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Hello fellow enthusiasts. I have a 74 olds cutlass with the 350 in it. As many of you know this is the detuned rocket, it went from 310hp to 180 ponies because of emissions regulations. I want to get some HP back but scouring the web has been, lets say difficult. I cant find heads for it and im not really sure where to start. Should i rebuild this motor up? or is it worth dropping a 455 crate in? What does the forum world think?
@Fun71 Its really going to be a weekend cruiser. I would just like it to have some good power for the fun factor when i drive it. Sometimes do local car shows. Budget great question, we all try to save money where we can but im not really thinking of that. I just dont want to spend like 30 grand you know? But if thats what HAS to be done.. Im also game for it if its the best solution.
Well, you have an engine with around 8.5:1 compression ratio so there are limited things you can do without some major surgery. Before doing that, plan what you want so you get the right parts that will work together as a system.
Dual exhaust is always good for some extra horsepower. The 71-72 350 engines were rated 180 hp / 275 ft-lbs with single exhaust and 200 hp / 300 ft-lbs with dual exhaust, so if you don't have duals, think about adding a pipe on the drivers side. You will need this to support any future performance engine mods.
One thing I found is that the rear gears on these cars are usually 2.56:1 or 2.73:1 ratios, which is great for highway cruising, but bad for performance. Swapping to lower rear gears, even 3.08 or 3.23, will make it feel as if you added more power to the engine. This is another thing that will complement future performance engine mods.
I have a bunch of new 350 parts that I don’t need as my new car has a 455. I have a set of 7 heads that have been rebuilt with 2.070 intake valves with screw in studs and guide plates. Comp cams ex 268 h cam and lifters. New set of .030 over speed pro flat top pistons. Comp cams roller tip rockers. Cloyes single row steel timing chain and gears.
desktop dyno specs this set up at roughly 360 hp 400 lbs. ft of torque plus or minus 15%.
let me know if your interested.
@Fun71 iv actually already added dual exhaust with headers. But regearing is an interesting option. I just regeared my Tacoma after the lift and was very helpful. Thank you.
I have a bunch of new 350 parts that I don’t need as my new car has a 455. I have a set of 7 heads that have been rebuilt with 2.070 intake valves with screw in studs and guide plates. Comp cams ex 268 h cam and lifters. New set of .030 over speed pro flat top pistons. Comp cams roller tip rockers. Cloyes single row steel timing chain and gears.
desktop dyno specs this set up at roughly 360 hp 400 lbs. ft of torque plus or minus 15%.
let me know if your interested.
When I did a bunch of work on my girlfriends '76 Salon a few years back I was in the same boat as to what I needed to do to make the car run better. The original 350 ran great but it was a slug. I went with a true dual exhaust with '71 350 manifolds & a '74 dual hump x-member. I was going to put a mild cam in it but the car only had 40k on it. I put an Edelbrock intake on it & I put a shift kit in the 350 trans. The best thing I did was get rid of the lazy 2.41 gears & switched to a 3.08 gear with an anti-spin case. The gears really made a huge difference!!! All I had to do was richen up the part throttle jet a bit.( I don't think the '74s had the part throttle jet) The car runs amazing & it's still a great cruiser!!
The difference in HP ratings between the earlier engines and the '74 is only partially due to changes made to comply with smog regulations. The biggest single change didn't actually remove any power but was just how the engine's horsepower was measured - gross horsepower (pre-1971) vs net horsepower (1971 onwards). https://www.autoblog.com/2013/08/15/...ugh-the-years/
Any heads for a 350 sbo should work, but I don't think changing the heads will have much impact unless you change the pistons as well. I believe part of the emissions modifications included dished pistons for lower compression ratio which directly reduces HP production. So to really wake that 350 up, at a guess I'd say you're looking at carb, intake, heads, pistons, cam...and how close is the engine itself to needing a rebuild?
A "crate" 455 (I don't think those are available anymore but I'm sure I'll be corrected if I'm mistaken) or a properly rebuilt 455 probably won't cost much more than doing all the work on your 350. So if your wallet can handle the bigger gas bill I suspect you'd get more thrills from the BBO up front.
The difference in HP ratings between the earlier engines and the '74 is only partially due to changes made to comply with smog regulations. The biggest single change didn't actually remove any power but was just how the engine's horsepower was measured - gross horsepower (pre-1971) vs net horsepower (1971 onwards). https://www.autoblog.com/2013/08/15/...ugh-the-years/
Any heads for a 350 sbo should work, but I don't think changing the heads will have much impact unless you change the pistons as well. I believe part of the emissions modifications included dished pistons for lower compression ratio which directly reduces HP production. So to really wake that 350 up, at a guess I'd say you're looking at carb, intake, heads, pistons, cam...and how close is the engine itself to needing a rebuild?
