[nicksbigblock]

I am looking to prioritize future performance mods so I know what to save up for in the right order. Below is everything I know about the car and what I am looking to do...

What do you think?

1970 Chevelle SS

Engine
454 .030
Flat top pistons
Crane 226@.050 .533 lift 108 LSA
781 Oval Port heads with upgraded larger valves and fresh springs/components
Full roller rockers
Edelbrock Performer 2-0 Intake
Edelbrock 750
GM HEI distributor

TH400
stock converter
12 bolt non posi with 3.73 gears (decodes as originally correct 3.31 gear as this car was a 396/402 car)

Hooker Competition Headers 2"
2.25" exhaust pipes no crossover 2,25" Flowmaster 40's 2.25" crush bent tail pipes with stock chrome tips

14" SS wheels with 225/70/14 BFG's


Goal: maximize current block/cam/heads while keeping it very streetable and fun. Drive car to cruise-ins, shows, occasional 1/8 mile blast, and possible 2-3 hour trip with stops along the way. I like a somewhat period correct look and feel. I would love to be able to run high 12's with DR's someday with good 60 ft.

These are the mods I have in mind...how would you prioritize them or what would you change?

• Add an Eaton Posi unit
• Mickey Thompson Sportsman S/T 275/60/15 or 295/50/15 tires to the new set of 15x8 SS wheels sitting in garage
• Holley Street Avenger 770 or 870 VS carb (ease of tuning and streetability)
• 2600-2800 stall converter (car lurches at stoplights now with tight converter)
• 3" exhaust with 2.5" tailpipes
• Edelbrock RPM Intake
• Good Dyno tune after each mod (carb, exhaust, etc...)

Thanks in advance! I am new to the BBC world!

-Nick

 

[mfret1970]

You've got a decent combo now, and your plans are good as well. First question: Are you positive you have flat-tops? Are you positive about the 781's?

If both are true, you are lacking a good bit of compression. Flat tops with an open chamber head like the 781 will produce roughly around 8:1.

If you're happy the way the motor runs now, then enjoy the cheap(er) fuel and carry on with tires and a posi.

Rpm intake will make an improvement, and I would recommend a 1" spacer on top of that. The 2" headers are too big IMO, would be more responsive with 1.75's.

The converter will probably make the most noticeable difference in how it performs on the street.

Good lookin car.



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[nicksbigblock]

Hey thanks for your feedback. I love the way the motor runs as it has good torque and is pretty responsive. I am also new to big blocks so having such a mild iron headed engine with small cam perform like this is very nice.

I was told it was built with flat tops about 3000 miles ago but have not seen the internals. I also don't know if it is zero deck block, milled heads, or anything that would give me a more realistic idea of static impression ratio.

I agree that stall converter would help acceleration and drivability. I am very reluctant to do much right now because this car runs 190-195 degrees in all weather conditions with a stock style radiator and mechanical fan.

I really just want to see if 400hp is possible out of this cam/head combo with minimal work. I should probably put it on a dyno to see where the a/f and power curve is now before I change carbs and such.

-Nick


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[1968 hot rod]

with 781's & flat top pistons compression will be too low imho.
have someone with experience rework the hei for a better advance curve

 

[mfret1970]

400 should be a cake walk. Look up sweaton's posts about a properly functioning factory cooling system. Cliff notes--factory shroud, gm part# 772 fan, gm HD fan clutch, water and water-wetter. 160 stat with a couple relief holes drilled in it.

The alum rpm intake will help too. Very similar to my combo except I have closed chamber 96cc heads. Makes long black marks in the road.


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[mfret1970]

Edit: go read the "67 chevelle fan" thread in the engine section. Scott just posted his cooling tips there yesterday.


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[MrToadsWildRide]

Spray it!, with a Nitrous Pro Flow system from Wilson Manifolds. Well that may be overkill but you'll wreck a pair of rear tires in the most impressive way. A moderate stall converter (25-2800rpm) makes it more fun also, just keep everything cool temps wise.

 

[plain 69]

I don't think you need more than a 2500 stall. I have pretty much the same combo with 049's heads, 3.42 gears, Wieand Action + series intake, I do have close to 9.7 to 1 compression with the L2465F pistons heads have been milled to 116 cc's. If the weather is good I will be running mine for the first time at the track. Long black tracks are a norm here and maybe about 20 ft of tire pain when it shifts to second. Sticky tires a must.

What RPM does your cam idle at in park and drive? Just curious because mine is idling at about 1,000 and 700 in gear. Just wanting to see if that is normal with that cam.

1. The eaton posi unit is a must if you don't have posi already.
2. At least a 2.5" in mandrel bent exhaust

I don't think I would worry about the intake since the cam is done by 5400 as far as pulling power. It might rev to 6,000 but is not making any power there.

 

[-SS454-]

If it were me I would do the exhaust and the converter first. You and I think alike and have similar combos. I wanted to keep the guts of my 454 the same but add a few things to it. So I did an oil pan (since the engine was out), car spacer, threw a full 3 inch exhaust on it and rectified some issues and picked up over 40 rwhp. I think if you are going to go with 15x8s, then the 275s are the way to go as 295s like a 15x10 best.

 

[nicksbigblock]

Guys this is all good feedback and let's me know I am going in the right direction.

