350 HO upgrade recommendations
Thread Starter
6th Gear
Joined: Mar 2021
Posts: 6
Likes: 0
350 HO upgrade recommendations
Hi, I have a '73 with a 350 HO crate motor that the previous owner installed. I was wondering what simple bolt-on upgrades there are to increase it to 400-450 hp/tq.
I came across this article from Motortrend which has a parts list (recreated below) that is close to what I want. Does anybody have alternate recommendations for any of these items? Thanks in advance!
I came across this article from Motortrend which has a parts list (recreated below) that is close to what I want. Does anybody have alternate recommendations for any of these items? Thanks in advance!
- Headers: Hedman 151/48-inch long-tube headers
- Mufflers: 211/42-inch Borla Pro X/S mufflers
- Distributor: HEI distributor
- Intake: Edelbrock Performer RPM Air Gap dual-plane intake
- Carburetor: Holley 0-4779 750-cfm carburetor
- Camshaft: Chevrolet Performance 24502586 - Chevrolet Performance LT4 Hot Cam
- Cam retainer plate: Chevrolet Performance 10168501 - Chevrolet Performance Camshaft Locking Plates
- Lifters: Chevrolet Performance 12371042 - Chevrolet Performance Hydraulic Roller Lifters
- Pushrods: Chevrolet Performance 12371041 - Chevrolet Performance Pushrods
- Springs: COMP Cams 26918-16 - COMP Cams Valve Springs
- Retainers: COMP Cams 774-16 - COMP Cams Steel Valve Spring Retainers
- Rocker arms: Chevrolet Performance 12370839 (replaced by 19210729?) - Chevrolet Performance Small Block V8 or V6 Rocker Arm Kits
Racer
Joined: Feb 2001
Posts: 405
Likes: 15
From: Minneapolis
I went that route 10 years ago with my ‘79. It made alot more power, but the low to mid range torque was disappointing. I recently installed a Blueprint 383, 430/455. What a huge improvement!! By the time you’re done with heads (which aren’t on your list) plus a rebuild kit, you’ll be spending the same $$. Get the crate and hang on!
Cheers,
AJ
Cheers,
AJ
Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
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WHat compression does your motor have? If its less than 9.5:1 you wont get the power you want. IF you dont know you may need to take of the heads and get a part number. For power you need some basics.
I would look at your crate motor choices and what you desire and see if there is one ou want in theprice range you can afford. I personally love building my own motors but some just want to drop it in and be done with it. I cant spend your miney for you but let us know what you are thinking budget wise
- good compression, I like 10.5:1, it gives you more options and is still under the pinging threshold for pump gas. If you are below 9.5 then you could add a power adder like, a turbo or a blower...
- then you need the best flowing heads you can afford for the cam you want to run or the power you want. For your range 185 to 195 cfm intake runner head would suffice. More air in = more power out
- RPM intakes are a great carbureated intake choice with a 750 carb
- depending on your compression, you would find a cam for your driving needs whether its street or street strip.
- Then a big flowing exhaust
I would look at your crate motor choices and what you desire and see if there is one ou want in theprice range you can afford. I personally love building my own motors but some just want to drop it in and be done with it. I cant spend your miney for you but let us know what you are thinking budget wise
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,212
Likes: 9,350
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Now a days heads are the best bang for the buck but you need the big 3 to make it all work. headers are 10 ft/lbs at the bottom and15-20 hp at redline, intake is 5 across the board and the cam is dependant on how big your heads and compression will allow. If you select the correct heads that increase compression and flow you could see 100 hp over a stock head with the same performance cam in each iteration. Again you need to know your piston numbers
Thread Starter
6th Gear
Joined: Mar 2021
Posts: 6
Likes: 0
I went that route 10 years ago with my ‘79. It made alot more power, but the low to mid range torque was disappointing. I recently installed a Blueprint 383, 430/455. What a huge improvement!! By the time you’re done with heads (which aren’t on your list) plus a rebuild kit, you’ll be spending the same $$. Get the crate and hang on!
