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I have to build a 355 SBC from my old 383 SBC. So i have to change the crankshaft, the connecting rods and the pistons. I think, i want to reuse most of the "old" parts.
- 4.030" bored block of course
- AFR 195 (#1040) heads
- 1:1,6 roller rockers and push rods
- Edelbrock Airgap intake manifold with TBI adapter plate
- 454 TBI ported throttlebody with 80´injectors (not sure for reusing, please take a look to my other thread in this forum)
- 4" snorkle homemade air cleaner (bought from a thirdgen-member before a few years)
- Rob´s great EBL
- Zeitronix WBO2
- Flowmaster American thunder exhaust system 3" with high flow cat
- heavy duty oilpump
Followings parts will not be reused:
- Eagle Stroker 383 rotating assembly with harmonic balancer
- 7 qt oilpan ( big pan, terrible y-pipe construction at the moment)
- Stroker 383 valve covers (silly to use them on a 355 cui engine)
- Old headers and ypipe (terrible in cause of the big oilpan)
I ordered the following parts:
- Scat crankshaft
- Badger pistons 4.030"
- New connecting rods 5.7"
- headers and y-pipe from topdown-solutions
- Bearings, piston rings, gasket and other small things...
So, i bought the 383 sbc shortblock before a few years. A friend of me bought the same shortblock for his TransAM. I asked him for cam specifications. They should be:
Mike Jones cam design
280/286 duration; 224/226 @0.05
lift .535 intake; .528 exhaust with 1:1.6 roller rockers
110 degrees lobe centerline.
How do you think about my setup ? Of course, i have to remove the engine from the car and disassembling completely.. So, the big question is, how do you think about the cam specs ?
"badger" is just the name of the manufacturer. Made in USA. I never heared by myself before ordering... I´ll call the seller tomorrow for more informations about pistons. I know only, these are 4.030" pistons for L98 engines, flat top.
Badger's product line is what we call "rebuilder" pistons. Cheap. They're not performance pistons. Be careful with the compression height. Many "rebuilder" pistons have low compression height, which kills quench. The piston manufacturer may call them "destroked", but of course this has nothing to do with changing the stroke that the pistons are made for.
The partnumber of the badger pistons is P566 030. The compression height is 1.540". Do you think, i should go with other pistons ? I think, these badger pistons are just to rebuild stock L98 engines ?!
The 350 stroke is 3.48". Half of that is 1.74.
The rods you bought are stock 350 length, 5.7". 5.7 + 1.74 = 7.44.
The pistons have a compression height of 1.54. 7.44 + 1.54 = 8.98.
The Chevy small-block has a nominal deck height of 9.025. If your block is correctly machined (most aren't) those pistons will be 9.025 - 8.98 = 0.045 in the hole.
Add a typical .040 head gasket, and you're EXACTLY in the worst possible distance for quench--about 0.085. Good quench is from "just enough clearance" to about 0.45. An open chamber has no quench, the nearest distance from piston to head is on the order of 0.100 or 0.110, or more. In between--from about 0.050 to 0.100, is the region where lazy combustion leads to detonation. Even if your block has already been decked 0.025, your "quench" will still be on the order of 0.060, which is still WAY TOO MUCH unless you also use very thin, steel-shim 0.020-thick head gaskets--which drops you to about .040 quench--acceptable.
If you can cancel the Badger pistons, and buy a performance piston with a taller compression height, the engine will be much more lively, and probably less-sensitive to fuel octane rating. Otherwise, you're going to have to have the block machined (if it isn't already) to lower the deck height, and you're going to need steel shim head gaskets.
Flat top, two valve reliefs totaling 5 cc. 1.565 compression height--0.025 taller than the Badgers. If the block has been decked so it's closer to 9.0 than 9.025, a typical 0.040 gasket puts you right where you'd want to be. If the block hasn't been decked, you'd still need to shave it or use thin head gaskets.
I am not saying that those pistons are the best possible solution. They're relatively inexpensive and they should be readily available. Yes, you could do better.
The 350 stroke is 3.48". Half of that is 1.74.
