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Old 08-30-2007, 12:45 PM   #1
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Somender grooves + compression?

I've been doing a lot of research on Somender Grooves. The results seem to always point to a FE increase, so I think I may try it out on my '93 accord. I paid 200 dollars for this car, it has 274,000 miles on it, what's there to lose?

My question is, do you lose some compression when you do this? And if so, would it be advisable to mill a bit off the head to bring it back? In fact, could I take the opportunity to increase my compression from what it is now?
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Old 08-30-2007, 08:16 PM   #2
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I specifically did the grooves without raising the compression because many people think it is the compression change that makes the difference. The grooves help without changing the compression. With that out of the way I would say that it is almost always preferable to increase the compression a half step or even a whole number. The grooves are supposed to help with detonation. My Saturn has never pinged so I have no input there. The volume of the groove with respect to compression ratio borders on negligible.

Thats my free advice and it is worth every penny you paid for it .
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Old 08-31-2007, 07:37 AM   #3
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Cool. According to everything I've read about compression says that you get about a 30HP improvement with each atmosphere you increase compression with no other changes, and mileage improves as well. Detonation is the killer though.

Another way to increase compression is to increase dwell time at TDC. Increasing rod length allows you to do this. Hot Rod magazine (unfortunately it's no longer free access) was able to build an aluminum head 350 that used a 4.155 inch bore, 3.25 inch stroke and 6.2 inch rods instead of the factory's 4 inch bore, 3.48 inch stroke and 5.7 inch rods. Using this small change in dynamics they were able to increase compression to 11 to 1 and burn not only 87 octane, but they burned the crap you get from Joe's Bait and Gas with no pinging. They put the engine on a dyno and ran it to maximum timing advance with no pinging. The only difference running 8 vs 93 showed was more power, with 87 I think they had 406HO and with 93 they had something like 420HP. I'd not want to mess up a set of aluminum heads, but wonder how well a set of those grooves would work if combined with a long rod engine, might be able to get compression up to 12 to 1 or better off 87 octane. If you could boost an engine from 9 to 1 to 12 to 1 and still run 87 octane, that would mean a considerable increase in power, and of course more power means less fuel needed to maintain a specific level of power. You could even increase the rear end gear ratio without killing acceleration since more power would be available. Might be able to add 10-15MPG with these changes on a small car.
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Old 08-31-2007, 06:12 PM   #4
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you must have been in my room reading my notes for an upcoming post...

actually, what i understand long rods do is that by increasing dwell time, there is a longer time for the air/fuel mixture to burn completely, which means that you wouldn't have to add as much fuel to get the stoicheometric 14.7:1 air/fuel ratio.

and i personally agree that grooving the heads while raising compression is a brilliant idea. raising the compression increases the thermal efficiency of any engine. but it also requires higher octane fuel due to detonation, and also increases nox emmisions. but the grooves work against detonation and a three way high flow cat can take care of the emmisions.
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Old 08-31-2007, 07:47 PM   #5
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In another section I mentioned an experimental cam engine that held the piston at TDC for about 18 degrees. This raised the head temperature and lowered the exhaust temperature but I did not see any numbers on the efficiency. It was hoped that it would run quite lean.

If dwelling at TDC is really all that beneficial someone should build the engine with the rod pointing away from the head and connected to a slipper that went around the crank shaft. I know that would add a horrible amount of reciprocating mass , but the typical engine spends a lot more time near BDC than near TDC. I was just trying to think of a way to reverse that relationship.
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Old 09-02-2007, 02:47 AM   #6
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Think the goal is grooves...10:1 ratio...regular fuel? While it's apart you want to at least match the ports? Some change the valve timing?
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Old 09-03-2007, 02:56 PM   #7
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Quote:
Originally Posted by theclencher View Post
The bored out/destroked 400 Chev was done a long time ago. Ifn that geometry worked, why don't the new clean-sheet engines have it?
thats not to say that it did or didn't unless someone measured it, and if it does help it doesn't meant that it would be worth a complete rebuild for new crank, pistons and rods

im not so sure that they don't i would have to do some serious digging and math to find out.

i suspect that the northstar (i love this engine) and possibly the ls2 as well

i might try to do some looking.
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Old 09-04-2007, 11:27 AM   #8
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Quote:
Originally Posted by theclencher View Post
The bored out/destroked 400 Chev was done a long time ago. Ifn that geometry worked, why don't the new clean-sheet engines have it?
I'd have to guess it was the bigger is better concept. Either that or they only considered bore/stroke without considering dwell time or rod length. The manufacturers aren't perfect. If they were, there'd be no need to modify our vehicles to make them right.

I do know a fellow who put one of those long rod 350s together, said it pulled great, had tons of power, and very slightly better mileage.
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