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Old 11-12-2012, 06:01 PM
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Detune 388 Stroker

Hello All,

Was looking for some advice on a cam selection.

Here is my current setup:
388 stroker
bored over .060
Speedpro powerforged flat top pistons with 6 cc 2 valve
Eagle 5.7" rods and forged crank
deck clearance .010
Felpro head gaskets 1003
Edelbrock Perf RPM heads 64cc
Comp 268XE cam and springs
Edelbrock Perf RPM intake with Holley 4160
Edelbrock double roller chain
Milodon high vol oil pump, windage tray, 7qt deep sump pan
MSD 6AL and Procomp billet dist
Hooker Header 1 5/8" with 2 1/2" Flowmaster 40's



79 Caprice 4 dr. TH350 built with shift kit, 2,000 B&M converter and 3.42 gears. The car weighs 3600lbs empty.

I am going to pull the engine and swap out the pistons to these:
Sealed Power #844-8-KH859CP60
383ci w/5.700'' Rod, Hypereutectic Pistons, .060'' Overbore
Piston Dia.: 4.060''
Piston Top: -12cc Dish, 2-Valve Reliefs
Pressed or Floating Pin
Comp Ratio: 10.28:1 w/58cc Heads, 8.65:1 w/76cc Heads
5/64'', 5/64'', 3/16'' Chrome-Moly Rings
These should net me right around 10.1 CR

I also want to change the came to the Comp cams XE252H. Will this cam work ok. I really want to de tune this combo as it is to radical and I want to just make a strong daily driver. I built this engine when I was a teenager and Hot rodded alot.

Thanks for your help.

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Old 11-12-2012, 06:14 PM
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honestly, I think you're going about it all wrong.

The engine you have is built to very mild specs. The only thing I'd look at doing for a daily driver is swapping to a good fuel injection system- it can really tame the engine.

A well prepped and tuned carb can come close to a FI system when everything is warmed up and you have consistent weather. But for ever changing real world conditions EFI makes a big difference in both mileage and drivability.
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Old 11-12-2012, 06:44 PM
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If it is in good shape? maybe a smaller cam and or what AP said.
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Old 11-12-2012, 06:45 PM
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I know the car is not tuned right. I have been messing with it for the last year and still don't have it driveable. I just dropped the tank and drained out all the gas as it was past its prime and causing it to blow white smoke.

Over the last year I rewired all of the underhood wires and installed the Procomp distributor to work with the MSD. I guess I need to start at square one on tuning. I know the distributor is in right. I have messed with the timing from 8* up to 18* and it is just rattling the valves not matter where it is at. I also put some octane booster in the tank but that didn't help either. The vacumn advance is working properly and I have tried ported and manifold source with no difference.

I feel like I have a timing issue of some kind.

What FI would you recommend?

Bret
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Old 11-12-2012, 06:50 PM
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Quote:
Originally Posted by bj383ss View Post
I know the car is not tuned right. I have been messing with it for the last year and still don't have it driveable. I just dropped the tank and drained out all the gas as it was past its prime and causing it to blow white smoke.

Over the last year I rewired all of the underhood wires and installed the Procomp distributor to work with the MSD. I guess I need to start at square one on tuning. I know the distributor is in right. I have messed with the timing from 8* up to 18* and it is just rattling the valves not matter where it is at. I also put some octane booster in the tank but that didn't help either. The vacumn advance is working properly and I have tried ported and manifold source with no difference.

I feel like I have a timing issue of some kind.

What FI would you recommend?

Bret

BACK THE TRUCK UP!!! you're "rattling the valves"? what is that supposed to mean exactly? What gas are you running in it? BTW off the shelf octance booster isn't worth anything, so save your money.
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Old 11-12-2012, 06:54 PM
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It has real bad detonation when I try to drive it. Its a little beyond pinging. It runs fine while idling. I can accelerate it with no problems. Put it in gear and it just pings real bad. My dad always called it "rattling the valves" for detonation.

Bret
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Old 11-12-2012, 07:11 PM
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start with some fresh 93 octane or better and a spotless carb that is one size larger than stock on the jets. Set your timing to 12 base and 36 total and a slow advance curve. That should be a relatively safe tune to start with.

your compression is really high but it MAY run on premium gas if you get it tuned perfectly. Again, FI can help with that but it can't fix everything.
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Old 11-12-2012, 07:17 PM
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Start at the beggining, find true TDC with a stop, then confirm your timing marks at the balancer, get it advanced to app 14 to get it up and running. Make sure your vacuum advance is dissconected and capped. Worry about that later...assuming stock curve in your Pro comp dist with 14 initial it should be around 34 total, plenty safe with halfway decent gas. If it still "rattles" lets check lash, is it way loose and that's your noise? If the timing is confirmed correctly I would pull a valve cover and and check that as silly as it sounds.....
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Old 11-12-2012, 07:29 PM
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It does have fresh 93 has in the whole system. I have never rebuilt the carb. It has less than 30,000 miles on it, but has sat for the last 8 years started about once a month

I have not messed with the dist it is stock. I tried ported and manifold vacuum. The vac adv is not adjustable

Bygddy you mentioned the valve lash. I readjusted them last year. I did it while running with a half turn past zero lash. Now I'm wondering of I need to readjust them. They valve train is noisy but it always has been with the edelbrock valve covers
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Old 11-12-2012, 07:46 PM
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Ok will work on the procomp I think I have some lighter springs. On the plugs I am using autolite copper plugs that are 2 stages colder than stock. Thanks for all the advice guys. I am off on thurs and will see what I can do. I am getting ready to move it out to my mother in laws garage and bring my 64' stepside home to tinker with. If I can't get it drive able I am going to haul it on a car dolly.