A "crate" 455 (I don't think those are available anymore but I'm sure I'll be corrected if I'm mistaken) or a properly rebuilt 455 probably won't cost much more than doing all the work on your 350. So if your wallet can handle the bigger gas bill I suspect you'd get more thrills from the BBO up front.
A local shop says they can do a RV style cam and high comp pistons on it. All for about 2800 I think that's a pretty good deal and should give it quite a jump in power. What do you all think?
That sounds good. That will be Speedpro forged pistons that need .004" clearance or scuffing and overheating will occur. The box says .001" clearance and the instructions say .002", not enough. You will need the block decked .025" and the heads milled to be over 9 to 1 with stock #8 heads. The DSS forged pistons have a better ring pack, taller compression height for less milling and are lighter. A bowl hog cutter in both bowls, exhaust especially will help flow a bunch. Then either a 2" or 2.07" intake valve along with upgraded springs. You want 9.5 to 1 with your altitude and the 204/214 RV cam as small as I would go.
I believe part of the emissions modifications included dished pistons for lower compression ratio .
Actually the 73-76 engines had smaller dishes (14cc) and larger head combustion chambers (79cc) whereas the earlier 71-72 engines that had 24cc piston dishes and smaller 68cc chamber heads. So in theory you could replace the large chamber #8 heads with earlier heads and gain some compression, but likely not enough to make a significant difference.
Hello fellow enthusiasts. I have a 74 olds cutlass with the 350 in it. As many of you know this is the detuned rocket, it went from 310hp to 180 ponies because of emissions regulations.
Spike a 4DR Cutlass Salon was quite healthy for 1974. 350 or 455 they automatically came dual exhaust. So your car is 200 HP and 300 lb ft net base.
Luckily your grandfather bought it before cars were forced to have only single exhaust and the dreaded pellet catalytic converter for 1975 forward. That was the real death knell for performance.
Originally Posted by VI Cutty
The difference in HP ratings between the earlier engines and the '74 is only partially due to changes made to comply with smog regulations. The biggest single change didn't actually remove any power but was just how the engine's horsepower was measured - gross horsepower (pre-1971) vs net horsepower (1971 onwards).
Yes this is key, the auto 310 HP 390 lb ft gross 350 was likely 250 HP and 330 lb ft net. So not nearly as bad as it seems on the surface.
Originally Posted by spikehockey75
I want to get some HP back
Since you already went with headers you have definitely begun this process. As your engines 260 gross HP was attained with headers in the mix.
Originally Posted by spikehockey75
Should i rebuild this motor up? or is it worth dropping a 455 crate in? What does the forum world think?
Originally Posted by VI Cutty
a properly rebuilt 455 probably won't cost much more than doing all the work on your 350. So if your wallet can handle the bigger gas bill I suspect you'd get more thrills from the BBO up front.
As much as I am a 350 enthusiast I am going with VI Cutty on this one. Your ride is heavy, 4127 lbs base curb. I have a healthy 310 HP 350 and I think you would be disappointed if you threw it in your car as is.... Some kick *** gears a shift kit and a converter will definitely give you more hustle but your still asking it to move well over 2 tons. Your gonna want an earlier 455 or definitely a built one. As the 455 that came in a 74 Salon had less HP than the dual exhaust 310 HP 350.
If you want to test the waters as is I would only change the rear for now. Your car came either 2.73 or 3.08 so I would think 3.42 is what you would want with limited slip. If you go with a 455 I recommend the TH400 trans, so doing anything to the TH350 could be a waste of money...
Last edited by 69CSHC; May 9th, 2020 at 04:48 AM.
Reason: clarity
Spike a 4DR Cutlass Salon was quite healthy for 1974. 350 or 455 they automatically came dual exhaust. So your car is 200 HP and 300 lb ft net base.
Luckily your grandfather bought it before cars were forced to have only single exhaust and the dreaded pellet catalytic converter for 1975 forward. That was the real death knell for performance.
Yes this is key, the auto 310 HP 390 lb ft gross 350 was likely 250 HP and 330 lb ft net. So not nearly as bad as it seems on the surface.
Since you already went with headers you have definitely begun this process. As your engines 260 gross HP was attained with headers in the mix.
As much as I am a 350 enthusiast I am going with VI Cutty on this one. Your ride is heavy, 4127 lbs base curb. I have a healthy 310 HP 350 and I think you would be disappointed if you threw it in your car as is.... Some kick *** gears a shift kit and a converter will definitely give you more hustle but your still asking it to move well over 2 tons. Your gonna want an earlier 455 or definitely a built one. As the 455 that came in a 74 Salon had less HP than the dual exhaust 310 HP 350.
If you want to test the waters as is I would only change the rear for now. Your car came either 2.73 or 3.08 so I would think 3.42 is what you would want with limited slip. If you go with a 455 I recommend the TH400 trans, so doing anything to the TH350 could be a waste of money...
