Need some help w/the 406
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From: [Quote=WOEII] Is dried brown doodie powders man! [/Quote]
Need some help w/the 406
Here is my issue: After spending the day at Lebanon Valley Dragway I have been seriously bitten by the mod bug . I do have a complete 406 in my S-10 that I really want (esp. after today) to put in the vette, However my fundage is short. The 406 has stock heads, and a relatively tame cam that is around .480 lift on both sides.
My compression is already at 9.5:1, with 76cc chambers. I would like to take the D-Ports and TPI from the 88, put them on the 406, and stuff a different bump stick in. I fear I may end up with to much compression and an engine that runs like a pig because of the TPI. Unfortunately I do not have the full specs to calculate the new CR. Given my limited funds what do you think I should do? Thanks! :)
My compression is already at 9.5:1, with 76cc chambers. I would like to take the D-Ports and TPI from the 88, put them on the 406, and stuff a different bump stick in. I fear I may end up with to much compression and an engine that runs like a pig because of the TPI. Unfortunately I do not have the full specs to calculate the new CR. Given my limited funds what do you think I should do? Thanks! :)
Team Owner
Joined: Nov 1999
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From: This vette goes to 11 Milford MA
St. Jude Donor '03-'05
Re: Need some help w/the 406 (Upstate)
You've had that car for two weeks and its already engine pulling time? That didn't take long. :) If you're running big cubes, the stock TPI is going to choke it. Contact Ken,L98Terror. He has his Super Ram for sale. As far as a cam, I had a custom ground roller from Comp that was desigend specifically for THAT car with the 3.07's and 2,600 stall. I can try to dig up the specs.
[Modified by Fastguy, 8:57 AM 6/28/2003]
[Modified by Fastguy, 8:57 AM 6/28/2003]
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From: The Top of Utah
Re: Need some help w/the 406 (Upstate)
You DO have all the info to figure the new compression ratio...*IF* you believe in your own numbers. A 4.155" bore X a 3.75" stroke, equals (pi*r*r*h) 50.866 cid per cyl. Times 16.3870 = 833.2232 cc's. If you have a 9.5:1 compression ratio, you have 98.0262 cc's above the piston. This includes the head chamber volume, deck clearence, piston reliefs (or dome), and gasket thickness. The L98 aluminum heads have a 58 cc chamber. That is 18 ccs less. With no other changes, including head gasket thickness, you will end up with 80.0262 cc's above the piston, total. 833.2232+80.0262 = 913.2494. 913.2494 / 80.0262 = 11.38:1 Compression ratio. VOILLA! The answer of course, depends on the accuracy of the input.
If this is higher than you want, volumes can be adjusted. Deck height, gasket thickness and chamber volumes can be changed. Possibly the easiest and most effective change could result from unshrouding the valves toward the edges of the larger bore. I would NOT increase the deck height, or use a thicker gasket.
A big enough cam may allow an elevated CR. Good luck, and...
RACE ON!!!
1984 Crossfire
Member NHRA
If this is higher than you want, volumes can be adjusted. Deck height, gasket thickness and chamber volumes can be changed. Possibly the easiest and most effective change could result from unshrouding the valves toward the edges of the larger bore. I would NOT increase the deck height, or use a thicker gasket.
A big enough cam may allow an elevated CR. Good luck, and...
RACE ON!!!
1984 Crossfire
Member NHRA
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From: [Quote=WOEII] Is dried brown doodie powders man! [/Quote]
Re: Need some help w/the 406 (Fastguy)
Thanks for the reply. It was getting to be too quiet in here. The g/f saw your reply and said um no freakin way are you doing that. I think I'll go unplug a spark plug wire or two and say see honey, it's broke. I could get away with swapping parts to the 406 for the cost of some gaskets and a new cam. The car would be far from running it's full potential, I just want a little more go while I wait to get a different set of heads and an intake. I might have to wait for the car to break and given the way this thing runs it might be awhile. :)
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From: [Quote=WOEII] Is dried brown doodie powders man! [/Quote]
Re: Need some help w/the 406 (CFI-EFI)
Those numbers where pretty much what I was looking for, thank you. 11.38:1 does sound a little high. I will have to ask my friend and machinist if he can unshroud the valves and hog out those chambers just a little bit. I would think getting down to 11:1 with a proper cam would be acceptable with some 94 octane sunoco. Remember this would all be under the stock TPI whilst I scrimp and save for something better. Thanks muchly for the reply. :)
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From: The Top of Utah
Re: Need some help w/the 406 (Upstate)
Happy to help.
In that case, be careful not to over cam it. A healthy high rpm cam that would tolerate a higher CR will want to just start working where the stock TPI will refuse to feed it. I think a little chamber enlargement plus the aluminum heads will get you to a reasonable number. Good luck, and...
RACE ON!!!
1984 Crossfire
Member NHRA
Remember this would all be under the stock TPI whilst I scrimp and save for something better. Thanks muchly for the reply. :)
RACE ON!!!
1984 Crossfire
Member NHRA
