circinus Posted December 22, 2009 Share Posted December 22, 2009 I hope the title is ok. I really didn't know how to title for this post so feel free to change it. Long story short. Original 6 in car blew up its pistons. Take engine out. Was going to replace with a v-8. Fast forward 10 years I now have a bunch of parts and thats it. Found an engine for $50 and headed out and got it. Now here is my question. Got the engine home and did the look over. I haven't cracked a bolt on it except for the clutch assm. It's a 81' f54 block with a p79 head. And by the looks of it its never been apart. But I have no idea of the history. It turns by hand and feels good with the way it turns. If that makes any sense. You can feel its smooth and has good comp. At this point I have a few options in front of me and here they are. When I got my original car it had the twin weber downdrafts that came from victoria british. The original owner hacked the injection system off. Remember this is back in the early 90's and I was 18 when I bought it so it happened. I also have a nice header and exst to put on it as well. Now the big question. I have my bare n42 block. I also have a n42 head and a n47 head. Should I leave well enough alone and just put a new gasket kit on the engine I just got and throw in a new bumpstick and be done or start swapping things out for one another. Heres what I'm looking for. Good power without dumping a fortune in the engine. Real life comes first thats why its sat for 10 yrs. $100 buys a gasket kit from northern auto so if I'm going that far swapping heads or blocks and so on is an option. I plan on buying a cam and thats going to be about it for the engine. With the carbs, header, and stuff I have I was looking for your guys recommendations and what you would use if it were you. I've done plenty of searches since I decided to stick with the l6, I guess I need a push in what direction to take. Quote Link to comment Share on other sites More sharing options...
Challenger Posted December 22, 2009 Share Posted December 22, 2009 Title isnt ok. Doesnt mean anything. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted December 22, 2009 Share Posted December 22, 2009 Your question has been discussed many times - I'd suggest spending an hour searching and you will find some very good discussions about mixing/matching heads, blocks, pistons, and cams. This one http://forums.hybridz.org/showthread.php?t=156953 is recent and filled with good stuff. There is a strong case to be made that putting an N42 or N47 head on an N42 block with dished pistons, a mild cam and decent intake and exhaust (nothing too exotic - well-sorted SUs are fine) and you'll have a very fun motor that is cheap to build and also reliable and reasonably economical. Once you go much farther the law of diminishing returns begins to take over quickly with NA L engines and turbo or engine swap becomes the next step. Quote Link to comment Share on other sites More sharing options...
circinus Posted December 22, 2009 Author Share Posted December 22, 2009 I've spent 10 yrs. searching these threads. That thread thats linked here is one of the few that got me started thinking about this. The only thing I guess I'm having problems with is my carb set up. Theres not alot out there on these carbs. How close to su's are they and so on. Now that I read my thread after I posted it I see my wrong. I never really new how to dial this car in with these carbs. And still dont. I always had problems with them. If I had tripples I know what I would do. If I had injection I know what route I would go. With these carbs I'm spinning circles. And with the harness missing some wires The injection system isnt going on. For at least now it isnt till I sort the wiring out one day. Quote Link to comment Share on other sites More sharing options...
Mack Posted December 22, 2009 Share Posted December 22, 2009 KEEP the F54 with the P79 intact. It will be a better choice than the N42 dish/N42 or N47 combo. Itll have more compression and better quench. Not that it will really matter on a 8.8:1 engine....... Or if you want to get nuts and run some high octane fuel or plan on a mild cam, run the N42 head on the F54 flat top block. That will give you slightly over 10:1, and with a decent cam, you should be able to run it on pump gas. Or, if you want to get a little more involved, mildly clean up the ports on the N42 head and have the valves unshrouded, that would drop the compression a little and improve the flow. Lots of stuff you can do...... How much time do you want to put into it? P.S. First thing Id do would be to ditch the downdraft webers and get a nice set of SUs or convert it back to EFI. Quote Link to comment Share on other sites More sharing options...