Cheers,
AJ
Cheers,
AJ
Pro
Joined: Jul 2021
Posts: 719
Likes: 156
All '73 came OE w/ true dual exhaust & no cats. Headers will helps some.
350 HO has Vortec heads so it most certainly already has a performance intake manifold; it and a well-sorted Quadrajet is enough
A well-sorted OE '73 points distributor is enough. '73 has Mechanical-drive tach. A good quality HEI with mech tach drive is $$$ and it's large cap may, repeat may, interfere with OE '73 air cleaner assembly. If stuck on using electronic, perhaps retrofit OE Dist w/ a "Breakerless-SE" or Pertronix points eliminator conversions.
LT4 Hot Cam 24502586 is good but Very expensive today: instead, choose 8802 or 8803 from this list. plenty of lift without need of higher-ratio rockers. About Half the cost of today's 586. Same USA Billet Steel core as the GM 586
https://www.summitracing.com/search/...-sbc-camshafts.
instead of comp springs, use a set of Drop-In springs & retainers from Alex's Parts
https://www.alexsparts.com/valve-spring-kits/
get the dog bones, hold down, thrust plate etc in a kit from enginequest pn EQ-RLRDLXB
https://www.ebay.com/itm/175066595777
350 HO has Vortec heads so it most certainly already has a performance intake manifold; it and a well-sorted Quadrajet is enough
A well-sorted OE '73 points distributor is enough. '73 has Mechanical-drive tach. A good quality HEI with mech tach drive is $$$ and it's large cap may, repeat may, interfere with OE '73 air cleaner assembly. If stuck on using electronic, perhaps retrofit OE Dist w/ a "Breakerless-SE" or Pertronix points eliminator conversions.
LT4 Hot Cam 24502586 is good but Very expensive today: instead, choose 8802 or 8803 from this list. plenty of lift without need of higher-ratio rockers. About Half the cost of today's 586. Same USA Billet Steel core as the GM 586
https://www.summitracing.com/search/...-sbc-camshafts.
instead of comp springs, use a set of Drop-In springs & retainers from Alex's Parts
https://www.alexsparts.com/valve-spring-kits/
get the dog bones, hold down, thrust plate etc in a kit from enginequest pn EQ-RLRDLXB
https://www.ebay.com/itm/175066595777
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Thread Starter
6th Gear
Joined: Mar 2021
Posts: 6
Likes: 0
Thanks for your recommendations. The 350 HO crate motor I have (12486041) has 9.1:1 compression. As for heads, I have the stock Vortec heads that came with the motor. I'm looking for a cam for street or better low end torque since I don't plan on taking it to the strip. I'm hoping to spend under $5k.
Pro
Joined: Jul 2021
Posts: 719
Likes: 156
Thanks for your recommendations. The 350 HO crate motor I have (12486041) has 9.1:1 compression. As for heads, I have the stock Vortec heads that came with the motor. I'm looking for a cam for street or better low end torque since I don't plan on taking it to the strip. I'm hoping to spend under $5k.
no strip ... choose the summit 8802
No need to buy Chevy/GM overpriced lifters. Elgin pn HL-2148 or HL-2148S
Pro
Joined: Jul 2021
Posts: 719
Likes: 156
a little more compression; cheap & easy
on 350 HO old pn 12486041; essentially same motor (same heads, pistons, cam) but new pn 19420878
easily improve (shorten) quench And increase (raise) compression about 1/4 point from about 9:1 to about 9.23:1
OE composite gasket is pn 10105117 ... R&R with steel shim Fel Pro 7733SH1
5.766 cc = GM 10105117
3.245 cc = felpro 7733SH1
--------------------------------------------
2.521 cc
easily improve (shorten) quench And increase (raise) compression about 1/4 point from about 9:1 to about 9.23:1
OE composite gasket is pn 10105117 ... R&R with steel shim Fel Pro 7733SH1
5.766 cc = GM 10105117
3.245 cc = felpro 7733SH1
--------------------------------------------
2.521 cc
Racer
Joined: Feb 2001
Posts: 405
Likes: 15
From: Minneapolis
Thanks for your recommendations. The 350 HO crate motor I have (12486041) has 9.1:1 compression. As for heads, I have the stock Vortec heads that came with the motor. I'm looking for a cam for street or better low end torque since I don't plan on taking it to the strip. I'm hoping to spend under $5k.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
I agree read David Vizards book
For your stated goals (more low end for street) the 8803 is not the cam you want. 8802 or 8801 might be a better choice. 8801 looks to be close to what's in there now except it's a roller = better IMO.