In terms of the temp I think running at 190 in all conditions is good so I didn't mean to sound like it was too hot.

Ss454 - how do you like your new aerochamber exhaust? I have always admired those mufflers. What issues did you sort out to make that gain in power? Any cleaner sound clips without wind noise yet? I actually really like how the flowmaster classic 40's sound on my big block but am open to more performance if I still dig the sound.

Anyone want to recommend a brand or part# of a 2500ish converter?

Also I could use my 15x8 in front and buy some 15x10 for rear if I want to go 225 I suppose. I love the wide tire look. 275 will be much improved and fit well though. I have 225 now.

Also to answer the question on my idle RPM. You are dead on. I idle just around or under 1k in park and around 600-700 in gear. I really love the sound and torque of this little cam. I ran a cam with 108LSA in a small block ford and it had that nice lope.

-Nick


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[buenymayor]

What kind of traction are you getting now? Probably not alot. I think the biggest bang for your buck right now would be to get the car to hook. That would provide the best seat of the pants feel. Nothing worse than getting your doors blown off by a car with 100 less HP while you send the back tires up in smoke. I'd opt for a the differential and tires, first. Sounds like the engine should be fairly healthy as is for now.

 

[nicksbigblock]

Traction is an issue. If I take off in first it is all rubber...shifting to 2nd chirps tires and after that it moves fine.

Do you recommend the Eaton posi or another option? I LOVED the Detroit Locker in the 9 inch in my 68 mustang.


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[Twins Fan]

I think you're spot on with your mod list, Nick.

I have a very similar combo to yours, so whatever that makes my advice worth. ... 454 with 063's, flat tops, same cam...

I'd say your exhaust system is the biggest mismatch now, and should be first on the list. If you're willing, I'd say go with some 1 3/4 headers instead of the 2 inch and at least 2.5 inch after the headers, if not 3 inch. I have 1 3/4 headers and a 3 inch Pypes Race Pro system for my exhaust set up.

Then the intake and carb. I think your choices are just fine there. The 770 Avenger will be fine. I have a good old Holley 3310 750 VS carb and Weiand Stealth intake.

Then the converter. The range of 2600 - 2800 you mentioned is just right. I have an "Edge" converter that stalls right in that range and highly recommend them. A little more $$, but worth it, IMHO. http://www.edgeracingconverters.com/

Then a posi for the rear and Eaton is the way to go, again.. IMHO

Then wheels and tires.

Easy high to mid 12 second car with a set up like that and all tuned well. :thumbsup:

 

[nicksbigblock]

Thanks Twins Fan! Nice to hear so many use the same or similar combo and are running strong. I think the torque tech system looks nice so I'll probably talk to them about a 3" setup.

I say my headers are 2" primaries but can't verify that. They certainly look big but then again my small block had 1 5/8 so maybe they are only 1 3/4 or 1 7/8. How can I tell for sure?


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[kettbo]

396 now or 454 now?

2.5 to 3" exhaust 1 7/8 headers
keep what I believe to be the Performer intake if it is opened to the regular oval port size
Eaton Posi works well, lasts a long time
3.73 gears a bit much for that combo but if you have it already, run it

I'd prefer the earlier closed chamber heads like Twins Fan Brad mentioned (063s, 360, 216) with the flattops to get something in the 8.8-0:1 range. However, many people do run with flattops and OC 781/074 heads

I ran factory shallow-dished flattops, 063 heads and the .533"/226*/108 cam with 3.42s and '2400' stall. It ran 13-flat. I swapped in a 3000 stall, it went 12.7s. Probably could have worked down to 12.5s had I not sold the engine. All through 2.5" exhaust and drag radials....and a few well-chosen tips to get traction and free some power up

454, biggest thing to do, bottom line, is to get traction. After that, all gravy

several of my threads on this
SUPER BUDGET 454

 

[Twins Fan]

If you can get a brand and part number off the headers... or, if you take a good pic of them some of these guys can probably tell from the pic... or, you can unbolt one side, pull it away from the heads a little, and measure the opening form the inside. Those are my best guesses. I don't know if measuring the outside of the tube would be accurate?

I mention the headers becuase if you have 2 inch headers, it's probably losing some power/torque in the low rpm range compared to a 1 3/4 header. Which is pretty much where mild combos like these operate.

 

[kettbo]

Having said this, would grow the cam a bit more at 8.8-9:1 from 226*
thinking, actually had a cam ground
233*/.545/110 would give a moderate 454 just a bit more fire

 

[rel3rd]

Just an FYI...

Automotive Tubing, as in header primary pipes or exhaust pipes, are measured at the outside diameter. :thumbsup:

 

[nicksbigblock]

Rel3rd...thanks I measured circumference and divided by pi and verified that they are 2" primaries. Not sure I am willing to ditch them or buy a smaller set since they are nice ceramic coated hookers that seem to fit really well.


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[rel3rd]

Rel3rd...thanks I measured circumference and divided by pi and verified that they are 2" primaries. Not sure I am willing to ditch them or buy a smaller set since they are nice ceramic coated hookers that seem to fit really well.


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No problem. :beers:
I am in the same boat, but with my little 402...has 2" primaries, 3.5" collectors, then down to 2.5" pipes from there to the tailpipe tips. The only reason I'll probably go ahead and swap mine is due to the lack of ground clearance. (Hooker Super Comps)