Quick '86 iron head question
Safety Car
Joined: Aug 2009
Posts: 3,752
Likes: 276
From: Melbourne, Victoria, Australia
Well the flow limitation is the TPI inlet isn't it ?!?
Way back wheni had the old standard engine, simple add on's like headers cold air intake, airpump delete and adjustable fuel pressure regulators. Tuning and trail and error i managed to get my 85 from the standard 14.4 seconds quarter mile to 13.2. Not bad for TPI and std cast iron heads.
Now with my 383 i could not justify spending thousands on AFR heads, mini ram manifold to make it worthwhile. with a blower i just get more h/p torque everywhere and can spin into the redline easily.
The cast iron heads are not as bad as people make out, my old 350 did more than 170,000 miles no head gasket problems like alloy heads. The rings were not coping with the boost and could not seal, the heads were checked and were good to go.
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 764
three of the four C4's I've owned have been L98's - two aluminum head, and one iron head. my preference, my 2 cents, and FWIW - I'd take an iron head L98 over the aluminum head version any day of the week. heat wise, my old 85 has been to hell and back - more than once. I doubt, either of my 90's would have faired as well.
flow wise,
w/ gerardvg - limited by the TPI inlet - 
sorry to get OT -
flow wise,
w/ gerardvg - limited by the TPI inlet - sorry to get OT -
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
I disagree with the iron heads flowing well claim. I had a flat tappet zz409 cam, headers, miniram, 3.75s, 58mm throttle body, and all the free mods and some miscellaneous mods, and I couldn't even keep up with a stock C5. Now I have AFR heads, and I can guarantee it'll blow them away!
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Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 764
I disagree with the iron heads flowing well claim. I had a flat tappet zz409 cam, headers, miniram, 3.75s, 58mm throttle body, and all the free mods and some miscellaneous mods, and I couldn't even keep up with a stock C5. Now I have AFR heads, and I can guarantee it'll blow them away!
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
I disagree with the iron heads flowing well claim. I had a flat tappet zz409 cam, headers, miniram, 3.75s, 58mm throttle body, and all the free mods and some miscellaneous mods, and I couldn't even keep up with a stock C5. Now I have AFR heads, and I can guarantee it'll blow them away!
Something was very wrong w/your original combo if you couldn't keep up w/a stock C5, with the parts you listed.
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
my statement wasn't very clear. The iron heads AND the alum heads don't flow any better than the old fuelie heads., The vortec and aftermarket heads flow better , hands down. Sure, the old heads could help your car go fast, and many did, but they need expensive work to flow as well as newer heads.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Well apparently you haven't been seeing anything. If you read my previous threads you would have seen that I have been driving it. And yeah, what was wrong with the previous combo was the iron heads!
Burning Brakes
Joined: Jun 2000
Posts: 865
Likes: 6
From: Auburn Michigan
And the "624's" in the day were put in V8's (76cc b.t.w.) on several different GM vehicles and were not Corvette specific like the aluminum "113" heads.
But if you wanted to sell your 624 heads on Ebay, be sure to say "Corvette" heads so someone will pay more money for them....
Last edited by cohocarl; Mar 18, 2014 at 11:51 AM.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Since your driving it, and you can make a "guarantee" on your C5 beating performance, what are you 1/4 mile times?
Last edited by Tom400CFI; Mar 19, 2014 at 09:52 PM.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Haven't run it yet.
Drifting
Joined: May 2006
Posts: 1,428
Likes: 7
From: Chewelah Wa
Here are the flow rates i could find in the 624's and 113's.
624 heads-
198/134@.400
216/139@.500
113's-
189/157@.400
190//171@.500
The iron heads have the advantage on intake flow, the 113's on exhaust. The D shape raised port does the job. Seems like a wash, except the small chamber on the 113's seem to give a compression advantage, and of course, a weight advantage. But even a crappy pair of aftermarket heads are superior performance wise. Flow numbers for the 624's was hard to come by, so I cannot confirm them as they came from one source. These were the 1.94's.
624 heads-
198/134@.400
216/139@.500
113's-
189/157@.400
190//171@.500
The iron heads have the advantage on intake flow, the 113's on exhaust. The D shape raised port does the job. Seems like a wash, except the small chamber on the 113's seem to give a compression advantage, and of course, a weight advantage. But even a crappy pair of aftermarket heads are superior performance wise. Flow numbers for the 624's was hard to come by, so I cannot confirm them as they came from one source. These were the 1.94's.
Last edited by powerpigz-51; Mar 19, 2014 at 08:50 PM.
Instructor
Joined: Apr 2007
Posts: 225
Likes: 1
From: Highland Village texas
Here are the flow rates i could find in the 624's and 113's.
624 heads-
198/134@.400
216/139@.500
113's-
189/157@.400
190//171@.500
The iron heads have the advantage on intake flow, the 113's on exhaust. The D shape raised port does the job. Seems like a wash, except the small chamber on the 113's seem to give a compression advantage, and of course, a weight advantage. But even a crappy pair of aftermarket heads are superior performance wise. Flow numbers for the 624's was hard to come by, so I cannot confirm them as they came from one source. These were the 1.94's.
624 heads-
198/134@.400
216/139@.500
113's-
189/157@.400
190//171@.500
The iron heads have the advantage on intake flow, the 113's on exhaust. The D shape raised port does the job. Seems like a wash, except the small chamber on the 113's seem to give a compression advantage, and of course, a weight advantage. But even a crappy pair of aftermarket heads are superior performance wise. Flow numbers for the 624's was hard to come by, so I cannot confirm them as they came from one source. These were the 1.94's.
Burning Brakes
Joined: Feb 2013
Posts: 1,173
Likes: 152
From: norway
Safety Car
Joined: Nov 2008
Posts: 4,328
Likes: 15
From: Jacksonville FL
They may not flow like aftermarket but if I would have had aluminum heads when I blew my head gasket, they would not have survived. Exhaust into coolant raised temps higher than I thought the gauge went. Had to nurse it home a couple of miles at a time with 30 minute cool down cycles. Hit 260* and pull over, Repeat, repeat, repeat. Took the iron heads in and they did no more than do a light mill and freshen the seats and valves with new seals. I woulda been shopping for new heads had they been aluminum. Until I break down and throw some thousands at the engine, I will stick with iron and be thankful.