circinus Posted December 23, 2009 Author Share Posted December 23, 2009 I had a feeling I was going to see dump the downdrafts. I do like them I just never got them to run right and learned what I needed to do after the car was tore apart. My only other option for fuel is the efi and I would have to figure out where the wires were cut and so on. My n42 is all ported out I just remember I always had timing problems with the head. but than again it was a stock cam and the carbs were a factor. Any feedback on these carbs. I've seen them bashed up pretty good but never highlighted. There had to be an advantage to them at one point. Going to do some google searches on them and see what I can learn. I realized this topic has been covered a billion times and sorry for that. Its kinda going to what would work best for my carbs thread. How do I change the title? Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted December 23, 2009 Administrators Share Posted December 23, 2009 I do like them... Why? My only other option for fuel is the efi and I would have to figure out where the wires were cut and so on There are lots of options. The cut wires are not that big of a deal. The EFI harness is entirely separate and easily removed/replaced. With the Megasquirt craze, I'd be surprised if you couldn't get another harness on the cheap. Any feedback on these carbs. Sure. 1 of 1000 people like them, and no one knows why There had to be an advantage to them at one point. No. Just a gullible market. Many enterprise's care about what sells, not what works. Its kinda going to what would work best for my carbs thread. If you're open minded and motivated, you're not stuck with those. How do I change the title? You can't. Staff can. I'm *this* close to shedding this one. Simply because you need to spend more time searching/reading. This stuff has been discussed and discussed and discussed. No one here can tell you what's right for you. Let's put this on a specific track or it goes to jail Quote Link to comment Share on other sites More sharing options...
cockerstar Posted December 23, 2009 Share Posted December 23, 2009 ...run the N42 head on the F54 flat top block. That will give you slightly over 10:1, and with a decent cam, you should be able to run it on pump gas... How much port work has been done on your n42? If it's decent, you should be able to put it on the f54 block if you run a pretty aggressive cam to help lower your dynamic compression ratio. Ditch the dual webers on eBay and pick up a set of stock SU carbs. Round tops work well for mild street applications, and it's entirely possible to feed a strong fun engine with them. They're fairly straight forward to tune, and are reliable when set up properly. Let everything breathe through the header you have with a 2.5" free flowing exhaust and you'll have a decently potent street engine that you can run on 91 octane Quote Link to comment Share on other sites More sharing options...
circinus Posted December 23, 2009 Author Share Posted December 23, 2009 I should have thought this thread out better. It is beating a dead horse. Thats what happens when you are on here at 1am. It all sounds good to me tired thinking. I know all about the heads and and it was more what would work with the carbs and I was hoping to hear something I haven't read. I didn't realize till last night that they really are not anything special. I always thought they were. I've spent the last 8 yrs focused on a v-8 swap that never got done so It is all a big refresher on the l6. There was no internet back when I was running a l6, so I didnt know about the efi/carb systems. We had az zcar, msa and victoria brittish catalogs to tell us and car shows. Looks like efi will be the route I take. I have 2 of them and money is an issue. What are the carbs worth and who uses them? P.s. you can shed this I never ment for it to be another head/block combo thread. More a what works best with dvg's and I found my answers. Really nothing. Just glad I never got rid of my l6 parts during my v-8 gather. And thanks for the input guys. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted December 23, 2009 Share Posted December 23, 2009 Sure. 1 of 1000 people like them, and no one knows why I would NOT say "I liked them". Rather, they were adequate for a street driven car where everything was stock. I ran them on an L28 because the original SUs had worn throttle shafts and were impossible to tune with that much air leaking around them and the DGVs were $100. I suspect that for many people, that was the main advantage/lure of the DGVs - it was easier to find a set in decent mechanical condition than SUs. I had no problems tuning them and they were equivalent to the SUs with the stock engine. I wouldn't recommend anyone go out looking for them, but if they are what you have, and you're going to leave the engine stock for now, then a simple rebuild will probably solve your issues with them. FYI, I ran them with an N42 head and didn't have any issues with timing - not sure what you're referring to. I think you need to think about what your goals and budget are for the engine first. If you just want to get it so that it's reliable and fun to drive, and don't want to spend more than a few hundred dollars, then fix up the DGVs, put them on the F54/P79 engine and drive it. Megasquirt is a great solution and offers far more potential, but even doing it on the cheap, it will be several hundred dollars just for parts, depending on what you already have and their condition. But once you get it sorted, if you plan to build from there for more power, MS will be able to handle that easily while the DGVs will not. Quote Link to comment Share on other sites More sharing options...