Bret
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Old 11-12-2012, 07:46 PM
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Quote:
Originally Posted by bj383ss View Post
It does have fresh 93 has in the whole system. I have never rebuilt the carb. It has less than 30,000 miles on it, but has sat for the last 8 years started about once a month

I have not messed with the dist it is stock. I tried ported and manifold vacuum. The vac adv is not adjustable

Bygddy you mentioned the valve lash. I readjusted them last year. I did it while running with a half turn past zero lash. Now I'm wondering of I need to readjust them. They valve train is noisy but it always has been with the edelbrock valve covers
start it at 1/8 turn past zero lash- it doesn't take much preload at all. And your carb definitely needs some good attention. you need to get it clean enough to bring into a surgical suite. Freaken immaculate. Then bring it back to stock specs and increase the jet size just a little to be safe.
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Old 11-12-2012, 08:07 PM
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Quote:
Originally Posted by bj383ss View Post
It does have fresh 93 has in the whole system. I have never rebuilt the carb. It has less than 30,000 miles on it, but has sat for the last 8 years started about once a month

I have not messed with the dist it is stock. I tried ported and manifold vacuum. The vac adv is not adjustable

Bygddy you mentioned the valve lash. I readjusted them last year. I did it while running with a half turn past zero lash. Now I'm wondering of I need to readjust them. They valve train is noisy but it always has been with the edelbrock valve covers
I guess it depends on what exactly your hearing and how loud, the XE cam doesn't help, they really are loud, and you wouldn't by chance be running procomp roller rockers would you? Also been through that and they can be pretty loud as well. Assuming you get the timing curve "safe" and are running 93 in it it shouldn't be pinging when just dropped into gear....that sounds more like a mechanical issue to me.....assuming those valve covers in your pic are on it there should be no clearance issue for rollers....like I said, jmho but it sounds more of a mechanical issue, check rockers for anything weird, set your lash, confirm timing, 14, 16 ish initial....if I rember right the procomp hei is around an 18 to 20 curve and in by about 2600 or so....that's should be safe enough not to ping the hell out of it unless its running hot as balls, or real lean.....but even then, you said when in gear it rattles......mechanical noise to me......
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Old 11-13-2012, 04:44 AM
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Wow thank you guys for all the suggestion. F-Bird I like the cam choice you suggested. Are the Summit lifters ok or should I get GM ones.

The rockers are Summit roller tip stock style with 1.6 ratio. I never got around to getting full roller rockers.

I originally had a 3,000 stall converter in it, and it launched great but my gas mileage was about 8. When I did the last rebuild, (I had one of the Edelbrock cams from China and one of the lobes went flat chewed the lifter up and flushed it through the motor) I changed to the XE268 and it ran great never had any problems with it. It just for some reason developed all these problems while sitting over the last 8 years.

I would much rather just change the cam and lifters and not pistons and rings.

And I will definately look at the timing curve. I may need some help on that though.

Bret
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Old 11-13-2012, 07:34 PM
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Detune 388 Stroker

Here is a good article to read before you start setting up your distributor. Listen to F-BIRD'88 on setting up your distributor. Your compression ratio is 10.792 and your DCR is 7.860. If the pistons are .010" from the top of the deck at TDC + .041" compressed gasket thickness your quench is .051". If you had set the quench to .040 your static compression would have been 11.097 and the DCR would have been 8.073. Is the Comp Cams valve springs you are using Part# 981-16? If so the installed height should be 1.700", 105 lbs. seat pressure at installed height, 1.250" open height, 273 lbs. open pressure. Stock pushrod length is 7.800" and Edelbrock recommends .100 longer than stock. But it would be best to measure with an adjustable pushrod after you have it set up correctly. The engine should run without pinging if you have the correct springs, pushrods, and the timing curve is right. What brand lifters are you using with the XE268H cam and have they been sitting 8 yrs. too. BTW Edelbrock recommends Champion RC12YC spark plugs for your heads. If you have any weird ignition problems thrash the ProComp distributor.
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Old 11-13-2012, 09:15 PM
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Detune 388 Stroker

Quote:
Originally Posted by bj383ss View Post
Wow thank you guys for all the suggestion. F-Bird I like the cam choice you suggested. Are the Summit lifters ok or should I get GM ones.

The rockers are Summit roller tip stock style with 1.6 ratio. I never got around to getting full roller rockers.

I originally had a 3,000 stall converter in it, and it launched great but my gas mileage was about 8. When I did the last rebuild, (I had one of the Edelbrock cams from China and one of the lobes went flat chewed the lifter up and flushed it through the motor) I changed to the XE268 and it ran great never had any problems with it. It just for some reason developed all these problems while sitting over the last 8 years.

I would much rather just change the cam and lifters and not pistons and rings.

And I will definately look at the timing curve. I may need some help on that though.

Bret
The summit cam 1103 will not work in your engine unless you plan on buying racing gas. The intake valve closes at 34 degrees ABDC and will raise your DCR to 9.471 which will not run on pump gas. To run pump gas you need a good DCR of 7.5-8.5.
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