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Old 02-17-2013, 11:37 PM
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1.6 Ratio Roller Rockers

I have not had any experience in building Chev engines.
Our engine is a 1984 Goodwrench 350 with dish and chamfered pistons.
Car: Camaro 71 TH350 trans.

I have not purchased any parts as yet but would love some advise if you have done something similar or have the experience to comment.
This is a budget build. We are aiming for 400hp and do not want to pull huge revs as the bottom end is bog standard.

This is the way we are thinking at the momment:

We will fit a 2600 stall converter to the trans.

Heads: Jegs Alloy

Cylinder Head
Small Block Chevy
195cc Intake Ports
64cc Combustion Chambers
2.020"Int./1.600"Exh. Valves
1.440" Valve Springs, .600" Max Lift
3/8" Rocker Studs
Straight Plug

Expected compression ratio: 9.5 to 9.7:1.

Cam: Comp Cams XE268H-10
Duration @ 0.006": 268° / 280° Duration @ 0.050": 224° / 230° Max Lift w/ 1.5RR: .477" / .480" Lobe Separation: 110° Lobe ID#'s: 5443 / 5203 Intake Centerline: 106°

Carburator: 750cfm Quick Fuel Slayer

Headers: 1" 5/8

Intake: Elderbrock RPM Air Gap [SIZE=5]
[/SIZE]
Rockers: Comp Cams#249-17002-16
High Energy Rocker Arms
Ratio: 1.6
Stud Diameter: 3/8"

Is it worth going to the 1.6 ratio rockers. Are there any potential problems with the 1.6 ratio or in fact the suggested build?

We would look at the Jegs Vortec Iron heads if these would deliver the HP we would like. It appears from the info on their website that the cam we are looking at has to much lift (they say .475'' Max Lift)

Good advise at this point would be hugely appreciated.

Cheers

[COLOR=#800000]
[/COLOR][FONT=Calibri][SIZE=3][FONT=Calibri][SIZE=3][/SIZE][/FONT][/SIZE][/FONT]Duration @ 0.006":268° / 280°Duration @ 0.050":224° / 230°Max Lift w/ 1.5RR: .477" / .480"Lobe Separation:110°Lobe ID#'s:5443 / 5203Intake Centerline:106°

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Old 02-18-2013, 12:00 AM
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sounds like a possibility.You might make that much power.
I hate flat tappet hydraulic cams. You need to rev to 6k to make 400 hp.
depends what the heads flow,,,, should go well
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Old 02-18-2013, 05:06 AM
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That's more spring pressure than you need and the port volume is high for a low rpm/400hp peak engine. You could use the 180cc heads w/1.25" springs and have a good responsive engine.

Personally I like the Vortec heads but they need a Vortec-specific intake, even if the heads have dual bolt patterns. More than enough head to reach 400-plus hp.

I don't much care for the Air Gap, but the RPM is a good intake.

1.6 rockers aren't a problem if used on aftermarket heads. Production heads may require the push rod slot (or hole in the case of the L31 Vortec head) to be elongated towards the stud to provide enough clearance. But even w/1.6 rockers and decent heads, IMHO that's not quite enough cam for 400 hp. That said, that cam IS a good choice for a nice performing street engine, and unless there's a need for 400 hp it would be a good engine IMO.

You already know the piston design sucks. And unless the block has been decked, the quench distance is going to be higher than you'd like it to be unless you use a 0.015" coated steel shim head gasket.

Assume nothing, though. Everything needs to be measured physically to know what you're working with.
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Old 02-18-2013, 11:26 AM
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Quote:
Originally Posted by Predator4 View Post
I have not had any experience in building Chev engines.
Our engine is a 1984 Goodwrench 350 with dish and chamfered pistons.
Car: Camaro 71 TH350 trans.

I have not purchased any parts as yet but would love some advise if you have done something similar or have the experience to comment.
This is a budget build. We are aiming for 400hp and do not want to pull huge revs as the bottom end is bog standard.

This is the way we are thinking at the momment:

We will fit a 2600 stall converter to the trans.

Heads: Jegs Alloy

Cylinder Head
Small Block Chevy
195cc Intake Ports
64cc Combustion Chambers
2.020"Int./1.600"Exh. Valves
1.440" Valve Springs, .600" Max Lift
3/8" Rocker Studs
Straight Plug

Expected compression ratio: 9.5 to 9.7:1.

Cam: Comp Cams XE268H-10
Duration @ 0.006": 268° / 280° Duration @ 0.050": 224° / 230° Max Lift w/ 1.5RR: .477" / .480" Lobe Separation: 110° Lobe ID#'s: 5443 / 5203 Intake Centerline: 106°

Carburator: 750cfm Quick Fuel Slayer

Headers: 1" 5/8

Intake: Elderbrock RPM Air Gap [SIZE=5]
[/SIZE]
Rockers: Comp Cams#249-17002-16
High Energy Rocker Arms
Ratio: 1.6
Stud Diameter: 3/8"

Is it worth going to the 1.6 ratio rockers. Are there any potential problems with the 1.6 ratio or in fact the suggested build?

We would look at the Jegs Vortec Iron heads if these would deliver the HP we would like. It appears from the info on their website that the cam we are looking at has to much lift (they say .475'' Max Lift)

Good advise at this point would be hugely appreciated.