circinus Posted December 23, 2009 Author Share Posted December 23, 2009 I really want to drive my car. its been over 10 yrs since I drove it and I have the itch. Bad! My 5 lug conversion is done and paint is in the spring. I dont know much about the megasquirt systems at all. For right now my goal is to buy a victor r gasket kit, Throw a quick hone in it to freshen it up if needed but really dont want to remove the crank. Leave it together if it looks good. I was going to spend a couple of hundred and get a cam and put it in. I have a couple grand in sbc stuff laying around so as I sell that crap off I will have more money to put back in my z. So thats my goals. As for power, sure everyone wants 400-500hp but lets get real. 250 would be awesome for me. heck even 200 would be good. If the megasquirts are only a few hundred and it gives me more options I'm in. I always thought they were a couple of grand, so, I just have to learn it. Back in the late 80's early 90's I didnt understand injection and computers and turbo's and to get more power was to stroke your l6 (big$) or to (little$) sbc it and you have 300hp like that. In 20yrs I never messed with the efi cause I thought it was too complicated and stuck with the dvg's cause I thought they were better. Little did I know. Quote Link to comment Share on other sites More sharing options...
Mack Posted December 23, 2009 Share Posted December 23, 2009 what Ive read and heard about the DGVs is the fact that its just a bad design on a side draft engine. the fuel tends to puddle in the elbow and you lose performance when the air has to switch from moving downwards through the carb to moving sideways to get into the engine, especially while its carrying fuel. they were better than a set of hitachi SUs on an L26 that had a few years of heat and vapor lock on them, as a stock replacement. but I have never really heard of or seen them used in a performance application. MS is the way to go and you can do it for CHEAP with a little knowledge, time and some rudimentary soldering skills. you can probably have EVERYTHING you need for under $1000 on MS. and its the gift that keeps on giving, as you can re-tune it everytime you upgrade your engine. I think if you have a P&P N42, with a nice cam and put it on top of an F54 flat top block, 200 crank should be NO problem. Depending on how nuts yo ugo with the cam, and if you get an afetmarket intake manifold, you *might* see 200rwhp, maybe more. depends on the porting and the cam. you should not need to remove the crank or replace any bearings unless the engine had a previously known bottom end problem. these old I6s are tough and can go 300,000+ with out needing a rebuild. infact, I probably wouldnt even worry about honing it out. Id keep the P79 incase you ever want to go turbo. Quote Link to comment Share on other sites More sharing options...
circinus Posted December 24, 2009 Author Share Posted December 24, 2009 I've been reading up on the megasquirt. Wow there is a lot to read there. Plan is for now, Run 54 block with 79 head with the downdrafts to get started. Remember its been 10yrs since I drove it so this is a starting point. And I get to drive it while I get rid of all the sbc crap and raise some $. During this time I can get my research done on intakes, rails and so on. Really sucks that I learn now the dvg's are ok carbs. I always thought it was a performance upgrade. Lucky for me my original efi wiring was chopped at the big part before it splits to go to the contacts. And during this time while I'm getting the efi around get my 42 head on my work bench and look it over. Its been sitting for almost 15yrs. The 47 always ran better on my engine back then for me. Not as hot of a set up as my 42 but I got better mpg. Car use to be a dd. The thread got off track a little bit going in the head/block thing but What I really wanted to know was about the carbs and Got my answers I needed. And with that I thank you guys. Its been a long time since I played with a l6 and I cant beleive I was going to dump it for a sbc over some wrecked pistons. What was I thinking? lol. Thanks guys. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted December 24, 2009 Share Posted December 24, 2009 IIRC the N42 and N47 have the same shape and size combustion chambers, so I'd be surprised if you could notice any significant differences with fuel economy or power, unless one of them was modified. And improving flow on a head to improve power is likely to improve fuel economy as well. You might want to try to remember if other things were changed as well. Quote Link to comment Share on other sites More sharing options...
circinus Posted December 25, 2009 Author Share Posted December 25, 2009 Yeah my 42 had valves and the whole nine yards done. I think the shop was called Dr. Z's or something like that. He was in Orlando Fl. Thats who did it for me. Its a nice head and I'm very lucky I was able to hang on to it all these years. I had triples at one point with that head. I had to sell them when I was 21 to pay for a plane ticket home to ohio for a funeral. Thats when I went back to the dvg's. I did try the 42 with the dvg's but I was getting popping and backfire thru the carbs and I didnt have enough know how back then to figure out the right vac, adj, and so on. So the 47 went back on. Do wish I still had the triples. But when your young and poor and an emergency comes up you do what you gotta. Quote Link to comment Share on other sites More sharing options...
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