The rods you bought are stock 350 length, 5.7". 5.7 + 1.74 = 7.44.
The pistons have a compression height of 1.54. 7.44 + 1.54 = 8.98.
The Chevy small-block has a nominal deck height of 9.025. If your block is correctly machined (most aren't) those pistons will be 9.025 - 8.98 = 0.045 in the hole.
Add a typical .040 head gasket, and you're EXACTLY in the worst possible distance for quench--about 0.085. Good quench is from "just enough clearance" to about 0.45. An open chamber has no quench, the nearest distance from piston to head is on the order of 0.100 or 0.110, or more. In between--from about 0.050 to 0.100, is the region where lazy combustion leads to detonation. Even if your block has already been decked 0.025, your "quench" will still be on the order of 0.060, which is still WAY TOO MUCH unless you also use very thin, steel-shim 0.020-thick head gaskets--which drops you to about .040 quench--acceptable.
If you can cancel the Badger pistons, and buy a performance piston with a taller compression height, the engine will be much more lively, and probably less-sensitive to fuel octane rating. Otherwise, you're going to have to have the block machined (if it isn't already) to lower the deck height, and you're going to need steel shim head gaskets.
Flat top, two valve reliefs totaling 5 cc. 1.565 compression height--0.025 taller than the Badgers. If the block has been decked so it's closer to 9.0 than 9.025, a typical 0.040 gasket puts you right where you'd want to be. If the block hasn't been decked, you'd still need to shave it or use thin head gaskets.
I am not saying that those pistons are the best possible solution. They're relatively inexpensive and they should be readily available. Yes, you could do better.
Thank you very much ! Yes, i can cancel the badger pistons. How much is the compression height from stock L98 engine pistons ? Thx
How much is the compression height from stock L98 engine pistons ?
I don't know. Might be listed in the service manual. Perhaps someone else here knows.
What's actually important is:
1. What is your block deck height NOW?
2. Does the block need to be planed to repair warpage or roughness on the gasket surface?
How do the authorities check the displacement of your vehicle? Depending on their methods, I'd be tempted to tell them you have a 350, while keeping the 383 as-is.
Yes, of course, it is crazy... I think, i am the only man, who downgrades his 383 stroker to a 355 cui engine.. In my country, changes on cars are associated with many problems. Police is always watching you and we have to show our cars on german TUEV every 2 years with emission control and and and... I want to have proper papers really matched to my car. The only way is to enter the 350cui engine to my papers...
They can enter the 383 stroker engine, too. But this costs really 10000 Euro !!!!!! To enter the 350 cui engine costs 300 Euro.. Small difference... I decided me to go the "downgrade-to-355-cui-way". I just want to drive my TransAM without problems... :-)
So, i don´t know my block deck height.. I bought it from a professional engine builder, engine looked like new before assembling. The stroker kit is from Eagle. As i know, the connecting rod length is 5.7" (stock) and the compression height is changed on these stroker-pistons. I think, the deck height was changed.
Engine is in car, i will remove it on saturday. You are right with the pistons. I´ve seen, most wanted compression height is 1.560.
Piston pin diameter of badgers is 0.9275". I´ve seen, there are .927" and .928" on summit, too. Which diameter do i need ? No matter ?? thx
You need whatever appropriately fits the pin bore of the rods you're buying.
Be careful not to confuse the PIN diameter with the PIN BORE diameter. The pins must float in the pistons...they may float in the rods, or they may be a press-fit in the rods. If the pins float in the rods, you're going to need pistons that will accept pin retainer clips, and you'll need the clips. The pins (and retainer clips) are probably supplied with the pistons.
Thank you for the answers. I will remove and disassemble the engine tomorrow. Then, i can take a look to the pistons and find out the right compression height to order the new pistons..
Is the deck clearance MEASURED, or CALCULATED? Calculating deck clearance doesn't allow for machining inaccuracies in the block deck height. Better to actually measure it.
With 0.025 deck clearance, you'll want a thin head gasket to obtain appropriate quench/squish. Or you "zero-deck" the block, and use a typical .0.039--0.040 head gasket.
