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Discussion Starter · #1 · (Edited)
This is my first build/restomod. (1964 El Camino)

SBC 350 engine LM1, #10066036
Pistons 12514101 (effective dome volume?)
200-4R transmission, torque converter 2,000 stall
3.08 10 bolt rear end (stock)...*edit maybe 3.42 or 3.55 in the future
stock exhaust manifolds
Edelbrock 1406 carburetor, 600cfm
Edelbrock 2601 intake manifold
I just bought Edelbrock e-street heads (*edit 64cc) and comp cam CL 12-246-3 with new lifters, pushrods and stamped steel roller tip rocker arms from JEGS that I haven’t installed yet.
(*head gasket is jegs 555-210035, 0.040 thickness)

What do you think of this cam selection?
(I made another post in the exhaust section to figure out how I can make this quiet. I want weekend stealthy/quiet power on a budget)
 

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Its a little rowdy but ought be fine. I might have picked less duration with the 3.08 gears to generate more torque, but you'll have some lope at idle, and the ability to pull thru 6000 rpm.

 

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If you were to back off about 10 deg. duration it would suit the rest better.
 

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I have the same Cam in a 383 with trick flow heads, headers, 700 R4, 2,800 stall and 3.73 gears. Works great for my combo and is very notable at idle. Nothing stealthy. Car runs 12.70.

To use that cam in your car, change the rear gears, run headers and more stall. Or, go with a smaller cam.

I agree, about 10 degrees less duration would be better. Call comp cams and get a recommendation.
 

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Exactly what I was thinking 218-220 on the intake tops. 210-215 preffered. More TQ = More Fun!

If you were to back off about 10 deg. duration it would suit the rest better.
.
 

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Discussion Starter · #6 ·
Thanks for the feedback. In the future I want to change the rear end gear to 3.55. Would I still need to back off about 10 degrees duration?
 

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Discussion Starter · #7 ·
Jegs recommended the cam above but now I know it’s too big with my application. I called comp cams and they recommended 12-242-2 with a 3.55 gear ratio. They said it will be lazy with the 3.08 until I switch to 3.55.
 

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68 has that cam in the system it would prefer.
 

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Too big in some and just right in others.

I do not feel it is too big at all even with the .308 gear.
I ran 3.00 rear gear in my 57 chevy 4 door and the 280H magnum cam.
RPM intake and 750 carb.
Pulled my 20 foot pontoon just fine and ran very well.

Yes a gear will help low end but even the little 268H wants more gear for more low end.

My 350" engines have a minimum of 10.3 compression though and that really helps.

I do not like the intake choice.
Spread bore with a square bore carb will need an adapter plate.
I ran an air gap RPM intake and here in the winter in Oklahoma it was no fun.
Nail it and bog.
I had to add a lot more fuel to make it work.
I kept it on for a few months trying different carbs and fuel curves and timing curves.

I finally pulled it off and put the regular RPM intake on and WOW! NO more bog any where.
I then pulled a lot of fuel out of it and it still never bogged anywhere.

The Air gap RPM worked well in the 85+ degree days.

3.08 rear gear and TH 350 in first gear is a 7.76 ratio.
.308 rear gear and 2004R in first gear is an 8.43 ratio.

3.34 rear gear would be needed with the TH 350 to match the ratio of the 2004R.

Just depends on how you drive and what you like.

I have a set of 2.29 rear gears and those are a hoot with something that pulls a lot of RPM.
95 MPH in first gear :)
 

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A cam that's too big for street driving is misery. Put the right one in there now or you'll be sorry.. You have a real nice rear end ratio for a street ride but it needs low end torque to work...
 

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How about the comp cams magnum 270h?

 

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That LM1's compression ratio is what 8.25 - 8.5 - 1? I'd cut back to the XE 262 ( 12-238-2). It has a little lope at idle and good throttle response. I ran that XE268 ( 12- 242-2 ) in a 9.5 c/r 350 with a M-20 and 3.55s in the rear. It was a little soggy below 3000 rpm. You might want to look at some older, lazier lobes and get away from the fast ramp stuff for quieter operation and longevity
 

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I may be assuming here but I read he used E street heads.
I also assume jelco went with a 64cc head.
Maybe not though.
Changes the compression a bit. VS the 76 cc heads that came on that crate engine.

12cc dished pistons possibly.
Read more here on that crate engine.
GM 260 horse engine?

I ran the XE268H in a 66 327 Vette with 9.4 compression and ported 492 heads with RPM intake and 750 Edelbrock.
22 initial timing and 38 total all in by 2,200rpm.
4 speed car with 3.36 rear gear.
You did not even need to side step the clutch at a roll from 10 mph it would fry the tires and get sideways.

Actually scared the owner my high school friend that I built the engine for.
He was not ready for that.

I had the timing curve very lazy for the first 2 weeks he had the car all in by 3800 rpm and only 35 total.
I also had the carb set up on the rich side.
He said it was less power than he expected and after 2 weeks I had him bring it to the house for a final tune.

When it got the added timing and leaner fuel curve done it scared him and he actually let off the throttle because it was getting sideways.
Then he froze up.
He just does not have the racer bug in him.
He has a 2018 LC 500 Lexus now and thinks it is fast also.
Hate to break it to him but that car is a putz for what it cost him.
75K.
My 305 head 57 chevy 4 door 350" with 280H comp cam will spank it.

His Vette now has a 276HR and another 327" with 180 AFR competition heads.
Same 9.4 compression.
Made 421 HP and 419 TQ or the other way around..On an engine dyno.
Still not able to beat my 57 though.
Could be his driving.
 