Cheers

[COLOR=#800000]
[/COLOR][FONT=Calibri][SIZE=3][FONT=Calibri][SIZE=3][/SIZE][/FONT][/SIZE][/FONT]Duration @ 0.006":268° / 280°Duration @ 0.050":224° / 230°Max Lift w/ 1.5RR: .477" / .480"Lobe Separation:110°Lobe ID#'s:5443 / 5203Intake Centerline:106°


This is pretty similar to the Chevy High Performance magazine builds on the Goodwrench block of several years ago. They pulled a bit over 400 horses with ported Vortec heads, a thin Felpro gasket, Comp XE268H cam and kit, 1.6 rockers, Edlebrock Performer RPM intake, Holley 750 with vacuum secondary’s I think was used, 1-3/4 diameter long tube headers, HEI ignition with a high RPM kit. Seems like it pulled the power under 6000.

I lack enthusiasm for the stock bottom end, not too sure this will stay together for long if you get on it much. Dyno runs are one thing, the street something else. Lubrication for one is a huge difference, a dyno doesn't put the motions and G forces on the engine that running on the street does. I seriously would recommend an aftermarket baffled pan, a crank oil stripper, and a good quality and well vented windage tray. I'd pick a better pump with a secure pickup, this needs to be at least a mounting bracket between the pickup and the pump housing. I'm not a fan of welded or brazed pickups as that can warp the lower pump housing resulting variously in the gear teeth peeling metal off the cover or allowing an oil leak around the bottoms of the gear teeth. I really like the Melling with the bolt on pick up, unfortunately it's only available with a lot of excess pump capacity which isn't desirable for an engine with production clearances. I, also, am not crazy for GM's stock pistons or rods, but if you don't get on it a lot they'll work. The D dish aftermarket piston allows you to manage compression and retain the high amount of squish/quench for optimum compression without so much risk of detonation as is present with the factory's round dish piston. The OEM rods have proven to be risky at this power level I don't use them in my builds as well as I prefer a floating pin, but that's me. I think a lot of stock rod issues in high output street engines are often due to lubrication issues as I described earlier. I’d say that OEM rod issues at this power level don't crop up often, but when they do it's devastating to the engine; a low to moderate risk, high consequence kind of thing.

Bogie
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Old 02-18-2013, 12:55 PM
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The build sounds nice. However, the 268 cam may be on the small side if matched to the 195 cylinder head. The 268 cam would work well with a vortec head with a 170 or 180 intake runner. If you definitely are using the 195 head, step the cam up 1 or 2 steps for a better match of parts.
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Old 02-18-2013, 09:05 PM
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Really appreciate the input and your time time.
Cheers
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Old 02-18-2013, 09:17 PM
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Thanks for your reply. Yes I did read the Chevy High Performance article on their website and it is the inspiration for this build. It is unfortunate that I have the crap bottom end but can not afford to do the whole thing. The car is intended for cruising with a day or two at the strip. I will take your advice on the sump and oil pick up. I see what you mean about the dyno. Thanks for your input and time.... Cheers

One thing... what do you think of the 750 CFM Quick Fuel Slayer as a reasonable option for the build?
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Old 02-18-2013, 09:39 PM
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You are going to come up way short on compression ratio with the dished pistons and 64cc heads.
Order the $200 summit engine rebuild kit with flat top pistons.
Give the stock bore cylinders a quick re hone and re assemble with the new flat top pistons, rings and new bearings.

now you got the compression ratio and don't need to worry about reving it up.
Get the next bigger Comp cam and a 3000+ stall 10" converter and some 4.10's

Any good used 650-700-750-800 DP holley carb can be nicely upgraded using the Proform 750HP carb body kit.
The money you save buys the engine rebuild kit.

if you got money left over get the stock block 0 decked before reassembly
so you have a true 0 deck clearance @TDC with the new summit pistons.

Measure the piston deck clearance of the present assembley before disassembly.
Now you know before hand how much to deck the block.
This will save you money at the machine shop.
Old saying measure twice, cut one
Check the big end of the rods for roundness and diameter spec for grins
they should be fine but only takes a minute to check.

Now you got a much more powerfull reliable build and a much faster car for the same money.

Last edited by F-BIRD'88; 02-18-2013 at 09:59 PM.
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Old 02-18-2013, 10:47 PM
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750 cfm is perfect for the average 350.
love the 70-73 Camaros. I built a 350 for my wifes 70 split bumper back in 1980.My duty was to get good mileage. I managed 28mpg Canadian gallon. we traveled a few times towing a little tent trailer and the mileage was excellent and power decent.
I hope your project goes well
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Old 02-19-2013, 04:59 AM
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Avoid the 1.6's. Those are band aids for a stock low lift cam. and can cause a fast ramp cam go flat even faster.

Avoid xe or voodoo cams. Very quick ramps tend to go flat.

Avoid the air gap intake. Very slow warm ups which cause the engine to stumble for an extra long time when temp drop below 60.

Why use a cam with more duration on the exhaust? Do the heads flow that poorly on the exhaust? You are using headers, right?

I recommend the regular RPM intake with a holley 750 3310 and a compcam 280H with 10:1 cr.

Use 20 degrees of timing at idle, 37 total mechanical, plus another 12 from the vacuum advance.
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Old 02-21-2013, 10:24 PM
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Cool..... Have updated my wish list to the Compcam 280H and regular RPM intake. Thank also for the timing advice ...Cheers
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Old 02-21-2013, 10:27 PM
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Love it did you turn off the other 4 cylinders. lol
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Old 02-21-2013, 10:30 PM
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Thanks for your help...yes compression is a problem that we will need to address...cheers
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Old 02-22-2013, 10:46 PM
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I have a new Isky 280 cam that has only been installed but never run I would sell. Think I might go bigger in my 406
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