Originally Posted by Jan1980
So, i have to go with pistons with compression height 1.560" to get the same deck clearence.
I've never heard of DSS pistons before. I can't give you any advice about them.
Originally Posted by Jan1980
Piston ring thickness is the same. Can i use the piston rings from my old pistons ? Then, i don´t have to file new rings to the gap.
Most folks will not suggest re-using the rings. I've never done that, so I can't help you there either. Given a choice, I'd look for a piston that used lower-friction, narrow rings.
Originally Posted by Jan1980
With these pistons, Felpro 7733PT2 (compressed 0.039") and 355 cui, i will get a compression ratio 9.71:1.
With my old stroker setup, i had a compression ratio 10.52:1.
I think, 9.71:1 should be ok.
9.7 sounds good except you're going to have too much piston-to-head clearance (quench/squish) so combustion will be lazy. Depending on fuel quality, you could go higher--but you know that. Obviously you were able to get fuel suitable for the 10.5 of the old engine.
EDIT 2: Or, perhaps, it is the easiest way for me to buy a balanced rotating assembly. I was looking for assemblies in Summit and Jegg´s but i can never find the compression height from the pistons. Can you recommend a good 355 cui rotating assembly for me ?
I´ll go with 1.560" compression height. I think, it is safe with the same clearance than before.
As I said previously, you'll be in the worst-possible region for detonation and lazy combustion unless you deck the block or use a thin head gasket.
Originally Posted by Jan1980
Balancing. I am using a brandnew scat crankshaft with harmonic balancer from 350 cui engine. Is that ok ?
Probably not. What is the bobweight that the crankshaft is intended to be used with? What is the bobweight you will actually have?
Were you using a neutral-balanced flexplate? SBC tend to use one of three balancing styles on the flexplates: Neutral, offset weight for one-piece seal cranks, and offset weight for 400-stroke cranks. The one-piece seal flexplate won't bolt to a two-piece seal crankshaft.
Originally Posted by Jan1980
perhaps, it is the easiest way for me to buy a balanced rotating assembly.
I would go with hypereutetic pistons on a fuel injected engine, they are dimensionally more stable with the usual temperature variations. Forged only if using forced induction, Nitrous or a carb.
Floating pins with spiral lock rings would also be a smart choice.
I have KB series hypereueutetic pistons, ring gap is very important, file to fit is probably best. https://www.uempistons.com/catalogs/...ve_catalog.pdf
Check out the head gasket choice for your heads and pick a good one widely used. Compressed thickness mesure is important in order to achieve an optimal 0.040-0.045 piston to head distance (quench), for effective squish effect and optimal combustion. Like Shurkey already pointed out.
If you'r not able to achieve proper quench, with your selected parts, you will need to mill the deck of the block.
The goal is to get the quench distance as close as possible to 0.040-0.045 and this is supposing the deck is nice and straight, otherwise you also need to take into account the amont that will get removed when milling the deck.
Ok, i think, it's the easiest and best way. You are right. I wrote to Mike.
I was looking to rotating assemblies from knowed manufactures. Scat and Eagle. I was never finding a kit with a good compression ratio, piston compression height.
Looking good there now but I don't really get it why you are going to 355 - when you're reusing aftermarket heads and everything, it's still as easy or as hard to spot engine modification as it was with the 383. Hell, without looking at the tune or tearing the engine apart no one could ever tell a 350 from a 383?
Hi. I am Jan1980... i found my old account again.. :-)
Just want to give feedback. Engine runs fine. It is running with 65pph police car injectors @454 bbc throttlebody with mike jones cam and afr 195 heads. I have to make small changes in ecu maps, but i cannot drive at the moment, licence plate is expired till may.
@owner: I own 88´transam. In 2018 i can make german "historic license plate", it is much more cheaper then. And german "TUEV" inspectors check everything before exhibiting this plate, i think you know the procedure. BTW, owner, we wrote a lot on ICQ before years. You remember ? I bought your PMD seats. And you made your Fiero project.
03-28-2016, 01:54 PM
Good job! 
Nice to hear that thing is (still) running and getting better and better 
I guess you put it in storage now for the winter? 
