Re: [Chevelle-list] 396 Rebuild - Piston Question

[Clint Hooper]

There are always exceptions to every rule as I mentioned. The 427 I had built last year was a true 10.0:1 compression engine. It would not run on Regular Unleaded. Most of the old engines were nowhere near their rated compression ratio,though. Switching to fuel injection would help a detonation problem,not make it worse,due to its superior fuel burn. Clint Hooper H&H Custom,owner 1969 El Camino ProTourer 2001 H-D FLHR custom bagger http://dalesplace.com/misc/friends/clint/clint_hooper.htm ----- Original Message ----- From: Dale I rebuilt a 396 (1969 model) twice and retained the 10.25:1 pistons in both .040 and .060 overbores and still ran regular gas 99% of the time – even after switching from a 3310-x Holley/Edelbrock 2PO intake to an Accel/DFI fuel injection.  Never had any pinging problems with either the 2.79 or 3.07 rear ends used.  I hear a lot of folks say they can’t run over 9:1 or 9.5:1 without premium fuel or a fuel additive, but I never had to.   Dale McIntosh 67 El Camino 1967 Chevelle Reference CD in progress ACES #1709/TC Gold #92 From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Larry Shouse Sent: Friday, May 27, 2005 11:31 AM To: The Chevelle Mailing List Subject: Re: [Chevelle-list] 396 Rebuild - Piston Question   Thanks for your wisdom Clint. The pistons I have are domed. All I want to do (at this point) with this 396 is drive it on the street on sunny days, take it to meets and shows, and run the track once or twice a year against my boy...   Do you (or anyone on the list) have experience with water injection as a means to deal with detonation?   And to all the list members who have rebuilt their engines, did you replace your pistons? If so, was it because you had to?   Thanks, Larry Shouse ----- Original Message ----- From: Clint Hooper To: The Chevelle Mailing List Sent: Friday, May 27, 2005 12:05 PM Subject: Re: [Chevelle-list] 396 Rebuild - Piston Question   Are those pistons flat topped or do they have any dome,Larry? Most standard 396 pistons of the 1966-1970 era were at least 10.25:1 compression and weren't flat topped. The 375hp L78 units were 11.0:1 compression. Anything over 10.0:1 with cast iron heads is pushing it with regards to detonation. Aluminum heads allow you to run a half to full point higher. Anyway,getting back to your L78 heads,,those are rectangular port units that aren't very efficient below 5,000 rpm. If I were building a pure street motor,I would sell or trade them for a good pair of 781 or 049 oval port castings. These would really improve the engine's street manners by flattening the torque curve,work well with the lower compression needed for pump gas,and will improve the fuel mileage over the rectangular units,too. Something else to consider is the rpm limits of those rectangular port heads will tax the limits of that two bolt 396 block,if you decided to build a screamer BBC to take advantage of the superior high-rpm power of the heads. However,it all boils down to what you want to do with that 396. Clint Hooper H&H Custom,owner 1969 El Camino ProTourer 2001 H-D FLHR custom bagger http://dalesplace.com/misc/friends/clint/clint_hooper.htm ----- Original Message ----- From: Larry Shouse   Digging through my "basket case" 396 parts, I've discovered I have a set of "hi perf" rectangular port heads used on the 375HP 1968 Chevelles - casting number 3919840. The block I got is just a 2 bolt main block. The block is still standard bore, and the stock GM pistons look to be in good shape.   Based on your experience, would you reuse the used pistons? If so, do you think the compression will be low enough to avoid detonation issues?   If you recommend I replace the pistons, what would you suggest I install? I'm looking for a setup where I can maximize power/torque, normally asperated, running on pump gas.   Thanks for your help!   Larry Shouse