What I'm seeing listed for that engine is a 212/222 @ .050 with .435/.460 lift on a 112 LSA. Would that be correct for your motor?
This book by Vizard is pretty good too. Not as good as the first one I listed but good for maxing what you have.
If you're looking to go roller though I think that is a good idea vs the flat tappet route. That Chevy performance cam is a decent looking cam with a little too much exhuast duration. For your CR of 9:1 it may struggle a bit too. The advertised duration is 279/287 vs the @ .050 duration of 218/228 which means it has low intensity lobes on it. Note the 8801 has decent intensity specs with an advertised duration of 261/267 for the @ .050 of 212/218.
Or the 8802 which has 267/275 for an @ .050 of 218/227. Much better intensity on these cams which means less overlap and better down low (street) performance.
For your stated goals (more low end for street) the 8803 is not the cam you want. 8802 or 8801 might be a better choice. 8801 looks to be close to what's in there now except it's a roller = better IMO.
What I'm seeing listed for that engine is a 212/222 @ .050 with .435/.460 lift on a 112 LSA. Would that be correct for your motor?
This book by Vizard is pretty good too. Not as good as the first one I listed but good for maxing what you have.
If you're looking to go roller though I think that is a good idea vs the flat tappet route. That Chevy performance cam is a decent looking cam with a little too much exhuast duration. For your CR of 9:1 it may struggle a bit too. The advertised duration is 279/287 vs the @ .050 duration of 218/228 which means it has low intensity lobes on it. Note the 8801 has decent intensity specs with an advertised duration of 261/267 for the @ .050 of 212/218.
Or the 8802 which has 267/275 for an @ .050 of 218/227. Much better intensity on these cams which means less overlap and better down low (street) performance.
Last edited by REELAV8R; Jan 22, 2022 at 05:09 PM.
Pro
Joined: Jul 2021
Posts: 719
Likes: 156
GM HFT cam pn 24502476 is what comes OE in 350 HO = 212/222 @ .050 with .435/.460 lift on a 112 LSA
400/400 is easy w/ right cam ... easier w/ 10:1 than w/ 9:1.
reference mild GM street crate pn 19367080
GM already gets 357 hp from the very same 9:1 350 HO motor ... but with GM roller pn 12677151 = 215/223 @ .050 w/ .473/.473 on a 108 LSA
and No, this 151 cam is Not the HFT 151 from days of yore.
go w/ the 8802 & don't look back.
400/400 is easy w/ right cam ... easier w/ 10:1 than w/ 9:1.
reference mild GM street crate pn 19367080
GM already gets 357 hp from the very same 9:1 350 HO motor ... but with GM roller pn 12677151 = 215/223 @ .050 w/ .473/.473 on a 108 LSA
and No, this 151 cam is Not the HFT 151 from days of yore.
go w/ the 8802 & don't look back.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
If this is an automatic, you may want to consider a higher stall torque converter.
With those vortec heads you also may run into a max lift issue with a new cam. gonna have to check to see if coil bind or valve seal limits will be reached without modification to get more lift.
Ok found it.
https://www.karlkustoms.com/product/...head-assembly/
So yes, to use either the 8801 or 8802 some mods will be required.
With those vortec heads you also may run into a max lift issue with a new cam. gonna have to check to see if coil bind or valve seal limits will be reached without modification to get more lift.
Ok found it.
