I like the Hedman in ceramic coating. No dinging needed and the ceramic helps with the heat factor.
If you really want the old school / hot rod look you could always wrap painted headers with the fiberglass wrap.

Just my $.02

Bman

 

How about these:
http://forums.corvetteforum.com/c3-p...low-heads.html

I believe they just need drilling and threading for standard valve covers use.

 

Not targeting you, but IMHO it's a lousy article - as is just about everything that comes out of CHP. They don't say anything about the head design or give any information on their "test". The guys there aren't wrenches...they set up dumb tests and take them to dumb shops (that want the free ad) for the most part - they never spin a wrench themselves and the editor noted last year that he keeps all of his tools in a milk crate

That sounds like a nit...but I prefer to take guidance from guys that spin wrenches and have been doing it successfully for a while.

Quench has a huge impact on power and detonation sensitivity - not the 3 or 4 HP claimed in the article - and it's worth the effort to achieve the .040 ideal. I typically square and zero-deck the block if the engine is going to make > 1 HP/CID so I can control quench with the gasket compressed thickness.

I don't really have any back-to-back comparisons, but I would note that I have seen GEN I stock pistons .040+ down in the hole (!)

 

I have something similar. 350/4 sp, 3:55 gears,218-224HR, 1.6RRs, TFS heads, ag, 650 Demon, 2" RHs,stk dual ex w/H pipe.
This put down 315 rwtq @4100 and 280 rwhp @5100.
You can see where the engine runs out @5K. I know the 2.5" RHs should put me over 300 rwhp. The mid range TQ is awesome!

This cam is a little flat off idle, I wouldn't use it w/stk converter. On a 4 sp, no problem. I have debated headers for years in my mind. The best part is, You can always add them later!

A 3:55 cruises at 3K on the freeway, how fast do you intend to spin your engine? You have been given some valuable advice, perhaps not what you wanted? Think it through, try and do it right the first time!
Unlike most of us who have made many expensive mistakes.

R

 

I'm not absolutely positive about this, so feel free to tell me I am wrong, but I believe that the .040" quench recommendation is the figure that allows a little leeway for street use. Racing engines take the quench down even tighter than that.

Scott