I have been shopping around a bunch best deal I think it's actually a 403 built by mondello with 450hp. Don't have to change anything on the car it drops right in according to them. But that's 12 grand... Im having a hard time finding a better deal than just rebuilding the 350 with a RV style cam and higher comp pistons for 2800. I just haven't been able to call them back to get an estimate on what the actual gains are so I'm unsure also im wondering if I should put on an eldelbrock performer intake as well. All that plus a regear on the rear I can probably get done for half the price of the motor... I'm just unsure so thank you all for my ignorance and your patience
I have been shopping around a bunch best deal I think it's actually a 403 built by mondello with 450hp. Don't have to change anything on the car it drops right in according to them. But that's 12 grand... Im having a hard time finding a better deal than just rebuilding the 350 with a RV style cam and higher comp pistons for 2800. I just haven't been able to call them back to get an estimate on what the actual gains are so I'm unsure also im wondering if I should put on an eldelbrock performer intake as well. All that plus a regear on the rear I can probably get done for half the price of the motor... I'm just unsure so thank you all for my ignorance and your patience
Spike your 74 350 is a superior engine structurally to any stock 403. With that said if the build up to 450 HP in that 403 that's advertised includes structural upgrades then maybe.... From 1964-1988 the best Olds V8s were made from 1964-1976. After that the company intentionally weakened things because of the demands at the time. 1977 forward they made some decent engines as long as they are kept stockish and not overly beat on, in my honest opinion.
403s are 1977-1979
Another thing to keep in mind is there are 2 Mondello Olds companies. One highly regarded the other lightly regarded. I would definitely keep that in consideration if you are going that route.
P.S. a 403 will drop into a Olds 350s slot. The engines are externally identical.
Originally Posted by Fun71
That's probably a good estimate. The 1971 engines were rated both GROSS and NET in the Owners Manual:
GROSS = 260 hp @ 4600 RPM, 360 ft-lbs @ 3200 RPM
NET = 200 hp @ 4600 RPM, 300 ft-lbs @ 3200 RPM
Good to hear, I only recently adjusted this estimate. Now lets see if I can get my 69 to get close to showing that 250 HP. So far I have seen 217 HP according to 1/4 mile MPH. Funny thing is I have seen that 217 twice. Once with the car fully factory loaded and again with the car close to bare bones. I'm thinking 3.42s vs my 2.78 rear will definitely do the trick. But it does have 123,000 plus miles so I need to be realistic also.
When I did a bunch of work on my girlfriends '76 Salon a few years back I was in the same boat as to what I needed to do to make the car run better. The original 350 ran great but it was a slug. I went with a true dual exhaust with '71 350 manifolds & a '74 dual hump x-member. I was going to put a mild cam in it but the car only had 40k on it. I put an Edelbrock intake on it & I put a shift kit in the 350 trans. The best thing I did was get rid of the lazy 2.41 gears & switched to a 3.08 gear with an anti-spin case. The gears really made a huge difference!!! All I had to do was richen up the part throttle jet a bit.( I don't think the '74s had the part throttle jet) The car runs amazing & it's still a great cruiser!!
@rob1960 where did you get this gold air intake O.O
I have been shopping around a bunch best deal I think it's actually a 403 built by mondello STOP HERE with 450hp. Don't have to change anything on the car it drops right in according to them. But that's 12 grand... Im having a hard time finding a better deal than just rebuilding the 350 with a RV style cam and higher comp pistons for 2800. I just haven't been able to call them back to get an estimate on what the actual gains are so I'm unsure also im wondering if I should put on an eldelbrock performer intake as well. All that plus a regear on the rear I can probably get done for half the price of the motor... I'm just unsure so thank you all for my ignorance and your patience
Anything built by Mondello suggested by the Mondello website will cost a lot and underperform and most likely fall apart where he will then blame it on the installation procedure or some other simple problem. Short answer, stay far far away from that website and Lynn Fredehamberders or however you spell his name. ANYWAY....a 3.23 or 3.42 gear will make that thing feel like it has 200 more hp. If you want to dig into the engine, keep in mind stock replacement head gaskets will add an additional .024" of deck surface compared to the factory .017 ultimately reducing the compression ratio. A set of #3 or #4 heads from a 330 will bump the compression up closer to 9:1. That engine can handle a cam with more duration than an "RV" cam. I'm sure CutlassEFI will chime in and say an Erson TQ40...ha. Otherwise, long tube headers and an Edelbrock performer RPM to top it off.
@brownbomber77 thank you for the information! I actually came up with a good plan with a shop I trust here. We are going to do a mild cam with flat top pistons, of course rebuilding / replacing internals. Give the motor a good work over. He expects compression to be about 9:1 maybe slightly more. But he gives a 6 year warranty on all his builds and will do all the work of removal, rebuild, reinstall all for 5 grand out the door. I think this is the best and most trustworthy deal I have found. I think it will give the motor some new life and I'll do gears on top of that.
May 7th, 2020, 12:24 PM
74 Rocket 350 Help
