I bought this motor a while back for an old project I had... Long story short, that project went down the road and the motor sat. Now, a new project is in the works and looking to make some minor changes. Below is what I started with... However, I'm looking at lowering the compression and maybe going to a roller cam. Running 93 pump gas, what would be the highest compression I could safely run and what would be the most radical cam I could use without jeopardizing performance? I also no longer have the 850 Proform carb so will be taking suggestions for a new one. 377 stroker - 13.5-1 compression, SCAT steel crank, 5.7 rods, forged Speed Pro Pistons, World Sportsman 200cc iron heads with 64cc chamber and 2.02/1.60 stainless valves, chrome moly pushrods, aluminum full roller rockers, Comp solid lifter cam (250/60 duration @ .50 532/558 lift, Pete Jackson, Victor Jr intake w/850 Proform carb on top of a Wilson spacer with full length headers Also, how do you think the new set-up would respond to a 150 shot? Any ideas on HP/TQ with lower compression and new cam?
Depends on how you want to lower the compression. Aluminum heads tend to dissipate heat better than Iron ones. If you lower the compression by swapping to aluminum heads with larger chambers, you might be able to get away with higher compression than you could with Iron ones. I ran an all Iron 377 in the late 80's in my Malibu. Many nights were spent putting the 2.56:1 rear gears to good use, making the speedometer needle disappear.
What's the weight on the car Need more details on what you expect out of the motor , 9-1 to 10 -1 on 91 38-42 total timing , each motor and combinations are different on timing, 10.5-1 to 11.1 On 91 , I have not seen 93 on pump 30-34 total timing 12-1 on 100 Aviation fuel ,Blue with 38-42 total timing If you go Roller , I would do a Hydraulic for Street
More than 10:1 can and has been done on 93 pump. Be safe especially if you plan on using that 150 shot with pump gas also. Stay below 10...Just my thoughts...
As said , aluminum heads and bigger chambers to lower comp. Hydr. roller. Any engine will respond to spray, the question is , how long will it last, or hold together?
If I was doing it..depending on budget of course.. I would just change Pistons to correct the comp ratio ... The cam is not too big to live with by any means.. then carb accordingly with NOS taken into account .. Change cams if budget allows too.. If not you can make that combo make good power and still be... somewhat streetable... everyone likes a lumpy cam..
Do not forget when you add the NOS the timing needs to be retarded especially when on pump gas. That combo with a 150 shot should easily make over 500 both HP/TQ without issues...providing it is done properly. More is easily there with the proper steps taken.
The 377 is a great combination... I ran one for a few years in the Scout. The problem with this combination is it's based on a 400 block which is notoriously weak. My engine builder loves this combination but warns everyone off when the HP climbs over 550. That 150 shot will put you in the danger zone. The fun part about nitrous is it's easy Hp but it gets tricky when you step up to anything over a 50 shot. Now you're talking about retarding the timing, heat dissipation, valve damage and ensuring you have adequate fuel - otherwise you end up with cutting torches in the cylinders. A lot of the advice above are good tips to follow. If I may add one of my own - think about putting in a decent nitrous / blower / turbo cam (all the basically the same) with some exhaust overlap. Have fun
I agree if you are adding the 150 I would add a nitrous controller to your ingintion or change it manually before playing with the NOS. If you plan on using NOS a lot cam accordingly ... A " blower,turbo " grind and lower compression too. Plus makes for a good "sleeper" until until the button is used ! I would also run a quality racing fuel when on NOS both for the motor and NOS system... Have fun !
Do you know what the thickness of the head gaskets are ? You might be able to swap them out for thicker head gaskets to lower the compression enough to run on 93 pump gas. If you want to add an electronic injection you can run 93 with 12.1 compression. When choosing cams as someone else mentioned I would go with a retro fit hydraulic roller cam.
Yeah.... thicken them to about ... 1/8 inch... yeah that out to do it ..really ...electronic fuel injection... . Ok let's start from his post
If it was mine and giving what was posted I would want it to perform and survive ... on a budget .. New pistons , cam , make sure bottom end is in good shape... Stay easy on NOS and Carb according to motors needs and MOST important ... Enjoy the noise of HP !
Hey here is another idea... forget the NOS ...leave it the way it is ...get a .new carb .... go by a 55 gal can of Methanol !!! Tune accordingly !!
