Originally Posted by: castellan 253 Performance wise is mainly in the exhaust, you need a 2 1/4 free flowing single and that's all, with a 253.
A mate had a 308 HQ with stock dual exhaust but someone put the 253 Stromberg on it, but it went surprisingly well, just that the top end of the rev range lacked over the 4 barrel, but it had good grunt. I thought it would be crap like the 302 fords were that had the same 2 barrel Stromberg, not to mention the Carter 2 Barrel that was a bigger CFM and I never seen any 2 Barrel 302 perform well and that HQ of my mate had would kill them.
I had a HG Premier 253 auto 2.78 diff with just 2 1/4 free flowing exhaust and had many drags. one was a stock XC 5.8L auto with dual exhaust and 2.75 diff and they were neck and neck all the way to 110mph all the time. I met a bloke some years ago who came out with Kenny in that XC and he thought that I had a 327 in my Premier, that was just old Kenny telling porky pies just to try to save face.
I tried 3.55 and a 3.36 ratio diffs in that 253 and them ratios were rubbish such just killed it's performance there was nothing good about them ratios at all, I would of liked to try a 3.08 ratio but they were like hens teeth to find back in the day. Kenny would flog my 253 with 3.55 and 3.36 ratios.
One of the tricks to make the auto 253 perform better was to drop the rev when it changes up mine was 5500rpm when it changed up, so I would have to take the foot off and hit it again about 4500 to 4800 at most on a stock engine is all you need.
you can adjust a cable to make it not rev so high and on newer Holden's they have a kick down sensor, I dust toss that away, you do not need it as they change up at 4500 rpm anyway and drop back just the same regardless and if I needed to go over 4500 I just used the T Bar for that. easy as piss.
I don't think that a stock 253 needs any thing more than a 2V 350 Holley, using a big carby is just BS as the size of the engine will only use x amount of CFM so going above that is just stupid. one has to remember that measuring CFM is different between 2 barrel and 4 barrel, so a 500 CFM 2V carby will flow much more than a 4V of the same 500 CFM.
If the Holden 202 did come out as a 202 'S' 2V Stromberg I think that they would of had to use bigger valves to take better advantage of such. a mate had a stock 202 HQ as mine was both with 2 1/2 exhaust and extractors but he put a 350 Holley on it and yes it did drag mine off but not by that much really at all, just walking away like, so I never put a 350 Holley on mine, I was thinking a 2V Stromberg would be good.
I think a 202 with a small cam of 20/60 and a YT Head and 2V Stromberg will be a good strong stock type of engine that no one could bag at all, as it will have all the torque down low and more than stock and good useable stock range power all the way past what a stock could make and matching it with the stock factory run of the mill 253 that got about.
I agree that the 308 with the 2BBL will be OK. It will lose power (as you witnessed) but will have good low end torque. I had a 307 in an FJ40 that was pretty much stock except it was bored to 4" (327ci) and had a 500 Holley 2BBL on it. Was awful. I pulled the 2BBL off and put a 4BBL manifold and 600 vac sec 4BBL Holley on it. Went well with heaps more power but didn't have the low end torque needed. In the end I put an original 307 manifold and 2BBL Rochester on it, was brilliant. When I converted my Nissan Patrol MQ ute to a 302 SBC and TH400 I fitted a WW Stromberg 2BBL initially, but it wasn't good. I actually fitted a 4BBL intake and a VK Quadrajet, was perfect, had low end grunt and revved out well with good power production. So when you put a Quadrajet on a 253, and set it up like GMH did for the VC/WB they do go really well. A 308's Quadrajet isn't setup right for a 253. Thebest 253 I ever drove was a sweet little motor. Nothing special, was a later one (HZ/VB) with the dome top (9.4:1) pistons. It was fitted with earlier HQ heads and 308 intake with a blue 4.2L Quadrajet. It had HEI ignition, extractors and a single system, and was fitted with the better HJ onwards 308 cam. It was a 5spd manual with a 3.55 rear end. Was a sweet car to drive. Engine was nothing special, but was just right for a daily driver.
A 202S would go better with big valves, but GMH would never have done that in 1970 era. They were a big volume auto producer, just like GM. They built stuff to be used wherever practical across the board. Remember GMH had Perfectune do the XU1 and L34 heads, they didn't do it in house. Pretty much the same for the bigger cams done for race teams to fit themselves, they were done by outside suppliers. As it was a 186S had 145hp, that is 15hp more than a stock HT 186 from the identical engine specs bar induction, headers and timing (HT onwards 186 used the 186S cam in most applications, earlier HK and HR 186 had a smaller cam and was 19hp less than the 186S). All GMH would have done with the 202S was to fit the same stuff the 186S had: better bearings, valves and springs, the induction and headers. Using the same % gain for the 186S over the 186 (same cam between them) this would put the 202S at 151hp (stock HQ 202 was 135hp). It'd probably have been actually higher with the 186S cam, the stock HQ 202 cam was the original 161 cam: 35/75 70/40. The 186S was 43/85 95/48 (these are both including ramps, but you can see the comparison). So if a stock 202 went from 135hp to 151hp with the small 161 cam, with a 186S cam it might have seen 160hp. Add big valves and porting maybe closer to 165-170hp. Getting way too close to the claimed 185hp 253 and thus the HQ GTS would have made a HQ V8 GTS manual with single exhaust and 3.08 rear axle feel slow compared with the GTS's 202S with the same ratio aussie 4spd and a 3.55 rear axle. Plus the 202 would be less restricted with the single exhaust than the 253.
Mick is right about modern technology especially cams. GMH did exactly what GM did with cams, just had a handful and used them across the board. For the later 60's and 70's GM only had 3 production SBC cams, two hydraulics and a solid. The one hydraulic cam was used from 8:1 truck engines through to 10.25:1 300hp 350, this was the same grind as the HJ-VL 308/304. Their next hydraulic was used in the L79 327 350hp (Corvette, was 325hp in others) and 350hp 350 in Corvette. The solid (Duntov cam) was used in the 365hp L76 327, 375hp L84 327 and in Z28 302 plus the 1970 LT1 360hp/370hp engine. As I said, GMH did the same, they developed a better cam for the 308 right at the start (the HJ onwards 308 cam) but saved their pennies and used the 253's cam and retarded it, this was simply done to reduce costs and to have one less part. When they wanted more power they stuck the other cam in and it stayed there on all production GMH 308/304 vehicles until the end of VL (Group A engines excluded). Today with modern roller cams, you can wring huge increases over flat tappet cams especially hydraulics. Modern head chamber designs (plus modern porting practices) also make a huge difference. A simple look at the power output from stock alloy LT1 Corvette heads from the 80's or stock cast 350 Vortec heads compared to the old big port, closed chamber, big valve fuelies of the 60's shows you that the newer heads function far better than the old ones. EFI 304 heads compared to the older heads especially with the 5.7L/350ci versions is another example. Look at LS engines, they are a simple old fashioned pushrod engine, that will outperform old 350ci and 377ci engines with factory componentry, it is all in the heads and roller cam. Put modern alloys and a roller cam on an old rebuilt 350 and it'll perform just as well. I bet those Commodore Cup 253 engines have some hard work gone into their cam designs! If you read the last bit of this article, it shows what they got out of a repro L84 by simply using a modern cam grind versus the original solid cam:
http://www.superchevy.co...ie-motor-on-engine-dyno/Edited by user Thursday, 31 January 2019 4:19:03 PM(UTC)
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