How bad would the 2 inch foxbody headers hurt a 800 h.p. 521? Here some engine specs and Ideas.
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How bad would the 2 inch foxbody headers hurt a 800 h.p. 521? Here some engine specs and Ideas.
ED468 May 25th 2020, 5:19 am
Made around 750 hp with 501. Would like 50 more h.p. out of 521. Putting 2.25 valves in the streets, should be close to 400 cfm , Thats 10 cfm more @ .750. Cam is where I hope to help crutch the parts to work as best they can. Had XR304R SR cam and for street can't go too much bigger with my budget and Valve train parts. Had it installed at 108 IC because felt 268 dur. was a little small. Won't a new cam with a earlier exhaust opening help with exhaust evacuation? Also if I pick intake port flow up, wouldn't going to a wider Lobe Center like from 110 to 111 work good and help a exhaust limited motor? I feel the less over lap wouldn't work the ex. as hard so it could better evacuate ? Thinking around 272-276 and maybe .700 lift on a XR street grind. If drag only it would have more lift. Trying to make a power band between 5500 and 7000 max. Also doing work on manifold to help power, outer runners need help bad.
ED468- Posts : 200
Join date : 2013-03-27
Location : Maunie il.
Re: How bad would the 2 inch foxbody headers hurt a 800 h.p. 521? Here some engine specs and Ideas.
rmcomprandy May 25th 2020, 10:26 am
ED468 wrote:Made around 750 hp with 501. Would like 50 more h.p. out of 521. Putting 2.25 valves in the streets, should be close to 400 cfm , Thats 10 cfm more @ .750. Cam is where I hope to help crutch the parts to work as best they can. Had XR304R SR cam and for street can't go too much bigger with my budget and Valve train parts. Had it installed at 108 IC because felt 268 dur. was a little small. Won't a new cam with a earlier exhaust opening help with exhaust evacuation? Also if I pick intake port flow up, wouldn't going to a wider Lobe Center like from 110 to 111 work good and help a exhaust limited motor? I feel the less over lap wouldn't work the ex. as hard so it could better evacuate ? Thinking around 272-276 and maybe .700 lift on a XR street grind. If drag only it would have more lift. Trying to make a power band between 5500 and 7000 max. Also doing work on manifold to help power, outer runners need help bad.
To get a 521 with those heads to still be making power up near 7,000, you will need a lot more exhaust cam than that.
A 2" header is not a problem.
rmcomprandy- Posts : 6157
Join date : 2008-12-02
Location : Roseville, Michigan -
2 inch header
ED468 May 25th 2020, 3:15 pm
Good to hear! The 501 needed shifting to 7. 000 rpm minimum or it slowed down. Converter seemed plenty loose. Would like to make a Flat power band and go from 4.11 to 3.55s and shift around 6500 ideally. I think the bigger valve will pick up alot of flow low and mid lift. The limited exhaust Dur. is because that takes away street ability , don't think lifters and springs would live long. Less gear might work since was around 7,000 RPMs @ 120mph at the 1/8th. I'm in the Planning stage, been a while since it ran and need something to keep my mind Busy stuck in house. 
ED468- Posts : 200
Join date : 2013-03-27
Location : Maunie il.
Re: How bad would the 2 inch foxbody headers hurt a 800 h.p. 521? Here some engine specs and Ideas.
Curt May 25th 2020, 6:55 pm
We run 1-7/8" stepped to 2" in the midget at about 360hp and 2" straight on the sprint car at just under 800. We don't think bigger headers would help any. Both SBCs, well, the midget is the left bank of a SBC.
We're actually talking about going to a 1-3/4 - 1-7/8" on the midget.
We're actually talking about going to a 1-3/4 - 1-7/8" on the midget.
Curt- Posts : 2791
Join date : 2009-02-08
Age : 62
Location : Henrietta, Texas but mostly on the road
Re: How bad would the 2 inch foxbody headers hurt a 800 h.p. 521? Here some engine specs and Ideas.
Curt May 25th 2020, 7:04 pm
We turn the midget 8700 rpm and the sprint car 7800
Curt- Posts : 2791
Join date : 2009-02-08
Age : 62
Location : Henrietta, Texas but mostly on the road
ED468- Posts : 200
Join date : 2013-03-27
Location : Maunie il.
Doesn't the exhaust valve on kaase heads flow better too, got 262cfm now and going to work on head bolt bump a little more.
ED468 June 11th 2020, 10:07 am
rmcomprandy wrote:ED468 wrote:Made around 750 hp with 501. Would like 50 more h.p. out of 521. Putting 2.25 valves in the streets, should be close to 400 cfm , Thats 10 cfm more @ .750. Cam is where I hope to help crutch the parts to work as best they can. Had XR304R SR cam and for street can't go too much bigger with my budget and Valve train parts. Had it installed at 108 IC because felt 268 dur. was a little small. Won't a new cam with a earlier exhaust opening help with exhaust evacuation? Also if I pick intake port flow up, wouldn't going to a wider Lobe Center like from 110 to 111 work good and help a exhaust limited motor? I feel the less over lap wouldn't work the ex. as hard so it could better evacuate ? Thinking around 272-276 and maybe .700 lift on a XR street grind. If drag only it would have more lift. Trying to make a power band between 5500 and 7000 max. Also doing work on manifold to help power, outer runners need help bad.
To get a 521 with those heads to still be making power up near 7,000, you will need a lot more exhaust cam than that.
A 2" header is not a problem.
ED468- Posts : 200
Join date : 2013-03-27
Location : Maunie il.
Re: How bad would the 2 inch foxbody headers hurt a 800 h.p. 521? Here some engine specs and Ideas.
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