Thanks for all the replies fellows... To answer some of the questions: This is a budget build so I'm trying to use as much from the previous build as I can. Heads will definitely stay the same and more than likely, I'll use the same cam. There is a small chance I would consider going to a hydraulic roller, but I doubt it. The motor will also stay carb'd, not going over to F.I. I by no means am an a engine guru so I apologize for some of the basic questions, but I've had a few people suggest simply changing head gasket thickness... I know this method can be used, but going down from 13.5:1 to something suitable for pump gas, say 10.5:1 just seems to be a stretch. Can this effectively and safely lower the compression enough? As far as the 150 shot goes... I have a NOS Cheater system sitting around and was simply thinking of finally hooking it up on something. It would rarely be used.... maybe a handful of times per summer, but I know it only takes one time. I am familiar with retarding the timing/running race gas when using it, but would not want to jeopardize the motor and would not need to spray it at all. Motor would potentially be going into 2 door Biscayne. Also, I'd prefer to run it on pump gas - 50/50 mix when at the strip. E85 is not ruled out yet, but I would need to do a little more research before I went that route.
I have had some experience with nitrous (good and bad) so let me share some of my hard earned wisdom. Based on your requirements / engine set up / experience I would strongly recommend sneaking up on the 150 shot. In this day and age of multiple stage 500+ hp nitrous systems people tend to trivialize how much a 150 shot really is. This level is a serious kick in the ass - performance wise and just a hair past safe for a non purpose built engine (Cam, valves, rings) and the vehicle itself. Start at a safer 50 shot and see what happens. The nice thing about a 50 shot is you can get away without messing with your timing - but I do recommend a 1 degree retard for a 50 shot. After 50 hp the general rule is to retard your timing 1.5 - 2 degrees per 50 shot increase. (3 - 4.5 for 100, 3.5 - 6 for 150 etc). You're two worst enemies are: 1. Too much nitrous / not enough fuel 2. Detonation. We've burned forged pistons with a 50 shot (fuel solenoid failed) and I've seen broken ring lands and broken pistons through detonation. Run good fuel to start and better as the shots increase. For your first few passes, put in a fresh set of plugs (gapped for nitrous: .030 - .035) and arrange to have someone tow you back to the pits from the top end. (it's important - driving back will mess up the readings) At the end of your pass shut it off immediately and get a tow back so you can read your plugs (or have someone read them for you). Check every plug !! - if this is not practical, check one of the middle plugs as those cylinders run hotter. If it's all good and you want more then retard the timing (1.5 - 2 degrees - cumulative to the previous adjustment) and go to a 75 (Shut off, tow back, read plugs etc) then if all good, retard the timing a bit more and go to a 100... and repeat. Jets for a nitrous kit are not expensive. Learning the basics for plug reading isn't that hard. You may also find that the performance increases may put you on the edge of how much the car can safely handle and may max out the safety equipment for the times you are turning. This simple creep up method may provide an opportunity to save your engine, and not run afoul with your track if you go to fast. Good luck
Thanks for the detailed response Saxxon... This will not be a serious track machine, just a weekend street/strip warrior so I'm still up in the air about the nitrous.
Don't use thicker head gaskets!!! You'll want the head surface to be in close proximity (.040") to the piston at TDC for maximum quench area. That will help keep the chances of detonation to a minimum. Especially if you use a lot of NOS. Don't ask me how I know... Besides that, you'll want to bring the CR down to about 8.5:1 - 9.5:1 (maybe lower depending on how much NOS) with dished pistons and use the NOS to make the boost in power. Sort of like the same principle as blowers and turbos. Or just leave it like it is and use less NOS. Be careful and have some fun!
The old saying was 10cc's equals 1 point of compression. If you want 10.5:1, from 13.5:1, you will need to gain 30cc's somewhere. That is 1.8307 cubic inches of space. At a stock 4.125" bore, you'd need a gasket that is 0.137" thick.
Yea that would make it a little rough to keep your quench @ .040 ( or close to it). LOL If I am building an iron headed motor for someone else and cannot keep my finger on the tune always I build them @ 9.5 to one and keep the quench around .040. That usually involves using a dished piston when using heads with a small combustion chamber. As far as cam loosing performance is relative. You can run a lot of cam shaft @ 9.5 to one and keep good performance, the problem is you have to decide what good performance means. Are we talking being able to lug it around or are we talking keeping the revs up and going for it?
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