Camshafts with more than 0.475″ lift require machining valve guide bosses and checking valve seal to valve spring retainer clearance
So yes, to use either the 8801 or 8802 some mods will be required.
Last edited by REELAV8R; Jan 22, 2022 at 08:03 PM.
Thread Starter
6th Gear
Joined: Mar 2021
Posts: 6
Likes: 0
If this is an automatic, you may want to consider a higher stall torque converter.
With those vortec heads you also may run into a max lift issue with a new cam. gonna have to check to see if coil bind or valve seal limits will be reached without modification to get more lift.
Ok found it.
https://www.karlkustoms.com/product/...head-assembly/
So yes, to use either the 8801 or 8802 some mods will be required.
With those vortec heads you also may run into a max lift issue with a new cam. gonna have to check to see if coil bind or valve seal limits will be reached without modification to get more lift.
Ok found it.
https://www.karlkustoms.com/product/...head-assembly/
So yes, to use either the 8801 or 8802 some mods will be required.
Thread Starter
6th Gear
Joined: Mar 2021
Posts: 6
Likes: 0
All '73 came OE w/ true dual exhaust & no cats. Headers will helps some.
350 HO has Vortec heads so it most certainly already has a performance intake manifold; it and a well-sorted Quadrajet is enough
A well-sorted OE '73 points distributor is enough. '73 has Mechanical-drive tach. A good quality HEI with mech tach drive is $$$ and it's large cap may, repeat may, interfere with OE '73 air cleaner assembly. If stuck on using electronic, perhaps retrofit OE Dist w/ a "Breakerless-SE" or Pertronix points eliminator conversions.
LT4 Hot Cam 24502586 is good but Very expensive today: instead, choose 8802 or 8803 from this list. plenty of lift without need of higher-ratio rockers. About Half the cost of today's 586. Same USA Billet Steel core as the GM 586
https://www.summitracing.com/search/...-sbc-camshafts.
instead of comp springs, use a set of Drop-In springs & retainers from Alex's Parts
https://www.alexsparts.com/valve-spring-kits/
get the dog bones, hold down, thrust plate etc in a kit from enginequest pn EQ-RLRDLXB
https://www.ebay.com/itm/175066595777
350 HO has Vortec heads so it most certainly already has a performance intake manifold; it and a well-sorted Quadrajet is enough
A well-sorted OE '73 points distributor is enough. '73 has Mechanical-drive tach. A good quality HEI with mech tach drive is $$$ and it's large cap may, repeat may, interfere with OE '73 air cleaner assembly. If stuck on using electronic, perhaps retrofit OE Dist w/ a "Breakerless-SE" or Pertronix points eliminator conversions.
LT4 Hot Cam 24502586 is good but Very expensive today: instead, choose 8802 or 8803 from this list. plenty of lift without need of higher-ratio rockers. About Half the cost of today's 586. Same USA Billet Steel core as the GM 586
https://www.summitracing.com/search/...-sbc-camshafts.
instead of comp springs, use a set of Drop-In springs & retainers from Alex's Parts
https://www.alexsparts.com/valve-spring-kits/
get the dog bones, hold down, thrust plate etc in a kit from enginequest pn EQ-RLRDLXB
https://www.ebay.com/itm/175066595777
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
there are other cams that would work. Look around at summit see what you can find.
Pro
Joined: Jul 2021
Posts: 719
Likes: 156
OP
Asking same question as ddawson above. Who's doing the install & changeover of the roller conversion??? You ???
another question ... have you heard of a "ghetto grind" on Vortec retainers ??? if not, look it up and advise if that's something you feel comfortable doing yourself ???
and yes, seems like Alex is out of the vortec drop in kits ... as well as nearly everything else.
Asking same question as ddawson above. Who's doing the install & changeover of the roller conversion??? You ???
another question ... have you heard of a "ghetto grind" on Vortec retainers ??? if not, look it up and advise if that's something you feel comfortable doing yourself ???
and yes, seems like Alex is out of the vortec drop in kits ... as well as nearly everything else.