Correct 58 fuelie heads
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Correct 58 fuelie heads
OK, I am confused. Per the NCRS technical guide, my 1958 290HP fuel car should have 3748770 (stamped X58) heads which are 1.72 intake and 60cc's. It calls them out for all the fuel cars.
However, when I look up casting numbers on the internet etc., I see a lot of reference to the 3740997 heads (and a couple of other numbers) which have 1.94 intake and were used on 57 fuel cars and possibly early 58's.
It seems to me I should have the big valve heads on this engine. (My current engine is not original, has a 59 block, correct casting number wrong date, and I think 1960 heads, but is at least conceptually correct for the car.)
I want to have the car judged this summer, but before I go buy "new" heads, I want to be very sure that I get the correct ones.
This car is an early car, built Janaury 58, with the hood support on the right side. The fuel unit is not the '57 carryover but the later 58-59 unit, so, I wonder if this was built during a transitional time.
Your comments/opinions would be helpful. (Yep, I am an NCRS member, just looking for a broader range of expert opinions on this.)
Thanks.
However, when I look up casting numbers on the internet etc., I see a lot of reference to the 3740997 heads (and a couple of other numbers) which have 1.94 intake and were used on 57 fuel cars and possibly early 58's.
It seems to me I should have the big valve heads on this engine. (My current engine is not original, has a 59 block, correct casting number wrong date, and I think 1960 heads, but is at least conceptually correct for the car.)
I want to have the car judged this summer, but before I go buy "new" heads, I want to be very sure that I get the correct ones.
This car is an early car, built Janaury 58, with the hood support on the right side. The fuel unit is not the '57 carryover but the later 58-59 unit, so, I wonder if this was built during a transitional time.
Your comments/opinions would be helpful. (Yep, I am an NCRS member, just looking for a broader range of expert opinions on this.)
Thanks.
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Re: Correct 58 fuelie heads (Lee)
The first "big port" "big valve" heads were the 461s that were used on '61 FI engines, and that's why they are rated at 315 HP. Everything prior to that is "medium port" with 1.72" inlet valves.
For '60 there was an aluminum version of the 461, but it had problems and was cancelled. A few might have gotten into customer hands, but probably didn't last and were replaced on warranty with medium port iron heads.
If you're going to get your '58 judged I'd recommend you contact the '58 Team Leader for clarification. In general, the NCRS Spec Guides are very accurate, and I would put more credence into NCRS publications than some site on the "misinformation highway".
Duke
For '60 there was an aluminum version of the 461, but it had problems and was cancelled. A few might have gotten into customer hands, but probably didn't last and were replaced on warranty with medium port iron heads.
If you're going to get your '58 judged I'd recommend you contact the '58 Team Leader for clarification. In general, the NCRS Spec Guides are very accurate, and I would put more credence into NCRS publications than some site on the "misinformation highway".
Duke
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From: Washington Michigan
Re: Correct 58 fuelie heads (SWCDuke)
You want the "770" heads, which were used on ALL 58's. All heads of that era had 1.72/1.5 valves, including the "539" head used on '57 283/283 fuelies and the "997" heads used on all other 57's. Oddly enough, the "539" heads are readily available and cheap, as they were used on many '57 passenger cars too, but the "997" heads used on 90% of all 57's are VERY rare and expensive (about $2,000/pr. bare these days), as they were only used on '57 Corvettes (and a very few '57 2x4 and fuelie passenger cars).
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Re: Correct 58 fuelie heads (JohnZ)
John - It's always been by understanding that the 1.72"/1.5" valve heads have essentially the same "medium" inlet port size, and the 461s included a "large" port along with the larger inlet valve size.
If my understanding is correct, then what are the differences between the various 1.72"/1.50" valve heads?
Duke
If my understanding is correct, then what are the differences between the various 1.72"/1.50" valve heads?
Duke
Team Owner
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From: Washington Michigan
Re: Correct 58 fuelie heads (SWCDuke)
Duke -
The family of early heads with 1.72/1.5 valves all shared a 140cc intake port volume, while the later 461-family heads with 1.94 valves had a 160cc intake port. The early small-valve heads differed mainly in chamber size (58-64cc), and mainly in how the spark plug shrouding and quench "bumps" were handled through several different chamber shapes, looking for better flame front propagation. The later "461"-family heads came with both 1.94 and 2.02 valves, and with 2.02's, the chamber got an extra machining operation to unshroud the intake valve - this also carried into the later "186" heads (with accessory holes, starting in '69). When 1.94's are enlarged to 2.02's in the field, if the chambers aren't modified to unshroud the intake valve, they will actually flow less with 2.02's than they did originally with 1.94's.
The family of early heads with 1.72/1.5 valves all shared a 140cc intake port volume, while the later 461-family heads with 1.94 valves had a 160cc intake port. The early small-valve heads differed mainly in chamber size (58-64cc), and mainly in how the spark plug shrouding and quench "bumps" were handled through several different chamber shapes, looking for better flame front propagation. The later "461"-family heads came with both 1.94 and 2.02 valves, and with 2.02's, the chamber got an extra machining operation to unshroud the intake valve - this also carried into the later "186" heads (with accessory holes, starting in '69). When 1.94's are enlarged to 2.02's in the field, if the chambers aren't modified to unshroud the intake valve, they will actually flow less with 2.02's than they did originally with 1.94's.
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Re: Correct 58 fuelie heads (JohnZ)
Interesting. When I rebuilt the 461s from my SWC I kept the same valve sizes as the 2.20/1.6 combination has a tendency to crack between the valves, but I did a nice pocket port and port match with the inlet manifold. I tapered the chamber walls on both sides to eliminate the bore overhang, and I figure that the overhang on the exhaust side is the worst offender, as it is bound to disrupt exhaust flow.
Duke
Duke