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Discussion Starter · #14 · (Edited)
I should have mentioned what my compression ratio is estimated to be now. I did get the 64cc combustion chamber and with the pistons that came with that crate engine, I calculated my compression ratio to be 9.48:1 incorrectly assuming 7cc dome volume (if 12 cc then 9:1, if 15cc then 8.74:1). It's been difficult to find out what the effective dome volume is with the 12514101 pistons. Maybe I should get a different head gasket. Comp cams recommended the 12-242-2 with 9.5:1 compression but to have more fun at a street light/more torque maybe I should go with 12-206-2 (12-210-2 is choppier) or 12-238-2. I’m still trying to make sense of cam specs so I appreciate all the input. The intake and carb came with the engine, all for $300. Not sure if I’ll have problems with it.

Compression ratio: 4in bore diameter, 3.48in stroke volume, 64cc combustion chamber, effective dome volume (-15cc dish piston 12514101 according to link below), deck clearance (? assuming 0.025"), gasket thickness 0.040
= 8.74:1

It's looking like the 12-238-2 cam will be a better fit.

699303
 

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12-210-2 is the old 268H and it looks to have more overlap than the other 12-238-2 which is the XE262H.
Odd how a cam with less exhaust duration can have more Overlap.
The 268H also closes the intake valve 3 degrees later than the XE262H.
It will not trap as much cylinder pressure.
But you may be hard pressed to tell the difference in those 2 cams in the engine.

Measure the deck clearance if the heads are off.
You may be able to run the .025" head gasket.

Read all this if you have not.

some more.

Date the Crate: GM 350 Power Mods


very good one here also.
 

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Discussion Starter · #17 · (Edited)
12-242-2, 268H
Great for street machines, largest cam for stock converter.
Operating Range:1600-5800 RPM
Duration Advertised:268° Intake / 280° Exhaust
Duration @ .050'' Lift:224° Intake / 230° Exhaust
Valve Lift w/1.5 Rockers:.477'' Intake / .480'' Exhaust
Lobe Separation Angle:110°

12-238-2, 262H
Excellent response, good mid-range, noticeable idle.
Operating Range:1300-5600 RPM
Duration Advertised:262° Intake / 270° Exhaust
Duration @ .050'' Lift:218° Intake / 224° Exhaust
Valve Lift w/1.5 Rockers:.462'' Intake / .469'' Exhaust
Lobe Separation Angle:110°

12-206-2, 260H
Vans, pickups, 4WD & towing, in 350ci, good idle, strong mid-range torque.
Operating Range:1200-5200 RPM
Duration Advertised:260° Intake / 260° Exhaust
Duration @ .050'' Lift:212° Intake / 212° Exhaust
Valve Lift w/1.5 Rockers:.440'' Intake / .440'' Exhaust
Lobe Separation Angle:110°

Current stock camshaft:
Hydraulic Flat tappet Camshaft: #14088839
Valve Lift : .383" Intake / .401" Exhaust
Duration at .050" Lift: 194 Intake / 202 Exhaust
Lobe Seperation: 112
This is a low end Torque oriented camshaft.
 

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12-210-2 is the old 268H and it looks to have more overlap than the other 12-238-2 which is the XE262H.
Odd how a cam with less exhaust duration can have more Overlap.
The 268H also closes the intake valve 3 degrees later than the XE262H.
It will not trap as much cylinder pressure.
But you may be hard pressed to tell the difference in those 2 cams in the engine.

Measure the deck clearance if the heads are off.
You may be able to run the .025" head gasket.

Read all this if you have not.

some more.

Date the Crate: GM 350 Power Mods


very good one here also.
This is my first build/restomod. (1964 El Camino)
SBC 350 engine LM1, #10066036
Pistons 12514101 (effective dome volume?)
200-4R transmission, torque converter 2,000 stall
3.08 10 bolt rear end (stock)...*edit maybe 3.42 or 3.55 in the future
stock exhaust manifolds
I just bought Edelbrock e-street heads (*edit 64cc) and comp cam CL 12-246-3 with new lifters, pushrods and stamped steel roller tip rocker arms from JEGS that I haven’t installed yet.
"Which that piston CC don't sound right for a dish 4vr piston. That sounds more like a flat top 4vr"
_

A factory stock piston would have that slight dish with the 4 valve reliefs machined in.

Jeff, Thanks for all that great information.
& Jelco it's great that you brought this up as I have a 350 crate that is the same # as your engine.If those are stock pistons you may want to use a thinner head gasket to bump your compression a little or at least investigate if that will help your engine.
Also even with stock exhaust manifolds either H-or -X crossover type exhaust system type w/minimum of 2 1/2 pipes will increase the low end torque over a stock dual exhaust system.
 
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Discussion Starter · #19 · (Edited)
I added a photo of the 12514101 pistons above. The pistons aren’t great because I don't believe they burn fuel well as the unburned fuel mixture can hide down in the chamfer area and in the unneeded extra valve reliefs...resulting in less power out of the fuel used.
Is this statement correct?... "If you use factory dish pistons and a 64cc head you are at least 9.5 or higher depending on deck and gaskets. It would take a big dish piston to get down to 8.5-9:1 with 64cc heads."...I think this assumption is incorrect and I have to assume 12cc dome volume and assume 9:1 cr.
 

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Discussion Starter · #20 ·
Another question....is a double roller timing chain very beneficial in my build? Is it an overrated fad?
Is the Cloyes 9-1100 a good buy?
Maximum Advance/Retard at Camshaft: 2 degree
Maximum Advance/Retard at Crankshaft: 4 degree
Timing Chain Style: Double roller
Cam Sprocket Material: Iron
Crank Sprocket Material: Billet steel

 
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